Water Heater fire (brief but scary)

[SteveSgt]

This morning, while out for a week on the Central California coast, we fired up the gas burner in our (previously) trusty Suburban gas/electric water heater, and we instantly smelled smoke. Upon inspection, we saw soot on the side of the trailer and burns on the inside of the cover piece. Obviously, we shut it down quickly.

Have any of you had similar experiences?

The Suburban manual is pretty terse and not very informative on the maintenance of the unit. It's possible that I neglected something that's not very well explained. It's possible that foreign substances invaded the burner chamber (such as insects). But at this point I'm guessing parts may need to be replaced.

Lesson to remember: Things that have fire in them need to be maintained more than we might think.

 

[hugh]

Wow, that's scary. I'm glad you caught it early and everything was ok!

I'm wondering if you have a clogged venturi tube.

 

[edlynnrich]

There may have been something in the burner tube that caught fire (such as a wasp nest) when you started your water heater. Remove the burner tube cover and take a good look. If you do find foreign material in there clean consider getting an insect screen for the vent in the access door if you don’t already have one.

 

[SteveSgt]

I'm wondering if you have a clogged venturi tube.

I just went and took a look at that. The venturi tube looked quite clean inside. The burn chamber itself is rather rusty.

The burn chamber had a bit of flakey ash in the bottom. It doesn't look like it could have been the remnants of anything big enough for this fire.

I think I'll get someone with more training and experience to look at it. While I understand the mechanics and basic physics of it, I'm not ready to play with fire.

 

[Mike Lewis]

You can blow out this area with canned air. But beware-- canned air is flammable, as I discovered, so make sure the burner is off first. FOOM!

 

[Mike Lewis]

In the 12 years including 2025 that I've used my trailer, I have spent over 1,000 nights in it. I've used the water heater every morning. The only maintenance I've done to it is occasionally blow out the burner area with compressed air, flush out the tank with a wand made for that purpose, and replace the anode when necessary.

At what point should I consider replacing the water heater just due to its age and wear? Should I be having other maintenance performed on it?

 

[Dplandry]

I had a similar experience and it turned out to be a mud dubber had stopped up the burner tube. The mud was at the far end of the tube. I could not see it until I removed the tube. I have added an insect screen since. Thankfully you caught it in time!

 

[Thrak]

That looks nasty. I considered getting insect screens and then inspected several ports and found no insects. Perhaps I will revisit the idea of adding screens.

 

[CharlesinGA]

On RVForum I posted a resources file on bug screens. You log in with the same log in you use here, they are both RVLife forums. When you get to that resource, click the red download button and its a PDF file. I don't have anything on the Suburban WH however what I did for the Atwood would work on the Suburban. I didn't use the external store bought screen, but rather used #8 woven stainless wire mesh, which is what the bug screen makers use. (eight opening per inch, minus the thickness of the wire.)

Charles

 

[brroberts]

Nice write up. This is the first RV I haven’t screened. The fridge works pretty hard and the furnace needs all the free flow in and out it can get. The WH works better at higher elevation with the door open. I’ve been hesitant to screen things out of concern the slight airflow reductions might be the tipping point for problems. Of course not screening can also have consequences. So far I’ve only fought mud daubers and wasps in the A/C.

 

[SteveSgt]

I considered getting insect screens and then inspected several ports and found no insects.

While I will probably also do this, it may not have prevented my fire. After talking to a service technician for Suburban water heaters, there are several possibilities that I cannot rule out based on what happened:

1. Low propane pressure due to a flakey regulator (which could have caused a big gas build-up before ignition).
2. Contamination in the propane tank, causing a slow and incomplete burn. (I guess it could happen to any of us.)
3. Hydrogen venting from the pressure release valve (possible but extremely rare).
4. And what we've been discussing: Foreign materials or blockage in the venturi tube or combustion chamber.

A closer inspection inside the water heater makes it clear to me that it got quite hot all through the area behind the hinged cover. Insulation on the DC wires near the gas valve look to have softened and melted, but they did not burn--there is no bare wire exposed. The rubber cover over the two reset buttons seems dried and cracked. The caulk around the outside edge of the water heater, where it meets the fiberglass, has burned or melted away where it would have been under the hinged cover. The majority of the soot seems to be on the exhaust output of the burn chamber, but there's a little bit above the carburation openings in the venturi tube. There is some kind of melted clear plastic at the bottom, below the venturi tube that I don't remember seeing before.

This is an early 2023 Escape, so it's not that old. I used the gas burner the two previous mornings, so if some wildlife obstructed the combustion chamber they would have only had the overnight to move in.

My investigation will continue until I can take it into an authorized servicer for the Suburban water heater.

 

[Kingfisher]

How many times does the igniter click before the burner ignites? My brand new water heater would click eight times or more and then ignite with a loud “whoosh”. Or not ignite at all. Or the “whoosh” would blow out the flame. I would often get the fault light, so I’d turn it off and on, then try again. The “whoosh” was from lots of propane getting ignited late.

I traced this problem to the location of the igniter leads. They were above the burner tube and not in the path of the flame at all. I adjusted the leads so they were directly in the flame path. The igniter leads also part of the flame detection circuit after the heater ignites, so this is where the leads should be positioned.

Now the heater ignites after two to three clicks and I never get a fault. This fix involves removing the heater’s internal sheet metal heat shields to get access to the igniter, so the heater came from Suburban with this flaw.

 

[Thrak]

Good info. I think I'll run a test with my wife and have her fire up the water heater while I stand outside next to the unit. An easy check to avoid a possible future issue.

 

[SteveSgt]

How many times does the igniter click before the burner ignites?

Before my recent fire incident, 1-2 times. That is, if I remembered to open the valve on the propane tank. If I forgot, I'd figure it out after 4-5 clicks.

 

[Shiny]

I am very glad you caught it before there was more damage and feel badly this happened to you.

We are headed out tomorrow so this caught my attention. I verified ours was working normally and the burner flame was mostly blue.

I'm also curious about recommended maintenance for the system, beyond flushing.. I check mine for bugs in the tube and blow it out with compressed air. If there is anything WRT maintenance, adjustment, or inspection of the regulator, igniter, and/or burner, please share!

I'm ignorant, so forgive me, but can burning propane generate that much soot, or could that only happen if something else burned? I understand the air/propane mixture can affect efficiency, but don't know, for example, if propane combustion generates soot with too little air (ie super rich).

Mike

 

[Viajante]

Mike, yes I believe a rich propane flame puts out enough soot to show up on the trailer body as shown in OP post 1.

For example, the yellow flames of a propane fire pit are terribly dirty. They are a product of a propane rich mixture. If you were to put a cooking pot over a yellow propane flame the bottom would be completely soot covered in a short time. The opposite of a leaned out blue flame.

 

[Shiny]

Thanks!

Will be interesting to know what is learned, if it's possible after the fact.

When SteveSgt smelled smoke, that sounds like something was burning beside propane. To me, even if the burner was rich and generating soot, the exhaust path would be "normal". To generate smoke, wouldn't either the exhaust path have to be blocked to get other parts hot enough to generate smoke? Or would "sooty" combustion of a rich propane/air mixture also smell like smoke?

 

[friofreddy]

As a licensed, certified HVAC contractor and technician, I can vouch for the good fortune (read Divine protection) you have experienced, in that your trailer wasn't badly damaged and that no one was injured in this incident. When an atmospheric, non-induced (no combustion fan or blower) gas burner is operating properly per design, the velocity of combustion gases exiting the system is adequate to completely and safely clear external surfaces of the appliance. If 'something' disrupts proper flow of the flue products, clean combustion is compromised and they slow down, sometimes enough to just barely drift out of the exit, as it appears to have happened in your case, Thus, the skin of your trailer was scorched, and sooted by whatever was burning inside, probably a wasp nest, producing the ashes you described. With the offending material eliminated from the flue path, has performance of the water heater returned to normal?

 

[Mommoves]

Nice write up. This is the first RV I haven’t screened. The fridge works pretty hard and the furnace needs all the free flow in and out it can get. The WH works better at higher elevation with the door open. I’ve been hesitant to screen things out of concern the slight airflow reductions might be the tipping point for problems. Of course not screening can also have consequences. So far I’ve only fought mud daubers and wasps in the A/C.

When we first used our WH with our new 23 something burned and it showed up on the outside of the trailer like the picture shows and we had ash all around d when we opened the vent. I had purchased screens but we hadn’t gotten them on yet. We have not had a problem since. We live in S Utah and camp at high elevations often (Bryce, North Rim). Our heater has never had a problem since with the screens on. Sometimes it takes a few tries to start up but it always works.

 

[SteveSgt]

With the offending material eliminated from the flue path, has performance of the water heater returned to normal?

After the fire I removed the sheet metal and didn't see any obstructions in the venturi tube or in the burn chamber. I did see a tiny pinch of ash at the bottom of the burn chamber.

However, I haven't tried it (nor any of my propane appliances) since the incident. I'm taking it to a shop tomorrow where it's their insurance problem if they burn it down.