RECOMMENDED START-UP PROCEDURE

FOR KRAMER
THERMOBANK HOT GAS DEFROST SYSTEMS

• Review system refrigerant piping layout. All piping must be

adequately clamped and supported, (particularly at valve stations), to
prevent possible movement during system operation which can
result in line breakage and refrigerant loss. All suction risers over
(2) feet must have a P-trap at the bottom of the riser. All suction
lines must be pitched a minimum of ¼” per foot in the direction of
flow to ensure proper oil to the compressor(s). All field piped
suction line(s) must be insulated wherever practical to minimize
excessive return gas temperatures on suction cooled compressors
and prevent condensate dripping and potential safety and / or
product damage. Confirm ALL lines are properly sized for the
intended operating design conditions in accordance with the
Operation & Installation manual supplied with the equipment. Note:
To minimize pressure drop through the liquid line during the defrost
cycle the common liquid line on Thermobank systems is typically at
least (1) size larger than required for normal liquid line duty on a
conventional refrigeration system.

• With ALL electrical power disconnected and locked out to the

system, check ALL factory and field electrical connections for
tightness, including at compressor motor terminals.

• Visually verify the correct settings of all operating and safety

controls as per the supplemental data provided. Adjust as
necessary and confirm actual cut-in & cut-out settings of all pressure
controls after system has been placed in operation.

• Remove pipe fill plug and add 100% tap water to Thermobank(s) to
the point of overflowing. Remove immersion heater cover and adjust
thermostat setting to maintain approx. +120 degrees.

• Remove fan guards and check all fan / motor assemblies. Check
motor mounting bolts / brackets & fan blade set screws for proper
tightness. Confirm proper location / height of fan blade with respect
to venturi. Manually rotate fan blades to confirm proper blade
clearance and motor rotation. (Perform this check on ALL
evaporator and condenser fan assemblies).

• Turn off, (down position), both manual pumpdown and compressor

kill switch.
• TEMPORARILY place a jumper wire around the post defrost pressure
control to force evaporator fans to run and also to prevent excessive
cycling of suction and liquid line solenoid valves due to abnormally
high suction pressure during initial room temperature pulldown.

• TEMPORARILY remove all defrost tripper pins from the outer defrost
timer dial to prevent the system from initiating a defrost cycle while
the post defrost pressure control is jumped out. Note: Do not under
any circumstances allow the system to initiate a defrost cycle while
the post defrost control is jumped out or the compressor may suffer
irreparable liquid damage.

• TEMPORARILY lower the control settings or otherwise jump out all

condenser fan cycling controls to force all fans on during the initial
refrigerant charging process. Remember to remove all jumpers and
re-adjust these controls after the initial charging process is
completed.

• Calculate the approx. year-round operating refrigerant charge for

each system. Manually open the liquid line solenoid valve via the
manual lift stem on the bottom of the valve body. Attached the high
side hose of a service gauge manifold to the ¼” service gauge fitting
on the receiver outlet, (king), valve and attached the charging hose
to a cylinder of the appropriate system refrigerant. Purge the service
gauge hoses and set the refrigerant cylinder for liquid charging.
Open the receiver valve stem to the mid-seat position and introduce
liquid refrigerant directly into the receiver and liquid line until the
pressure equalizes. Once the pressure has equalized and refrigerant
flow has stopped, front seat, (close), the receiver outlet valve so that
the refrigerant tank is open directly into the liquid line downstream of
this valve. Note: Once this initial liquid refrigerant charge has been
added to the system, be sure to close the liquid line solenoid valve
manual lift stem.

• Attach a service gauge manifold to the suction and discharge service

valves of each compressor in the unit. The discharge valve(s)
should be front seated approx. (1/2) turn to allow gauge pressure
reading. Completely close, (front seat), the suction service valve on
each compressor and then open the valve approx. (2) full turns.
Manually attend to this valve throughout the initial start-up period to
help prevent excessive, (high), suction pressure or any potential
liquid refrigerant return to the compressor(s).

• Momentarily apply main power to the system and verify correct

rotation of all condenser and evaporator fans. If the unit is equipped
 with the optional phase loss monitor, it may be necessary to switch
any (2) of the (3) main power leads feeding the phase loss monitor in
order to energize the unit control circuit. (Compressors are not
rotation sensitive). If any or all fan motors are running backwards,
disconnect main power and switch any (2) of the (3) power leads
feeding these motors. Verify correct power supply is available, (+/-
10% of unit nameplate rating), between all (3) phases at main power
terminal block.

• Re-establish main power and turn on, (up position), both manual
pumpdown and compressor kill switch(es). Allow compressor(s) to
start and cycle off on low pressure control.

• Continue to add liquid refrigerant directly into the receiver outlet /

liquid line to speed the charging process. Since the compressors
can essentially only be operated in short bursts during this time, it
may be necessary to manually adjust or otherwise close the contacts
of the low pressure control in order to maximize the compressor(s)
run time and introduce as much liquid refrigerant into the system as
possible. Note: If compressor oil levels should happen to drop
below the visible level in the oil sight glass during this time,
discontinue refrigerant charging by turning off the charging manifold
gauge attached to the receiver outlet, (king), valve, then opening,
(backseating), this valve to allow full refrigerant flow through the
liquid receiver, then open, (backseat), the suction service valve. If
sufficient liquid refrigerant has been added to the system to maintain
a reasonable, operating suction pressure at the compressor, then the
velocity of the refrigerant gas through the suction line should be
enough to return any excessive oil laying out in the system back to
the compressor(s).

• Add the remainder of the refrigerant charge as a vapor through the

suction filter gauge access fitting or directly into the suction service
valve at the compressor(s). During the initial room temperature pull
down, it is not unusual to observe flashing in the liquid line sight
glass due to high load conditions and / or high superheat at the
evaporator outlet. Note: If bubbles are observed in the liquid line
sight glass after the system is completely charged, DO NOT add any
additional refrigerant beyond the quantity originally calculated for
the system unless a refrigerant leak is confirmed.

• Continue to manually monitor all system operating conditions and

controls throughout the entire, initial room temperature pull down
period. Periodically check system oil levels, compressor and fan
motor amperage draws, refrigerant system pressures and
compressor suction superheat during this time. High superheat
 would be considered normal during this time but if excessive
floodback, (ie. low), superheat is observed it may be necessary to
begin adjustment, (closing), of the thermostatic expansion valve(s),
particularly as the room temperature is reduced.

• Normal “wetting” of all internal system piping components may

necessitate that additional oil be added to the sealed system. If this
becomes necessary, use only a POE lubricant approved by the
compressor manufacturer. On parallel compressor systems utilizing
an oil equalization system, (discharge oil separator, oil reservoir and
individual compressor oil floats), the operating oil level should be
maintained between the (2) sight glasses on the oil reservoir.

• Remove ALL jumper wires from operating controls, (fan cycling

controls and post defrost control), and return ALL controls to
recommended factory settings.

• After the system has operated for several hours and the room
temperature has been reduced to a minimum of +40 degrees, the
tripper pins should be reinserted into the outer dial of the defrost
time clock and the timer manually advanced to initiate a defrost
cycle. A MINIMUM of (2) service gauge manifolds should be installed
to adequately monitor the operating system pressures during the
defrost cycle. Install (1) set of service gauges at the compressor(s)
service valves and a second set on the gauge port fitting of the
suction line filter. NOTE: Due to the high pressure, (approx. 200
P.S.I.G.), produced in the suction line during the defrost cycle, we
recommend that you attach the high side gauge to the suction
connection at the suction line filter connection.

• Manually advance the timer into defrost and observe readings at

both service gauge manifolds. Be prepared to make quick
observations of both pressure gauge readings as the defrost cycle
may progress quite rapidly, particularly if little frost build up is
present on the evaporator coil(s) when the defrost cycle is initiated.
Initially, both operating suction and discharge pressures will drop at
the compressor, temporarily stabilize after a short period of time and
then begin to steadily increase as the defrost cycle progresses. The
suction pressure at the compressor should never exceed 15 - 20
P.S.I.G., based upon the setting of the holdback valve(s) located at
the suction inlet of the Thermobank(s). The high side gauge
pressure measured at the suction filter connection, (upstream of the
holdback valves), will continue to rise steadily until the evaporator
coil temperature exceeds +32 degrees, then level off for a short
period of time as the frost build-up is melted from the coil surface.
Once all frost is melted from the evaporator coil surface, the
 “suction” pressure will rise rapidly towards defrost termination
pressure, (approx. 200 P.S.I.G.). When the defrost termination
pressure control closes energizing the “X” terminal on the defrost
time clock, the clock will be automatically switched back into the
refrigeration cycle. For the next 2 - 3 minutes, (approx.), the post
defrost pressure control will remain open as the suction pressure
upstream of the holdback valve(s) is reduced to the cut-in setting of
this control, (approx. 25 P.S.I.G. on low temp. systems). This
provides for a “pump-out” cycle, continuing to run the high pressure
liquid still contained in the low side through the Thermobank(s),
where it is reduced to a low pressure vapor. This post switch also
prevents the liquid solenoid valve from opening and allowing any
additional liquid refrigerant into the evaporator and also provides an
evaporator fan delay.

• If the operating suction pressure during the defrost cycle exceeds 15

– 20 P.S.I.G. at the compressor suction service valve, then the
adjustment caps should be removed from the holdback valve(s) and
the valves adjusted during the next subsequent defrost cycle. Using
a 5/16” hex wrench, the valve(s) should be adjusted slowly, (approx.
(1) turn at a time, (counterclockwise), to decrease the pressure
setting. On systems employing (2) holdback valves, both valves
should be adjusted simultaneously in order to equalize refrigerant
flow through both Thermobanks. NOTE: In order to avoid potential
compressor damage, DO NOT RUN THE SYSTEM THROUGH
MULTIPLE, BACK TO BACK DEFROST CYCLES. Always allow the
system to “regenerate” the heat stored in the Thermobank(s) by
allowing the system to operate continuously for a minimum of (1)
hour in the normal refrigeration cycle before initiating a second
defrost cycle.