What causes flame rollout or scorching?

[Jon mackay]

I was curious what the cause of this scorching above the burner chamber might be.

The vent was off a bit so I was thinking possible back drafting but did not detect any during the inspection.

I find this condition from time to time and try to provide as much information as possible when noting the conditions.

[Scott Patterson]

I was curious what the cause of this scorching above the burner chamber might be.

The vent was off a bit so I was thinking possible back drafting but did not detect any during the inspection.

I find this condition from time to time and try to provide as much information as possible when noting the conditions.

Poor draft/draft problems
Flue pipe height or location at roof
Rust/scale covering burners
Hole in heat exchanger

I think that is pretty much the list of common problems.

[Rod Butler]

Poor draft/draft problems
Flue pipe height or location at roof
Rust/scale covering burners
Hole in heat exchanger

I think that is pretty much the list of common problems.


I concur with Scott adding lack of adequate combustion air with the poor draft situation.

[mike huntzinger]

ive seen bird nest in the flue , ie. poor draft.

[Eric Barker]

I had this on recent Carrier unit. Contractor wrote up cause was due to "cigarette smoke and tar." Just in case you wanted another possibility as per one of the many fine HVAC experts in the field.

[Markus Keller]

Scott pretty much nailed it. As far as you not finding anything during the inspection that doesn't surprise me. The problems often occur in the dead of winter when the unit is running a lot, cold air, bad chimney, etc.
I hope you wrote it up for replacement. It's always good to take the little front cover off along the burners so you can get a good pic of all the rust flakes on the cement below the unit.
Eric, Gale st. dinner is next Monday night. Hope you can maybe make it. Now that motorcycle season is back, I have little excuse not to make it out to the Pheasant.

[James Duffin]

Scott pretty much nailed it. As far as you not finding anything during the inspection that doesn't surprise me. The problems often occur in the dead of winter when the unit is running a lot, cold air, bad chimney, etc.
I hope you wrote it up for replacement. It's always good to take the little front cover off along the burners so you can get a good pic of all the rust flakes on the cement below the unit.
Eric, Gale st. dinner is next Monday night. Hope you can maybe make it. Now that motorcycle season is back, I have little excuse not to make it out to the Pheasant.

Why do you think it can't be repaired and needs to be replaced?

[Eric Barker]

Eric, Gale st. dinner is next Monday night. Hope you can maybe make it. Now that motorcycle season is back, I have little excuse not to make it out to the Pheasant.

Next Monday - Memorial Day???? What happened to the first Monday of the Month?

[Zibby Bujno]

Not sure when was the last time that steam beast was serviced, but it definitely has back draft problems, like house going negative. Whole house exhaust fan maybe?

[Markus Keller]

Sorry Eric, got the weeks mixed up. It is 6-6, which is obviously NOT next monday.
Sure the thing can be fixed, sort of, but I would recommend replacement. Unless they spring a leak those old beasts can pretty much always be fixed forever. I've babied old units along for years. The problem is that at that age you are paying a lot in fuel and it could go anytime. Replace it in the summer and you can do Ok on price. Call somebody in January, pay through the nose.
The key, for me at least, in looking at any old unit like that is to pull the burner cover off and see a) how much rust flakes are on the floor under the unit and b) if there are any signs of drips under the unit.
Lots of rust flakes or signs of drips, its gotta go.
No drips or very little rust flakes, I tell the client to leave it as long as they want to pay that bill.
- gas bill can't be cheap
- probably has an open 8" flue blasting hot air up the chimney
- draft hood assembly is probably rusted out
- flame roll out could be a fixable chimney issue or less reasonably fixable draft hood, jacket, burner related issue
- still has an old manual blow off, what an PIA
- see the bucket on the left side of pic, that's what they use when the blow off the system periodically, nice water color
- put a CM detector in a room with one of those and it usually goes off

[Bob Spermo]

Jon,

Could be negative pressure in the mechanical room.

[Bob Knauff]

Bob may be on to something there. Once inspected a 70's ranch style home that has a gas water heater in the basement. Tons of scorching at burner chamber door. The owner had remodeled the main level kitchen and installed a mega CFM hood over the gourmet, 8 burner range. With the hood operating, the door to the landing to the basement would close itself if open an inch or so! The owner was present and stated that it was not a problem as long as he kept the door closed. Ignorance is bliss but it can also kill ya!

[H.G. Watson, Sr.]

Notice also the labeled pre-manufactured gas appliance connector dangling to the right.

This leads me to suspect either being used as improper gas system piping intermittant "upstream" of the gas pipe to the gas valve and/or presence of yet another combustion air hog in the enclosed space in addition to the boiler and storage type W/H.

History of flooding, water level in the basement, unit not decommissioned after same, defeated safety wiring - and shared incorrect venting, that's my primary WAG.

[Jon mackay]

Not sure about the negative pressure, I don't think so. No large exhausting appliances.
Possibly a blockage at the flue but everything seemed to vent well during the inspection. Possibly back drafting during the cold season as the chimney was exterior stone.. Tough to warm up I would imagine..

[MARVIN TOWNSEN]

Jon,

Could be negative pressure in the mechanical room.
Hello, I am new to this site, also I am not a inspector at this time, but I have been a licensed cotractor, and a top technician and service representative for a major home company. I am not familiar at all with your area or gas and steam systems, since they are rare in this area in residential construction. Here is my 2 cents, in our area weatherization is a major concern for our local energy suppliers, so most homes are extremely air tight. This energy saving effort has created issues with air circulation, especially in the manufactured home industry, to the point that whole house exhaust fans need to be installed and used 24 hours a day to remove moisture and co2. What i have run into is that anything that creates negative pressure (ie, exhaust fans, bathroom fans, or any appliance that vents air from the home to the exterior) will draw flames from woodstoves(require a 4 inch fresh air intake to the fire box) or any other flame into the living area. Is this a possibility for your area? Hope this makes sense i am fighting the flue right now, so i am not thinking quite clearly. Anyway i am enjoying reading the posts on this website.

[Jon mackay]

Hello, I am new to this site, also I am not a inspector at this time, but I have been a licensed cotractor, and a top technician and service representative for a major home company. I am not familiar at all with your area or gas and steam systems, since they are rare in this area in residential construction. Here is my 2 cents, in our area weatherization is a major concern for our local energy suppliers, so most homes are extremely air tight. This energy saving effort has created issues with air circulation, especially in the manufactured home industry, to the point that whole house exhaust fans need to be installed and used 24 hours a day to remove moisture and co2. What i have run into is that anything that creates negative pressure (ie, exhaust fans, bathroom fans, or any appliance that vents air from the home to the exterior) will draw flames from woodstoves(require a 4 inch fresh air intake to the fire box) or any other flame into the living area. Is this a possibility for your area? Hope this makes sense i am fighting the flue right now, so i am not thinking quite clearly. Anyway i am enjoying reading the posts on this website.

Welcome to the site Marvin.

The building was constructed in the early 1900s so not very air tight.
I think when it comes down to it, there are a handful of possible causes to consider. The bottom line is that it is having or has had problems that need addressing.

[MARVIN TOWNSEN]

Welcome to the site Marvin.

The building was constructed in the early 1900s so not very air tight.
I think when it comes down to it, there are a handful of possible causes to consider. The bottom line is that it is having or has had problems that need addressing.
Most homes built in the 1900 era in this area were log cabins:rolleyes: Most of the rest are landfill:eek: What recent weatherization? is that any factor for the issue in your area? I find the differences on the east coast informative, so thanks for your time and also thanks for the welcome to the site. ps i go by Rob:)

[Dan Hagman]

I have seen and fixed this many times when I used to do HVAC, most all of the things you all listed can be true but I have seen where the burners have all kinds of dirt, rust, chips of rust, all kinds of junk on them and when the gas valve opens 2-3 burners lite and the rest don't lite due to all the stuff in the way. and then, boom----flame rollout occures when the other burners finally light. It needs a good cleaning, burners, heat exchanger, check the draft, is combustion air present?? Also on an atmospheric burner flame rollout can be constant with a plugged heat exchanger and poor draft.

[Roger Hankey]

Poor draft/draft problems
Flue pipe height or location at roof
Rust/scale covering burners
Hole in heat exchanger

I think that is pretty much the list of common problems.

This is a low pressure steam boiler, not a gas forced air furnace. "hole in heat exchanger" is NOT one of the possible causes.