Gas pressure problems


 
Erick Graham said:
The burners are original as far as I know. I sanded the exterior of the tubes than blew them out thoroughly with air.
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Sanding things with fine orifices is not a good way to do it. Wire brushing is preferrable. Sanding can force invisible debris into the orifices and contribute to just what you're seeing
 
LMichaels said:
Sanding things with fine orifices is not a good way to do it. Wire brushing is preferrable. Sanding can force invisible debris into the orifices and contribute to just what you're seeing
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I'm now getting back to trying to fix this grill after taking some time off from it. I did check all the burner tubes for any debris and made sure they were clean and clear. When I sanded them I had them out of the grill so no debris got into the orifices but I checked and cleaned them as well.

Which brings me to where I am now. I took the manifold out to check the lp pressure at the orifices. I found with only one valve open there was 11" wc of pressure but when opening a second valve the pressure dropped to 5" and dropped lower with the third valve open. I have done everything recommended to avoid going into bypass mode, used different lp tanks and checked for leaks with an electronic leak detector and found none. My next step was a new regulator where I have received the same results.

This would suggest the valves/manifold are the problem. I did take apart and clean the valves a second time and could not find anything wrong. I am wondering is there any fix or something I am overlooking before ordering a new manifold?

Thanks to everyone for all the help and suggestions so far!
 
Can you describe where and how you are measuring the gas pressure?

Edit: I'm just seeking to understand.
 
DanHoo said:
Can you describe where and how you are measuring the gas pressure?

Edit: I'm just seeking to understand.
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I took the manifold out of the grill than I used a pressure gauge with a rubber tube and nozzle pressed directly over the end of the orifice. The rubber sealed well enough if held steady over the orifice opening.
 
Erick Graham said:
I took the manifold out of the grill than I used a pressure gauge with a rubber tube and nozzle pressed directly over the end of the orifice. The rubber sealed well enough if held steady over the orifice opening.
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So downstream of the valve. Got it.

I would expect a larger pressure drop with more valves open as the larger pressure differential will lead to more flow.

Can you measure pressure upstream of the valves with one, two or three valves open?
 
I did not mean the metering orifices I meant the little "holes" cut or drilled into the burner tubes. To measure gas pressure, is easy. Put the manometer on the valve end (where the main metering orifice is), set it wide open. Read pressure. I SEROUSLY doubt you're having pressure issues though. You would have troubles elsewhere. Your furnace, gas stove, water heater, dryer, etc.
 
LMichaels said:
I did not mean the metering orifices I meant the little "holes" cut or drilled into the burner tubes. To measure gas pressure, is easy. Put the manometer on the valve end (where the main metering orifice is), set it wide open. Read pressure. I SEROUSLY doubt you're having pressure issues though. You would have troubles elsewhere. Your furnace, gas stove, water heater, dryer, etc.
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I think you need more coffee.
His grill is LP…
 
And in any case how to measure the pressure doesn't change. Simply a different fuel. So instead of looking for about 7"WC you look for 11"WC. Give or take a little. And what I indicated about "sanding" the burners still goes as well. I know because I once figured I'd outsmart myself and make cleaning up the burner ports "easy" and used a flap disc which instead made a bigger mess to clean
 
I don't know for sure, however I do not think measuring pressure on the down-stream side of the orifice is the way to test it.

I think the test should be upstream of the valves or in other words between the valve and the regulator.
 
If everything is working correctly it should be very close throughout the system. If a problem you then "work back" from there. At least how my friend showed me. Actual licensed fitter. I never had an issue doing it either. Of course could just check with a match :D
 
One thing to keep in mind is that flow runs counter to pressure. To have maximum pressure, you have minimal flow, and to have maximum flow, you have minimal pressure. On the surface, you seem to be flowing so much propane that you have a drop in pressure, which should not happen.

According to Google's generative AI, the flow rate of a Type 698 propane regulator is typically 250,000 BTU/hour. That's way more than your grill is rated for (32,000 btu/hr). With all burners open, you should still have the nominal 11" W.C. pressure on the supply side. It appears that you have a supply-side problem.

I think all of us are saying the same thing here. All 3 valves open should not cause a significant pressure drop, and if it does, your problem is supply-side, between the tank and the valves.
 
This makes me think back to that issue with a side burner not getting gas a while back, where the gas inlet was packed tight with dirt by ants? Could there be a similar situation?

That’s about all I can add to this conversation as there’s way more knowledge about propane and flow from others.
 
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