Duct work

[mjtjc]

Hi there,my name is Mike and I'm in commercial.We are about to put a furnice in a house that my friend bought.40 years old.Any tips on running the duct work?

[udarrell]

There are too many things ton list here.
Here is a little info:

http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_syste ms.html

http://ducts.lbl.gov/HVACRetrofitguide.html

First, contact your electric power company, or some other entity in your area, and find out if they conduct manual J heat-gain audits and if they can recommend things to do to reduce your home's energy usage.

"Only after you have reduced your home's energy heat-gain and heat-loss should you consider installing new equipment that has to be accurately manual J sized to the new lower heat-gain heat-loss conditions."

Air Conditioning Efficiency Recommendations Summary List:

* Wherever possible reduce the cooling load of the house. Overhangs above east and west windows are particularly effective in reducing cooling load.

* Perform Manual J for all installations and select equipment by using Manual S.

* Insure that the system installed never exceeds the capacity of the equipment suggested by Manual J or N for commercial buildings and Manual S for selecting equipment sizing.

* Size duct systems based on Manual D. (If in doubt size upwards.)

* Determine the grille location and characteristics using Manual T.

* Confirm proper evacuation of the line set and indoor coil with a micron gauge.

* Confirm proper charge using the manufacturers' suggested method.

* Confirm proper airflow by test. The flow can be determined from the coil pressure drop when pressure/flow data is available from the equipment manufacturer or can be determined with a duct test rig or flow hood.

* Increase the duct insulation to R-6 (at least on long runs in the attic).

* Confirm that the duct leakage is less than 3% of coil airflow for a new system and less than 6% of coil airflow for an existing system.

Do the ductwork installation right, or don't do it!
- Darrell