Thread: Water Heater Flame Roll Out

See soot and heat discoloration marks above the combustion chamber on an 8-yr old Rheem gas (propane) water heater. I did NOT see any flame roll out during ingition or while heating during inspection. Unit is installed in hall closet next to a mid-efficiency furnace. Combustion air is from 6" vent at top of closet into attic space. Closet doors are sliding, with about a 3/4 inch gap at bottom of doors. Exhaust vent looks fine, no sing of vent blockage, no indications of flame roll out around the draft hood. So, while there is no vent in floor of closet for combustion air, I stil hesitate to conclude the any past roll-outs are due to inadequate air supply. Also, I did not detect any excess CO or gas leaks with my testers.

I have read or heard someplace else that roll out can be due to the pilot flame being too far away from the burner, allowing some excess gas to build up just prior to ignition, but the pilot light did not look that far from the burner in this water heater. I also read somewhere that it may be due to too high gas pressure, and the gas pressure can be adjusted on some control valves.

Any other ideas? Again, I did not see roll out during the inspection, but the soot marks on the inside of the chamber cover looked pretty severe.

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There should be a high and a low combustion air intake in the room shouldn't there? It may be hidden behind the combustibles. Was the top vent open?
Mid efficiency furnaces move a-lot of air during operation, 6" seems minimal. Did you try your CO detector with both appliances running full out and the door closed?

Did you check for gas leaks all the way around the gas valve with the water heater idle and running, especially the pilot and burner supply tubes?

I can see the gas build up thing, but by the time you had enough to create that soot on the outside, it probably would have blown the flue loose. You mention that it is gas (propane). Is the water heater orrifice sized for natural gas or propane? If someone just bought a water heater at the big orange box and installed it themself, it may be gas. The orifice sizing on gas is much larger than one on propane due to the fact that propane burns much hotter. A natural gas sized orifice on a propane system will let too much gas through.

Does the home have a whole house fan? If you don't open the windows, the intake air has to come from somewhere.



A few observations:

1. No drip/sediment leg on either appliance, (from what I can see).
2. Combustible material near water heater.

It has been my experience that when I see burn marks like that, I will usually find a problem with the burner, interior baffle or the vent/flue.

Was the baffle in place and in one piece?

you said this was a propane, was the jet resized, or was it natural gas size, propane will burn at a much hotter rate and can burn out the tank

Good points, thanks. Unfortunately I was not able to quiz the sellers to see if they already had repairs done. I doubt it though since the soot and discoloration is not visible unless you remove the outer combustion chamber shield, so they may never have seen it.

To answer the first question, yes it is rated for LP gas (I always check, but forgot to mention it). No apparant blockage of the combustion air supply vent from attic to this utility closet (1-story house), and as I said before, no second combustion air supply vent near floor of closet. I briefly peeked into the burning chamber and did not notice anything unusual (no sign of the baffle slipping down), and the flame pattern looked normal. Exhaust vent did not have any sharp angles or anything wrong that I could see other than a very poorly installed firestop at the floor of the attic (the wye of the exhaust vent is too tall where the furnace and WH vents join at the ceiling of the closet).

Total height of exhaust from top of WH to top of chimney on roof is about 14 ft, and this particular part of the valley does get some occasional strong winds. This attic has more ventilation than ususal (soffits, hooded roof vents, and small gable vents) that might affect air flow pressures at the opening of the combustion air vent, and down a large gap that should be closed up by the firestop.

I had also noticed an unusual amount of snow melt on the roof around the chimney flue, indicating a lot of heat is escaping up into the attic space above the WH/furnace flue (therefore a strong flow of air from the utility closet). I'm beginning to wonder if there is some backpressure or drafting into the closet created by occasional air currents in the attic. Notice how the insulation seems to be blown away from the firestop opening.

Were you inside the closet with the door closed to observe for any roll-out? I'm assuming the closet is too small, therefore you were not able to due this.

Once the door is closed however, could be a different story in regards to combustion air and the possibility of observing roll-out. I would still say you need a lower combustion air source as others have suggested.

Looks like a clogged up water heater burner and the interior flame sheild was never installed properly. Propane is not a very clean gas and with a clogged burner and/or pilot light will produce a large amount of soot.

Looks like one or both of the doors may not have been installed correctly or at all. Did you try measuring for temperature and CO levels 1-2 inches above the door after the unit had been running for a few minutes? Any CO or higher then room temperature readings might indicate burner or venting problems.

Tom

Not sure why it happens, but when such indicators are found it's automatically assumed that there IS a problem. It's quite possible that the stains are from a previous condition that has been corrected.

Some of you seem to know what the cause was even though you weren't there. That's a neat trick! I'm envious.

I wonder if Eric Barker is still around or if Karma has caught up with him.

Originally Posted by willy wonka

I wonder if Eric Barker is still around or if Karma has caught up with him.

Have no idea, but coming from a fake character and being afraid to stand behind ones own name does not give you any credibility - Chocolate Factory fraud it looks like.

In many cases I came across flame roll out like that was there was a negative pressure in the home or building. What I end up doing is installing a new direct vent heater so it gets its combustion air from the outside at all times. Never had a call back.