help, gas fireplace cycles on and off a few times before burning steadily

[niccolo]

I have a Lennox MPD3530CNE built-in natural gas fireplace in a home into which I recently moved. It was working fine until recently. Recently I opened it up to clean the glass and vacuum up some dust. I put the fake logs and synthetic ember material back in place and closed the glass back up. Now it's doing something strange when I light it.

The pilot lights, the fireplace lights, it burns for about one minute, and it shuts off. About twenty seconds later the pilot lights, the fireplace lights, it burns for about two minutes, and it shuts off. The two-minute cycles repeat several more times, and then it starts burning steadily with no more unexpected shut offs.

There is no material blocking the pilot light area. I blew some air in there to try to clear any dust that might have gotten into the assembly. Anything else to try before I call a professional?

 

[DAKSY]

Not familiar with your particular unit, but it sounds like an electrical issue.Is the flame sensor rod clean?
There is an image of it on page 8 of the manual. Try scrubbing it with some steel wool...
I would also check the ground wire coming from that sensor,
which should be going to a screw that grounds it to the fireplace body.
Make sure the connection at the grounding screw is tight...
Let us know what you find...

 

[niccolo]

Not familiar with your particular unit, but it sounds like an electrical issue.Is the flame sensor rod clean?
There is an image of it on page 8 of the manual. Try scrubbing it with some steel wool...
I would also check the ground wire coming from that sensor,
which should be going to a screw that grounds it to the fireplace body.
Make sure the connection at the grounding screw is tight...
Let us know what you find...

Thanks! I will look into cleaning the flame sensor rod and check the ground wire, too.

Someone else suggested that maybe there was a drafting issue that was preventing it from getting needed combustion air until it had warmed up. I'm wondering whether I might have too many pieces of the synthetic ember material blocking the gas inflows and/or the artificial logs positioned to block one of the gas inflows.

 

[Millbilly]

Definitely could be a drafting issue. If your unit has a continuous pilot mode try turning that on and see how it functions .

 

[DAKSY]

OK, try this to test the draft: take the glass front off the unit & light it with whatever switch you use.
If it lights up & holds, then look at your venting.
If it continues to turn itself off & on, it's NOT the venting.
Just don't run it for any length of time without the glass sealed...

 

[niccolo]

OK, try this to test the draft: take the glass front off the unit & light it with whatever switch you use.
If it lights up & holds, then look at your venting.
If it continues to turn itself off & on, it's NOT the venting.
Just don't run it for any length of time without the glass sealed...

When I ran it open without glass, but also without the synthetic logs in place and without the synthetic embers, it ran continuously.

I'll take a look at the venting, maybe my opening things up led to me somehow closing/blocking the venting.

I should also remove the synthetic logs and embers and close the glass back up and see what happens.