Why is propane igniting at air inlet in hot water combustion pipe?

[Bob K]

185RB Baja. Water heater is an Atwood 6-gallon G6A-7. Propane only.

Why is propane igniting at the air inlet on the air shutter on the burner tube? A forum search didn't turn up anyone else with this same issue.

In use, propane will sometimes ignite clear back into the burner tube at the air inlet on the air shutter. It then produces that pulse-jet engine type of combustion sound and quickly heats up the combustion tube. Combustion and a flame still exist at the outlet of the burner tube but is diminished somewhat.


Things I've done:

• Checked for air leaks in the burner tube. All screws are tight.
• Adjusted the air shutter to give the proper blue flame IAW the owner's manual.
• Adjusted the air inlet along its entire length of adjustment to see if this would impact the fuel-air mixture and prevent the early combustion. No change.
• Checked to make sure there were no excessive gaps around the air shutter.
• Check the propane orifice for blockages
• Cleaned the burner tube.
• Checked pilot tube at the compression fitting for leaks that could be causing excess propane to be sucked into the air shutter. No leaks found.
• Checked all fittings for propane leaks. None found.

This seems to be a recent thing as I came down from 7,000' elevation to sea level. That could be a coincidence or it could be a proximate cause. Not sure other than thinking about the impact of fuel-air ratio changes.

Any suggestions on what could be causing the burner to behave like this?

[Grumpy]

You've already cleaned the burner tube and that is the only thing I can think of.

[Kim Gass]

Sometimes we have the same problem It seems that that tube attracts dust and we carry canned pressurized air. Sometimes it works and sometimes swearing works.. Seems to be intermittent

[Bob K]

Originally Posted by Kim Gass

Sometimes we have the same problem It seems that that tube attracts dust and we carry canned pressurized air. Sometimes it works and sometimes swearing works.. Seems to be intermittent

It can happen anytime the thermostat cycles. What do you do? Do you go out there each time and try to stop it or do you just live with it?

Does it ever just self-correct?

[us71na]

If the flame is igniting back in the tube, it sounds like you get low gas flow at times. When this problem occurs was anything else using propane? You could have a faulty regulator, that can't keep up with demand. You could have a faulty solenoid valve that isn't opening all the way each time. You may have an overly sensitive gas flow safety device that is triggering when it shouldn't (This device is only supposed to slow the gas flow in the event of a line rupture, but sometimes you can trigger them if you open a tank valve too quickly.

[JimD]

I had the same problem with my old Lance camper's water heater. It was intermittent and made the weirdest noise when it didn't ignite properly. I ended up just replacing everything basically. The tube came with everything attached and I also replaced the jet. The parts were very cheap as I remember and they solved my problem.

Previously I had tried cleaning the tube and jet but it never helped. I think I was able to manually blow on the flame when it was coming out the wrong end and it would clear up for that burn. Seems to me I also had pilot light problems but that was a long time ago and it has since been erased my my memory cells.

If you want to try anything, replace the jet. I know there isn't much to it but it is a cheap attempt.

[Bob K]

Originally Posted by us71na

If the flame is igniting back in the tube, it sounds like you get low gas flow at times. When this problem occurs was anything else using propane?

No other uses of propane at the time, and the propane flame is of the same quantity: It's just igniting back near the air shutter. It might perform like that for a few seconds or a minute before ignition transitions-at the same volume--back to the end of the burner tube.

Propane pressure was verified back in late January. I suppose it could have changed since then but it doesn't visually appear so on any gas appliance.

You could have a faulty regulator, that can't keep up with demand. You could have a faulty solenoid valve that isn't opening all the way each time. You may have an overly sensitive gas flow safety device that is triggering when it shouldn't (This device is only supposed to slow the gas flow in the event of a line rupture, but sometimes you can trigger them if you open a tank valve too quickly.

All good ideas. Thanks. I'll watch out for them.

[Dieselman]

I was wondering if you ever resolved your problem and what the solution was. I have been experiencing the same problem with my atwood gas only hot water heater in a 264bhw.

[Jagiven]

Originally Posted by Dieselman

I was wondering if you ever resolved your problem and what the solution was. I have been experiencing the same problem with my atwood gas only hot water heater in a 264bhw.

Spiders like to setup home around propane. They appear to be attracted to propane. My experience has been spider webs/nests have been made in the flame chamber, making for a bad burn. I clean the tube, and blow a lot of air through the combustion chamber.

Sometimes I have been able to blow compressed air through the mixing chamber, to fix the problem, sometimes I have removed the air mixing chamber, and brushed it out. Do not adjust the air inlet, if you feel you need to, scribe in a witness mark so you can find home again. If I am at home, I like to use my big shop vac and blow air through the combustion chamber. I have used canned air or my small portable air compressor while at at camp.

[Dieselman]

I have cleaned the combustion chamber and burner tube, replaced e.c.o and t stat, new dino electronics board, new regulator on tanks and new gas valve in heater. I'm about at my wits end. There is still no change. All I can think is to disconnect gas line from valve and manifold and blow it out to make sure there is no restrictions.

[Dieselman]

Well I finally figured it out. The gas supply line was pinched between the bottom of the hot water heater and a wood block support that was under the back of the hot water heater. I guess they must have pinched it when trailer was built and over time the rubber line collapsed under the weight on top of it. Hopefully after re routing line this will permanently fix problem. A big thanks to all the people on this site for all the wealth of info I have been able to access.

[JFlightRisk]

Thank you so much for the update. It's good to hear when things work out, and problems get resolved. Great job!

[Bob K]

Originally Posted by Dieselman

I was wondering if you ever resolved your problem and what the solution was. I have been experiencing the same problem with my atwood gas only hot water heater in a 264bhw.

Not yet. After returning to Wyoming from Louisiana and even camping at 10,700 ft for 4 days, I haven't experienced the problem again. I'm in that horrible "cannot duplicate" period of time. No cobwebs, no spiders, no carbon buildup, etc.

Best I can tell is that perhaps my air shutter was originally adjusted for Wyoming high altitude (more air let in) so that it was running ultra lean at sea level. This caused the ignition near the air shutter which heated up the tube and resulted in the same early combustion (because of the hot tube) until I let it sit and completely cool down.

Best I can say is fuss with the air shutter to get a proper burn, and make sure it's all clean and tight. I'll check in if I find anything different.

[Bob K]

Originally Posted by Dieselman

I was wondering if you ever resolved your problem and what the solution was. I have been experiencing the same problem with my atwood gas only hot water heater in a 264bhw.

No solution and it has gotten worse. Occurs almost every time the burner ignites now. I'm going to keep looking for a solution and perhaps give Atwood a call.

[Bob K]

Here's a video showing this crazy occurrence. It only seems to occur when I go down in altitude from Wyoming. The available range of adjustment on the air shutter does not eliminate the problem. I'm going to check to see if the PO changed out the original jet for a leaner high altitude jet, if such a thing is even available.

https://youtu.be/DZOe9-sddBw

[Gfdfhjjjgddfg]

I know it's not really part of the problem, but I was wondering about how ling does a tank of propane last heating water in a Atwood water heater. I have the 185rb jayflight

[Kim Gass]

Originally Posted by Gfdfhjjjgddfg

I know it's not really part of the problem, but I was wondering about how ling does a tank of propane last heating water in a Atwood water heater. I have the 185rb jayflight

Really don't know about the water heater. We have a 195 RB and typically a 20 lbs tank will last us four weeks when we don't have to use the furnace but do have to cook and about half tie time run the fridge on propane.. The furnace is a far bigger propane eater and we can run through that in four days at freezing.

[Gfdfhjjjgddfg]

Originally Posted by Kim Gass

Really don't know about the water heater. We have a 195 RB and typically a 20 lbs tank will last us four weeks when we don't have to use the furnace but do have to cook and about half tie time run the fridge on propane.. The furnace is a far bigger propane eater and we can run through that in four days at freezing.

Thanks a lot. I've been heating the water then shutting it off. Plus I didnt kn ou w if it was safe to leave it running all day while I was gone

[VKC]

I had a dirt dauber build in the exhaust tube on a camper once that caused a similar problem.

[Bob K]

Originally Posted by VKC

I had a dirt dauber build in the exhaust tube on a camper once that caused a similar problem.

I hoped a blockage of some sort would be the problem, but everything is perfectly clear.