Strange furnace problem

[Mike Lewis]

When I had a sail switch fail it would fail intermittently at first-- sometimes the furnace would kick on, sometimes it would not. So it's still possibly a bad / dirty sail switch. Blast it with canned air. Also, high altitude would reduce the mass of air hitting the switch, which might cause it to fail. That and, um, cat hair.

When I had my first sail switch problem it was misdiagnosed as a bad furnace blower motor because the fan turned so weakly. Apparently this furnace barely works with the voltage it is supplied, and anything like a lower voltage or junk on the sail switch is enough to make it fail. I recently cut a 4x8 inch hole in the front of the compartment that holds the furnace and covered it with a grill, just to make sure the furnace fan has enough airflow to push that sail switch.

[Perry Butler]

Originally Posted by rubicon327

I'm not sure I understand this. Please explain.

There is a very slight smell of LP at the stove top when the tank is nearly empty. I've tried finding the source using a spray-on soap, but to no avail. So far it has yet to ignite and we always have the top vent cracked with the MaxxFan running. Our LP detector has never gone off and since we sometimes use a catalytic heater I test it regularly. I've given up looking for the source.

Enjoy,

Perry

[rubicon327]

Originally Posted by Perryb67

There is a very slight smell of LP at the stove top when the tank is nearly empty. I've tried finding the source using a spray-on soap, but to no avail. So far it has yet to ignite and we always have the top vent cracked with the MaxxFan running. Our LP detector has never gone off and since we sometimes use a catalytic heater I test it regularly. I've given up looking for the source.

Perry: If you have the older Atwood DV20/DV30 or the newer Suburban SDS2 they have their own regulators that have a small vent. I suspect it could be coming from there.

[davidmurphy02]

Well, I switched to my second propane tank hoping that being full it will have better pressure. The tank I had running on still had a fair amount in it, probably a gallon so not down to the last bit.

Fridge seems happy and furnace lit and ran once, won't need it until tonight so I'll find out then if this makes a difference.

I know propane appliances in general can have issues at 8000 feet, will see what happens tomorrow when we move down to a lower elevation. Does anyone know of any other possi able points of failure in the furnace ignition process? Is there an electronic spark element that could fail? If so it does not look to be accessible from the outside.

[gyuill]

I had a “cold” solder connection that was intermittent. I could bang on the front of the furnace and it would run for a while. I visually found the problem and resoldered the connection and it has been fine for a few years now. I have 40 years of experience repairing electronic devices so that helped in finding the problem.

Graham

[Effie]

Late last year I was at Convict Lake, just shy of 8,000 feet, wake up in the middle of the night with 42 degrees inside the trailer, it was 16 outside. Ran out, switched the tanks, restarted the furnace and the fridge. and went back to sleep. The next day I stopped to fill the empty tank and found that it had about a gallon in it.

[davidmurphy02]

Switching to the full tank did not help, furnace still had problems igniting last night. Each time I was able to recycle it and try again and it lit and ran, so we were warm albeit a little sleep deprived.

Considering that my fridge also faltered once I am attributing this to high altitude and possibly an adjustment needed to the pressure regulator to bump up pressure a bit...will try to read up on that and search the forum later today after we travel back to Torrey.

Anyone happen to have handy a link or guidance regarding that adjustment screw on the regulator?

[Gasguy]

Typically propane tank regulators are fixed adjustment. If they can be adjusted, remove the threaded cap on the regulator body & turn adjustment clockwise to increase pressure. The size of the orifice on the burner manifold determines the amount of fuel that will flow to the appliance. There is also a orifice inside the regulator body. Everything is sized for the atmospheric pressure & altitude the manufacturing company determined the appliances will operate at.
If you do crank it up to get more fuel pressure count the turns & set it back to pre adjustment when you get to your normal operation altitude. Leaving the appliances in a over-fired condition can cause flame impingement, carbon monoxide conditions & premature failure. A manometer should be used to check the pressure if you suspect faulty regulator.
Should note as well the pressure could need to be adjusted down a bit to compensate for lower oxygen available at altitude causing to rich a fuel mixture.

[davidmurphy02]

Many thanks, gasguy!

[rubicon327]

Originally Posted by davidmurphy02

Considering that my fridge also faltered once I am attributing this to high altitude and possibly an adjustment needed to the pressure regulator to bump up pressure a bit...

Originally Posted by Gasguy

Should note as well the pressure could need to be adjusted down a bit to compensate for lower oxygen available at altitude causing to rich a fuel mixture.

I don't think you would be going up in pressure. As Gasguy indicates if you are at altitude you would more than likely need to reduce the pressure to compensate for the thinner air and propensity to run rich. This would be counter-clockwise on the regulator. If you have the propane quick-connect it would be best to attach a pressure gauge there and then you know exactly where your adjustments landed you and you can conveniently check your propane pressure at any time for future troubleshooting. From my limited experience adjusting regulators you really need to be reading the output pressure as you have no idea as to the effect of your adjustment otherwise. The pressure could change quickly with very little movement of the dial.

[davidmurphy02]

Thanks guys, that all makes sense. I don't have the external propane connection so no easy way to measure. Hopefully when we are back down in altitude tonight things will work normally again. If we wind up going to a high altitude again on this trip, this will give me something to try if needed.

[Tin]

Camping at Altitude
There are three major factors that affect propane appliances at altitude
• Altitude ( decrease in oxygen )
• Temperature
• Wind
Propane appliances are dependent on air/fuel ratio to function. Since there is less oxygen at higher elevations, appliances require less fuel (propane). In the past manufactures provided smaller orifices designed for use at high altitude to decrease the amount fuel (propane) and correct the air/fuel ratio.
From our experience the two main appliances affected are the fridge and water heater. In order to adjust the air/fuel ratio at altitude I use a manometer and adjust the propane regulator (clockwise to increase) to 12"w.c., I then mark the outside edge of the regulator to indicate the position of the adjustment screw. Next I adjust the propane regulator (counter clockwise to decrease) to 10"w.c., and again mark the outside edge of the regulator to indicate the position of the adjustment screw.
From our experience at 8,000 to 10,000 ft elevations the propane regulator set between 10" to 10.5 w.c. seems to work best. At lower elevations 12"w.c. works great, ultimately you will find what works best for you.
On the fridge I will also adjust the sheet metal wind guard to allow more air in for combustion.
On the water heater the electrode gap sometimes needs minor adjustments.


David I use the stove for measurement and adjustment, works good and easy.
Good Luck.

https://www.youtube.com/watch?v=X0dSSfSIayg

[davidmurphy02]

Thanks all of you for the education, I feel like I have a much better understanding now. Another thing we experienced at altitude was the exhaust from the hot water heater had a strong odor, no doubt from too rich a mixture. We may not be at such a high altitude again this trip so I am hands off for now. We are stopped for lunch at 9000 feet and the furnace is doing fine, no doubt because it is 50 instead of 25. We did have our most pronounced furnace issues in the wee hours when the temps were the lowest.

[Merlin]

David, some of your descriptions sound like a lock out condition. Heater not starting until after waiting a few minutes sound like a problem I had with a RPod heater. Other things I recall were: high altitude, cold temps, waking up in the middle of the night to a cold camper, not much sleep . The fridge was not running 100% as well.



I was able to view lights on the control board indicating a lock out. In my case the heater was getting too hot. And, the problem was not present during the warmer day time hours. Also, went away at 7000ft when we returned home.



I seem to be thinking you added a screen to your heater cover ? I don't know why, maybe someone else added a screen


Anyway, maybe try opening the doors below the fridge overnight when you camp up in the clouds. The space is open between the cabinets so it may get some additional air circulation for trouble shooting.


So, there's another 2cent opinion to think about...

[davidmurphy02]

Back down at lower altitude and the furnace ran fine all night. At 8000 feet the fridge, water heater and furnace all showed effects so I'm sure it was the altitude. In a few weeks we will be at 8100 feet for 4 days at Great Sand Dunes NP so I will get a chance to apply all of the knowledge and tips from you all, I will let you know how it goes.

The aftermarket furnace control board (not Dinosaur, this one is Fenwal) came with a good explanation of its operation. When the thermostat calls for heat the blower turns on. After about 12 seconds if the sail switch signals good air flow there is an audible click and the burner tries to ignite, another little click. If the burner ignites all is well. If not, another audible click as it turns off the gas (the blower continues running). In several seconds it repeats the ignition cycle. It will make 3 ignition attempts, if all fail it shuts down and locks. Then you have to turn the furnace off at the thermostat and back on to clear the lockout.

After several nights of this, in a quiet trailer in the still of night I am now very familiar with the sound and timing of each little click. Every time the furnace started up I'd be on pins and needles waiting to see if it was going to light or if I'd have to get up and reboot it to try again. But I was always able to eventually get it lit and we had heat through the night. Great Sand Dunes here we come!

[ksitte]

Sorry about your problems with your furnace, David. Nevertheless, this thread you started has been amazingly enlightening for us simpletons who need help understanding propane troubleshooting. Thanks much, all of you.



ksitte

[davidmurphy02]

One quick question regarding the propane regulator adjustment. I removed the threaded plastic cap expecting to find a metal screw head for adjustment. Looks like a black plastic insert with a hole in the center and a slit for a large flat blade screwdriver to turn it...is that the adjustment fitting? If we have trouble at altitude again this trip I would probably try adjusting the pressure down, counterclockwise slightly...maybe 1/8 of a turn, how does that sound?

[fudge_brownie]

That sounds pretty close. Up to a 1/4 turn. There is a port on the regulator for connecting a manometer, I was always connected to the manometer when at 9,000 feet so I could always read the column inches. Then make quick adjustments.

I think I paid a bit over 42$ for a digital manometer.

Counterclockwise is correct for altitude, thus lower column inches. The issue is there are a number of other variables in the mix. The quality/accuracy of the propane regulator, the quality of the propane and the willingness of the appliance to perform at altitude.

Sometimes it is out of your control.

[cpaharley2008]

I would not adjust the pressure without a ways to recheck it afterwards.

[Gasguy]

I would think you would be safe with that. Mark the preadjusted position with a sharpie & a picture for reference. If you started with 1/4 turn increments.