Propane dancing manometer

[Deleted User]

I recently converted a used (customer purchase) furnace and converted it to propane. The propane came to make the fuel connections and fire it up. They placed a manometer on the test port and they read a 3" WC when fired, then 3-4 seconds later it jumps to 13" of water and run fine. Then without reason it jumps back to 3" of WC and the flame travels back to the manifold orfices. Any suggestions?

Al Letellier

dancing pressures

I think I would start at the regulator. Check your pressures before the gas valve and at the manifold. It the pressure in the piping is bouncing, it's at the regulator. IF at the manifold, but not the piping side, suspect a bad gas valve.

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Dale

Factory conversion kit

My feeling is that the valve is bad, however I would first lower the LP regulator to 11 inches at the furnace inlet. Did you use the factory conversion kit on the valve? With the kit the regulator on the valve should jam open and you get manifold what ever the LP inlet pressure is. I wonder if your gas valve was a step open model? Would also put a volt meter on the valve to see if it stays at 24V. The other post is correct of course in having a gauge at the valve inlet and manifold at the same time. Sometimes a valve that is in a flood act funny like this, let us know what you find out

Larry_7

Check upstream

to see if second stage reg is delivering the correct press to the furn. The reg may be pulsating (hunting) and you are seeing the results at the furn. Whats the connected load, reg model, and is piping sized properly?

Larry

Steve Whitbeck

gas pressure

Steve Whitbeck

gas pressure

If the incoming gas pressure is more than 14 inches WC the gas valve will act up and it may not even open at all.
If you want 11 inches manifold pressure then set the incoming gas pressure at 12 to 12 1/2 inches maximum.
Then set the manifold pressure at 11.