Old Heatilator Fireplace Retrofit

[TomSeller]

One of my houses has an older Heatilator fireplace that I want to retrofit with a high efficiency insert and a new SS liner up the masonry chimney to the roof. The fireplace is in the center of the house with the two heat pump forced air returns on each side about 15' away. So running the blower with the insert in use makes sense to get the heat distributed through the house. I'd like the masonry mass (large as you can see) to store heat but it seems all the inserts these days only vent to the room. There are two vents into the crawlspace for combustion air, but the inserts that I have seen are not set up to take in outside air and use room air. Any ideas on what you would do?

 

[TomSeller]

Bump..

 

[Egon]

Outside air to very near the combustion inlet. Ducting to come off of insert hot air outlet to the Masonary.

 

[RNeumann]

I doubt the insert is taking combustion air from the room. Most would use the outer "chimney" for intake and the middle for exhaust. With regards to the mass- you will need to allow the warm recirculating air (fan on insert) to heat that mass. Their is no venting of combustion air into the room and the chimney and outside firebox cover (exterior of insert) aren't that warm.
Bottom line is the inserts are designed to work as is. You trying to reengineer and overthink things ain't gunna work like you want or think it should. Plus a thermal mass doesn't need to be heated from the inside out.......

 

[TomSeller]

Outside air to very near the combustion inlet. Ducting to come off of insert hot air outlet to the Masonary.

So in my case where the crawlspace air comes into the sides of the existing fire box, you would fabricate a duct that routes the crawlspace air beside the new insert up to near the insert's combustion inlet?

 

[TomSeller]

I doubt the insert is taking combustion air from the room. Most would use the outer "chimney" for intake and the middle for exhaust. ...

I thought the inserts used room air for combustion like a typical wood stove. If they use combustion air from the outer chimney, that would be ideal. I've never had an insert.

 

[RNeumann]

I assume the insert has a sealed front door? When I hear insert I think wood burning stove that is made to be inserted/retrofitted into an existing open wood burning firebox. It will make a huge difference and once warm the rock will help hold heat and make the place comfortable. It will be a nice addition! Good luck and enjoy the project.

 

[RNeumann]

So in my case where the crawlspace air comes into the sides of the existing fire box, you would fabricate a duct that routes the crawlspace air beside the new insert up to near the insert's combustion inlet?

The new unit is sealed and probably won't use anything from the crawlspace. If the insert doesn't take combustion air from the chimney then it will have a 4" inlet in the back or side of the unit. This is the same size a dryer duct. If that is the case you could duct that down into your VENTED crawl space.

They circulate air around the firebox (between the firebox and outer metal skin) with a little recirculating fan.

A third combustion air option (and something I haven't seen) is taking combustion air from the room. Note that is what they do with the install below.
How to Install a Wood-Burning Fireplace Insert - This Old House - YouTube

 

[teejk]

I thought the inserts used room air for combustion like a typical wood stove. If they use combustion air from the outer chimney, that would be ideal. I've never had an insert.

Can you find an insert small enough to fit the existing firebox? My MIL wanted to do something similar to what you have but nobody could help her.

 

[TomSeller]

Can you find an insert small enough to fit the existing firebox? My MIL wanted to do something similar to what you have but nobody could help her.

It is a fairly large fireplace, the ones at the local wood stove place looked like they would fit but I need to get to measuring.

 

[Egon]

So in my case where the crawlspace air comes into the sides of the existing fire box, you would fabricate a duct that routes the crawlspace air beside the new insert up to near the insert's combustion inlet?[/QUOTE]

Not sure what you mean by crawl space but my assumption is outside air with no connection to the Masonary area.
Just ductwork to the insert combustion air inlets.
Again no idea of how Masonary is laid out but ductwork from the insert hot air outlet to the Masonary inlet. I'm assuming the Masonary has an outlet to the room. An extra fan could be added.

Duct work should not be attached to the insert. The insert must also have approved installation area. Ie a former wood burning open fireplace type. There are fireplace inserts that are insulated and installed in wooden/drywall framed areas faced with brick. These probaly will not meet any clearance codes.

Regency small fireplace insert:
Combustion air in @ front bottom, hot air out @ top of insert. The circulating fan is at the bottom.

 

[TomSeller]

Not sure what you mean by crawl space but my assumption is outside air with no connection to the Masonary area.
Just ductwork to the insert combustion air inlets.
Again no idea of how Masonary is laid out but ductwork from the insert hot air outlet to the Masonary inlet. I'm assuming the Masonary has an outlet to the room. An extra fan could be added.

Each side of the existing firebox has a rectangular opening (picture). Inside the masonry there is a flex tube imbedded and routed into the vented crawlspace. So my thought, if enough space exists, adapt to these for combustion air rather than draw cold air across the room.

 

[RNeumann]

If the unit takes combustion air from the side that would work. As the video shows not all retrofit units have a separate intake for combustion air. It would be an abnormal situation, in a retrofit, to have a provision for combustion air- remember most fireplaces don't have an outside combustion air provision. So a retrofit unit that required outside combustion air from a side or rear 4" duct would be limiting. New construction style units (sometimes called zero clearance) do typically take combustion air from a 4" duct on the side or back.

To be clear. A retrofit style insert is a specific product offered by manufactures. So when you say retrofit I'm assuming that is what you are talking about.

 

[Egon]

Ahh -- I'm slow. You have a metal built in heatilator wood burning fireplace. You want to put a fireplace insert into the existing firebox. The Masonary is just surface cladding on the wall?

Please disregard my previous statements as your local code/insurance would dictate the installation conditions.

 

[RNeumann]

I think you bring up a good point. OP may not end up with a retrofit style and, if that is the case, the combustion air will come into play.

Problem with fireplaces is every manufacture does different things and has different requirements. It's a matter of measuring and then hunting for a unit that will fit and meet manufacture requirements. Or making a phone call and paying retail plus installation from a contractor/installer/retailer.

 

[TomSeller]

Ahh -- I'm slow. You have a metal built in heatilator wood burning fireplace. You want to put a fireplace insert into the existing firebox. The Masonary is just surface cladding on the wall?

Please disregard my previous statements as your local code/insurance would dictate the installation conditions.

The existing firebox could come out, it wouldn't serve a purpose once the insert is in place. That decision may be driven by the dimensions and what would need to be done to get a modern vent tube up the chimney through what is now the old style damper. The fireplace is free standing in the room, with a full concrete base in the crawlspace and masonry all the way through the attic and through the roof.

 

[Egon]

Okay. Then some of my previous remarks can stand.

I would suggest the existing damper be removed. There are continuous flexible stainless steel chimney inserts.

 

[patchnball]

that heatilator is quite big. Taking it out without disturbing the brick face will prove challenging. The outlet pipes are behind the soldier corse bricks above the doors. I guess anything can be done with a cutting torch.

 

[TomSeller]

Okay. Then some of my previous remarks can stand.

I would suggest the existing damper be removed. There are continuous flexible stainless steel chimney inserts.

How are those flexible stainless chimney inserts to clean? Seems the corrugation would be troublesome as far as getting it clean. Seems smooth would be better.

 

[Egon]

Haven't had any problems with mine. Hot fires and creosote chemical seems to be working.