Furnace quits at high attitude (Isata 5 30FW)

[Space Cowboy]

While camping in Colorado last week I experienced the furnace stopped working.
Several times it would quit working in the middle of the night. We were at 10,000 feet 33 to 37 degrees, outside temp. I woke up to a 55 degree temp, turned furnace off, waited a minute or two, restarted furnace and it would run. Sometimes it would run till morning, 9 a.m. ish, when we would turn off furnace because it was warming up outside. One time it would not restart so we ran the generator and used the electric heat. I have not had the opportunity to try the furnace again with similar temps because it's been warm at home in Wisconsin. Question: Could the attitude have effected the furnace? Dues something need to be checked or cleaned? Thank you.

[Bill Davis]

Originally Posted by Space Cowboy

While camping in Colorado last week I experienced the furnace stopped working.
Several times it would quit working in the middle of the night. We were at 10,000 feet 33 to 37 degrees, outside temp. I woke up to a 55 degree temp, turned furnace off, waited a minute or two, restarted furnace and it would run. Sometimes it would run till morning, 9 a.m. ish, when we would turn off furnace because it was warming up outside. One time it would not restart so we ran the generator and used the electric heat. I have not had the opportunity to try the furnace again with similar temps because it's been warm at home in Wisconsin. Question: Could the attitude have effected the furnace? Dues something need to be checked or cleaned? Thank you.

The altitude definitely affects the operation of the furnace. I would call the manufacturer and ask them what to do in a high altitude situation. I’ve used mine at 6800 feet a lot and it works fine but 10,000 would be a whole different animal. I know propane efficiency degrades as altitude increases but I would suspect the problem your experiencing is lack of oxygen.

[Space Cowboy]

I will check with the manufacturer and or Dynamax. Thought I would start here in the forum. Thanks Bill!

[Rumline]

What make/model is the furnace in your unit?

I live in CO and we regularly camp around 10000 feet. We haven't had a furnace issue yet, knock on wood. It gets cold up there at night even in the summer. Our travel trailer has an 18k BTU Atwood, AFSD20111

[Bluepill]

I would think than an adjustable regulator would be an answer to high altitude performance; Set it a bit lower at altitude, then back to 11" WC below 6000 feet.

https://propanegear.com/adjustable-p...ator-0-10-psi/

[Maggiewaggie]

Be sure you have propane and not butane at cold temps and altitude.

[dbledan]

I had issues like this. I live in Ks and filled my propane before leaving. I thought it was butane/propane mix. It would sputter when the WH and furnace both kicked on and other high demand situations. A month later I had more issues in MO camping where altitude was not an issue.

For me it ended up being the regulator and a pigtail to it. The regulator was not allowing full amount of gas through. Turns out many of them let less through when on the backup tank. The one tank never would work and that took a pigtail swap to make everything right after the regulator swap...I found this out because I tried swapping the tanks and everything worked so then I swapped hoses and it did not again.

Cheapest order to check is pigtail, regulator, locally purchased propane tank...you can troubleshoot a bit as well and know if you are wasting time on the first two options by swapping things you know work.

Best of luck and let us know what you figure out.

[markb422]

Had the same thing last year at Yellowstone at about 8,000 ft. Next stop was at around 5,000 ft and the furnace worked fine.

[Larry-NC]

Originally Posted by markb422

Had the same thing last year at Yellowstone at about 8,000 ft. Next stop was at around 5,000 ft and the furnace worked fine.

The Suburban SF-series furnaces are really sensitive to propane pressure. We had a regulator that was just a bit off and it would only light with the plenum cover off (causes slightly lower fan speed). I had to build my own water column manometer to test the regulator (under $5 in parts from Lowes, and some scraps from around the house).

Replacing the regulator fixed it.

[TimVWulp]

Below is a link from the library at the top of the page. This link is a trouble shooting guide for suburban furnace.

Forest River Forums - Downloads - Furnace - Suburban Operation (Various models)

hope this helps Tim

[Space Cowboy]

Thanks for all the info. I will check on a few of the things that were mentioned.

[fstclyz]

I have a new 2020 30FW and my furnace (gas setting) is shutting off sporadically as well prior to reaching the set temp on the thermostat. I have to turn it off via the thermostat and wait a minute, then turn if back on. I,m at 5200 ft in Colorado. Maybe it's the regulator?

[Larry-NC]

Originally Posted by fstclyz

I have a new 2020 30FW and my furnace (gas setting) is shutting off sporadically as well prior to reaching the set temp on the thermostat. I have to turn it off via the thermostat and wait a minute, then turn if back on. I,m at 5200 ft in Colorado. Maybe it's the regulator?

It sounds it could be the high-limit switch. If the firebox gets too hot, it will shut the furnace down. This is caused by airflow restrictions.--either too little air through the firebox or too little air through the plenum, so the furnace gets too hot.

There are two completely independent aur circuits:

• One from the outside intake vent, through the firebox, and back through the outside exhaust vent.
• One through the grille on the front of the furnace (cold air return,), through the plenum (wrapper around the fire box), and out the heating vents.

If either is restricted, you can have this problem.

For the first case, look for the outside vent, a silver-colored plate with two round holes, one above the other. Poke around in the vents for a few inches deep and make sure the mud dauber bees have not built mud tubes inside the vent.

For the second case, make sure you have not restricted any vents. No carpets or mats on any floor vents, no restricted vents. If you have hairy dogs, take off the vent covers and furnace grille and vacuum thoroughly.

[TitanMike]

Just to toss this in the mix.

You could also have a temperature problem along with altitude.

When the temps are low propane actually "shrinks" in the tank. More remains as liquid and you don't have as much vapor as readily available. When cold you may think you've run out of Propane yet when the day warms, like magic, the tank seems more full.

To make matters worse, as you draw propane from the tank in quantities like a furnace can the temperature of the propane drops considerably below that of the outside air.

This is why tank heating blankets are often needed when camping in cold weather and propane demand is high.

[fstclyz]

Helpful stuff guys. I could be dealing with airflow restrictions given my current situation.

[fstclyz]

My furnace is still acting up and now I can't get it to light up and get warm. I was using it during the evenings and ran out of propane, so I filled the propane tank and now I can't get the pilot to light and get any heat from it. I tried turning the furnace on and off via the thermostat several times per a tech but nothing is working.

Anyone have some advise?

[AFDON]

Originally Posted by fstclyz

My furnace is still acting up and now I can't get it to light up and get warm. I was using it during the evenings and ran out of propane, so I filled the propane tank and now I can't get the pilot to light and get any heat from it. I tried turning the furnace on and off via the thermostat several times per a tech but nothing is working.

Anyone have some advise?

Have you tried to light the range? May have trapped air in the lines and need to purge them, turn on the burners and light them, keep at it until they burn with a nice steady blue flame. Then go back and try the furnace. May still take a few times for it to light. Also, first try closing your tank valves, open a range burner until that flame goes out, now go back to your tanks and open very slowly, sometime the valve will lock up inside the tank if opened fast. This is a built in safety feature in case you cut or break a propane line. Let us know what you find.

[Larry-NC]

Originally Posted by fstclyz

My furnace is still acting up and now I can't get it to light up and get warm. I was using it during the evenings and ran out of propane, so I filled the propane tank and now I can't get the pilot to light and get any heat from it. I tried turning the furnace on and off via the thermostat several times per a tech but nothing is working.

Anyone have some advise?

When you run out of propane and change tanks or fill, air gets into the lines and the furnace won't light. The easiest way to purge the lines is to light the range and run all the burners for 30-60 seconds. It may take a while for the range to light--just keep trying.

[Mr. Dan]

Originally Posted by fstclyz

My furnace is still acting up and now I can't get it to light up and get warm. I was using it during the evenings and ran out of propane, so I filled the propane tank and now I can't get the pilot to light and get any heat from it. I tried turning the furnace on and off via the thermostat several times per a tech but nothing is working.

Anyone have some advise?

Are you sure your furnace has a pilot light? Most don't... maybe none do.
You wrote "my furnace (gas setting) is shutting off". What other setting is there?

[fstclyz]

Thanks guys. I do have gas to the range and they are burning but didn't run them for longer than 15 seconds or so. I'll try your steps and see if that works.

I have turned my propane on/off switch on and off a few times. It's next to my propane filler nozzle but I didn't know I have a knob. I'll have to look for one.

I can hear the electric ignition working within the furnace and it attempts to light 3 times before quitting. Maybe I just still have air in the lines.

My electronic gauge in the multiplex showed 1/2 tank of Propane but I was OUT. I'm wondering if that's part of the problem? I didn't check the gauge on the tank until I filled it and that and the multiplex gauge showed FULL.