Furnace won't light when at higher elevation.

[SteamboatSailor]

Hi, all;
We're having a problem with our 2018 RW 427 Suburban furnace. We picked the new coach up from the dealer in Ohio 5/02/17, spent two weeks in it in Ohio & OK with furnace working fine.The weather was rainy & cold, so we used the furnace constantly the first week, & intermittently the second. When we arrived back in Steamboat Springs, elevation approx. 6,000 ft, the furnace would not light. Full propane bottles, furnace would go through the start cycle, I could smell propane at the exhaust when it would try to light, could hear the clicking of the electrode trying to spark the propane, then it would do the "3 strikes & you're out" system lockout. Tried numerous times over a 2 week period with no success.
We loaded up, headed to Goshen for the rally, then called Heartland service. Robert Miller in service suggested we try the furnace here. I did, it fired right up & works fine. Robert is contacting Suburban to see if they have any suggestions, but I've found that many times owners on the forum have at least as much knowledge as the techs.
Anyone have any suggestions?

 

[danemayer]

Check the vents on the outside of the furnace for debris or insects. Also make sure there is nothing blocking any ducts or the air return inside the coach.

The failure to get flame when the air is thinner might be aggravated by restricted air flow in one of these areas. Btw, our furnace operates just fine at 9,200 feet, or at sea level.

 

[jleavitt11]

I had the same problem in my Cyclone. I called and talked to the service rep at the dealer and he told me sometimes at higher elavations the LPG regulator needs to have the pressure setting lowered. At higher elavations the pressure increases and the gas itself actually blowes the flame out while its trying to light. He explained a way to adjust it without a manometer. Im not going out again until next weekend so I dont know if it has solved the problem. It is something to check into.

 

[danemayer]

I had the same problem in my Cyclone. I called and talked to the service rep at the dealer and he told me sometimes at higher elavations the LPG regulator needs to have the pressure setting lowered. At higher elavations the pressure increases and the gas itself actually blowes the flame out while its trying to light. He explained a way to adjust it without a manometer. Im not going out again until next weekend so I dont know if it has solved the problem. It is something to check into.

I don't think you want a solution that requires adjusting the regulators when you change locations. Even if it gets you working, it's probably not the real fix, but may just be masking the real problem. We spend a lot of time at 9,200 ft. along with 180 other RVs. Never heard of anyone having to adjust a regulator to get the furnace working.

Also, some regulators may not be designed to be adjustable.

And of course, care is required when working on the propane system because a mistake can be catastrophic.

 

[jleavitt11]

Just to clarify the option was not to adjust the regulator everytime you move. Just once to lower the pressure so it will work everywhere you go.

 

[SteamboatSailor]

I don't think you want a solution that requires adjusting the regulators when you change locations. Even if it gets you working, it's probably not the real fix, but may just be masking the real problem. We spend a lot of time at 9,200 ft. along with 180 other RVs. Never heard of anyone having to adjust a regulator to get the furnace working.

Also, some regulators may not be designed to be adjustable.

And of course, care is required when working on the propane system because a mistake can be catastrophic.

Thanks much for the input. I just got off the phone with Robert Miller in HL service; he contacted Suburban yesterday & Suburban said they don't guarantee their furnaces to work at an elevation higher than 4200'........SAY WHAT??? Suburban suggested changing the orifice size every time we change elevations, & of course they HIGHLY recommend the work be done by a certified tech.

Dan, I'm curious what brand of furnace you have? When in Steamboat as part of my diagnosis I went through & checked all vents & intakes....clear. I'll go through again & make sure I didn't miss any.

The regulator adjustment for different elevations doesn't make sense.....that's a very precise adjustment necessary with, as you say, potentially catastrophic consequences. Besides the fact that that's the whole reason for a regulator....to automatically maintain 11 in. Water column of pressure (.6psi if I remember correctly?).

 

[JohnD]

Not sure why you are having that issue . . .

Like Dan, we are in Colorado and camp in the mountains several times a year and have not had a problem like this at high altitude.

We live just north of Denver and the elevation in our driveway (just checked my Rand McNally GPS in the car) is 5308 feet above sea level.

We did have an issue where the furnace in our Prowler wouldn't light up but turned out to be a loose wire on the circuit board.

 

[danemayer]

Thanks much for the input. I just got off the phone with Robert Miller in HL service; he contacted Suburban yesterday & Suburban said they don't guarantee their furnaces to work at an elevation higher than 4200'........SAY WHAT??? Suburban suggested changing the orifice size every time we change elevations, & of course they HIGHLY recommend the work be done by a certified tech.

Dan, I'm curious what brand of furnace you have? When in Steamboat as part of my diagnosis I went through & checked all vents & intakes....clear. I'll go through again & make sure I didn't miss any.

The regulator adjustment for different elevations doesn't make sense.....that's a very precise adjustment necessary with, as you say, potentially catastrophic consequences. Besides the fact that that's the whole reason for a regulator....to automatically maintain 11 in. Water column of pressure (.6psi if I remember correctly?).

We have a Suburban SF4200.

11" of water column pressure is nominal. I think the furnace may work as low as 9 or 9.5. If you're paying for service on a problem like this, the servicer should be using a manometer to establish that you have adequate propane flow at the furnace service port. A lot of techs like to guess their way through problems. Measuring is better.

Over the years I have had problems with regulators, and with oil buildup in the flex tubing coming out of the dual regulator. In my case, the oil restricted propane flow enough to make the generator operation marginal, but the furnace worked ok. In the course of trying to figure out the problem, I had to disconnect that hose and found the problem.

Regulators and pigtails can also become clogged, resulting in poor propane flow.

The gas valves on the furnace are very reliable, but that's another possible trouble spot. The ignition gap and position are another possibility.

If something is slightly off, it may be enough to cause your altitude problem.

The flame sensor, which I think is part of the igniter, could also be a problem. If someone else operates the thermostat while you observe the furnace, you may be able to tell if the igniter is getting you a flame. If you have a flame, but it doesn't keep going, the signal from the flame sensor may not be getting to the circuit board to signal that it's ok to keep the gas valve open.

I'm not sure how much of this you can investigate yourself. If you have the correct teflon tape for the fittings, you can check the hoses. And pigtails are cheap and easy to change.

As for the 4200 ft answer from Suburban, you might ask your Customer Service Rep whether trailers shipped to Denver get that different orifice. Denver is at 5200 ft. Unfortunately, that's Suburban dodging and weaving.

 

[SteamboatSailor]

Not sure why you are having that issue . . .

Like Dan, we are in Colorado and camp in the mountains several times a year and have not had a problem like this at high altitude.

We live just north of Denver and the elevation in our driveway (just checked my Rand McNally GPS in the car) is 5308 feet above sea level.

We did have an issue where the furnace in our Prowler wouldn't light up but turned out to be a loose wire on the circuit board.

I'll check for a loose wire, but it's interesting that the furnace fires fine here at the rally. I would think a loose wire would make the furnace not light at any elevation, no? What brand of furnace do you have?

 

[JohnD]

Ours is a Suburban . . . not sure of the model number.

 

[wdk450]

You might want to carry an electric space heater as a back-up heat source, but this will only be practical where you have a shore power hookup.

 

[SteamboatSailor]

We have a Suburban SF4200.

11" of water column pressure is nominal. I think the furnace may work as low as 9 or 9.5. If you're paying for service on a problem like this, the servicer should be using a manometer to establish that you have adequate propane flow at the furnace service port. A lot of techs like to guess their way through problems. Measuring is better.

Over the years I have had problems with regulators, and with oil buildup in the flex tubing coming out of the dual regulator. In my case, the oil restricted propane flow enough to make the generator operation marginal, but the furnace worked ok. In the course of trying to figure out the problem, I had to disconnect that hose and found the problem.

Regulators and pigtails can also become clogged, resulting in poor propane flow.

The gas valves on the furnace are very reliable, but that's another possible trouble spot. The ignition gap and position are another possibility.

If something is slightly off, it may be enough to cause your altitude problem.

The flame sensor, which I think is part of the igniter, could also be a problem. If someone else operates the thermostat while you observe the furnace, you may be able to tell if the igniter is getting you a flame. If you have a flame, but it doesn't keep going, the signal from the flame sensor may not be getting to the circuit board to signal that it's ok to keep the gas valve open.

I'm not sure how much of this you can investigate yourself. If you have the correct teflon tape for the fittings, you can check the hoses. And pigtails are cheap and easy to change.

As for the 4200 ft answer from Suburban, you might ask your Customer Service Rep whether trailers shipped to Denver get that different orifice. Denver is at 5200 ft. Unfortunately, that's Suburban dodging and weaving.

I would hope that on a rig & components that are less than 60 days old clogged lines/regulators would not be an issue..?? Also, when diagnosing the problem in Steamboat doing the "sniff" test at the furnace exhaust as the furnace was trying to start up I could smell propane coming out the exhaust after the furnace had finished it's initial cycle of clearing the combustion chamber. I thought of the improper gap at the igniter as I could hear the igniter clicking with no resulting fire up, but on the the Suburban (on mine at least) the igniter is buried inside the furnace & apparently requires pulling the guts out of the furnace to access it. Is that how your SF4200 is? I'm not sure which model mine is.....failed to look at the label when i had the exhaust grill off in Steamboat. I'll see if my manual says, but it seems like the manual covered several model #s.

You might want to carry an electric space heater as a back-up heat source, but this will only be practical where you have a shore power hookup.

We do have the back up electric, as well as the electric fireplace. But it's a PITA, as well as annoying to the neighbors, to have to run the generator to stay warm when not on shore power.

 

[TedS]

My furnace lights at 7500 ft elevation.

 

[SteamboatSailor]

My furnace lights at 7500 ft elevation.

My Heartland Service Rep has suggested I ask Heartland owners what experience they are having with their furnaces. Guess I have my answer to that.


I just turned the furnace on to make sure it's still working. It fired up fine, however as it runs I hear a high pitched whine or ringing while it's running. According to what I learned earlier this week in the RV Academy class that's possibly a bad control board. The ringing is loud enough that I can hear it inside the coach. When I turned the furnace off, just as it was shutting down the ringing got very loud....I suspect you could have heard it from 50' away. Anyone have suggestions?

 

[Lynn1130]

4200 ft

Nah something is wrong with that answer. Mine is Suburban also and there has never been an issue at our regular camps at or above 8000 ft.

 

[danemayer]

I've seen one service guide that says a symptom of too much primary air will be a howling or screeching noise when the burner is on.

A bad air/propane mix might react differently at different altitudes. But If you have too much air, I would think in thinner air it might do better. So it's not intuitive.

I'm not sure this is something that a user can adjust.

 

[jayc]

When we had a house we lived about 25 miles inland from the Gulf of Mexico or just a few feet above sea level. We spent a good amount of time in the mountains of Colorado and other mountainous states and never had to reset anything on our Suburban furnace.

Good luck in finding the real problem.

 

[awfinney]

My suburban furnace also would not light at higher elevations but worked just fine at lower ( -3000') elev. Had it into dealer four times for this problem and it always would light for them. They did replace the regulators but that didn't help. By accident, I noticed that the hose on the driver side, past the change over valve, that feeds everything was pinched between the propane tank and the strap. I rerouted the hose outside the strap and now he furnace will light. Just my experience. Good luck.


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[TravelTiger]

We've not had problems taking our previous rig to Durango, elevation 6500+ feet, and Breckenridge, 9600 feet.


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[wdk450]

SteamboatSailor:
I did a websearch on your problem, and saw some interesting responses (with stuff I hadn't heard before) including response #3 about butane being mixed in the propane, which seemed to possibly match your problem. Check it out: http://www.rvforum.net/SMF_forum/index.php?topic=23694.0

Another forum mentioned the airflow detector sail switch possibly not being tripped due to the thinner air. I think sail switch problems are a very common cause of Suburban furnace problems. http://www.forestriverforums.com/forums/f113/suburban-furnace-at-high-altitude-60240.html

I found this concise description of the operation of the furnace in the RVMechanic.com website: "The operation of the furnace is as follows: Thermostat calls for heat, 12 vdc is sent to the control board, the blower motor RUNS (going through a 1 min. purge cycle), during the airflow purge air passes the sail switch, which is in series with the overtemp switch (the overtemp switch OPENS on overtemperature) (both switches have to close to allow the control board to energize-open the gas valves), 1 second after the gas valves open to allow gas to flow, the high voltage ignition circuit fires, and you have heat... " I would think that some sort of flame detect safety switch would also be involved so that gas doesn't flow with no flame present.