I've got a set of vented gas logs that are monessen I believe the model is bdv400. They've only been in use a couple of years. They have been converted to propane and I followed the instructions to a T. From day 1 of use the glass will soot up very bad in just a couple of days and the vent is black as midnight. The pilot flame touches the bottom of one log so I modified that log so it doesn't touch anymore and that solved the glass sooting up but now the pilot itself soots up in just 24 hours shorting out the flame sensor and shutting the system off. I checked the pressure and it's where it's suppose to be. Can anybody tell me why this is happening?
Black soot everywhere!!
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The BDV400 is a direct vent fireplace. Post a pic of the pilot running. That is a SIT valve which normally doesn't even have huge flames. Maybe the air hole in the pilot assembly is clogged up.
I don't see the air shutter or venting affecting the pilot very much if any at all.
The air hole is free and clear. It has to have a pretty decent size flame to reach the flame sensor or it'll never run. It's weird how it does. It will start building hair like soot right on top of the pilot then creeps over to the flame sensor and shorts it out which faults it out. It can do this in just a matter of hours some times. I've got a pic of the build up I'll post.
![[Hearth.com] Black soot everywhere!!](https://www.hearth.com/talk/attachments/hairypilot-webp.306475/ "[Hearth.com] Black soot everywhere!!")
The air hole is free and clear. It has to have a pretty decent size flame to reach the flame sensor or it'll never run. It's weird how it does. It will start building hair like soot right on top of the pilot then creeps over to the flame sensor and shorts it out which faults it out. It can do this in just a matter of hours some times. I've got a pic of the build up I'll post.
The reason I asked how it was vented is two-fold…
1. Horizontal venting when burning LP has been known to cause issues when the cap is facing the prevailing wind. Too much of the exhaust gases gets reintroduced to the unit & that screws up the ATF ratio.
2. I have seen instances where horizontal venting sections have become separated, allowing exhaust to get sucked into the intake, causing the same ATF issues…
1. Horizontal venting when burning LP has been known to cause issues when the cap is facing the prevailing wind. Too much of the exhaust gases gets reintroduced to the unit & that screws up the ATF ratio.
2. I have seen instances where horizontal venting sections have become separated, allowing exhaust to get sucked into the intake, causing the same ATF issues…
And I don't see how that would have very much affect on the pilot. Main burner yes but not the pilot. I've already established that it's the pilot causing the sooting when I cut away one of the logs so the flame wasn't touching it anymore.
Are there different orifices for the pilot burner for the two gases? Sounds like it still has the natural orifice in it. Some gas valves (or thermostats) have a setting for gas selection, (orifice built in valve) others change orifice.
The soot on log doesn’t have to be from a rich mixture. The flame hitting an object is flame impingement cooling the flame tip, depositing unburned fuel on the log.
Is the pilot flame all blue? Any yellow flame will deposit unburned fuel on the nearest cool surface. ( glass with main burner off) Yellow flame tip is either too much fuel from incorrect orifice, or not enough air from blocked pilot air intake.
Picture of the pilot in the dark would help.
The soot on log doesn’t have to be from a rich mixture. The flame hitting an object is flame impingement cooling the flame tip, depositing unburned fuel on the log.
Is the pilot flame all blue? Any yellow flame will deposit unburned fuel on the nearest cool surface. ( glass with main burner off) Yellow flame tip is either too much fuel from incorrect orifice, or not enough air from blocked pilot air intake.
Picture of the pilot in the dark would help.
A natural gas pilot orifice with LP fuel generally doesn’t soot, but it looks different. The pilot flame will curl up at the end. This is known as “candling.” The smaller orifice allows LESS fuel, which leads to a lean condition. Soot is caused by a rich condition. Too much fuel. Something is choking the combustion air.
Yeah, if they didn’t change the orifice when converting to LP it would have the larger NAT orifice still in it burning rich. This was converted from Nat to Lp. With that much soot, either way too much fuel or no air.
My worst nightmare was removing a glass one time with what looked like a big black wasp nest on the glass. Huge soot ball! Pure white carpet, had to get it out without becoming airborne. I did ok. In hindsight I would go get a tarp since I’m a little shaky to such nonsense anymore.
Pilot orifice was changed with what came in the conversion kit. Yes it's a yellow flame, air hole is completely free of anything blocking it and gas pressure is set where it should be according to the conversion kit. I'm starting to think the little pilot "hood" is messed up some kind of way. If I can find a new one I'll buy it and try it.
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