A/C CALCS FOR COMMERCIAL

smoore

Does anyone have a quick formula to size a/c for commercial applictions. I would like to use this for a quick quote and then a detailed heat loss/gain if I get the job.


thanks

bigugh_4

A/C calcs

You might try contacting mecahnical engineering firms in your aera and ask if they have a A/C average guess as to square foot loads you might use for your guess. offering to pay for the guess A/C load calc may help. It comes under the consultation idea. Most of those guys have done a lot of that, and may be willing to give up their idea for a small fee. In the mean time keep a record of all your calcs and make your own quickie guess calculator

John Mills_3

EVEN

Even for a quick quote, loads in commercial vary so widely based on what the space is used for I'm not sure how far I'd trust them. You could do a very simple Manual J (even though it is for residential) and try to throw in people & appliance loads then follow up with a good Manual N if you get the job.

Mike T., Swampeast MO

AMEN

And don't forget lighting! Easily thousands of watts of incandescent (typically halogen) lighting in a not particularly large retail space where products (not boxes) are shown.

Steve Ebels

Very rough

Rule of thumb for here in Michigan. 1 ton per 400 sq ft. plus 150 btu's per person, plus wattage of lighting. (wattage X 3.1 = btu's)

Again this is very rough and can be high as easily as low. Either way you are burned because the customer will hold you to your first "guesstimate" 9 times out of 10. Take the time to do it right.

kf_2

Be Careful

Almost every commercial building has some sort of ventilation. Usually by code 20 cfm per person, plus any mechanical exhaust.

This can throw off calcs in a big way very fast.

Just 1,000 CFM's of ventilation can increase a heat gain by almost 2 tons, and thats just to cover 50 people.


kf

steve_26

calcs

400 cfm per ton is used a lot in N.E. but its only a rule.
depends on the space,to much internal gain to guess,computers,coolers, kit areas have refrig,ect.
Jewelry stores will kill you with lighting loads 3.41BTU'sper watt.people as much as 300 BTU's per person, fresh are requirements.Solar gain....good luck
steve

Otto

commercial load calculation

HVAC Equations, Data and Rules of Thumb By Arthur A. Bell Jr. is a great source for a quick estimate. Amazon.com for about $60.00

rich_16

load calc

for new construction 2x6 walls 500 sq. feet per ton. for existing marginal insulation lots of windows 375 sq. feet per ton.

JimGPE_3

News?

So did you get the job?

What factor did you use for capacity?

What part of the world is the project in?