Inverter Air Con: Beware Of High Standby Power

[DaveLee1688 1]

have you tried to use those clamp meters, eg like Kyoritsu http://www.kew-ltd.co.jp/en/products/clampmeters/index.html to tong one of the live or neutral (but not both together) wires to find out what is the actual current when on standby mode?

cos i believe the clamp meter is calibrated in RMS values, which is the actual heating effect, multiply the current by 230V and you shd get the correct power consumed by any device.

also, side track a bit, i read the starmex series of condenser units have this (switch) settings for HDB flats with and without current limitations. max operating current is 8.5A for MXY-3A28VA (system 3 with up to 14.6kW) for limited current applications and 12.65A for unlimited current applications...

now, we all know that the higher the current, the more energy the aircon consumes, so to save power, can installers simply configure the condenser to run at lower current and save power bills?

NEA used the clamp to measure. However, without actually measuring the voltage and current at the same time, the clamp only indicate RMS value of the current waveform sensed, which include both the real and reactive current (because phase information is missing). What we (NEA and I) did eventually is to use a digital watt meter, which measure real-power only because both voltage and current are measured for calculation. BTW, Singapore mains' voltage is 240V.

The current limiting is to meet HDB limits, thereby limiting cooling effect, which does not affect standby power.

The problem with Starmex is not only high standby power, but high reactive power at standby - this result in high circulating power. Though Starmex resulted in savings in active usage, for those installations which are not heavily used (infrequent turn on), the high standby power may end up using more energies than, say a non-inverter aircon.

Reading some responses here, I come to another conclusion: For those rooms which will have aircon turned on most time of day, inverter aircon may still make sense - the bills saved may well make the high standby power comparatively acceptable. For those rooms where the aircon is for occasional use, inverter aircon may not make sense - you will end up paying and wasting energy for nothing.

[neubie 2]

so did ME or NEA revert on the measured values of the starmex?

[booksntoys 0]

U mean, even if we switch off the air-con's main switch, there's still stand-by power; meter will still be running; electricity is still being consumed??

[first 0]

U mean, even if we switch off the air-con's main switch, there's still stand-by power; meter will still be running; electricity is still being consumed??

No.

As long as you turn off the mains, there will be no power to the aircon. Thus, no wastage.

We are saying that the aircon is having high standby power... this is a waste of energy especially for those who does not use their aircon often i.e. aircon is always on standby only switch off by remote control.

[dankoo 0]

Using a Mit too...I always switch it off in the morning...although my energy meter shows a difference of ~10W when the switch is off....

[DaveLee1688 1]

Using a Mit too...I always switch it off in the morning...although my energy meter shows a difference of ~10W when the switch is off....

Confirmations are in:

a) The air-condition contains a heater that consumes average 80W for 40 minutes, 20W for 20 minutes each hour when in Standby.

Our factory reported the following;

1) The reason why pre-heat is necessary

• Compressor pre-heat function is equipped to MXY series in order to prevent liquid refrigerant accumulation in compressor that causes damage to compressors.

• Pre-heat function improve the reliability of compressors and contribute to reduce the defect caused to compressor. (some may impact long term energy performance also).

2) Pre-heat pattern and power consumption

• Pre-heat is switched “ON” for 20 min and “OFF” for 40 min in an hour when ambient temp is over 21 degree.

• Average standby-power is 20w (when pre-heat is “OFF”) and 80w (when pre-heat is “ON”)

• Of course stand-by power is not applicable during operation.

b) The past two months of electrical bills reduces by about $50 by switching off the power to 2 units of condensers in the morning before leaving the house, and turning on only at night.

There is no confirmation whether this technology which require pre-heating the condenser is specific to Mitsubishi or across all Inverter-based aircon.

For me, this thread of investigations helped me identify the source of mysterious energy consumption in my house.

For people who are considering installing a new aircon, this is the moral of the story: the amount of standby power consumption need to be factored into the total cost of installing the aircon. If one were to do that, you will realize that over 5 years (the expected life of a condenser) aircon with this technology that requires pre-heating will be at least 20% more expensive than any other Inverter - you need to add in the standby energy consumed.

The other thing that I have learned in this investigation is: Singapore's green energy policies are still in stone-age. Manufacturers are conforming to standing policies that are not in tune with the global trends in energy policies. Our government has openly stated the support of green energy, but policies are in the infant stage. Unless citizens proactively encourage policy makers to step on the gas, we will end up being deceived by cleverly crafted advertisement. Unless you are prepared to switch on and off the mains power to the condenser everyday, you better make a wise choice and not take the image projected by advertisements at face value, and ended paying the bills.

Edited September 11, 2010 by mit3a28

[neubie 2]

Confirmations are in:

a) The air-condition contains a heater that consumes average 80W for 40 minutes, 20W for 20 minutes each hour when in Standby.

b) The past two months of electrical bills reduces by about $50 by switching off the power to 2 units of condensers in the morning before leaving the house, and turning on only at night.

There is no confirmation whether this technology which require pre-heating the condenser is specific to Mitsubishi or across all Inverter-based aircon.

For me, this thread of investigations helped me identify the source of mysterious energy consumption in my house.

For people who are considering installing a new aircon, this is the moral of the story: the amount of standby power consumption need to be factored into the total cost of installing the aircon. If one were to do that, you will realize that over 5 years (the expected life of a condenser) aircon with this technology that requires pre-heating will be at least 20% more expensive than any other Inverter - you need to add in the standby energy consumed.

cool... will try to tong my toshiba inverter A/C during standby soon....

[Dr.Anarchy 0]

Do this only happen for MXY series only? How about Daikin? I'm curious.

[wolflet 1]

i dunno about the inverter units. but back when i was in the navy. condensation in the coil is a main killer of air con. anyone knows whether by switching off the aircon power and in turn turning off the heater. will it cause the condensor unit to have a shorter lifespan?

with that, does that mean that saving $50 every mth will cause u to pay 3k for a new aircon unit in a shorter period? 3k equates to about 5 years of condensor life.

maybe more research ought to be done on this issue before concluding that the heater is not required and a waste of electricity?

my mitsubishi inverter unit has been working well for 8 years with >15hrs usage per day. i believe the aircon unit is capable of more than 5 years of life.

Edited September 10, 2010 by wolflet

[manutd1972 1]

i dunno about the inverter units. but back when i was in the navy. condensation in the coil is a main killer of air con. anyone knows whether by switching off the aircon power and in turn turning off the heater. will it cause the condensor unit to have a shorter lifespan?........

based on this logic(not saying it's right or wrong), i suppose my practise would help to preserve the condenser, if my inverter aircon does employ a heater unit like the Mitsubishi unit.

what i normally do is i program the aircon to shut off about 1.5hrs before i'm suppose to wake up. and even though i set the temperature to 25 deg C, apparently my dog and i dun seem to have any problems with the humidity or lack of aircon during that 1.5 hrs.

now since the aircon is technically still on standby during that 1.5hrs, the heater shld be working to prevent condensation in the coil. when i get up 1.5hrs later, i switch off the aircon's main switch.

i've been doing this ever since i got my aircon slightly less than a year ago, and i've noticed, even with about 6-8hrs of usage everyday, rain or shine, my utilities bill have only gone up by no more than $10 per month.

[neubie 2]

now since the aircon is technically still on standby during that 1.5hrs, the heater shld be working to prevent condensation in the coil. when i get up 1.5hrs later, i switch off the aircon's main switch.

dun tink the heater is designed to heat up condensation on the coil, if you are referring to the indoor FCU. what has been said is the heater is built into the outdoor condenser unit, not the indoor FCU....

[DaveLee1688 1]

i dunno about the inverter units. but back when i was in the navy. condensation in the coil is a main killer of air con. anyone knows whether by switching off the aircon power and in turn turning off the heater. will it cause the condensor unit to have a shorter lifespan?

with that, does that mean that saving $50 every mth will cause u to pay 3k for a new aircon unit in a shorter period? 3k equates to about 5 years of condensor life.

maybe more research ought to be done on this issue before concluding that the heater is not required and a waste of electricity?

my mitsubishi inverter unit has been working well for 8 years with >15hrs usage per day. i believe the aircon unit is capable of more than 5 years of life.

You interpreted the crux of the issue here wrongly, let me put it another way. Now, if you have brand D & M inverter aircon, if D cost $3200, and M cost $3000, both are inverter aircon. Now, let's calculate based on manufacturer recommended life-span of a condenser, which is 5 years for both brand D & M. Now, if each month, M will consume additional $10 per month because of the need to pre-heat the condenser, it will be $120 per year, and $600 for 5 years. Therefore, brand M will effectively cost you $3000 + $600 = $3,600, compared to brand D's $3200.

Now, all inverter aircon will give you 20 to 30% savings in energy usage compared with non-inverter. So, the logic of "inverter aircon from brand M reduce energy by 30% compared with non-inverter, therefore, the standby power can be ignored" is flawed. This logic is flawed for following reasons:

a) Not comparing apple-with-apple ; one should compare the installation cost of inverter aircon against another inverter aircon.

b) If we argue based on energy saved by using inverter-aircon, then if other manufacturer's technology do not need the pre-heating in a tropical climax to work properly, then, the one that requires it is not environmental conscious as compared to others in the same category. This is especially so because almost all inverter aircon makers advertise their product as environmental friendly. Getting 4 ticks but burning energy in the background is certainly not 'gentleman' like.

To give you a feel of what is 80W : When you turn on a Pentium 4 3GHz computer with 1 harddisk, and leave it idle, it consumes about 70 to 90W, not inclusive of energy used by monitor. So, the pre-heating is like leaving your Pentium desktop computer on for 45 (40 + 20/4) minutes each hour, for about 15 hours/day (depending on how long you do not use the condenser) . Do you think this makes sense ? If yes, leave your computer on then, nothing we do to try save the environment will change your thinking.

Edited September 13, 2010 by mit3a28

[wolflet 1]

valid point.

but taking the discussion between d & m into account. from my understanding. M brand aircons are using the R410a gas vs D brand using the older R22 gas.

the R22 gas is less cold compared to the R410a (told to me by the aircon salesman) and the R410a gas is more environmentally friendly.

since D is using R22 which is less cold, maybe the need for a preheater unit has yet to come up? Considering singapore having such high humidity, even a little chill factor will draw a high condensation rate. If the existence of a preheater unit that draws some power during standby can actually increase the lifespan of an aircon unit, reducing the need to replace, thereby reducing the CO2 production of an item during manufacture. Then it is probably justifiable.

only recently has D started using R410a (i'm not sure about the existance of the preheater element though). Also, please enlighten me on the usage of preheater in other makes of air con brands other than D and M.

I believe the energy consumption of an air con unit is not just the energy used while running the air con. But it is also not sufficient to just take in the standby energy into consideration. A more accurate gauge of an item's environmental friendliness should take into account the carbon produced from design to manufacture to operation.

Just take the hybrid cars for example. The hybrids promise very good fuel economy (2x compared to normal vehicles) but the manufacturing process produces alot of CO2 due to the usage of rare metals in the batteries. So it is actually not as environmentally friendly as promised.

I'm not trying to start an argument here, just sharing of ideas.

[MichaelAng 1]

I have just placed orders for the M brand for system 4 too. I do find the additional cost of maintaining the compressor on standby sounds a bit excessive at $50 for 2 condensers. So assume I only have one so that is $25 per month more?

If paying just $25 more per month keeps the inverter aircon working longer, I won't mind doing so. Reason being, most of us going to have some part of the piping hidden behind false walls, cabinets etc. If the compressor spoilt much earlier, that means having to tear down many of these to reach the piping so as to replace the aircons. Imagine the amount of work damage done.

My upstairs neighbours aircon compressor kept leaking and I have asked them to checked. THey claim they didn't switch it on. Now there is a possibility that this is due to this condensation. My point is, Singapore likely to have aircon condensation problems.

In any case, I do find the standby wattage a little high, wonder if we could verify this with the Mitsubishi Electric Japan. Wonder if the numbers were lost in translations. ha

Michael

[neubie 2]

Reason being, most of us going to have some part of the piping hidden behind false walls, cabinets etc. If the compressor spoilt much earlier, that means having to tear down many of these to reach the piping so as to replace the aircons. Imagine the amount of work damage done.

aircon spoil is replaced aircon, nothing to do with piping if they are installed well in the first place. they are independent cases.