Temperature and Electricity in AC Systems

It depends on the system and the losses in it.
Say you are heating up a tank of liquid to that temperature...once the liquid is up to temperature, if none is used and no heat escapes then very little extra power will be required.
If however the tank isn't insulated and liquid is constantly being drawn off and replaced with cold liquid then lots of power will be rquired.

So hopefully you see we don't have enough information to answer the question.

The best way in these situations is to measure it as there are often too many variable to make a meaningful calculation.

Del

As you are raising set point of AC from 22 to 23 deg C, effectively you will need less Kcal equivalent to Effective mass being cooled X effective equivalent specific heat X 1 (Deg).

Thus the equivalent electrical energy considering efficiency of AC system will be saved.

Obviously, to find out the effective mass and effective equivalent specific heat is very difficult. Best (and only) way is as Del say, measure practically, at same environment.

Yes there is a correlation between thermostat settings and power consumed. ASHRAE manual J provides heat load and cooling load formulas for various types of residential construction materials. Result is in BTU/H which can be converted to watts. The design indoor air temperatures can be varied and the difference Will be the amount saved. The smaller the temp difference between indoor and outdoor air the less power consumed.

Yes the relation exists ; for example we are in hotel industry recording on a daily basis the outdoor max and min temprature and based on that we are calculating the monthly heating and cooling degrees.

If the load is constant ; of course the heating and the cooling degress along with the set point will contribute affecting the electricity power consumptions.

We are monitoring that trough the daily KWHr readings compared to the heating/cooling degrees and the set point of our chillers.

Files are vaialbe for share.

ESMAT

For central hydronic heating systems in Germany, there is a rule of thumb: If the set temperature (in the room) is lowered by 1 degree C this will result in approx. 6 % savings in heating energy.

I would guess that the relation should be more or less the same if you apply this rule to AC systems (I suppose moderate differences between indoor and outdoor temperature?). Of course, the figures may change dramatically with the quality of the insulating of the building (including windows!!), the heat gain through solar radiation and the efficiency of the AC system. Are you talking about a central AC or a number of single-room units?

regards nudnik

Thanks Nudnik,

That's what I am looking for. Rule of thumb

btw, term of " 6 % saving in heating energy", Could it be meant 6 % saving of AC's electrical usage ??

or maybe you have another conversion factor to convert it into KWHour.

I am talking about both AC you mentioned above. Trying to get saving by increase seting temperature of AC.

thank you

It is dependent on the outdoor air conditions. The losses through cracks, windows, walls, etc are greater the greater the temperature differential between your indoor system and outdoor system. Losses in the same house in 75F Los Angeles will be much different than 40F Seattle.

Hi Adrian,

as the other contributers have already mentioned, it is not possible to give reliable figures, without having knowledge of tyical outdoor temperatures, the thermal insulation standard of the room or house, the way you (in person) operate the AC system and so on. I have a pfd document published by toshiba in which they give some figures on relative energy consuption of their inverter AC systems compared to fixed speed AC systems. Unfortunately, the brochure is written in german and I do not know if a corresponding publication is available in english. The quote that the energy saving potential ist 4 % of the power input (electrical energy) per 1 degree C higher room temperature or setpoint temperature. But as far as I read this brochure this figure is only related the their inverter AC systems.

I would be happy to send you the pdf (with just a few annotations in english ) if you do not mind to provide me with an e-mail adress. Sorry, I do not know if it is possible to upload a pdf to this forum

nudnik