I'm always frustrated by the lack of information available when I need it regarding the HVAC load. I am typically asked for a price before an HVAC contractor is on board. Can anyone suggest a good watts per sqft type budget for a rooftop, gas heat HVAC unit? My work is in Chicago.
HVAC watts p/Sqft?
- Thread starter DHkorn
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mdshunk
Senior Member
- Location
- Right here.
An ACCA Manual 'J' calculation is the only method I know of. Anything else is just guessing. Like the old 'one watt per cubic foot' rule (resistance heat) is just a guess.
mdshunk
Senior Member
- Location
- Right here.
Any 'watt per square foot' rule of thumb will give you a sort thumb. It might work on the building with 8' ceilings today, but it will not work on the building with 24' ceilings tomorrow.
I've been informed that AC for a dwelling will run abut 1 ton per 400 Sq Ft of cooling area some contractors well not carry lavs etc. some will
You used to be able to figure 10Amps per ton at 240 Vbut the newer SEER (12 - 13) do not always hold to that rule of thumb.
I would be careful if the eq cuts are not available.
You used to be able to figure 10Amps per ton at 240 Vbut the newer SEER (12 - 13) do not always hold to that rule of thumb.
I would be careful if the eq cuts are not available.
bphgravity
Senior Member
- Location
- Florida
Does Chicago have an energy efficiency code? It is fairly easy to calculate what the HVAC requirements will be figuring the required energy calcs for the occupancy...
DaveTap
Senior Member
- Location
- Currently Flowery Branch, GA
HVAC load
HVAC load
Over 25 years working for, and as, an electrical/ HVAC/ refrigeration contractor in and around Chicago and I still don't have any easy way to estimate. It depends on building use, materials, insulation, windows, doors, ceiling heights, above or below grade, how many floors, heat or cooling exchange between floors, building shape and/ or surface area, personel and usage equipment providing additional heat/ cooling loads, and now we'll even have to factor in global warming since Chicago just set a new record for the number of days above 100 degrees this summer, and I expect will see blizzards like '79-80 again too.
We use 4 different calculation programs and even they never agree on the loads... then we select equipment... which is never availible in the exact size specified ... and then each manufacturer and equipment type has a different electrical efficiency. If you find an easy way to estimate PLEASE let me know!! At least in my case I'm usually doing both so I get the advantage of having the HVAC calcs first.
HVAC load
Over 25 years working for, and as, an electrical/ HVAC/ refrigeration contractor in and around Chicago and I still don't have any easy way to estimate. It depends on building use, materials, insulation, windows, doors, ceiling heights, above or below grade, how many floors, heat or cooling exchange between floors, building shape and/ or surface area, personel and usage equipment providing additional heat/ cooling loads, and now we'll even have to factor in global warming since Chicago just set a new record for the number of days above 100 degrees this summer, and I expect will see blizzards like '79-80 again too.
We use 4 different calculation programs and even they never agree on the loads... then we select equipment... which is never availible in the exact size specified ... and then each manufacturer and equipment type has a different electrical efficiency. If you find an easy way to estimate PLEASE let me know!! At least in my case I'm usually doing both so I get the advantage of having the HVAC calcs first.
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