Soot Build up after 20 years starts Heat-n-glo SL-36

[Plummer98]

I have noticed soot is building up in my 20 year old direct vent fireplace. I had a fireplace repairman come look at it he cleaned a few things, said it could be the log set has lived it's full life and maybe the cause if it continues I will need to replace. The parts I want to replace
simulated refractory base srv418-337
bottom log srv60-700
top right log srv98-724
top left log srv94-725
Please advise on best place to buy replacement parts and if this seems like the most possible cause. Nobody seems to recognize these parts with google taken from the original owners manual. Thanks in advance.

 

[DAKSY]

Have you verified the air shutter setting is STILL correct for your fuel type?

 

[Plummer98]

It has been used for 20 years with no problem. I am new construction plumber, that's why I hired a fireplace expert incase it was something like that. How would I check it or test it? My wife was home when he came. I assumed he checked that but who knows. A month latter and the inside glass is black.

 

[DAKSY]

Where is the build-up? On the glass or on the logs?
MAJOR sooting is usually caused by two things:
Air shutter opening too small, or a venting problem,
allowing clean combustion air to be mixed with exhaust
gases or blocking enough incoming air...
I took the page below from the install manual online...
If you look at the lower illustration, showing the ember placement
on the burner, you will see the burner tube at the bottom.
At the end of the burner tube is the air shutter.
Make sure the opening isn't blocked or closed off.
I can't find the actual opening required, but if you open
the shutter fully, there should be no sooting.
If the bottoms of the logs are sooty, re-positioning them
away from the burner ports can alleviate that issue.
If the air shutter adjustment or the moving of the logs
don't mitigate the sooting issue, then I would look at the venting.
There may be a beehive or a small birds nest in the cap or vent pipe.

 

[Plummer98]

Where is the build-up? On the glass or on the logs?
MAJOR sooting is usually caused by two things:
Air shutter opening too small, or a venting problem,
allowing clean combustion air to be mixed with exhaust
gases or blocking enough incoming air...
I took the page below from the install manual online...
If you look at the lower illustration, showing the ember placement
on the burner, you will see the burner tube at the bottom.
At the end of the burner tube is the air shutter.
Make sure the opening isn't blocked or closed off.
I can't find the actual opening required, but if you open
the shutter fully, there should be no sooting.
If the bottoms of the logs are sooty, re-positioning them
away from the burner ports can alleviate that issue.
If the air shutter adjustment or the moving of the logs
don't mitigate the sooting issue, then I would look at the venting.
There may be a beehive or a small birds nest in the cap or vent pipe.

I took some more pictures to add some info. We first noticed soot on outside above vent termination on side wall of house. Since the tech has been here the inside glass and walls are covered with soot. I can feel the fresh air coming from the back bottom of the fireplace. I have no embers in fireplace anymore or very few left I think I had them 20 years ago.

 

[DAKSY]

In pic number 3, the air shutter looks like it might be open about 1/8" - 3/16"
Loosen the screw & open it all the way & tell me what the flames look like after
about 20 minutes of burn time with the glass on...

 

[Plummer98]

I will try it this weekend and keep you posted. I do have one question, have you seen this happen before where the shutter was used for 18 years and then start having problems? Am I not doing some sort of maintenance? I'll take the pic at start and 20 minutes later. Thank You so much for your help.

 

[DAKSY]

All it can take is ONE INSECT to get into the air shutter. That would be the same as closing it.
Normally, it shouldn't happen, but if the screw that secures it in position isn't tight, anything
that causes a vibration - A blower. Vacuum cleaner. Dogs or kids running thru the house...

 

[Plummer98]

Opened air shutter about half way. Cleaned most of the soot off the walls of the fireplace and glass. It appears too not be building up at all. Ran it considerable amount yesterday. Can see a little on outside of house figure that could be what's built up in the flue working its way out. I will give you an update after I use it for about a month or so but it seems that may be the fix. I appreciate all the help.

 

[DAKSY]

After about 20 minutes of burn time, the flames should start to turn yellow.
If they don't, you can 'tweak' it closed 1/16" at a time. Unfortunately, letting it
cool down to make that 'tweak,' & then burning for another 20 minutes to heat
back up is ponderous, but that's the proper way to do it...