I have a masonry lined (firebrick) fireplace that was originally made to burn wood and the previous owner converted it to accept a vent free log set. I called the manufacturer of the insert and they confirmed it would take a vent free log set. I have a 24" vent free log set and I'm not happy with the heat output. Even with the flu closed I went outside and could see plenty of heat escaping the top of the chimney (35 feet above the insert) The snow that was on top today melted in about 10 minutes and now I can see heat radiating from the chimney. Is that from the insert getting hot and heating the air in the flu? It's really putting out a lot of super hot air at the top. Is normal? It does still seem to heat up the space but very slowly and never get really warm. There is a fan below the insert that I run that blows a small amount of air from the top of the insert. Please help.
Vent free log set in original wood burning insert problems.
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jtp10181
Minister of Fire
Most people here are familiar with wood products FYI. I am familiar with gas, but only direct vent and vented log sets. Normally vent free log sets can be 99% efficient with all the exhaust coming into the room. When you clode the flue is it fully closed, or is there gaps around the damper?
Also you keep speaking of an insert, I am not sure but I don't think you really have an "insert". I am guessing you have a ZC metal box fireplace with firebrick refractories inside it. Then in that firebox you have a 24" vent free gas log. Is that correct?
Also you keep speaking of an insert, I am not sure but I don't think you really have an "insert". I am guessing you have a ZC metal box fireplace with firebrick refractories inside it. Then in that firebox you have a 24" vent free gas log. Is that correct?
webbie
Seasoned Moderator
A vent free set puts out a LOT of heat, but in your case some of the heat (not most, but some) is going up (heat rises) and heating up the large sheet metal chamber around the damper area. That heat is soaking through to the chimney itself.
Keep in mind that VF logs are designed for a little supplement - not to heat a house or anything like that. They are for ATTENDED use, and for occasional use.
Based on your description, you might try something like this....make up a sheet metal "pan" - no need to have it fit tight, in fact you could almost attempt an experience with "broil foil" and have this be about even with the top of the fireplace opening on the inside. This may deflect a lot of that heat back into the room.
(Edit, fireplace model mentioned below does not have cooling vents, so this is a bad idea- even in cases where it could be done, folks must be careful of dumping heat onto the fireplace front or mantel - some VF log makers sell a deflector or mantel heat shield for this reason).
From afar, I don't know about your model of ZC...but a few older ones take in "cooling air" in the upper part of the firebox. If yours is one of those, you DON'T want to do what I just mentioned. But most newer models...especially those with vents on the front top and bottom, use those vents to cool the fireplace, so the block-off would be OK.
If you post the model # and brand, I will take a quick look and offer my opinion.
Keep in mind that VF logs are designed for a little supplement - not to heat a house or anything like that. They are for ATTENDED use, and for occasional use.
Based on your description, you might try something like this....make up a sheet metal "pan" - no need to have it fit tight, in fact you could almost attempt an experience with "broil foil" and have this be about even with the top of the fireplace opening on the inside. This may deflect a lot of that heat back into the room.
(Edit, fireplace model mentioned below does not have cooling vents, so this is a bad idea- even in cases where it could be done, folks must be careful of dumping heat onto the fireplace front or mantel - some VF log makers sell a deflector or mantel heat shield for this reason).
From afar, I don't know about your model of ZC...but a few older ones take in "cooling air" in the upper part of the firebox. If yours is one of those, you DON'T want to do what I just mentioned. But most newer models...especially those with vents on the front top and bottom, use those vents to cool the fireplace, so the block-off would be OK.
If you post the model # and brand, I will take a quick look and offer my opinion.
Thanks for the replies...I have a Superior BCF 3885 fireplace. The details are on the lower right corner of this page
http://www.lennoxhearthproducts.com/products/overview.asp?pid=315
Any advice would be greatly appreciated. Also there is a Cumbustion air control lever on the side of this box. Does it matter if that is open or closed when using gas logs? Manual didn't say.
http://www.lennoxhearthproducts.com/products/overview.asp?pid=315
Any advice would be greatly appreciated. Also there is a Cumbustion air control lever on the side of this box. Does it matter if that is open or closed when using gas logs? Manual didn't say.
webbie
Seasoned Moderator
That fireplace does not have big cooling vents at the bottom and top (visible), so it may be getting it's cooling air from inside the firebox - perhaps on the left and right behind the glass doors (in) and inside the upper part of firebox (out). In this case, you don't want to take my advice above and place a seal of any type above the logs....because that would mess with the fireplaces cooling mechanism.
Someday, they will make fireplaces (of all types) comply with building codes when it comes it insulation, etc. - but as of now, that fireplace is actually designed to rob heat from your house and itself - that is how it functions!
ZC fireplaces have actually went backwards in design! Early models had triple wall chimney which brought air from the top, circulated around the fireplace and then went up the middle wall and back to the top. No room air or chase (built in box) air was required. Newer models have all sorts of cooling schemes, with the result often being some cold air or cold radiation in the home.
At least you can rest assured knowing that your logs are using 1/2 the gas and putting out vastly more heat than vented ones!
FYI, I think combustion air lever could be closed in most cases.
Someday, they will make fireplaces (of all types) comply with building codes when it comes it insulation, etc. - but as of now, that fireplace is actually designed to rob heat from your house and itself - that is how it functions!
ZC fireplaces have actually went backwards in design! Early models had triple wall chimney which brought air from the top, circulated around the fireplace and then went up the middle wall and back to the top. No room air or chase (built in box) air was required. Newer models have all sorts of cooling schemes, with the result often being some cold air or cold radiation in the home.
At least you can rest assured knowing that your logs are using 1/2 the gas and putting out vastly more heat than vented ones!
FYI, I think combustion air lever could be closed in most cases.
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