Cold backdraft when insert not in use (Regency in masonry fireplace)

[bens_igloo]

Hi all,

Been reading the forum for some time but here is my first post. I had read many threads (including the sticky thread) about backdraft but I'm still having some issues.

In the fall I had a Regency i2400 insert installed in my masonry fireplace after a lot of research on this site and others. I am really happy with it but on a few occasions now I have had an issue with a cold backdraft when the stove isn't in use. I find that this usually happens when it's either windy or if it's very cold out.

When that backdraft comes down boy does it feel cold near the insert! In each occasion I was able to reverse the draft by sliding one of the baffles over and sticking a burning piece of newspaper as far as possible up the flue but that's not convenient and sometimes it can takes 2-3 pieces (and a smokey room) before the draft is reversed. In my case it doesn't seem like propping the window helps - so I wouldn't think it is an issue with negative pressure, but I'm not really sure.

I've noticed that if I leave the insert door slightly open when I'm not burning, the firebox stays warm and I avoid the backdraft, but I believe this is a poor solution that lets the heat my house escape.

The insert is on the main floor, connected to a 25", 6 inch full length SS liner running inside an exterior masonry chimney. There is currently no block-off plate installed (my installer removed the old blockoff plate to install the liner. Attached some pictures to show the setup I've got. Note that the exterior picture is from before I had the SS liner installed so that cap is no longer there.

Appreciate any insights on what might be causing the issue and if I can do anything about it. Thanks in advance!

 

[DAKSY]

Where is the draft coming from? Is it coming out of the Blower location at the bottom? If it is, it's reverse convection thru the heat exchanger. When the unit it burning, it will naturally draw colder air into the lower part of the unit & it'll pass up & across the heat exchanger & out the top. The blower causes this to happen more rapidly. When your unit ISN'T burning, warm air will enter the top of the unit & pass across the cold firebox, drop down the back & out. This could be the draft you feel. Gotta keep it burning. Then again, blocking off the rest of the flue will keep the whole system warmer...

 

[bens_igloo]

Hi Daksy,

The cold air is coming right from the SS flue. When I open up the insert door, I can feel the cold draft (it's pretty strong) coming down from above the baffles. Hope this helps.

 

[Hogwildz]

Putting a block off plate back would be a start. You may be getting cold air dropping down the chimney cavity and freely dumping into the room around the insert.
Keeping it burning is the right idea. That will solve any downdraft issues inside the liner, but without a block off plate, heat will be going up and being wasted in that chimney cavity, flowing just as free as the cold air coming down when not in use.

 

[Fireshoppe]

^ I concur, the entire brick structure outside will absorb cold but the 6" liner is a conduit to the outside that will fill with cold air chilling the stove a allowing the reverse convection DASKY spoke of. Insulating the firebox and adding an insulated block off plate may mitigate the cold from the masonry but will not stop the stove from being chilled. Either keep a fire in the stove or stuff the flue outlet above the baffle with insulation between fires.

 

[bens_igloo]

Good suggestions. I am planning to pull out the stove this spring and adding a block-off plate. Unfortunately at the time of the install I didn't know to install one.

What are your thoughts on keeping the stove door slightly open when NOT in use to keep a small flow of warm air (at least until I get the block off plate installed).

 

[mellow]

Where is the air leaking out of the stove into the room? Is the primary air control closed all the way? You could put a candle in it and leave the primary air slightly open when not in use.

 

[Fireshoppe]

You could put a candle in it and leave the primary air slightly open when not in use.

Interesting idea, I'd like to know how well that works.

 

[bens_igloo]

@mellow: I feel a strong draft coming down from the flue but also some cold air coming in near the blower assembly.

I generally leave the primary air open all the way when I'm not using the stove to have a little bit of air drafting up - I was hoping this would prevent a backdraft but apparently it's not working. Would it be better to close the draft control down when the stove is off ?

 

[mellow]

These new stoves can't be entirely shutdown so even if you close the primary air all the way it will just filter through and come out your secondary air intakes (by your blower), cold air is good at finding holes.

If the stove is not going to be in use for long periods I would drop the baffle and stuff a towel up the exhaust with a note on the outside to remove towel before using.

Letting your warm air go into the stove via a cracked open door sounds counter productive but might be your best solution, only other thing I could think of is running a draft inducing fan on it while it is not in operation but then again your spending money on electricity.

 

[bens_igloo]

Sounds like my best option is for the block-off plate and to insulate around the stove.

Thanks all for the suggestions.

 

[mellow]

That will help, but once a stove is cold all the insulation in the world wont stop a down draft.