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View Full Version : Sizing pipe for natural gas and fan runs continuously


bamamojo
Mar 6, 2007, 08:27 PM
Folks,
I've got a couple of question concerning a Goodman Furnace GPG13:

1. This furnace is rated at 138,000 BTU. My gas meter is a 2 pound system. The furnace is about 20 feet away from the meter. Currently I've got 1/2" pipe connected to it. Is this right? Or should I use 3/4" pipe? How do you size pipe for BTU ratings?

2. The fan for this furnace keeps running even after the thermostat is not calling for heat. Not a whole lot of air comes out but enough that you can feel it. The only way it shuts off is if I shut power off. What could it be?

Thanks in advance!

ballengerb1
Mar 7, 2007, 08:45 AM
In my area the code calls for 3/4 black pipe. The thermostat should have a control switch for the fan. Two options are normally given; fan-on and fan auto. Fan auto runs when the furnace is calling for heat, fan on runs 24/7. 24/7 is not a bad thing. It help to keep your home temp more uniform and actually does not use more electricity than fan auto. Once a fan stops running it takes quite a bit of power to get it spinning again. The start windings in an electric motor can draw 4X as much power compared to the running load.

juggallojed
Mar 7, 2007, 06:35 PM
Folks,
I've got a couple of question concerning a Goodman Furnace GPG13:

1. This furnace is rated at 138,000 BTU. My gas meter is a 2 pound system. The furnace is about 20 feet away from the meter. Currently I've got 1/2" pipe connected to it. Is this right? Or should I use 3/4" pipe? How do you size pipe for BTU ratings? pressure readings help to determine pipe sizes seems ok at 1/2 inch for the btu's required

2. The fan for this furnace keeps running even after the thermostat is not calling for heat. Not a whole lot of air comes out but enough that you can feel it. The only way it shuts off is if I shut power off. What could it be? look for a fault light to see if a safty has been trippde this may explane the continous fan opperation, then as allways check filters and evaporator coils for blockage

Thanks in advance!

Hope this has helped