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  • kw to btu?

    hi - i have an air con that is 650 kws [australian measure] and want to know what the comparable BTU measurement would be [usa measure for a/c's] - can't seem to find it! i.e. a regular room sized A/C is 5000-6000 BTU's... is that comparable to a 650 KW in Australia? I haven't a clue!!! thanks!

  • #2
    Re: kw to btu?

    Originally posted by eugenia
    hi - i have an air con that is 650 kws [australian measure] and want to know what the comparable BTU measurement would be [usa measure for a/c's] - can't seem to find it! i.e. a regular room sized A/C is 5000-6000 BTU's... is that comparable to a 650 KW in Australia? I haven't a clue!!! thanks!
    A BTU is a unit of energy and kW a unit of power. A/C ratings are actually BTU/h which is a unit of power.
    1000 W = 1 kW = 3412 BTU/h

    Are you sure there isn't a decimal somewhere in that 650 kW number. That's a HUGE a/c unit and residential electric service could not power it, but it might be typical of a large building or factory. A room sized a/c might have 1.5 - 3.5 kW cooling capacity (5000 - 12000 BTU/h, rounded) depending on room size. A (quite) large home could be cooled with 25 kW.

    Comment


    • #3
      Re: kw to btu?

      I live in Thailand, where a/c units are stamped with their cooling capacity in kW, which is not the same as the kW they consume! My 50 sq.m. living-dining room has a 44kW unit which hisses and gasps like an asthmatic octogenerian.
      I think it draws about 15kW but as it is a single-phase motor, the starting current is 22A, so I cannot run 3 units without blowing the main circuit breaker! It is grossly over-sized - I'd guess a unit drawing 3kW should cope. (Bangkok is rarely above 34C)
      How does one work out what size is required? My architect here says it goes purely on floor area, not on how much glass you have facing the sun! I don't agree. Help please!

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      • #4
        Re: kw to btu?

        Originally posted by Jonothai View Post
        I live in Thailand, where a/c units are stamped with their cooling capacity in kW, which is not the same as the kW they consume! My 50 sq.m. living-dining room has a 44kW unit which hisses and gasps like an asthmatic octogenerian.
        I think it draws about 15kW but as it is a single-phase motor, the starting current is 22A, so I cannot run 3 units without blowing the main circuit breaker! It is grossly over-sized - I'd guess a unit drawing 3kW should cope. (Bangkok is rarely above 34C)
        How does one work out what size is required? My architect here says it goes purely on floor area, not on how much glass you have facing the sun! I don't agree. Help please!
        See post #2 for conversion between BTU/h and watts.

        I think you may be missing a decimal in your numbers, as 15 kW of electrical power is 125 A at 120 V or 63 A at 240 V.

        You might need a new architect. Floor area is an overly simplistic way of rating required AC size. However, a more accurate estimate is considerably more complex. You need to consider the total exterior area and how well insulated it is. You always need the area of exterior walls, how much is window area, how well the walls are insulated, and if the space above and below is not cooled (or heated, in winter) the ceiling and floor area, with insulation details.

        Sunload through windows absolutely affects the total. However, estimates based on floor area work, if the window load is about average and similar to the rooms that were the basis of the estimating guide. I don't know if it is available there, but we have a magazine called Consumer Reports. They have a pretty good estimating guide that starts with floor area, but modifies the estimate according to window area and other factors.

        Still 50 m is a fairly large room. I would think you need at least 12000 BTU/h, 3.5 kW of cooling performance (about 1.2 kW electrical consumption, assuming a coeficient of performance of about 3). Another good guide is your present machine (but you have to sort out the rating). On the hottest days, is it adequate? Does it have adequate pulldown (if it has been off, can it cool a hot room quickly enough). On the hottest day, but after the room is cooled, does it run most of the time, but not ALL the time? If it runs too small a percentage of the time, it may not adequately reduce the humidity. If it runs all the time, it may not be cooling adequately.

        If the present machine has served fairly well and is simply old, you can estimate from its performance whether to go up or down one size. If you think it was significantly mis-rated to the room, you should locate someone qualified to rate your home considering construction and local conditions.

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        • #5
          Re: kw to btu?

          Thank you, John S, for this reply.
          The Amperage is stamped on the machine (which is new), might be the running current or starting current, one can't be sure. We have 240V here, but I think 63A would certainly blow the fuse!
          I draw my 'white-out' curtains whenever I am out for the day in summer, which means I don't come home to an oven. The tinted glass gets too hot to touch, but the large balcony doors are party shaded by the balcony above.
          I only cool the room to 27C (80F) to save energy, and that still feels cool, I suppose because the humidity is so much lower. But it still costs me more to maintain this 5 or 6C (10F) temperature difference for part of the day than it did to heat my 140 sq.m house in northern Sweden to 40 to 50C (70 to 90F!!) above outside temperature around the clock, using a heat pump drawing 2.5kW!! 40% of ALL the electricity used in Thailand is used in buildings, mostly for a/c! Doors to shopping malls are left wide open, blasting icy air across the street - it cools the city down, and counteracts Global Warming, doesn't it?!
          I stay in a $15-a-night hotel in Phnom Penh (Cambodia) on my visits there, and a 0.9kW unit is more than adequate, and completely silent!
          Yes, the machines are adequate in the summer, the draw-down time (to 27C) doesn't worry me too much. But to get the room down to 20C (68C) - which I never do - would take almost an hour, I'd guess.
          The initial cost is another factor - I paid $5,000 for these 3 machines (44kW, 20kW and 18kW) but to cool a similar flat in Phnom Penh I have been quoted $1,600 (two 1kW's and a 2kW). Maybe the Thai contractor was ripping me off?

          Comment


          • #6
            Re: kw to btu?

            I'll be blunt. I think your contractor has misled you on the capacity of these machines. 22 A is probably the starting current and probably drops once it is running. However 22 A x 240 V is is 5280 W or 5.28 kW.

            Even if it were the running current, I doubt the coefficient of performance is much better than 3, (state-of-the-art is around 4) so the cooling capacity is likely less than 16 kW, certainly less than 20 kW. (It may be considerably lower, I have tried to establish upper bounds.)

            What is the fuse or circuit breaker rating? It might give you a better upper bound on running current.

            If you can determine the brand and model number, you may wish to search on the Internet to determine the true capacity of these machines. You don't need 44 kW to cool that room, but then again, you don't really have 44 kW of cooling, either.

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            • #7
              Re: kw to btu?

              My internet search drew a blank - the Thai manufacturer's website centralair dot com gives no info on any of their products, and a search there for the 44kW unit's model number, CCS-N44SSY, lead me to a dating site!!
              I think I have a 60A circuit-breaker in the locked electrical room outside, which trips if I run 3 units!
              I am sure you are right that I do not need 82kW of cooling for 107sq.m! I think my next step is contractural, not technical, but thanks for your help!

              Comment


              • #8
                Re: kw to btu?

                1kw = 3,412 btu

                or

                10,000 btu = 2.93kw

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                • #9
                  Re: kw to btu?

                  12000btu convert in kw

                  Comment


                  • #10
                    Re: kw to btu?

                    Oversized ACs should make the air feel clammy.

                    Comment


                    • #11
                      Re: kw to btu?

                      Originally posted by Unregistered View Post
                      12000btu convert in kw
                      how much btu will an air conditioner be if it is 3.8 kw

                      Comment


                      • #12
                        Re: kw to btu?

                        Originally posted by Unregistered View Post
                        how much btu will an air conditioner be if it is 3.8 kw
                        1 kW = 3412 BTU/h, so 12970 BTU/h

                        Comment


                        • #13
                          Re: kw to btu?

                          Originally posted by Unregistered View Post
                          My internet search drew a blank - the Thai manufacturer's website centralair dot com gives no info on any of their products, and a search there for the 44kW unit's model number, CCS-N44SSY, lead me to a dating site!!
                          I think I have a 60A circuit-breaker in the locked electrical room outside, which trips if I run 3 units!
                          I am sure you are right that I do not need 82kW of cooling for 107sq.m! I think my next step is contractural, not technical, but thanks for your help!
                          Hi friend
                          Normal cooling load in Thailand we'like to use the std. number 600 btu/h / sq.m. of flooring room, as your room is 50 sq.m. you would be used A/C = 50x600=30,000 btu/h =8.8 kW

                          Korb

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