Manometer

[Kingfish]

For me better is consistently colder. Yes, I used a simple water column tube manometer. So at higher altitudes would one increase, or decrease, WCI pressure to maximize performance?

Also at 9,000 ft. the stove has a delay in lighting, and when it does light there is a whoosh.

[MVA]

Thanks for clarifying. I was concerned that you may be using an inexpressive manometer from Amazon; I don't have a lot of faith in their calibration. I also use a U-tube manometer. Gravitation constant of the earth is constant!

At higher altitude, the air pressure is less. AT 9000' (wow!) is 10.5 psi; sea level is 14.7 psi. Hence you are at 10.5/14.7 = 71% of sea level oxygen content. I would have expected your appliance to be running too rich with that loss of oxygen. There are a couple of competition issues. If you decrease the propane pressure to 11 w.c., then the lower propane pressure at the lower air pressure would have a better air:fuel ratio. The observed cooktop lighting (woosh!) indicates that the lower oxygen content is affecting the lighting of the appliance. I would be careful that some appliance may not light correctly causing a buildup of propane prior to igniting.

[SRS]

Could be wrong but I believe there is a diaphragm in the propane regulator to compensate for changes in air pressure. Daren of My RV Works has a YouTube that explains this. After adjusting the propane pressure on my trailer to 12 WC, I've had no problems with gas appliances up to 10,000 ft. elevation. YMMV

[MVA]

That is correct (the diaphragm). The adjustment screw increases/decreases the spring tension against the diaphragm thereby adjusting the relative pressure (i.e. psig or psi gauge) needed to allow gas to pass through the regulator. Hence, in your case it will be 12 inches w.c. (0.433 psi) pressure on the downside of the regulator regardless of atmospheric pressure (within reason).

As altitude increases, a significant concern is lack of oxygen to support combustion. Too low and a dangerous condition can occur where propane is released and the combustion cannot occur readily enough resulting in a hazardous situation.

[SRS]

Originally Posted by MVA

As altitude increases, a significant concern is lack of oxygen to support combustion. Too low and a dangerous condition can occur where propane is released and the combustion cannot occur readily enough resulting in a hazardous situation.

That would be the case as well for lower elevations where the fuel / air mixture also changes. But I'm not sure why you consider increased elevation to be more dangerous? Both my furnace and frig will not function and turn off the fuel supply if the appliance fails to light no mater what elevation I'm at. The reason I had frig problems, where it would not light or stay on, is because my regulator was set to 14 WC. Bringing it to 12 WC solved the problem. Any RV'er should keep an eye on whats going on when any gas appliance is running. I know lots of people run their frigs on propane when towing but I don't for the very reason there's flammable gas I can't keep an eye on.

So, I'm not trying to be contrary or combative, I just don't understand this particular concern regarding extreme elevation changes once WC is properly set. Admittedly, I may be missing something.

[MVA]

Fair and good points. I will try to clarify my concerns. If you are running rich, sooting up is a concern. For the cooktop, there is no thermistor control circuit to turn off the gas supply; hopefully the cooktop is used while being observed. Of course running rich can also evolve CO (carbon monoxide).

If one tries to compensate the rich air:fuel ratio by decreasing the w.c. pressure too low, then the flow rate at the orifice on the gas appliance will be less resulting in the flame front moving towards the orifice and away from the design location. So I would not decrease the pressure lower than what the appliance manufacturer spec requirement is.

Your observation on your replacement regulator pressure is consistant with a conversation I had with a Marshall Excelsior engineer. He told me that the regulators are all shipped at a set point of 13-14 w.c. When I picked up my trailer, the refrigerator would not stay lit; the flame kept blowing out. When I measured the regulator outlet pressure, it was 13" w.c. ; adjusted it to 11 w.c. has been fine.

I would adjust the pressure based on the appliance manufacturer specs. Given the change in what ETI has used over the years, that requirement may vary. High altitude can cause difficulty in maintaining complete and safe combustion. We learned that lesson when picking out appliances for our home at 7000'.

[Ron in BC]

Originally Posted by SRS

Both my furnace and frig will not function and turn off the fuel supply if the appliance fails to light no mater what elevation I'm at.

I know lots of people run their frigs on propane when towing but I don't for the very reason there's flammable gas I can't keep an eye on.

Don't those two statements contradict each other?

I can't keep my eye on my gas furnace at home when I'm away for weeks. I guess it's all about comfort level using the fridge on propane when towing. But given the huge amount of miles that folks have towed using propane without any incident it's not on my radar.

Ron

[SRS]

Originally Posted by Ron in BC

Don't those two statements contradict each other?

I can't keep my eye on my gas furnace at home when I'm away for weeks. I guess it's all about comfort level using the fridge on propane when towing. But given the huge amount of miles that folks have towed using propane without any incident it's not on my radar.

Ron

Thanks Ron for you comment. I actually don't think they conflict in that trailers are a rolling earthquake as someone, maybe you, have said many times. Many things can go wrong while towing and I've seen RV's with frig fires rolling down the road. Camped I can check things out when I turn them on or switch to propane.



True, one can't watch their home water heater or furnace while away and I guess that's the risk of travel. Can't control everything in life. I do agree that towing with the frig on propane or DC is a choice each of us have to make.

[SRS]

Originally Posted by MVA

Your observation on your replacement regulator pressure is consistant with a conversation I had with a Marshall Excelsior engineer. He told me that the regulators are all shipped at a set point of 13-14 w.c. When I picked up my trailer, the refrigerator would not stay lit; the flame kept blowing out. When I measured the regulator outlet pressure, it was 13" w.c. ; adjusted it to 11 w.c. has been fine.

That explains why the Marshall Excelsior regulator pressure was so high when I replaced the Camco, OEM regulator that came with my E17. I'd carried it as a spare in my previous trailer for a couple of years so I figured it maybe got knocked around a little.

[77FJ40]

I'd like to purchase a simple but reliable manometer for diagnosing possible problems. What do you guys use/recomend?

[MVA]

You have options:
- An electric or dial pressure meter. Small and compact, but IMO concerns with calibration. Was it calibrated correctly in manufacture, and is it still calibrated correctly as years of use? How would you know?
- Build you own. A simple U-tube manometer is larger and clunkier, but always calibrated; gravitational acceleration of earth is a constant!

No recommendation on the first option. I built the second option with materials I had around the house. Works fine.

[Ron in BC]

Originally Posted by 77FJ40

I'd like to purchase a simple but reliable manometer for diagnosing possible problems. What do you guys use/recomend?

I find it handy to have a manometer with me, ready to use.

This one was inexpensive and seems to give good results, I've been using it for several years. Out of curiosity I hooked up a manifold vacuum gage and the results were pretty close. I don't think that precision to the second digit is critical.

Ron