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aikhh
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Join Date: Mar 2009
Posts: 130

Air Conditioners: HP vs. BTU Per Hour

04/27/2009 7:55 PM

Dear All Gurus,

I have encounted some issue of air conditioner horse power vs Btu per hour (single phase power supply),i noticed some manufacturer produce their AC (Air Conditioner) with 1 HP at 11500 Btu/hr and some onlt at 8500 Btu/hr. Some AC 4HP produce only 37000 Btu/hr But AC 4HP with 3 phase power supply is able to produce more than 45000 Btu/hr .

Please guide me a little more what is the resons of this issue ?

Thank You Very much and Best Regards

I
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perry
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Join Date: Dec 2006
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#1

Re: Air conditioner Horse Power vs Btu per hr

04/27/2009 11:16 PM

aikhh; i use to figure 1 HP= 1 ton= 12000 btu's, but today every thing is different.perry
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sb
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Join Date: Mar 2007
Posts: 2550
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#2

Re: Air conditioner Horse Power vs Btu per hr

04/28/2009 12:10 AM

what you mean is the electrical KW consumed vs the BTUs ?

This is widely varying and the * ratings are now given (at least in India) based on the efficieny of conversion. Just today's news paper there was a KW cinsumed for different * ratings for a 1.5T AC and as far as I remember it was approx 1.6KW for 5* Vs approx 2KW for 2* AC (advertisement by LG)

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juliangelique
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Join Date: Oct 2006
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#3

Re: Air conditioner Horse Power vs Btu per hr

04/28/2009 2:10 AM

Hi;

Your KW is the rating of your compressor and your BTU's are the actual converted energy by your ACU. The Loads (Q) are computed as Q=Mass X Specific heat of the mass X temperature change divided by the time it reaches the desired temp, express in Btu per hr. ex, you have room 12' x 12' x 12' = 1728 cu.ft, initial temp 95 deg F, final temp 68 deg F, air density of 0.08 lb/cuft, specific heat of 0.17 lb-deg F. So you have Q=(1728 x 0.08) x (0.017) x (95-68) or Q= 138.4 x .017 x 27, Q = 634.52 Btu you will have half of the btu load in two hours.

This computation are regardless of other heat loads such as lightings, wall, ceiling, floor and its occupants.

KW to Btu ratio is called EER or Energy Efficiency Ratio

best regards.
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aikhh
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Join Date: Mar 2009
Posts: 130
#4
In reply to #3

Re: Air conditioner Horse Power vs Btu per hr

04/28/2009 11:40 PM

Dear juliangelique,

Thank you very much of your very good answer.

Regards
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flyinghigh
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#7
In reply to #3

Re: Air conditioner Horse Power vs Btu per hr

04/29/2009 12:02 PM

Good morning juliangelique, I appreciate your precise answer, but as a novice, I have a question. In my old ac & refrigeration textbook, in its chart of specific volumes, it shows a sv of 14.8cf/# at 95ºF, down to 13.61cf/# at 68º. If I take the reciprocals to get the densities, I get 0.0676#/cf to 0.073#/cf; so wouldn't a figure of 0.07 be closer to the correct density? This would give 555 Btu required. Or is the difference too small to worry about? Thx.
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Anonymous Poster
#13
In reply to #3

Re: Air conditioner Horse Power vs Btu per hr

07/01/2010 1:01 AM

hello, Excellent....
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YWROADRUNNER
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Join Date: Dec 2007
Location: Cypress Calif
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Good Answers: 23
#5

Re: Air Conditioners: HP vs. BTU Per Hour

04/29/2009 8:15 AM

Hello aikhh:

Hopefully I'm not injecting any confusion, as a correct answer has already been given, but it is sometimes helpful to think of the compressor as a pump. 1 hp= approximately 2542.5 BTU/H. 1 ton of air-conditioning relates to the energy required to change 2000 pounds of 32° water to 2000 pounds of 32° ice in 24 hours which equals 12000 BTU/H therefore a 1 hp compressor 1 ton compressor is moving approximately 4.73 horsepower worth of heat in one hour.

Which is the aforementioned energy efficiency ratio. The energy efficiency of an air-conditioning system is determined by several factors ,the electrical and mechanical efficiency of the compressor, the evaporator and condenser coils sizes, and the refrigerant. The new refrigerants and oils tend to be more efficient at transferring heat than older refrigerants.

An air-conditioning unit when in heating mode is usually referred to as a heat pump, which in actuality is what it is in either mode, in heating mode the units tend to be more efficient as their own internal waste heat is utilized to heat the condition space, so an efficient heat pumps in ideal conditions can return five times more heat to the space than the electricity used to power the device.

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Sasnak
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Location: Topeka, Ks.
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#6
In reply to #5

Re: Air Conditioners: HP vs. BTU Per Hour

04/29/2009 9:39 AM

Very good answer Beep-Beep, especially for a/c application. The 12,000/1 HP saying is from the days of R-12, basically from the formula Roadrunner mentioned. When the application is used for refrigeration purpose, the ratings will drop. The 8500 rating that was mentioned by the poster is the probably @ 0 degree evaporator (freezer application). 1 H.P. = 8500 B.T.U.'s, always go with manufacturer rating for application & refrigerant used.
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Anonymous Poster
#8
In reply to #6

Re: Air Conditioners: HP vs. BTU Per Hour

04/29/2009 12:39 PM

Awesone impressive data from all here, absolutetly. Very interesting how to calculated so far in order to determine capacities. Very good all and informative once again, thanks truly and now crank those puppies-up for summer time then.

A/C Juice,

MC

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aikhh
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Join Date: Mar 2009
Posts: 130
#11
In reply to #8

Re: Air Conditioners: HP vs. BTU Per Hour

04/29/2009 10:00 PM

Hi magwer,

Regards
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YWROADRUNNER
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Join Date: Dec 2007
Location: Cypress Calif
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Good Answers: 23
#9
In reply to #6

Re: Air Conditioners: HP vs. BTU Per Hour

04/29/2009 5:02 PM

Hello Sasnak:

Good Point, I had the misfortune at one time, to inherit a 20 below freezer maintenance, if memory serves me right there 30 hp compressor was only rated at about 150,000 BTU which is lower than your number, so memory may not be serving me right.

One thing's for sure the greater the temperature difference between internal and external environments, the more work that has to be done to transfer the heat.

Heat pumps work great in mild climates, and although the manufacturers have told me they will work in temperatures approaching zero Fahrenheit ,the older units that I've worked with didn't like sub freezing temperatures. Since I am currently located in Southern California I haven't checked their numbers, but I think they're full of hot air.

The other thing I'm sure about, is I want to stick to air conditioners and refrigerators, I didn't like subzero temperatures either.

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aikhh
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Posts: 130
#10
In reply to #5

Re: Air Conditioners: HP vs. BTU Per Hour

04/29/2009 9:58 PM

Dear YWROADRUNNER

Thank you very much of your very GA.

Regards
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DRFREON
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Join Date: Nov 2008
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#12

Re: Air Conditioners: HP vs. BTU Per Hour

04/30/2009 4:28 AM

I am impressed with some of the excellent answers. In my experience, the reason for the deviation is largly due to the ambient and load conditions the manufacturer uses to rate their equipment capacity. Check the engineering cut sheet, paying particular attention to
wet and dry bulb temperatures and the evaporator conditions at full or maximum load. Also, look out for the word "nominal" ; its a SOB!
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13 comments

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Users who posted comments:

aikhh (3); Anonymous Poster (1); DRFREON (1); flyinghigh (1); juliangelique (1); perry (1); Sasnak (1); sb (1); YWROADRUNNER (2)

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