With a U-tube manometer I have measured 11" WC at the propane regulator output. When I fire up the furnace the WC drops to just about 10.5". When I measure at the furnace, at the post-valve gauge output, I see just 6" WC when the furnace fires. Any idea what could be causing this?

A half-inch drop is the design.Bruce

Static w/c should be 11.5. You should NOT see a drop below 11 inches when an appliance is running. 6 inches at the furnace is strange. Regardless, IF you have to adjust a LP regulator that has been in use for years, it is BEST to replace the LP regulator. This is because a Regulator can get a weak spring/diaphragm and you can never get the W/C to stay on target as it will hunt and surge up and down. Doug

I read in the Dometic manual that you need 50% of the gas appliances operating then set the regulator to 11"WC. When I did my testing I had 8" at the Refrigerator test port and the reefer would not cool on gas so I replaced the regulator with 1 that I could adjust at the tanks I got it set to 11"WC with all 3 burners on the stove top on max and the reefer on, now the reefer cools to 34 degrees.

You should maintain minimum of 11" wc at the inlet of the appliance gas valve with the appliance running and when it shuts off the regulator should "lock up" at no more than 120% of flow pressure. If you check after the appliance gas valve refer to manufactures specs for manifold pressure.

Low propane at furnace | Good Sam Community

Garry_Gayle
Explorer
Aug 26, 2014
I read in the Dometic manual that you need 50% of the gas appliances operating then set the regulator to 11"WC. When I did my testing I had 8" at the Refrigerator test port and the reefer would not cool on gas so I replaced the regulator with 1 that I could adjust at the tanks I got it set to 11"WC with all 3 burners on the stove top on max and the reefer on, now the reefer cools to 34 degrees.
dougrainer
Nomad
Aug 26, 2014
Static w/c should be 11.5. You should NOT see a drop below 11 inches when an appliance is running. 6 inches at the furnace is strange. Regardless, IF you have to adjust a LP regulator that has been in use for years, it is BEST to replace the LP regulator. This is because a Regulator can get a weak spring/diaphragm and you can never get the W/C to stay on target as it will hunt and surge up and down. Doug
nomad297
Explorer
Aug 26, 2014
A half-inch drop is the design.

Bruce
Golden_HVAC
Explorer
Aug 26, 2014
This is normal.

Fred.

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