[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: The chilling truth about cold horsepower

Date: Tue, 10 Jun 2003 00:29:45 -0400
From: Bill Wichers <billw at waveform_net>
Subject: Re: The chilling truth about cold horsepower

I have a friend who is an ME with Trane (a big manufacturer of both air
conditioners and compressors). I'm going to see if maybe he can answer some
of the questions posed in this thread.


Thanks Bill, I hope he can come up with an answer for Scott. I asked one more person today and he is going to talk to some people in the AC field about this question. If he gets back to me I'll post it if it adds anything new.

Date: Tue, 10 Jun 2003 03:16:07 -0700 (PDT)
From: "S. Hieber" <shieber at yahoo_com>
Subject: Re: The chilling truth about cold horsepower

Thank you Jerry and Bill for taking the time to look into
this problem of mine more deeply.

Unfortunately, even as I read through your thoughtful
replies, the problem is not resolved.  A BTU/hr. is a unit
of Power, as are HP and Tons Refrigeration.  And with
airconditoners, the rated BTU/hr of cooling capacity is
much *greater* than the rated BTU/hr of energy input.  You
can leave HP out of it and just use the watts rating for
energy input and the BTU/hr rating for cooling capacity.

For example a 610 watt air conditioner is rated for 6000
BTU/hr cooling capacity.  610 watts=2077 BTU/hr yields 6000
BTU/hr cooling capacity.  Does this not seem odd?

There is something I am obviously missing here, but I'll be
darned if I can figure it out, so far. I'm checking this
further.  I'll let you know what I find out.

Scott H.


I am wondering how the conversion factor 1 HP = 2540 BTU/hr was derived. I do not personally know but I am wondering if it is being properly used in this case. I would like to see a step by step calculation using dimensional analysis. I won't have time to look into it at work until next week. Most of my reference books are there so I can't do it at home.

I also began thinking about the total electrical power a 1 HP motor draws. Bill is right when he listed many types of motors. I was just going to choose one and see what the locked rotor or full load amps rating is. That will give the total energy going into the motor. As Bill said that energy is partially converted to heat and lost( the label on the motor will list the Temperature rise). Most (we hope) is converted to rotational energy. I think that even the sound it produces as it runs is a source of energy loss even though it is probably an extremely small amount. Can you think of any others?

I am interested now to see what comes of this question.


Add photos to your e-mail with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail