Heat n glo FB-IN Startup starve problem

[tomtbone]

I have a Heat & Glo FB-IN installed with both Intake and Exhaust vents going all the way up the chimney.

Here is the latest problem with the unit that just started. Pilot flame stays on fine by itself. When I start the burner it starts just fine, but eventually dies off in about 10 seconds along with the pilot. I figure it is just not getting the oxygen it needs. When I crack open the glass, the burner stays on just fine and I then seal the glass back on and the unit will then be fine for hours. Its almost as if the unit just needs an oxygen kickstart and then runs fine.

What is causing this initial starvation? Anyone else have this problem? I really don't want to have to crack the glass everytime we run the fireplace. Maybe there is a clog in the intake? Any other ideas?

 

[DAKSY]

How long has it been acting this way? Has it ever worked correctly?
Sounds like it's having a hard time getting a draft going.
That would cause an oxygen depletion situation.
Then again, is your pilot REALLY agitated during the start up?
Could be a small restrictor is required on the intake side...

 

[tomtbone]

How long has it been acting this way? Has it ever worked correctly?
Sounds like it's having a hard time getting a draft going.
That would cause an oxygen depletion situation.
Then again, is your pilot REALLY agitated during the start up?
Could be a small restrictor is required on the intake side...

I installed the unit a week ago. It worked fine for three days and now I am having this problem. Whenever the unit is warm or has been used within the hour it will start up and work fine. I hadn't used it in about 2 hours, and I just went to turn it on and I have the issue again. I get the really loose blue flames that just float up to the top and the pilot also goes out. This morning, I had to crack the glass, let it warm up and then reseal the glass and it worked fine for a number of hours. Its like its not getting an initial draw of oxygen that it needs. I might take a quick video and post it here. Could the fact that intake goes all the way up to the chimney be a problem? Maybe running a short pipe or simply disconnecting the intake pipe will give some answers.

 

[DAKSY]

It sure sounds like the venting. My bet is it's probably reversed,
with the intake on the exhaust flue collar & the exhaust on the intake.
The flames are extinguished because the exhaust is above the intake on the cap.
With the vents hooked up wrong, the exhaust gets sucked UP into the intake &
the depleted air (no combustible oxygen) snuffs out the burner & pilot.
Once you get it going by cracking the sealed chamber, must be allowing
enough oxygen-rich air to get into liner to keep the unit burning.
Unfortunately, the only way to test this is to disconnect the liners & switch the positions.

 

[tomtbone]

It sure sounds like the venting. My bet is it's probably reversed,
with the intake on the exhaust flue collar & the exhaust on the intake.
The flames are extinguished because the exhaust is above the intake on the cap.
With the vents hooked up wrong, the exhaust gets sucked UP into the intake &
the depleted air (no combustible oxygen) snuffs out the burner & pilot.
Once you get it going by cracking the sealed chamber, must be allowing
enough oxygen-rich air to get into liner to keep the unit burning.
Unfortunately, the only way to test this is to disconnect the liners & switch the positions.

This is the cap I have.

I have the intake on the lower output and the exhaust on the higher output. Is this incorrect, I thought this was the way it was described in the instructions? You are saying the intake should be connected to the higher stack inside the cap?

Its not a big deal to switch the pipes on the fireplace. I will try that next if that's the case.

 

[DAKSY]

That is the correct hook-up, but the problems you're encountering sound like the connections are reversed.
If you DO remove the insert to look at the liner connection, make sure the slide plate they attach to doesn't
have the insulation pad bunched up under the intake side...

 

[tomtbone]

I am going to try running the fireplace with the intake disconnected for a bit. I don't really see a problem with that. So far its starting fine with the intake pipe disconnected, I'll have to see how the next couple of days go.. I can always try the technique of putting on a 6' piece of pipe on the intake and only going partially into the chimney. I'm wondering if the long 25' length of intake to the cap is what is causing this problem.

 

[tomtbone]

That is the correct hook-up, but the problems you're encountering sound like the connections are reversed.
If you DO remove the insert to look at the liner connection, make sure the slide plate they attach to doesn't
have the insulation pad bunched up under the intake side...

Well, disconnecting the intake sure seems to have fixed the problem. What do you think of this idea? Put a small hole in the intake pipe close to the fireplace so some oxygen can get into the fireplace on startup? I could also put another short pipe into the chimney.

 

[DAKSY]

Just run the short section up into the flue tiles. 5 - 6 feet oughta do it.