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Air conditioner "standby"

PostPosted: Tue Dec 29, 2009 4:55 pm
by zzsstt
Having acquired a Wattson a while back, I have been investigating the energy use in the small cottage where I fitted it.

After a few days of detecting "energy leaks", I found I still had about +/-140W of unexplained consumption. Removing this required a trip to the switchboard, where I discovered the power drain was to the three air conditioners. These are small "split system" reverse cycle units (current models from a big name brand) that are used on hot nights over the height of summer and at night through the coldest part of winter. For 6 months of the year - spring and autumn - they are never switched on.

My investigations have revealed that these units, even when "off", draw a residual "standby" of perhaps 50W each. After speaking to the manufacturers, I have discovered the reason is that they have to maintain a minimum temperature of the refrigerant at all times. If the fluid becomes too cool, it increases in viscosity and can damage or severely reduce the life expectancy of the compressor if it is started in that "cold fluid" situation. As a result, in order to be ready to be "instantly activated" the units have a small heater that constantly maintains the fluid temperature.

The advice from the manufacturer is that it takes at least 6 hours for the unit to warm the fluid sufficiently to allow a safe start, possibly slightly less on a hot summer day and probably more (ideally 12+ hours) in winter when the unit is very cold. However, to save this constant 50W draw, the air conditioners can be switched off at the switchboard AS LONG AS THEY ARE ALLOWED TO WARM UP FOR AT LEAST 6 HOURS OR PREFERABLY OVERNIGHT BEFORE THEY ARE ACTIVATED.

In my situation, I can save at least $100 a year by powering the three units down at the switchboard for spring and autumn!

I hope this information will benefit someone else too!

Re: Air conditioner "standby"

PostPosted: Tue Dec 29, 2009 8:48 pm
by Helipos
Perhaps a brand of aircon and model would be helpful here.

Re: Air conditioner "standby"

PostPosted: Wed Dec 30, 2009 7:31 am
by zzsstt
Helipos wrote:Perhaps a brand of aircon and model would be helpful here.

From the way it was described to me, this is fairly standard behaviour for all modern (we did not dicuss older models) refridgeration style air conditioners, which was why I did not bother to include a model or brand. These particular units are Daikins, however, and it was Daikins technical support team that provided the information.

Re: Air conditioner "standby"

PostPosted: Wed Jan 06, 2010 10:43 pm
by kalindriel
I have often wondered about the standby use of the airconditioner that our house had. Now I know how to turn it off safely and save the energy.

Re: Air conditioner "standby"

PostPosted: Thu Jan 07, 2010 12:01 pm
by munter
Interesting find zzsstt. It would certainly be worth saving a constant draw of 150 watts from your power bill. Some validation from consumers of manufacturers that other brands also have a similar power draw would be useful to ensure it isn't a case of one manufacturer mischievously advising that their unit is no worse than any others.
For reference - I have a mitsubishi unit in our house and I find that the billing meter dial does not rotate when I have all other circuits switched off and just the AC circuit left on and the AC in standby. This suggests minimal (or at least low) power consumption. I'll have to check what kind of consumption one spin on the dial represents to see if I can determine the sensistivity of the billing meter.

Re: Air conditioner "standby"

PostPosted: Thu Jan 07, 2010 10:03 pm
by Smurf1976
munter wrote: I'll have to check what kind of consumption one spin on the dial represents to see if I can determine the sensistivity of the billing meter.

Typically it's either 400 or 266.6 revolutions of the disc per kWh (at least that's for the meters we use in Tasmania). It normally says on the front of the meter somewhere what the revs / kWh figure is.

As for sensitivity, I haven't tested it but I've always understood that standard single phase rotating disc meters can record anything above 2 watts consumption and will thus, in practice, record all energy consumed since most households have a minimum load of no less than 4 watts and in most cases far higher.

Re: Air conditioner "standby"

PostPosted: Sun Jan 10, 2010 5:22 am
by greenfan
Ah, this explains the "Crankcase Heater (yes/no)" column for air conditioners on and the obscure comment in my Airwell's user manual that it burns 45W on standby.

Does anyone know if the "Dirty Filter" warning light needs continuous power to count the hours that the fan is running?


PostPosted: Sun Jan 10, 2010 8:38 am
by Tracker
As a generalisation, most of the normal split Air-Conds that we see, do not have case heaters.
I have only seen them on some larger US products, where Sub-Zero is the norm.
Being in Sydney, that might bias what I see..
Were I at Cradle Mountain or Jindabyne , it might be different.

Needless to say, if your RAC (Reverse-Cycle Air Cond.) is turned on by a remote control, then it does draw power on standby, just like every other "Electronic" appliance. How many people actually turn their Fisher-Paykel washer off when not in use ? If you have one, feel the warmth in the control head !

If you did have a case-heater in a bigger unit, I don't think I would hesitate to disconnect it , in any but the colder areas of Australia.
In the least, you could fit a new switch, so that you could disable it in summer, and turn it on an hour before using the RAC in winter.

Something to watch, for those who have the big 2 door refrigerators...
Many have Mullion-Heater... Door Jam heaters, intended to warn the metal at the seal..
The fridge-freezer is real cold on the inside.. The cold is transmitted through the skin at the seal and for an area near the seal, it gets cold.
On humid days, condensation forms and will even run to the floor forming pools.
The heater is designed to selectively heat these area of possible condensation.
Problem is that they typically draw 60 to 100 watts -- Continuously !
Most fridges use the hot-gas from the compressor to do the same job, but as I said , some of the yank products still have them, and have a small switch inside to disconnect it for low humidity times.
Be sure to turn it off , for as long as you can.

Re: "STANDBY" Power

PostPosted: Sun Jan 10, 2010 12:28 pm
by Smurf1976
Tracker wrote:.How many people actually turn their Fisher-Paykel washer off when not in use ? If you have one, feel the warmth in the control head !

Always switch mine off (always...). Left on, the electronics stay running 24/7 and fail within a few years, meaning you either pay a relative fortune for a new control board or scrap the whole machine. Much cheaper to just turn it off.

Re: Air conditioner "standby"

PostPosted: Mon Jan 11, 2010 12:35 pm
by munter
As mentioned by greenfan, the detailed spreadsheet available at shows which models have a standy heater and which don't. Mine doesn't have a heater but then with a little sorting of the filter I did see that there are models with higher COP effieciency than the model I had installed last year. I think I will make more use of the energyrating website *before buying appliances* in the coming years...