Rotary Heat Exchangers

for Heat Recovery in Ventilation Systems

Handbook for Design, Installation and Operation

Peripheral slide seal

Constant-force springs permanently press
the abrasion-resistant ring seal against the
casing. The patented system permanently
minimises leakage and allows the unit
to be sized for smaller air flow rates.

Drive motor
The 3-phase gear motor with belt pulley
and v-belt is installed on a rocker in
the corner of the casing. The speed
of rotation is infinitely adjustable.

Adjustable purge sector

The size of the purge sector can be adjusted
to suit requirements. The device (patent
pending) prevents contamination of the
supply air by the extract air and at the same
time minimises purge and energy loss.

Storage mass
Hoval supplies the storage mass in three types of
material: for condensation, enthalpy and sorption
wheels. The sorption coating guarantees a consistently high degree of moisture recovery efficiency,
even under summer conditions.

Content

1Process and function___________2

1.1Heat transfer
1.2Transfer of humidity
1.3Leaktightness
1.4Frost limit
1.5Heat recovery efficiency
1.6Pressure drop
1.7Pressure difference
1.8Hygiene

2Output regulation______________7
3Structure____________________8
3.1Wheel
3.2Casing
3.3Drive

4Options____________________ 11
4.1Drive
4.2Control unit
4.3Operating unit
4.4Rotational speed monitoring
4.5Inspection cover
4.6Purge sector
4.7Duct design
4.8Coated casing
4.9Offset wheel position

7.15Danger of contamination
7.16Condensation in warm air stream
7.17Technical data

8Transport and installation______23

8.1Transport
8.2Mechanical installation
8.3Installation of sensors
8.4Electrical installation
8.5Assembly of segmented rotary heat exchangers
8.6Storage

9Commissioning and maintenance_24

9.1Commissioning
9.2Maintenance

10Specification texts___________25
10.1Condensation wheel
10.2Enthalpy wheel
10.3Sorption wheel

5Dimensions of the exchangers__15

6Unit type reference___________16
7System design_______________18
7.1Hoval CARS design program
7.2Design data
7.3Checked data
7.4Requirements and directives
7.5Local conditions, installation position
7.6Wheel type
7.7Output regulation
7.8Using and setting the purge sector
7.9Bypass
7.10Frost limit
7.11Leakage
7.12Supply air humidification
7.13Corrosion
7.14Application limits
1

Process and function

1 Process and function

Hoval rotary heat exchangers are regenerators with rotating
heat accumulators (category 3) in accordance with the guidelines for heat recovery (e.g. VDI 2071).
The heat-dissipating and heat-absorbing air flows heat
or cool the rotating, air-permeable storage accumulator.
Depending on the air conditions and the surface of the
accumulator material, moisture may also be transferred in
the process. Supply air and extract air must therefore be
combined and flow through the heat exchanger at the same
time.
The storage mass consists of triangular, axially arranged
small ducts made of thin metal foil. The depth of the storage
mass (viewed in the direction air flow) is generally 200 mm;
the airway height is normally 1.41.9mm, depending on the
application. With these dimensions the storage mass generates a laminar flow in the wheel ducts.

Fresh air
t21
x21

Supply air
t22
x22

Exhaust
air
t12
x12

Extract air
t11
x11

Fig. 1: Function diagram and air conditions

Definition of key data according to VDI 2071

Heat recovery efficiency of cold air

t22- t21
2 =
t11-t21

Moisture recovery rate of cold air

x22-x21
2 =
x11-x21

Legend:

t = Air temperature [K; C]

x = Absolute moisture [g/kg]
1. Index: 1
2
2. Index: 1
2

Warm air
Cold air
Inlet of heat recovery unit
Outlet of heat recovery unit

Fig. 2: Geometry of
storage mass

1.1 Heat transfer

The wheel with its axially arranged, smooth ducts acts as a
storage mass, half of which is heated by the warm air and
the other half of which is cooled by the counter-flow of cold
air. The temperature of the storage mass therefore depends
on the axis coordinates (wheel depth) and the angle of
rotation.
The function is easy to understand by following the status
of a wheel duct through one revolution (see Fig. 3). The
following can be recognised with reference to the heat
transfer from this process:
The air temperature after the exchanger varies; it depends
on the location on the wheel.
The heat recovery efficiency can be varied by varying the
speed.
The heat recovery efficiency can be changed with the
storage mass. This can be done with different cross-sections of the wheel ducts, different thickness of the storage
material or by changing the wheel depth. However, in all
cases this varies the pressure drop.
The specific heat output depends on the temperature
difference between warm air and cold air. The rotary heat
exchanger is therefore suitable for heat and cool recovery,
i.e. for winter and summer operation.

Process and function

Warm air entry

The rotation of the storage mass has
moved the wheel duct from the cold air
to the warm air. The storage material is
cooled almost to the temperature of the
cold air. This applies particularly to the
entry side of the cold air (= exit side of the
warm air). The warm air now flows through
the duct with reference to the temperature
in the counter-flow and is cooled greatly.
The storage mass is therefore heated. The
local heat recovery efficiency, i.e. directly
at the inlet to the warm air, is very high.
Condensation can also occur very easily.

Mid warm air

The wheel duct now has passed half of
its time in the warm air. The storage mass
has been heated by the flowing warm air;
therefore, the warm air is not cooled down
as much as in entry inlet zone. The wall
temperature at the entry and exit is approximately the same. Condensation occurs only
with large moisture differences.

Warm air exit

The wheel duct is now shortly before entry
to the cold air. It has virtually reached the
temperature of the extract air at the entry
side. The transferred performance is still
only low.
The dwell time in the warm air and in the
cold air, i.e. the speed of rotation, is decisive for the performance of the rotary heat
exchanger. It depends on the storage mass
(thickness, geometry), the heat transfer and
the air velocity.

RM AIR
WA

CO

Cold air exit

The wheel duct has passed through the
cold-air section. The storage mass has
greatly cooled, almost down to the cold-air
temperature in the entry section. After
crossover to the warm air side, the cycle
starts anew.

L D AI R

Mid cold air

Half of the dwell time in the cold air is past.
The storage mass has already cooled
significantly. The temperatures at the entry
and exit are approximately equal.

Cold air entry

After the transition from the warm air to the
cold air, the wheel duct now has cold air
flowing through in the opposite direction
(referring to the temperature). With the
high temperature difference the transferred
performance is very high, i.e. the cold air is
very strongly heated; in reverse the storage
mass is strongly cooled. Any condensate formed on the exchanger surface is
(partially) absorbed by the heated cold air.

Fig. 3: States depending on the turning angle

3

Process and function

1.2 Transfer of humidity

Temperature

Relative humidity

Water

In addition to heat, moisture can also be transported with

rotary heat exchangers. The decisive factor here is the material and/or the surface of the storage mass. Characteristic
features for different designs have been developed with
detailed measurements of wheels from different manufacturers by the building technology test centre of the University
of Lucerne. The reference factor for the moisture recovery
rate is the condensation potential; that is the moisture difference between warm air moisture and the saturation moisture
of the cold air (see Fig. 4).

The following must be noted:

The greater the condensation potential the greater the
volume of condensate that can be expected at the warm
air side.
If the condensation potential is zero or negative, no
condensation can take place. Moisture transmission is
therefore only possible by sorption.
The derived characteristics reflect typical values of 1:1
for the mass flow ratio and the pressure drop of approx.
130Pa at an airway height of 1.9mm.
The area of application of reference magnitude , i.e.
the condensation potential, is restricted to the standard
conditions of ventilation technology. The heat recovery
efficiency must be at least 70%. The moisture transmission must not be restricted by the saturation curve (e.g.
with very low outside temperatures).

Warm air entry (t11, x11)

Cold air entry (t21, x21)
Saturated cold air
Condensation potential of warm
air

Fig. 4: Definition of condensation potential

Sorption wheel

Moisture recovery rate 2

1.0
0.9

Enthalpy wheel

0.8

Condensation wheel

0.7
0.6
0.5
0.4
0.3
0.2
0.1
0

-4

-2

Condensation potential [g/kg]

10
Bild 5: Typical course of moisture recovery rates of
various wheels depending on the condensation potential

Process and function

There are 3 different designs:

1.3 Leaktightness

Condensation wheel
The storage mass consists of smooth, untreated aluminium,
which only transmits moisture if condensation occurs on the
warm air side and it is picked up by the cold air (partially).
Moisture recovery rates greater than 80% can be reached if
the temperature difference is high.
The use of condensation wheels for heat and moisture transmission is recommended primarily for ventilation systems
without mechanical cooling, i.e. for winter operation.

Components used in air handling units, such as dampers,

ducts or casings, are normally never 100% leaktight.
However, leakage must remain within technically acceptable
limits. VDI guideline 3803 sheet 5 defines the calculation of
the leakage of rotary heat exchangers and its influence on
the design calculations.
A distinction must be made between leakage to the outside
(external leakage) and leakage between supply air and
extract air (internal leakage). While sealing leaks to the
outside is normally not a problem (it is primarily a question
of installation quality), internal leakage primarily depends
on the design. Three items are important for rotary heat
exchangers:

Enthalpy wheel (hygroscopic wheel)

The metallic storage mass has been treated to form a capillary surface structure. The moisture is transmitted by sorption
and condensation, with the sorption component being very
low. Moisture transmission in summer operation (<0) is
also very low.
Sorption wheel
The storage mass in this case has a surface that transmits
moisture by pure sorption (i.e. without condensation). The
moisture recovery rate is therefore virtually independent
of the condensation potential. The low decrease can be
explained with the simultaneous reduction of the temperature
difference.
Sorption wheels are recommended particularly in systems
with mechanical cooling. The high moisture recovery efficiency, even under summer conditions, dries the fresh air.
This requires less cooling capacity and reduces energy costs
for cooling up to 50%.

Carryover
The rotation of the storage mass causes a minor mixing of
the two air streams. This is approximately 1% to 3% of the
total air flow depending on the face velocity and speed of
rotation. The transmission of the exhaust air to the fresh air
can be greatly reduced by a purge sector.
Radial sealing
A decisive feature for internal leakage of the rotary heat
exchanger is sealing around the circumference. Hovaluses
a patented system in which an abrasion-resistant ring seal
is permanently pressed against the casing by constant-force
springs. This minimises the leakage via the internal space of
the wheel casing throughout the service life.
Transverse seal
A seal is also required between cold air and warm air. Hoval
uses a triple-lip seal. This reduces the direct transmission
from warm air to cold air (and vice versa) to a minimum.

Notice
On request, Hoval rotary heat exchangers can also
be supplied with other sealing systems.

Process and function

1.4 Frost limit

If the warm air stream is very strongly cooled condensate
can be formed and it may even freeze. The cold air temperature at which this starts is referred to as the frost limit.
Condensation wheel, enthalpy wheel: The condensate
generated by cooling the warm air may freeze at low
outside temperatures. There is a frost hazard at equivalent mass flows for cold air and warm air if the average
inlet temperature of the two air streams is less than 5C.
tm=

The pressure difference in the rotary heat exchanger

should be as low as possible.
In applications that involve the danger of odours the pressure gradients and therefore possible leakage from the
fresh air to the exhaust air must be considered.
However, the internal pressure difference may also cause
deformation of the casing; a pressure difference of more than
1500Pa should therefore be avoided.

t11 + t21
< 5 C
2

Sorption wheel: The gaseous moisture transmission by

sorption generally prevents condensation; the frost hazard
is reduced.

1.5 Heat recovery efficiency

Appropriate design and serial layout allows virtually any heat
recovery efficiency to be reached. The 'correct' heat recovery
efficiency depends on the applicable regulations and the
economy calculations, i.e. the operating data such as energy
price, service life, operation time, temperatures, maintenance requirements, interest etc. It is important that values
calculated to be optimum in the design are also present in
the installed equipment. Even minor changes (a few percent
lower heat recovery efficiency, a few pascals more pressure
drop) can mean significantly poorer results for capital value
and amortisation period.

Notice
The pressure difference depends on the layout of the
fans. Overpressure on one side and underpressure
on the other side add up.

External pressure difference:

This is a major factor for the external leakage of the heat
exchanger. If a duct system is correctly and carefully
installed, this effect can be ignored.

1.8 Hygiene
Hoval rotary heat exchangers have been tested for
conformity with hygiene requirements at the Institute for Air
Hygiene in Berlin. The test criteria were the requirements
relevant to hygiene for applications in general building ventilation and in hospital applications. All hygiene requirements
were met.

1.6 Pressure drop

Heat recovery units cause pressure drop and as a result
operating costs for exhaust air and fresh air. With current
general conditions the economical values for wheels are
between 80Pa and 130Pa. However, to reduce costs,
more and more heat recovery units whose pressure drops
are above these economically reasonable values are being
installed. This affects the feasibility of the system.

1.7 Pressure difference

A distinction is made between internal pressure difference
(between fresh air and exhaust air) and external pressure
difference (between the exchanger and the environment).
Internal pressure difference:
The internal leakage between the two air streams depends
greatly on the pressure difference. Hoval rotary heat
exchangers compared with other designs are certainly very
leak-proof, but the following information should be taken into
account in the design:

Fig. 6:
Certificate of hygiene
conformity test

Output regulation

2 Output regulation
The Hoval rotary heat exchanger always operates as a
temperature rectifier between the two air streams. The
flow direction of the heat is irrelevant in this context, i.e.
depending on the temperature gradients between extract
air and fresh air either heat or cold is harvested. Therefore,
regulation of the output of the Hoval rotary heat exchanger
is not necessary if the extract air temperature is identical to
the setpoint temperature. In this case, the fresh air is always
heated or cooled in the direction of the setpoint temperature
by the heat exchanger.
However, in most cases there are heat sources in the
ventilated rooms (people, machines, lighting, solar radiation,
processing systems) that increase the room temperature,
i.e. the extract air temperature is higher than the setpoint
temperature. In this case, check the outside temperature
from which the system is heated at full performance of the
rotary heat exchanger and if this cannot be tolerated the
performance of the heat exchanger must be controlled.
It is very simple and economical to reduce the performance
of the rotary heat exchanger for heating and also for moisture transmission by reducing the speed of rotation. All
Hoval rotary heat exchangers can therefore be supplied with
speed-controlled drives.
There is also the option of diverting one or both air streams
past the wheel by a bypass. The method used primarily in
process technology and at different air flow rates must be
installed by the customer.

Relative moisture recovery efficiency

Relative heat recovery

100 %
80 %
60 %
40 %
20 %
0%

10

15

Speed of rotation [rpm]

Fig. 7: Dependency of the heat recovery on the rotational speed

20

25

100 %
80 %
60 %
40 %
20 %
0%

10

15

20

25

Speed of rotation [rpm]

Fig. 8: Dependency of the moisture recovery on the rotational speed
7

Structure

3 Structure
A functional rotary heat exchanger consists of the wheel, the
casing and the drive.

3.1 Wheel
Storage mass
A corrugated and a smooth metal foil are wound together
as the storage mass. This forms triangular, axial ducts. The
material is 60m thick.
The surface treatment also depends on the use; there are
3series:
Series A: condensation wheel, consisting of high-quality
aluminium.
Series E: enthalpy wheel, consisting of aluminium with
enthalpic coating.
Series S: sorption wheel, consisting of an aluminium
substrate foil coated with a sorption substance (e.g. silica
gel) for moisture transmission. This transmits moisture in
the form of a gas without condensation.

Fig. 9: A corrugated and a

smooth metal foil are wound
around each other.

Fig. 10: Production on stateof-the-art machines ensures

consistently high quality.

Fig. 11: Large wheels are cut

into several segments.
8

Fig. 12: The wheel is permanently stabilised by internal welded double spokes.

Fig. 13: Hub with long-life, permanently

lubricated inner bearing

Design
The depth of the wheel is 200mm. The wheel is stabilised by
double spokes, screwed (and welded) to the hub and welded
to the wheel mantle (see Fig. 12). This guarantees a long
service life.
For stability and performance large-diameter wheels must be
made in a segmented design. The diameter of the wheel can
be freely selected in 10-mm steps.
The outside of the wheel is held together by an aluminium
jacket plate (welded). This guarantees uninterrupted radial
runout and enables maximum usage of the wheel surface.
Hub with inner bearing
The hub, whose size depends on the wheel diameter, is
fixed to the axle with 2 internal ball bearings. It is fastened
to the crossbars of the casing. This design has the following
advantages:
The internal bearings are protected against contamination
and require little space.
The axial lock with circlips makes installation and removal
quick and simple.
Both bearings are integrated into the hub, i.e. in the
same component. This ensures that they mesh together
perfectly (in contrast to external bearings). This does not
reduce the service life of the bearings.
The position of the axle, hub and wheel is precisely fixed
by the fastening of the internal ball bearings by the hub
and the circlips.
The fixed axles connects the two crossbars of the casing.
This greatly increases its stability.

Structure

3.2 Casing
There are different casing designs, depending on the wheel
diameter and whether the wheel is 1-piece or segmented.
Sheet-metal casing
Self-supporting aluzinc sheet steel casing are standard for
1-piece wheels with diameters up to 2620mm. The sheetmetal casing is strengthened with galvanised steel profiles
from wheel diameters of 1800 mm.
Profile casing
A profile design of aluminium is used for wheels above
1500mm diameter. The casing is extremely stable and the
dimensions are flexible. The plate covers can be removed
and replaced quickly and easily, a factor which is important
for installation of segmented wheels.
The height and width of the profile casing is limited to 4.2m.
Larger casings (welded construction, galvanised) are available customised for specific systems.

Casing types
Different types of casing are also available for adaptation to
different installation situations (see also Section 4 'Options'):
Special size:
Height and width of the casing can be selected as
required (for example for adjustment to the internal
cross-section of a ventilation unit). The hub can also be
placed away from centre.

Notice
The casing design may be different for special
sizes compared to Table 1.

Duct design:
The side walls of the casing are closed (for the duct
connection).

5000

3800

2500
2620

Wheel diameter (in mm)

1500

600

The casings are designed for installation in a ventilation unit.

Therefore, the sides are open; this allows inspection and
maintenance as required.

Wheel 1-piece
Sheet-metal casing
(Delivery assembled)
Wheel 4-piece
Profile casing
(Delivery in parts)
Wheel 8-piece
Profile casing
(Delivery in parts)
Required torque

500 Nm
400 Nm
300 Nm
200 Nm
100 Nm
0 Nm

Table 1: Overview of designs and wheel dimensions (for standard casing)

9

Structure

Peripheral slide seal

In rotary heat exchangers with sheet-metal casing automatically adjustable constant-force springs are mounted on
the wheel mantle; they press the abrasion-resistant slide
seal against the casing. The patented system permanently
minimises leakage and allows the unit to be sized for smaller
air flow rates.
In the profile casing a ring seal with externally accessible
double springs is used. They press the seal to the casing
and to the wheel.
Transverse seal
The transverse seal between the two air streams consists of
adjustable aluzinc sheet steel with a triple rubber-lip seal.

Notice
On request, Hoval rotary heat exchangers can also
be supplied with other sealing systems.

Fig. 14: Automatically adjusting peripheral slide seal in sheet-metal casing

Fig. 15: Peripheral slide seal in profile casing

10

3.3 Drive
The wheel is driven by an electric motor and belt. The motor
is generally fastened on the left or right on a rocker in the
casing. Because manufacturers of ventilation units and
installers sometimes install their own drive, Hoval offers this
component as an option.
2 versions are available:
Constant rotational speed
The motor is switched on and off by a single switch or
contact. Output regulation (i.e. changing the heat recovery
rate or moisture recovery rate) is not possible.
Controllable rotational speed
The drive motor is controlled by a control unit. A frequency
converter (FU) is generally used. Common additional functions are speed monitoring (by inductive sensors) and intermittent operation. If heat recovery is not required, the wheel
is moved slightly at intervals to prevent dirt build-up.
The control unit and as a result the wheel are normally actuated by the room temperature controller, for which the rotary
heat exchanger is perceived as an energy resource for both
heating and cooling, which forms part of the cascade control
concept.

Options

4 Options
4.1 Drive
The wheels are driven by a worm gear or a spur-gear drive
motor using a v-belt; the type and size of the motor depends
on the wheel diameter:
Drive Y
for direct drive by mains power. On/Off operation at
constant speed only.
Drive A
The motor speed and therefore the performance of the
rotary heat exchanger can be controlled. A control unit
(option R) is required.

Motor designation

A 60

A 250

A 370

A 750

Motor power

kW

0.06

0.25

0.37

0.75

Output shaft

mm

18 x 34

20 x 55

20 x 65

25 x 60

Current Y (direct operation by mains power)

0.25

0.83

1.09

1.92

Current (with control unit)

0.30

1.44

1.90

3.40

Drive Y

IP 44

IP 55

IP 55

IP 55

Drive A

Protection rating

IP 54

IP 55

IP 55

IP 55

Motor nominal speed n1

min

-1

1600

1320

1380

1400

Output speed n2 at 50 Hz

min-1

100

132

138

140

Motor nominal torque m1

Nm

0.5

1.81

2.60

5.10

Output torque m2

Nm

6.1

14

21

45

Rotor diameter

mm

up to 1300

up to 1800

up to 2620

up to 3800

Control unit

Type

R / 370

R / 370

R / 370

R / 750

Table 2: Data sheet for rotary drives

11

Options

4.2 Control unit

Structure
A frequency converter with a modular design is used as the
control unit; it can adjust the speed of three-phase motors
infinitely. Protection rating IP 54 is required for installation in
the ventilation unit. The power unit is protected from undervoltage, overvoltage or non-approved converter temperature.
The aluminium casing and the standard input and output
filters increase the immunity to interference. Error messages
can be read out directly at a flashing LED.
The control unit is delivered ready for operation with the
factory-set parameters. Various settings can be changed with
an optionally available operating unit.
Function
The control unit can be used for condensation, enthalpy
and sorption wheels that require speed control. All
standard control signals are accepted.
A quadratic (standard) or linear implementation of the
setpoint into the rotary field frequency based on the
maximum frequency of the selected parameter set is
used.
As soon as the input signal is below the defined threshold
value, the wheel stops rotating. After an adjustable holding
time intermittent operation is started and the wheel rotates
at the defined speed for a few seconds.
An inductive sensor can be connected for speed monitoring (option D).
Readiness for operation and any fault messages can be
output via a relay.

Installation
Caution
All work for transport, installation and commissioning
as well as maintenance is conducted by qualified
technicians (note IEC 364 and VENELEC HD 384 or
DIN VDE 0100 and IEC Report 664 or DIN VDE 0110
and national occupational health and safety regula
tions or VGB 4).
Qualified technicians as defined by the basic safety instructions are persons who are familiar with the setup, installation,
commissioning and operation of the product and are appropriately qualified for their activities (defined in IEC 364 or DIN
VDE 0105).
Commissioning
Before commissioning the control unit the rotary heat
exchanger must be operating correctly.
The direction of rotation of the wheel can be changed by
reversing 2 phases of the motor.
A green LED lights when the unit is operating without
faults.
Causes of faults are displayed on the control unit.

System design
The control unit is not designed for outside installation.
The control unit is normally installed in the side wall of the
casing.
The normal installation position is vertical. Sufficient ventilation for heat dissipation is essential.

Fig. 16: Control unit R

12

Options

R/370 (Type: F-D 370-WT VECTOR IP54)

R/750 (Type: F-D 750-WT VECTOR IP54)
10k

+10 V reference voltage

Analogue setpoint input
GND (analogue)
Analogue output
+15 V (max. 100 mA)
Start clockwise
External sensor
Priority speed
Parameter set switching
Release
GND (digital)
Relay output 1 (normally open contact)
Relay output 1 (as per contact)
Relay output 1 (normally closed contact)
PTC motor temperature monitoring
PTC motor temperature monitoring

1
2
3
4
5
6

B1

7
8
9
10
11
12
13
14
15
16

Relay output 2 (normally open contact)

Relay output 2 (as per contact)
Relay output 2 (normally closed contact)

17
18
19

Terminals 1, 2, 3

Connection of control signal

Terminals 5, 7, 11

Connection of inductive sensor for speed monitoring

Terminal 6

Start of wheel (terminal 10 must be under power)

Terminal 9 not under power

Sorption wheel operating mode

Terminal 9 under power

Condensation/enthalpy wheel operating mode

Terminal 10

Reset-function by short-term voltage cut-off,

acknowledgements of faults

Terminals 15, 16

Connection of thermal contact from motor

Terminals 17, 18, 19

Potential-free output for output of faults via relay

Table 3: Circuit diagram of control inputs for control units

Output motor-side

Mains input

General data

Dimensions

R/370

R/750

0.37

0.75

Max. motor power

kW

Nominal output current

2.2

4.0

Max. output voltage

3 x 230

3 x 230

Output frequency

Hz

0..500

0..500

Rated voltage

230

230

Mains frequency

Hz

50/60

50/60

Fuses

A(t)

Protection rating

IP 54

IP 54

Ambient temperature

0..40

0..40

Air humidity

20..90

20..90

Power dissipation

35

45

HxWxD

mm

282 x 112 x 70

282 x 112 x 70

Table 4: Technical data for the control units

13

Options

4.3 Operating unit

4.6 Purge sector

The control unit settings can be customised with the operating unit. Parameters can be configured quickly and easily
with the LCD graphical display, the menu structure in
German or English and the parameters displayed in plain
text.

When correctly laid out, the purge sector reduces the

transmission of extract air to the supply air. The size can be
configured individually to reduce the purge and energy loss
to a minimum.
Instructions for the optimum settings can be found in
Section '7.8 Using and setting the purge sector'.
Factory setting: 3

Fresh air

Exhaust air

Fig. 17: Operating unit

Fig. 18: Purge sector

4.4 Rotational speed monitoring

4.7 Duct design

The speed of rotation of the wheel can be monitored with an

inductive sensor. Stoppages, e.g. caused by a broken v-belt,
can be detected quickly and the cause can be corrected.

The side walls of the casings in Hoval rotary heat exchangers

with ducts are enclosed. This makes them suitable for the
duct connection.

4.5 Inspection cover

4.8 Coated casing

The motor and the v-belt can be inspected through inspection covers on both sides. This is recommended if inspection
from the side is not possible.

Hoval rotary heat exchangers with coated casings are available for applications with very high hygiene requirements
(e.g. hospitals): powder-coated red (RAL 3000).

14

Notice
Inspection covers cannot always be installed in small
casing dimensions. If applicable, this is shown in the
Hoval CARS design program. Detailed information
can be obtained from Hoval's application consulting
service.

4.9 Offset wheel position

The hub can be offset for optimum adjustment to the installation situation (such as installation in a ventilation unit).


Dimensions of the exchangers

5 Dimensions of the exchangers

The minimum size of the casing depends on the wheel diameter. The external dimensions can be individually adjusted.

70

70

70

30

70

60
A

430

290
Casing dimensions

min.

max.

Casing dimensions

min.

max.

Dimension A

+ 80

1350

Dimension A

+ 200

4200

Dimension B

+ 80

1350

Dimension B

+ 200

4200

Table 5: Dimensional drawing for small sheet-metal casing (dimensions in mm)

Table 7: Dimensional drawing for profile casing (dimensions in mm)

45

40

100

45

40

80
A

320

320

Casing dimensions

min.

max.

Casing dimensions

min.

max.

Dimension A

+ 80

2850

Dimension A

+ 80

2850

Dimension B

+ 80

2700

Dimension B

+ 80

2700

Table 6: Dimensional drawing for large sheet-metal casing, wheel diameter up to 1800mm
(dimensions in mm)

Table 8: Dimensional drawing for large sheet-metal casing, wheel diameter from 1800mm
(dimensions in mm)

15

Unit type reference

6 Unit type reference

Example of unit type reference Part 1

AV- A1- 1500/1.6- A1580xB1580

Air flow
Case A, B, C or D
Installation position
V = vertical to 20% inclination
H = horizontal
Rotor model
A = condensation wheel of aluminium
E = enthalpy wheel with enthalpy coating
S = sorption wheel with sorption coating
Wheel construction and casing design
1 = wheel 1-piece, sheet-metal casing, supplied assembled
4 = wheel 4-piece, profile casing, supplied unassembled
8 = wheel 8-piece, profile casing, supplied unassembled
Wheel diameter (in mm)
Any required size in steps of 10 mm
Airway height (in mm)
1.4 mm
1.6 mm
1.9 mm
2.9 mm
Casing size (in mm)
Dimension A x dimension B
Any required size in steps of 1 mm

16

Unit type reference

Example of unit type reference Part 2 (options)

A1,RN,B,D,SR,I1,K,AX0830BX080 0
Drive
A = drive controllable
Y = drive for constant speed of rotation (direct drive from mains power)
13 specifies the position
Control unit
RN = control unit, supplied uninstalled
Operating unit
B = operating unit in German
O = operating unit in English
Rotational speed monitoring
D = rotational speed monitoring
Purge sector
SR = purge sector, mounted in position for clockwise direction of rotation
SL = purge sector, mounted in position for anticlockwise direction of rotation
SN = purge sector, supplied uninstalled
Inspection cover
I = inspection cover on 2 opposite sides
13 specifies the position
Casing model
K = duct design
C = coated casing
Offset (in mm)
AX = distance of casing edge to wheel axle in dimension A
BX = distance of casing edge to wheel axle in dimension B

17

System design

7 System design

7.2 Design data

7.1 Hoval CARS design program

The Hoval CARS design program is available for fast
and accurate design of Hoval rotary heat exchangers
(=Computer Aided Rotary Heat Exchanger Selection). It
runs under Microsoft Windows and offers the following
applications:
Secure planning with Eurovent and TV-certified data
Accurate calculation of a specific Hoval rotary heat
exchanger
Calculation of all applicable rotary heat exchangers for a
specific project
Calculation of the efficiency class in accordance with
EN13053
Calculation of leakage number in accordance with
VDI3803 (Draft)
Prices for the selected rotary heat exchangers

Notice
You can download the Hoval CARS design program
free of charge from our home page (hrs.hoval.com).

The program is also available as a Windows DLL file and can

therefore be integrated into other spreadsheet programs (on
request).

Fig. 19: Design for

installation of rotary heat
exchangers is made quick
and easy with the Hoval
CARS PC program.
18

As with all design, achieving the setpoint values depends

on the correct starting data. This often causes problems,
particularly in ventilation applications. The reason is the
dependence of the temperature of the specific density and
the specific heat. Water vapour in the air is also very important for the design. This is why the data available on entry to
the exchanger are essential for accurate calculation of a heat
exchanger.
Warm air Air flow rate on entry to exchanger

Cold air

V11

m/h

Rel. humidity at entry to exchanger

RH11 %

Temperature at entry to exchanger

t11

Max. pressure drop

p1

Pa

Air flow rate on entry to exchanger

V21

m/h

Rel. humidity at entry to exchanger

RH21 %

Temperature at entry to exchanger

t21

Max. pressure drop

p2

Pa

Table 9: Design data

The following errors must be avoided with data recording:

Volume flow is not equal to mass flow. The mass flows
of supply air and extract air must be known for correct
design.
The moisture in the extract air is generally estimated too
high, particularly for winter operation. (Where does the
moisture come from?)
Are the temperatures (fresh air, extract air) accurate
during practical operation (or are they the temperatures
that would be liked)?

System design

7.3 Checked data

Particularly for rotary heat exchangers with the relatively
complex processes during heat and substance transmission
it is important to confirm the theoretically calculated values
with measurements. Hoval rotary heat exchangers are therefore always tested by independent test organisations (e.g. at
the building technology testing laboratory of the University
of Lucerne). All technical data are based on these measurements. This means that they are reliable data for planners,
installers and operators.

VDI 3803 Page 5 also specifies that the leakage must be

expressed depending on the average differential pressure
over the wheel. This depends primarily on the layout of the
fans and strongly influences the leakage of the wheel. It is
calculated as follows:
pm=

p11 p22 + p12 p21

2

The Hoval CARS design program automatically calculates

the leakage number in accordance with VDI 3803 based
on the specific design data and the average differential
pressure. With the data ventilation units with rotary heat
exchangers can be minimally dimensioned and money can
be saved in manufacture and energy used in operation.

7.5 Local conditions, installation position

Where should the heat recovery unit be installed?
Which is the optimum air path?
What dimensions are approved?


Fig. 20: Hoval Aktiengesellschaft is a
participant in the Eurovent certification
programme for rotary heat exchangers;
the certified data of the certified types
are listed in the Eurovent directory.

Fig. 21: The design software for

Hoval rotary heat exchangers is tested
and certified in accordance with RLT
Directive 01 of the Raumlufttechnische
Gerte e.v. [ventilation equipment] manufacturer's association.

7.4 Requirements and directives

The applicable directives and requirements must be checked
before design. For example, many heat recovery systems
are not acceptable or only approved with appropriate confirmation for many applications (e.g. hospital).

Notice
Hoval rotary heat exchangers are tested and certified for operation in hospitals in accordance with
DIN 1946-4. Install rotary heat exchangers with the
'coated casing' option for such applications.

Design in accordance with VDI Directive 3803 Page 5 (Draft)

VDI Directive 3803 Page 5 defines requirements for heat
recovery systems. The April 2011 draft discusses the topic
of leakage with wheels for the first time. It specifies a basic
leakage rate of 10% for wheels. This means that the design
must dimension the two air streams of a ventilation unit 10%
larger, unless there is wheel-specific data on the leakage. In
these cases the actual leakage can be used in the calculations.

Notice
Please note that the wheel must be accessible for
maintenance and cleaning. Hoval therefore recommends to provide 600 mm free space in front of and
behind the wheel (= width of an inspection door).

7.6 Wheel type

The wheel type must be selected depending on the application. The following are recommended:
The condensation or enthalpy wheel is suitable for ventilation systems without mechanical cooling and without
moisture control.
Sorption wheels are recommended for ventilation systems
with mechanical cooling. The high moisture recovery efficiency, even under summer conditions, dries the fresh air.
This requires less cooling capacity and reduces energy
costs for cooling up to 50%.

7.7 Output regulation

Check what internal heat loads are in the ventilated room.
If the extract air temperature is expected to be significantly
higher than the set value, output regulation (speed control)
should be planned.

19

System design

7.8 Using and setting the purge sector

The purge sector reduces transmission of extract air to
supply air. It virtually bypasses the fresh air through the
wheel to the exhaust air. To avoid deterioration of the heat
recovery efficiency the purge sector must not be too large.
The size of the purge sector in Hoval rotary heat exchangers
can be individually adjusted to reduce the energy loss to a
minimum. The optimum size of the purge sector depends on:
the wheel type,
the existing purge pressure,
the airway height of the storage mass.

Optimum setting of the purge sector []

The required purge pressurepp depends on the layout of

the fans:
pp = psupply air pexhaust air

pp = pfresh air pextract air

Both fans suction side:

A minimum purge pressure of 100 Pa is required.
Supply air

Fresh air

Extract air

Exhaust air

Fresh air

Supply air

Exhaust air

Extract air

Exhaust air suction side, fresh air pressure side

Keep the purge pressure as low as possible to minimise the
air flow rate through the purge sector and thus the energy
loss. A purge pressure > 800 Pa must be avoided.

4
3

Supply air

Fresh air

Extract air

Exhaust air

Fresh air

Supply air

Exhaust air

Extract air

2
1
0
0

100

200

300

400

500

600

700

800

Existing purge pressure [Pa]

Condensation/enthalpy wheel airway height 1.9 mm

Condensation/enthalpy wheel airway height 1.6 mm

Both fans pressure side:

A minimum purge pressure of 100 Pa is required.
Supply air

Fresh air

Extract air

Exhaust air

Fresh air

Supply air

Exhaust air

Extract air

Condensation/enthalpy wheel airway height 1.4 mm

Sorption wheel airway height 1.9 mm
Sorption wheel airway height 1.6 mm
Sorption wheel airway height 1.4 mm
Diagram 1: Purge sector configuration diagram

20

Extract air pressure side, supply air suction side:

The purge sector cannot be used with this layout.
Supply air

Fresh air

Extract air

Exhaust air

Fresh air

Supply air

Exhaust air

Extract air

System design

7.9 Bypass

7.11 Leakage

A bypass parallel to the wheel may be useful with different

volume flows with recirculation and mixed air operation. It
should be dimensioned so the pressure drop with the bypass
is equal to that of the wheel.

Generally a mixing of the air streams must be expected

with wheels. Without special precautions VDI 6022 must be
observed: 'Regenerators with wheels are to be used only if
for hygienic reasons recirculation could also be used.'
Causes for mixing of the air streams include:
Carryover
A specific volume of air (depending on the speed of
rotation, air velocity and wheel geometry) is rotated in the
other direction by an air stream.
Leakage
Leakage through the radial and transverse seals
according to the pressure gradients and the seal quality.
Extract air transmission
Because the storage mass is alternately in both air
streams, they each influence the other. For example,
odours can be transmitted with the smallest particles (e.g.
cigarette smoke).
Substance transmission
Wheels also transmit gaseous substances. The amount
transmitted depends on the wheel type and the substance
itself. Unfortunately, few measurements are available in
this field, and on the other hand it is known in practice that
this is not a problem for standard VAC systems.
In rare cases odourants from the extract air may be
'collected' in the wheel and under extreme fresh air conditions (very high relative humidity) may be emitted again. This
can cause odour problems. In general, this problem can be
prevented by special adjustments of the cleaning mode or
with a minimum speed of rotation.

Fresh air
Exhaust air
Bypass fresh air
Bypass exhaust air
Recirculation
Fig. 22: Bypass layout

7.10 Frost limit

If there is a danger of frost in the wheel during condensation,
appropriate precautions must be taken (preheater, bypass
etc.). There is a frost hazard if the average inlet temperature
of the two air streams is less than 5C.

Notice
Condensation is generally prevented with gaseous
moisture transmission by sorption; the frost hazard is
therefore greatly reduced with sorption wheels.

Consider also that air ducts may have condensation and may
even ice up at low supply air temperatures.

Notice
The high quality of the seals in Hoval rotary
exchangers minimises leakage. They are even
certified for operation in hospitals.

7.12 Supply air humidification

The humidification downstream from the wheel must be
dimensioned to ensure that the desired setpoint value is
reached even with minimum fresh air moisture. Because
the wheel speed is generally controlled by the supply air
temperature, the corresponding moisture content must be
considered when dimensioning the humidifier.

21

System design

7.13 Corrosion

7.17 Technical data

Hoval rotary heat exchangers have proven to be very

durable in VAC systems. The Hoval application consulting
service can provide information on what equipment to use for
applications where corrosion is potential danger, such as in
kitchens or specific industrial applications etc.

The selected rotary heat exchanger and its performance are

generally defined with the following data.

7.14 Application limits

Before selecting the rotary heat exchanger check that application limits are not exceeded during operation:

Temperature

-4070C

Pressure difference

max. 2000 Pa

Over-/underpressure

max. 2000 Pa

Pressure drop

Recommended 80 Pa to 130 Pa

Table 10: Application limits

7.15 Danger of contamination

In 'normal' ventilation systems the air streams are generally
cleaned with coarse filters. This ensures that there is no
danger of dirt build-up on the rotary heat exchanger. If this is
a potential problem with specialised applications, this must
be considered in the design:
Install the exchanger so it can be cleaned in its installed
position, or
provide inspection openings before and after the rotary
heat exchanger,
if possible, clean the air stream by filtering to prevent dirt
build-up or the cleaning intervals are extended.
In practice it has been demonstrated that the danger of dirt
build-up is much less than expected. Clear statements can
only be made on the basis of experience. The Hoval application consulting service can also provide information.

7.16 Condensation in warm air stream

If more water condenses from the warm air than the (heated)
cold air can absorb, condensate is formed. Because this
phenomenon primarily occurs in the first third of the warm
wheel side primarily because of the thermodynamic function,
some of it is removed by the warm air stream. This must be
considered for downstream components. In general, condensate drip trays should be installed on the warm air and cold
air side. The following must also be checked or implemented:
How is the condensate drained off?
Is there an icing hazard?

22

Type
Weight

kg

Height x width x length

mm

Rotor diameter

mm

Airway height

mm

Warm air:
Air flow rate on entry to exchanger

V11

m/h

Temperature at entry to exchanger

t11

Rel. humidity at entry to exchanger

RH11

Rel. humidity exchanger outlet

RH12

Temperature at exchanger outlet

t12

Pressure drop (with poss. condensation) p1

Pa

Cold air:
Air flow rate on entry to exchanger

V21

m/h

Temperature at entry to exchanger

t21

Rel. humidity at entry to exchanger

RH21

Rel. humidity exchanger outlet

RH22

Temperature at exchanger outlet

t22

Pressure drop

p2

Pa

Mass flow ratio

m2/m1

Notice
To define a wheel uniquely, its performance under
summer conditions should be specified in addition to
the winter design.

Transport and installation

8 Transport and installation

The following checks must be performed before installation:
Has the rotary heat exchanger been damaged during
transport (visual inspection of casing and wheel)?
Has the correct model been supplied (type, series, size,
options)?
How must the exchanger be mounted (purge sector)?
(Note labels!)

8.1 Transport
The wheel should always be vertical during transport.
The rotary heat exchanger should be attached to the
crossbars of the casing. The pulling direction should be
vertical to prevent damage.
The following general items are applicable: Do not lift the
exchanger at a single point but always suspend it by a
crane beam (Fig. 23).

Fig. 23: Recommended attachment

8.2 Mechanical installation

The casing for duct connection can be bolted or riveted at
the face area up to 4 cm from the outer frame (Fig. 24).

Caution
The wheel casing cannot take any additional load
(e.g. ducts).

When installing the wheel in a ventilation unit, the casing

should be reasonably adapted to the unit size (Fig. 25).
If necessary, baffle plates can be installed to adapt the
casing to the unit cross-section.

Caution
Ensure that the wheel is not drilled or blocked and
the sealings are not damaged during installation.

Fig. 24: Drill area

Hoval rotary heat exchangers are designed for vertical

installation (max. tilt 20).
Notice
Rotary heat exchangers for horizontal installation
are available on request. In this case the casing

must be supported at the bearings.
After installation check that the wheel runs smoothly.

8.3 Installation of sensors

If, for example, temperature sensors are installed, the function of the unit must not be affected.
Fig. 25: Casing dimensions adjusted for unit
23

Commissioning and maintenance

8.4 Electrical installation

Constant drive
The drive motor is electrically connected at the factory (in
Y-circuit). The motor must be correctly fused. The direction of
rotation can be reversed by exchanging the phases.

9 Commissioning and maintenance

9.1 Commissioning

The installation manual for segmented wheels can be

downloaded from the internet. To ensure correct function the
installation supervision by a Hoval technician or an authorised supplied is recommended.

Check the correct direction of rotation of the wheel; it is

marked by arrows on the casing.
Check the function of the control unit.
Ensure that the air streams of the rotary heat exchanger
can flow through without obstacles.
Check that the installation is correct and whether application limits (temperatures, differential pressure, material
etc.) could be exceeded.
Check the tension of the drive belt and the fastening of
the motor.
Inspect the sealings on the wheel. When making adjustments, ensure that the wheel rotates smoothly and is not
blocked. The drive torques listed in Table 1 must not be
exceeded.

8.6 Storage

9.2 Maintenance

Rotary heat exchangers with motors must be stored in a

dry, dust-free area which is free of vibrations.
Long periods of standstill can impair the function of gear
motors because after some time the bearings lose their
lubrication and the seals may become leaky. Too long
storage periods must therefore be avoided.
If a rotary heat exchanger is not installed and commissioned within 9 months from the date of delivery it must
be put into operation for minimum 5 minutes in order to
ensure the reliable operation of the motor.

Maintenance is restricted to regular visual inspections.

Inspections should be initially carried out about every
3 months and then after trouble-free operation can be
extended to 12months. The following must be checked:
Tension of drive belt
Sealing of gear motor
Quality of bearings (assess by bearing noise)
Function of slide seal
Function of transverse seal
Condition of casing
Condition of wheel
Long experience shows that clogging of heat exchangers is
not expected in normal cooling and air-conditioning systems.
However, if deposits accumulate on the exchanger when
used for special applications, it can be cleaned as follows:
Remove dust and fibres with a soft brush or vacuum
cleaner. Use caution when blowing dirt out with
compressed air to avoid damage to the wheel. Keep clear!
Oils, solvents etc. can be removed with hot water (max.
70 C) or grease-removing solvents or immersion.
Cleaning with pressure cleaners is possible if the following
is observed:
a flat 40 nozzle is used (type WEG40/04)
max. water pressure 100 bar

Variable-speed drive
The control unit is supplied with the unit. The motor must
be wired to the control unit and the control unit must be
connected during installation.

8.5 A
 ssembly of segmented rotary heat exchangers

24

Attention
Do not damage the exchanger mechanically or chemically during cleaning:
Select compatible cleansing agents.
Clean carefully. The thickness of the material is
less than 0.1 mm!

Specification text

10 Specification texts
10.1 Condensation wheel
Rotary heat exchanger for heat transmission consisting of
wheel and casing; suitable for optimum dimensioning in
accordance with VDI Directive3803 Page 5.
Wheel
The storage mass consists of corrugated and smooth
corrosion-resistant aluminium foil. The result is small, axially
arranged, smooth ducts for laminar flow of air. The outside of
the storage mass is supported by the wheel mantle; the hub
is inside with the permanently lubricated, maintenance-free
roller bearings and the axle. The wheel is permanently stabilised by internal spokes between the wheel mantle and hub.
The storage mass consists of uncoated aluminium.
Casing
Sheet-metal casing (for one-piece wheels)
Self-supporting construction of aluzinc sheet steel, suitable for installation in ventilation units. The automatically
adjusted, abrasion-resistant slide seal with constant-force
springs reduces internal leakage to a minimum. A lip seal
is used as the transverse seal. The motor for the wheel
drive can be installed in the casing.
Profile casing (for multi-component wheels)
Construction of aluminium extruded sections with aluzinc
sheet steel panels, suitable for installation in ventilation
units. The high-quality ring seal on both sides in the
double-acting support springs reduces internal leakage to
a minimum. A lip seal is used as the transverse seal. The
motor for the wheel drive can be installed in the casing.

Options
Drive: 3-phase gear motor with belt pulley and v-belt.
Control unit: for infinite control of speed of rotation; insulation class IP 54. The software includes the speed monitoring and intermittent operation for cleaning.
Operating unit: for modification of the control program and
manual operation (plugged into the control unit).
Speed monitoring: by sensor and an inductive sensor on
the rim of the wheel.
Purge sector: prevents rotation of the extract to the supply
air in the event of pressure gradients between supply air
entry and exhaust air, adjustable to minimise purge and
energy loss.
Inspection cover (on both sides): allows visual inspection
of motor and belt.
Duct design: casing with enclosed side walls for duct
connection.
Coated casing: for applications with very high hygiene
requirements (powder-coated red RAL 3000).
Offset wheel position: for optimum adjustment to the
installation situation.

25

Specification text

10.2 Enthalpy wheel

Rotary heat exchanger for heat and moisture transmission
consisting of wheel and casing; suitable for optimum dimensioning in accordance with VDI Directive3803 Page 5.
Wheel
The storage mass consists of corrugated and smooth
corrosion-resistant aluminium foil with enthalpy coating for
moisture transmission. The result is small, axially arranged,
smooth ducts for laminar flow of air. The outside of the
storage mass is supported by the wheel mantle; the hub is
inside with the permanently lubricated, maintenance-free
roller bearings and the axle. The wheel is permanently stabilised by internal spokes between the wheel mantle and hub.
The storage mass consists of corrosion-resistant aluminium
foil with enthalpy coating.
Casing
Sheet-metal casing (for one-piece wheels)
Self-supporting construction of aluzinc sheet steel, suitable for installation in ventilation units. The automatically
adjusted, abrasion-resistant slide seal with constant-force
springs reduces internal leakage to a minimum. A lip seal
is used as the transverse seal. The motor for the wheel
drive can be installed in the casing.
Profile casing (for multi-component wheels)
Construction of aluminium extruded sections with aluzinc
sheet steel panels, suitable for installation in ventilation
units. The high-quality ring seal on both sides in the
double-acting support springs reduces internal leakage to
a minimum. A lip seal is used as the transverse seal. The
motor for the wheel drive can be installed in the casing.

26

Options
Drive: 3-phase gear motor with belt pulley and v-belt.
Control unit: for infinite control of speed of rotation; insulation class IP 54. The software includes the speed monitoring and intermittent operation for cleaning.
Operating unit: for modification of the control program and
manual operation (plugged into the control unit).
Speed monitoring: by sensor and an inductive sensor on
the rim of the wheel.
Purge sector: prevents rotation of the extract to the supply
air in the event of pressure gradients between supply air
entry and exhaust air, adjustable to minimise purge and
energy loss.
Inspection cover (on both sides): allows visual inspection
of motor and belt.
Duct design: casing with enclosed side walls for duct
connection. Duct design: casing with enclosed side
walls for duct connection.
Coated casing: for applications with very high hygiene
requirements (powder-coated red RAL 3000).
Offset wheel position: for optimum adjustment to the
installation situation.

Specification text

10.3 Sorption wheel

Rotary heat exchanger for heat and moisture transmission
consisting of wheel and casing; suitable for optimum dimensioning in accordance with VDI Directive3803 Page 5.
Wheel
The storage mass consists of corrugated and smooth
corrosion-resistant aluminium foil with silica gel coating for
moisture transmission. The result is small, axially arranged,
smooth ducts for laminar flow of air. The outside of the
storage mass is supported by the wheel mantle; the hub is
inside with the permanently lubricated, maintenance-free
roller bearings and the axle. The wheel is permanently stabilised by internal spokes between the wheel mantle and hub.
The storage mass consists of corrosion-resistant aluminium
foil, which is coated with a highly effective sorption coating
for moisture transmission.
Casing
Sheet-metal casing (for one-piece wheels)
Self-supporting construction of aluzinc sheet steel, suitable for installation in ventilation units. The automatically
adjusted, abrasion-resistant slide seal with constant-force
springs reduces internal leakage to a minimum. A lip seal
is used as the transverse seal. The motor for the wheel
drive can be installed in the casing.
Profile casing (for multi-component wheels)
Construction of aluminium extruded sections with aluzinc
sheet steel panels, suitable for installation in ventilation
units. The high-quality ring seal on both sides in the
double-acting support springs reduces internal leakage to
a minimum. A lip seal is used as the transverse seal. The
motor for the wheel drive can be installed in the casing.

Options
Drive: 3-phase gear motor with belt pulley and v-belt.
Control unit: for infinite control of speed of rotation; insulation class IP 54. The software includes the speed monitoring and intermittent operation for cleaning.
Operating unit: for modification of the control program and
manual operation (plugged into the control unit).
Speed monitoring: by sensor and an inductive sensor on
the rim of the wheel.
Purge sector: prevents rotation of the extract to the supply
air in the event of pressure gradients between supply air
entry and exhaust air, adjustable to minimise purge and
energy loss.
Inspection cover (on both sides): allows visual inspection
of motor and belt.
Duct design: casing with enclosed side walls for duct
connection. Duct design: casing with enclosed side
walls for duct connection.
Coated casing: for applications with very high hygiene
requirements (powder-coated red RAL 3000).
Offset wheel position: for optimum adjustment to the
installation situation.

27

Notes

28

Hoval Rotary Heat Exchangers

Subject to technical changes.
Part. No. 4211005 Edition 07/2014
Hoval Aktiengesellschaft, Liechtenstein, 2011

Responsibility for energy and environment

The Hoval brand is internationally known as one of the leading suppliers of indoor
climate control solutions. More than 65 years of experience have given us the necessary capabilities and motivation to continuously develop exceptional solutions and
technically advanced equipment. Maximising energy efficiency and thus protecting
the environment are both our commitment and our incentive. Hoval has established
itself as an expert provider of intelligent heating and ventilation systems that are
exported to over 50 countries worldwide.

Hoval heating technology

As a full range supplier Hoval helps its customers to select
innovative system solutions for a wide range of energy sources,
such as heat pumps, biomass, solar energy, gas, oil and district
heating. Services range from small commercial to large-scale
industrial projects.

International
Hoval Aktiengesellschaft
Austrasse 70
9490 Vaduz, Liechtenstein
Tel. +423 399 24 00
Fax +423 399 27 31
info.klimatechnik@hoval.com
www.hoval.com
United Kingdom
Hoval Ltd.
Northgate, Newark
Nottinghamshire
NG24 1JN
Tel. 01636 672711
Fax 01636 673532
heatrecovery@hoval.co.uk
www.hoval.co.uk

Hoval comfort ventilation

Increased comfort and more efficient use of energy from
private housing to business premises: our comfort ventilation
products provide fresh, clean air for living and working space.
Our innovative system for a healthy room climate uses heat and
moisture recovery, while at the same time protecting energy
resources and providing a healthier environment.

Hoval indoor climate systems

Indoor climate systems ensure top air quality and economical
usability. Hoval has been installing decentralised systems
for many years. The key is to use combinations of multiple
air-conditioning units, even those of different types, that can
be controlled separately or together as a single system. This
enables Hoval to respond flexibly to a wide range of requirements for heating, cooling and ventilation.

Hoval heat recovery

Efficient use of energy due to heat recovery. Hoval offers two

different solutions: plate heat exchangers as a recuperative
system and rotary heat exchangers as a regenerative system.