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acerunner 06-09-2010 09:56 PM

Contractors Procedure for Quoting
 
What is a typical procedure that hvac contractors go through for quoting?

I had a couple guys show up to quote for replacing furnace & ductwork. No measurements were taken, no questions about wall/window insulation. Just gave me a few options of furnaces and counted the number of heat registers needed.

I expected at least rough measurements or else how would you properly size & price out the furnace & ducts?

beenthere 06-09-2010 10:38 PM

You've seen/called the rule of thumb guys.

Screen contractors over the phone. If they don't do load calcs. Tell thanks. And keep calling.

It can be difficult to find companies in some areas that do load calcs.

acerunner 06-14-2010 02:33 PM

Is there a newer/better rule of thumb than the 40btu rule? I wanna know if a contractor come back with a number and tell me if was a load calc, I can confirm by comparing to an approx btu I expected.

Also is there a rule of thumb for sizing a main trunk? One contractor told me approx the cross-sectional area of a 6" diameter pipe per room/heat register.

beenthere 06-14-2010 03:20 PM

Nope. All of that is garbage.

Take a garden hose. Connect it to your outdoor faucet. Run it straight out. Open the faucet wide open. See how long it takes to fill a 5 gallon bucket.

Now wrap that hose in a tight circle. And see how much longer it takes to fill a 5 gallon bucket.

Turns bends all add resistance to air flow. A 6" pipe that is straight and short. Flows more air then a 6" pipe that is 10 foot longer, and has 2- 90 ells in it.

You can do your own load calc.
http://hvaccomputer.com/talkref.asp

It well worth the 49 dollar fee. And will save more then it cost on the upfront cost of the equipment alone.


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