jammy23

15-03-2014, 12:33 PM

I am wondering if anyone knows of a standard way to work out the required system size for a room, and the calculations you would use to work this out.

I have looked online for a calculation to work this out and it varies a lot between each way of doing it...

so far I have found: multiplying the length of the room by its width to find the square footage and from this a table showing where that number falls and the amount of btus for that size room...it also says to add 10% to capacity for heavily sunny lit rooms and decrease by 10% for heavily shaded rooms...add 600 btus for every extra person if more than 2 regularly occupy the room...and add 4000 btus if its a kitchen or on second floor.

I have also found one: find the square footage and multiply by 25 to convert it into btus for that size room... then add x amount for heavily lit rooms etc same as above.

another I found was length x width x 337 and then add x amount for same variables as other 2 above.

But I have also tried calculators on other sites where you add the length width and height and then it calculates the total for you.

All of these methods create a vast difference in the total result, the top three methods are quite similarly matched but the other method adding the height of the room gives you virtually double the other 3 ways??

Is there an exact calculation which will give good accurate results every time.

The reason I am asking is I don't usually deal with room sizing as the place I work does it all and are reluctant to divulge it with me. My dads friend is having a new building built and wants an ac unit in the basement and was told to get a 7.6kw unit by the person hes buying it from on ebay but asked if I could confirm it for him, the methods I used above give different results and so am unsure what to suggest for him.

The basement is going to be 10m x 6m x 2.5m high.

I figured if anyone knows a calculation which is reliable it is something I can make note of for possible future use.

The size I got with the top method worked out at 3.7kw so use a 4.1kw unit.

The second came in at 4.7kw so use a 5.3kw unit.

so as you can see there is quite a big difference just between those 2, the calculators where you add the height of the room basically add about another 2kw to the total size. :confused: :confused:

I have looked online for a calculation to work this out and it varies a lot between each way of doing it...

so far I have found: multiplying the length of the room by its width to find the square footage and from this a table showing where that number falls and the amount of btus for that size room...it also says to add 10% to capacity for heavily sunny lit rooms and decrease by 10% for heavily shaded rooms...add 600 btus for every extra person if more than 2 regularly occupy the room...and add 4000 btus if its a kitchen or on second floor.

I have also found one: find the square footage and multiply by 25 to convert it into btus for that size room... then add x amount for heavily lit rooms etc same as above.

another I found was length x width x 337 and then add x amount for same variables as other 2 above.

But I have also tried calculators on other sites where you add the length width and height and then it calculates the total for you.

All of these methods create a vast difference in the total result, the top three methods are quite similarly matched but the other method adding the height of the room gives you virtually double the other 3 ways??

Is there an exact calculation which will give good accurate results every time.

The reason I am asking is I don't usually deal with room sizing as the place I work does it all and are reluctant to divulge it with me. My dads friend is having a new building built and wants an ac unit in the basement and was told to get a 7.6kw unit by the person hes buying it from on ebay but asked if I could confirm it for him, the methods I used above give different results and so am unsure what to suggest for him.

The basement is going to be 10m x 6m x 2.5m high.

I figured if anyone knows a calculation which is reliable it is something I can make note of for possible future use.

The size I got with the top method worked out at 3.7kw so use a 4.1kw unit.

The second came in at 4.7kw so use a 5.3kw unit.

so as you can see there is quite a big difference just between those 2, the calculators where you add the height of the room basically add about another 2kw to the total size. :confused: :confused: