Dometic DFMD30111 Furnace Won’t Stay Lit at 8200’ Elevation

[TAZ31G]

Brand new 31G purchased at end of April. We live at 8200 feet in Northwest Colorado. It still gets into the upper 30’sF at night. Got ready to take it out on maiden voyage. Running through things, I attempted to start the furnace (Dometic DFMD30111). The blower starts, hear ignition and then flame for 1-2 seconds and then goes out. Then reignites and repeats. This process continues with short burns. Other propane appliances work properly (water heater, range, propane tanks are full, no air in lines.

The furnace was running at delivery in Salt Lake City, UT.

We took the trailer to Moab, UT and was able to operate the furnace successfully (elevation ~ 4000 feet).

Our old travel trailer (2018 Coachmen Freedom Express 275 BHS) had a Dometic 30K BTU furnace (not sure which model) that we used extensively at this elevation (8200’) and higher with no issues.

I called Dometic direct and got told it might be an issue with the elevation. When I spoke to the Sales Manager at the dealership, I was told that he sold a different brand trailer to a friend and they were never able to get the furnace to work at higher elevations.

This is a major issue for me. I will be taking the trailer back to the dealer for other issues, but have already been warned that there may not be any adjustments that can be made to this furnace.

I have read about derating the furnace by putting a smaller orifice in the burner (a couple of folks talked about a “60” orifice) the furnace has a “52” in it now. Derating to a “60” also means that the furnace is really only capable of producing about 11,000 BTUs vice the rates 30,000 BTUs.

If there are other models that work at higher elevation, it seems there ought to be a better solution?

Thanks!

[howson]

TAZ31G -- Manuals available here if you haven't found them yet: https://www.dometic.com/en-us/outdoo...furnace-136631

Just one input (as there's nothing in the manual). Ask the dealer to check the LP pressure at the intake to the furnace gas valve. The furnace draws a significant amount of gas as compared to any other appliance in the RV. While everything else might run on marginal pressure, the furnace will not. Line pressure, with the furnace running, should stay around 11" W.C. ("W.C." meaning "water column", a pressure value). Pressure should not exceed 14" WC when the furnace is turned off. Your dealer should be able to do this test easily. (They'll likely want to do it at the regulator first, but don't let them declare it "good" without verifying at the gas valve input on the furnace if the primary regulator test passes.)

[TAZ31G]

Howson,

Much appreciate the response. Will definitely have them check it out.

Thanks!

[COReflection]

My propane fuel regulator pressure has had to be adjusted for altitude operations in the past on one of my other campers. My refrigerator was the affected appliance on one and then the furnace on the other. Super easy to do if you have the meter.

[Scott'n'Wendy]

Air fuel ratio is off at altitude. Previously rv fridges came with adjustable air shutters....but...no longer. Liability issues I'm guessing?
So now if the manufacturer doesn't have a solution for you.....you would have to make up your own air shutter and adjust as needed..... hint ...your burner needs a bigger access to air at altitude. Don't think any dealer would modify the air for you though.

[TAZ31G]

Thank you COReflection and Scott’n’Wendy!

[Scott'n'Wendy]

Curious though..is your fridge working normally at 8200'?

[TAZ31G]

I have a DC fridge. The stove and the water heater work fine at 8200’.