1. Junior Member
Join Date
Aug 2008
Posts
25

Hi, I am curious to know what is the approximate Power consumption of a 5 Ton AC, doesnt matter if it is single or 3 phase.

I have seen wide ranges of power consumption from different electricians.

Is is accurate to say the power from a 5 Ton AC is about 7 kW to 9 kW, with 9 kW being the starting power and it levels off to abut 6 or 7 kW?????

Is this roughly accurate???

The question of trying to convert a one ton A/C unit into VA or kw/hr consumed is very dependant on the make and model of the air-conditioner, as well as its EER (energy Efficiency Rate). These range from 6-14 EER. Standard average one ton A/C unit consumes 1.335 KW/hr. But you can only use that as an estimating tool.

3. Senior Member
Join Date
Aug 2007
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2,754
I am curious as to why you are curious about the average power consumption (care to explain ?) How does that help in engineering any specific job ? (I guess what I am trying to say is that it is easy to get into trouble using a number for a project which may or may not represent reality, when it is just as easy to get a spec sheet and specify an exact piece of equipment that will work and use that value, knowing that that equipment actually exists and can be used in the installation)

4. Junior Member
Join Date
Dec 2008
Posts
1
I could see where have a general number could be beneficial from a Utility's perspective in sizing the service conductor and/or XFMR. Very often homeowners only know the tonnage of their units and do not have a spec sheet readily availble for the power company. Thus the company would have to use judgement in sizing for the full load of the unit as well as any possible flicker from starting. I use 1.5 KVA per ton of AC for full load calculations and 1.5hp per ton for starting calculations(assuming code G). These are of course very very general and I encourage you to do more research if possible.

5. Originally Posted by cubdh
Hi, I am curious to know what is the approximate Power consumption of a 5 Ton AC
About 4 tons of electricity (thanks I will be here all week, tip your servers)

6. I think trying to convert AC tonnage to power consumption is like converting automotive engine HP to mileage.

7. Senior Member
Join Date
Nov 2007
Posts
314
Originally Posted by cubdh
Hi, I am curious to know what is the approximate Power consumption of a 5 Ton AC, doesnt matter if it is single or 3 phase.

I have seen wide ranges of power consumption from different electricians.

Is is accurate to say the power from a 5 Ton AC is about 7 kW to 9 kW, with 9 kW being the starting power and it levels off to abut 6 or 7 kW?????

Is this roughly accurate???
Your guesstimate is wrong; as it should be!

Here it is:
1 ton of cooling = 12,000 BTUs of heat = 3.513725 kilowatt-hours
5 tons of cooling = 5 X 3.513725 = 60,000 BTUs = 17.57 kWH

8. One horsepower per ton is still a pretty decent rule of thumb for condensing units. That goes up if it's an entire RTU.

9. Senior Member
Join Date
Sep 2004
Posts
1,432
Originally Posted by topgone
Your guesstimate is wrong; as it should be!

Here it is:
1 ton of cooling = 12,000 BTUs of heat = 3.513725 kilowatt-hours
5 tons of cooling = 5 X 3.513725 = 60,000 BTUs = 17.57 kWH
You're assuming there is a 1:1 conversion between cooling tons and applied energy. If an AC worked like a resistance heater, that would be a good assumption. But they don't work that way.

The EER is a factor that tells you how to divide the BTU usage to get the actual consumed power (but look out, the 3.412 BTU conversion factor is in there too). EERs vary by temperature and the design of the equipment (newer units being more efficient than old ones, mostly because they have larger coils). The KW value above needs to be divided by a factor between 2 and 4. Power use is roughly TONS * 12000 / EER. Note that this method is not a good way to derive amps or MCA -- need the nameplate or datasheet for that.

10. Marc and Mark are right. A rule of thumb is the best that you are going to get, without some name plate info. 1hp for 1ton split A/C single phase system, less for a 3 phase.

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