gas piping size

I have a question on gas piping. I have 2 packaged AC units(Comfortmakers). The gas piping to both of them, which are on the roof, is 3/4 inch, then there is a 3/4 to 1/2 inch elbow and then the 1/2 inch shut off valveand then a 1/2 OD inch flex pipe which is 3/8 ID. Is this to small for a 100,000 & 60,000 BTU furnaces in the Packaged systems? I did not measure the distance to the systems, the 60000 BTU furnace is approximatley 100 feet, the 100,000 btu furnace is approximatly 50 feet away from the main gas line. It just seems that a 3/8 ID pipe may be small. Can anyone give any input?






If they work fine, why question it?


The gas company or a qualified HVAC professional should be able to help with your question. That’s who sized our service lines before installation.

See sizing tables but it should be OK if I understand your post correctly. Sizing Tables

[FONT=Arial]This is the general “rule” for appliance connectors. . .

Appliance connections shall, at no time, have a diameter less than that of the inlet connection to the appliance as provided by the manufacturer.

If the connector is smaller than the inlet of the appliance, it should be changed.


I agree but Rom didn’t share with us the size of the appliance piping.

Thank you for your input. The pipe sizing of the appliance is 1/2"