Convert Fisher Grandma Bear from rear opening to Top opening?

[FISHERJohn]

I’ve been looking for a top-opening Grandma and just found a rear opener locally for a reasonable price——wondering how feasible a conversion is? Has anyone done it? Where would I get a heavy steel collar? Change from 8” to 6”? Etc.
Thanks,
JB

 

[FISHERJohn]

I’ve been looking for a top-opening Grandma and just found a rear opener locally for a reasonable price——wondering how feasible a conversion is? Has anyone done it? Where would I get a heavy steel collar? Change from 8” to 6”? Etc.
Thanks,
JB

Okay, this forum has answered my 8 to 6” question——don’t do it. And I found a source for an 8” collar.
Would still like to hear from anyone who has made the switch. Thanks

 

[coaly]

A 6 inch outlet straight up may work fine. It depends on pipe configuration and chimney. Is this going into a pole barn or large building where you want high heat output, or in a home where it will be used more at cruise most of the time? You are also not in a very cold area that will have exceptionally good draft most of the time, so go with a double wall chimney, not triple wall to stay hotter inside.

You will want to add a baffle plate under the outlet as well. Extend outlet pipe, like the original about 3 inches into firebox.

 

[FISHERJohn]

Thanks Coaly,
Just went and looked at the stove which is in nice condition. They have an 8” to 6” reducer on it.
My setup (presently has an old battered Vermont Castings Vigilant in place) is a masonry nook and the stove pipe does a ninety and goes into an 8x12 clay flue.
You are right, our winters are pretty mild and the stove is as much for atmosphere as for practical heat——I want to be able to burn it with the doors open at times.
I’ll just have to decide if I want to go through the welding hassle or wait for a top opener.
My parents have a Fisher fireplace insert that They’ve used for 30 years.

 

[bholler]

Thanks Coaly,
Just went and looked at the stove which is in nice condition. They have an 8” to 6” reducer on it.
My setup (presently has an old battered Vermont Castings Vigilant in place) is a masonry nook and the stove pipe does a ninety and goes into an 8x12 clay flue.
You are right, our winters are pretty mild and the stove is as much for atmosphere as for practical heat——I want to be able to burn it with the doors open at times.
I’ll just have to decide if I want to go through the welding hassle or wait for a top opener.
My parents have a Fisher fireplace insert that They’ve used for 30 years. View attachment 293428

Why would you reduce to 6" if you are going into an 8x12 liner?

 

[coaly]

That chimney absolutely needs a insulated liner the same size as the outlet you go with. (or for any stove connected to it) That is a lot of air space around the liner to cool it. The height is about the minimum for open door operation.

If you have the clearance for pipe behind it, a tee on the back of the stove, over the collar straight up works with a cap on the bottom. I find when reducing diameter it makes little difference for smoke roll in when a insulated chimney goes through a ceiling support box straight up with no els or tees. The more resistance added due to horizontal pipe, els and tees, the more likely for smoke issues inside. Reducing from 8 to 6 does reduce the capacity. So wide open will not allow the stove to reach full BTU output as the 8. Won't need that there anyway. You would want 8 inch connector pipe off the stove reduced at chimney liner. (Reducing 1 inch was allowed by NFPA 211, if your area adopted the International Building Code, that no longer allows any reduction, and also requires any appliance to be UL listed as well. This is only for new installations, not existing) You will need a flue damper for open door use to control the fire in Fireplace Mode with screen in place.

 

[coaly]

Why would you reduce to 6" if you are going into an 8x12 liner?

Good point. I would hope he's referring to a 6 inch liner all the way.

 

[Frankdozer]

Good point. I would hope he's referring to a 6 inch liner all the way.

I have a Grandma Bear. I’m also a retired steel worker and steel fabricator. I cannot comment on wether your chimney flue is the correct size, nor if it will draw sufficiently, nor if it is the correct height.
But I can comment on if you can move the outlet on Grandma from the rear to the top. It is an easily done move. A good steel fabricator could do the job for you and custom fabricate the 8” round outlet to accept stock small end pipe. Probably a 2 hour job.