Remove Green Power function from UPS: allow UPS work with low load

Published: 25 Nov 2019 | Updated: 13 Dec 2019 | Author: Mentor

Does your UPS turn off after exactly 5 minutes? Quiet, it's not broken, it's the fault of the Green
Power function.

In the past years, in fact, several brands manifactured their UPS with a function called Green Power,
and due to Green Power function the UPS shutdown in 5 minutes when it is on battery and the total
load on the UPS is equal or less than 10% of the UPS capacity, therefore if there is a blackout and the
devices connected on the UPS consume less than 10% of the UPS capacity, it will shut off in 5
minutes.

This is a totally unwanted function, specially if the UPS is used to power low voltage devices as some
router or some little arm soc and unfortunately there isn't any simple way to turn off the Green
Power function.

The only way to disable the Green Power function is to disassembly the UPS and remove from the
mainboard the resistor marked as R15A. Someone reported that in its UPS the resistor R15A wasn't
present and he was been able to disable the Green Power function removing the resistor marked as
R43.

In my personal case, I have an old TRUST 1000VA UPS PW-4100T, in the past I have used it with a
desktop computer without any problem but when I started use it to protect a modem/router and 4
IPCAM the Green Power function has started shut off the UPS in 5 minutes. To remove the Green
Power function and to use the UPS also with a low load, then I have disassebled it and I have
unsoldered the resistor R15A, once disassebled the UPS I have also unsoldered the buzz speaker to
remove the annoying beep that was played when the UPS was on battery.

UPS ECO-MODE: THE BENEFITS AND RISKS

Susannah Banks 22nd June 2019 Power

MANY OF THE LATEST MODELS OF UPS SYSTEMS NOW HAVE AN ENERGY SAVING OPERATING
MODE, OFTEN CALLED “ECO MODE” OR “GREEN MODE”, WHEN OPERATING IN THIS WAY THE UPS
CAN ACHIEVE HIGH NINES EFFICIENCY AT ALMOST ANY LOAD.

As good as this may sound, hardly any data centres choose to use eco mode because of a fear that
this mode doesn’t offer the same level of protection as a true on-line uninterruptible power supply.

It is true that in order to achieve improved efficiency, eco-mode operates the UPS at a reduced level
of power protection, but Eco mode will save energy. The decision that IT, Facilities and Finance
departments face is whether the savings made by running in eco mode justify the risks.

So what is Eco mode?

Eco-mode is very similar to the basic mode of operation used in an offline UPS where it is called
“standby” or “line interactive” mode. In these traditionally smaller, single-phase UPSs, the
inverter/rectifier circuits are “offline” standing by, ready to switch on if the power fails or a problem
is detected.

Similarly with an On Line UPS operating in eco-mode the load is normally powered by the bypass
path, allowing raw mains power to supply the load, and the UPS inverter is engaged only when the
utility mains fails. In normal eco mode operation, therefore, the load is exposed to essentially raw
mains power.

Rather than true online mode, where the UPS continuously regenerates the output voltage through
the inverter, in eco-mode the UPS inverter operates in a “standby” mode. In principle, this is a
simple change in the control software of the UPS. However, the reality is considerably more
complex.

Traditional UPS Eco Mode – In standard or “classic” eco-mode, the UPS system inverter is essentially
off. If there is a utility power failure when the inverter is in standby, then both the UPS’s output
voltage and current waveforms will be negatively affected. It takes time for the UPS to detect the
failure, turn on the inverter, and supply clean power to the load from the batteries. This transfer
time is what, in large part, allows the input disruption to briefly reach the output of the
uninterruptible power supply.

Advanced Eco Mode – However, it has been possible to greatly reduce this and other negative
effects of standard eco-mode. Advances in firmware control schemes and electrical design has led to
the creation of what is known as “advanced eco-mode”. This form of eco- mode is available in
varying degrees from a few UPS vendors today.

In advanced eco-mode the primary power path during normal operation is the same as standard or
classical eco-mode: through the bypass path. But with advanced mode, the inverter remains “on”,
operating in parallel with the input without actually handling the load current. Since the inverter is
already “on”, it can more seamlessly take over the supply to the output where there is a mains
failure.

While advanced eco-mode offers advantages over standard eco-mode, it does come with a trade off.
Since the inverter circuit is “on” in the advanced mode, the overall efficiency of the UPS is less than it
would be if it operated in standard eco-mode. The difference is small, however, having been
observed to be in the 0.5% – 1.0% range typically. So while advanced eco-mode efficiency is less
than standard eco-mode, it is still better than traditional online mode.

Benefits of Eco Mode

The benefit of eco-mode is that the efficiency of the bypass path is typically between 98.0% and
99%, compared to the base UPS efficiency of 94% to 97%. This means there is a pickup in UPS
efficiency of between 2-5% when eco-mode is used.

Risks of Eco Mode

The power problem is detected

The UPS determines whether and how to respond

The UPS inverter is energized (Note: in advanced eco-mode, it is already energized)

The static bypass switch is actuated (opened)

In practice these events may take from 1 to 16 milliseconds, during which the critical load is
subjected to the power problem.

While the loss of 1-16 milliseconds of power may not affect the typical 2U server, the loss of power
for 8 milliseconds to a power transformer can cause that transformer to saturate when voltage is
restored, tripping breakers.

The loss of power for even a few milliseconds on a circuit feeding a PDU equipped with a static
switch will cause a state change on that switch. This can lead to an undesirable state change of the
overall power system, including overloads and dropped loads.

The loss of power for less than 16 milliseconds can cause protective devices on pumps and fans to
operate, creating an unexpected and undesirable state change of the sys- tem.

There are non-server IT devices, such as switches and other auxiliary devices that may not be as
robust as servers are in handling dips and sags in the range of 1-16 milliseconds.

The risk of eco-mode is that the IT load is exposed to raw utility mains power without the
conditioning normally provided by the double-conversion, online UPS system. The UPS must
continuously monitor the mains power and quickly switch to the UPS inverter when a problem is
detected, before the problem can affect the critical load. This may sound simple, but actually is quite
complicated and entails a number of risks and has some potentially undesirable side-effects.
However, depending on how eco-mode is implemented by the vendor, the degree to which the load
is exposed to raw mains can be significantly minimized.

How much is really saved?

The energy savings associated with the use of UPS running in traditional eco-mode (standard) 100%
of the time are approximately 2.3%. In financial terms this equates to approx. £10,000 per year for a
1 MW rated da-ta centre running at 50% load with an electric rate of £0.10/kWh.

The savings in advanced eco-mode are likely to be approximately 0.5% less when compared with
standard eco-mode, or around 1.8%. If the system operates only part of the time in eco-mode, then
the savings are proportionally reduced.
So to sum up, eco-mode represents a potential way to save energy in data centres, hospitals, and
other UPS applications and Data Centre operators can expect to see savings on the order of 2-3% in
total energy if eco-mode is enabled.

A UPS with eco-mode also qualifies for the Enhanced Capital Allowance Scheme.

The use of eco-mode entails risks. Eco-mode introduces a number of new modes of operation of the
data centre, and reduces power protection. Current power supplies and IT equipment are much
more resilient to power variations than similar equipment of prior generations, suggesting that this
equipment should operate reliably using eco-mode. However, complex systems comprised of a mix
of IT equipment, transformers, transfer switches, and other possible non-IT loads are less
predictable in their response to infrequent and unusual power events, and their compatibility with
eco-mode is less certain.

For this reason, eco-mode should be used in situations where power quality is excellent.

As data center, hospital, and industrial designs become more standardized, equipment continues to
improve, and real world experience using eco-mode accumulates, predictability and confidence in
eco-mode will improve.

If you would like to discuss how Source UPS can help, get in touch with a member of our team today.

CALL: 01252 692559 OR EMAIL: INFO@SOURCEUPS.CO.UK