fireplace insert air intake

[Glenwood]

Anyone know how the combustion air intake works on a fireplace insert?
I have a pacific energy insert that worked well when we bought the house several years ago. Lighting the fire was no problem with the usual starter material, etc. Logs burned nice and the lever on the bottom to control the flame height works fine. Smoke rose easily through the baffle and out. The fireplace has a masonry chimney with a 5" ss liner and is swept/cleaned yearly.
Last season, I had a heck of time getting the fire to start and stay lit. Smoke would build and pressurize the firebox somewhat, sometimes forcing out of the sealed door. I took the baffle out and replaced the insulation which I thought may have been charred and too solid to pass smoke through, as well I replaced the small gasket at the rear, but not sure what that is for. No change, so I thought maybe the liner was somehow blocked by a squirrels nest, so I swept it and sent a camera in and seems clear.
This fireplace has a small vent outside in the chimney which I thought is some sort of air intake. It has a screen to keep vermin out, but I thought maybe mice built a nest in it from the house side. I cannot see if and how this vent/intake connect to the firebox or its outer housing. My manual says nothing about this, so I'm wondering what that vent is for and how it might connect to the fireplace so that I can inspect it and clean if necessary. The outside screen and rain hood for the vent is very secure and I hate to tear it all off if I can access it from the house.

 

[threewood]

How high is the chimney above the roofline? Sounds like it isn't drawing. My parents have an insert and some days you can feel a breeze blowing down the stack. We would wad some newspaper up and get it hot fast and the heat rise would get it to draw.

 

[Glenwood]

It's about 4 to 6 feet above.
I pulled the damn thing out and i think the vent was for the original fp before the insert. Probably not needed now?

 

[Glenwood]

The insert has a duct underneath and opens to the back. Probably for the intake I'm guessing.

 

[Auggie56]

Sounds like the air intake isn't functioning. Smoke building up inside the fire box not burning properly? You have no air draw taking place. If you leave the doors open does the fire stay lit, then go out when you close the door? If so you have no draft from a plugged or other intake route. If it worked all this time it has to be a failure of some kind and not the original installation.

 

[ws23jrt]

Combustion air has to come from somewhere. If the house is tight drafting is not easy.

I have an old house (mid forties)with a three flue chimney. One for the fireplace in the living room and a fireplace in the kitchen. The third flue I use for a wood stove in the basement. (used to be for central heating exhaust).

Over the years I have replaced windows and generally sealed the house well beyond how it was built.

Sometimes when the temp drops and I start a fire in the living room fireplace-- smoke from that fire comes down into the kitchen flue and fills the house until I open a door or window. This is because the house is tight and the draft for the fire needs to be fed from somewhere.

I at this point I am not up on the current way to plumb an insert but suspect that combustion air for it needs to come from outside the house. (and not from right next to a smoking flue). This makes simple sense that I have tested.

Your insert may be just fine as designed but a fire is a fire and needs airflow to work.
A good test would be to open a door or window to test this. You may need to get supply air for the insert from outside the house plumbed in to fix your problem.

 

[mopar 3 B]

Google searched this. Company appears the have a fire box crack problem. Also check the chimney liner real close. Hot gasses in the wrong spots will not allow fresh cool air in. Iliminates draw.
I know you stated the chimney was scoped from the inside but is there a way to check the outside?

 

[Glenwood]

Good points, thanks guys!
After pulling the insert out, I found that the air intake is drawn from the rear of the insert, which pulls air from below and around the insert. The fresh air intake looks like it was for the fireplace before the insert was installed if that makes sense. It is a hinged cover and is rigidly screened when pulled up. I wonder if this is supposed to stay upright as it close to behind the intake opening or slightly underneath. The combustion air then travels past a flap, controlled by the high/low flame lever, into a vertical rectangular pipe inside the firebox, which connects to the baffle. The insulation just sits on top of the baffle and really just filters the smoke I guess before it enters the flue.
I also have a three flue'r as well, but one is capped off. The second is in the basement and the smoke did work it's way out the cleanout doors down there. I've read that airflow or draft can be tough to start a fire without a liner, as it takes so long for the chimney to heat up before the smoke rises properly. This is the issue I have with the basement wood stove periodically as it is only a clay flue. The liner for the insert is supposed to aid with that I understand and this was the first time this insert acted this way, so I am a bit baffled.
Well it was a good excuse to give it a good cleanout and I was careful to re-install everything. The fan was pretty dirty and needed a good vacuuming. The flame seems back to normal, but I didn't find any blockages, so I'm not convinced the issue has been resolved. Maybe I somehow partially blocked the intake tube the last time I cleaned it out...who knows!
Soon time to order a few bush cords.

 

[Sonny Black]

Do yourself a favor& your heating bill.....convert to a a direct vent FP
I switched both of mine.
Direct Vent Gas Fireplaces do not require a chimney and can be vented directly through a wall or roof. In fact, a 25,000 BTU direct vent fireplace can heat up to a 1500 square ft. one-floor living space. Can save money.

cut my heating bill by about 1/3

 

[Glenwood]

Do yourself a favor& your heating bill.....convert to a a direct vent FP
I switched both of mine.
Direct Vent Gas Fireplaces do not require a chimney and can be vented directly through a wall or roof. In fact, a 25,000 BTU direct vent fireplace can heat up to a 1500 square ft. one-floor living space. Can save money.

cut my heating bill by about 1/3

Thanks Sonny. I have a dv fp on propane for the master bedroom and is nice on cold nights. The new furnace is also a dv on propane since there's no nat gas in this rural area, but heats the house quick. The wood insert does a good job heating the main floor though (when working properly!) and offsets the propane consumption. I like the crackling wood and smell too.

 

[mopar 3 B]

No log mess with gas, no wood smell and no ombvieonce.
That can not be spelled right. So much for spell checker.

 

[Glenwood]

ambiance? (I had to look that one up lol)