BTU's and blockoff plate

[chuckiep]

Heres a strange question. Anyone have any ideat how many BTU's can be saved with the addition of a blockoff plate. I'm thinking of putting one in my setup here soon. Thanks.. Where's Corey when ya need him? LOL.
thanks again,
chuckp

 

[Rudyjr]

Probably a lot of variables in that question, like location and construction of chimney, distance, number of flues, size of flue, etc.., I do not doubt the advantage of installing one after my installation. If it were not for the advice found on this forum I am certain I would have overlooked this step. The installation instructions for my insert only show it with a direct connect, not with a full liner. I was even told it was not necessary by several dealers and installers in our area, they all said to pack the opening with insualation.

 

[bren582]

Hey Chuck..

I think the BTU savings would vary for each install dependent on many variables. It's safe to say the savings will be greater when dealing with exterior chimneys as more heat will be lost in this misguided configuration. My Chimney is exterior, a hulking mass of brick and mortar perfect in its ability to wick copious amounts of valuable heat to the outside. I went totally overboard and installed block plates in the damper, rear, sides and bottom of the firebox all insulated with ceramic fiber. My firebox was on the large side so I could do this and still have plenty of breathing room around the insert. In the past when burning in the masonry fireplace I could feel significant warmth on the outside chimney structure. With the insert and insulated block plates it is now cool to the touch outside and the insert performs beyond my expectations so for my particular installation it looks like it was a good move.

As for the apparent conspiracy among installers out there concerning the need.. Sure it's not an absolute since the top plate should be sealed off but think about it.. What if a contractor installed a nice new EPA certified high efficiency window in your house but left the window cracked open and you asked him " Hey, shouldn't I close that?" and he replied "Naaa.. No need to.. Just stuff some fiberglass insulation in there.." OK.. a bit of a stretch but not by much..

 

[iceman]

ALOT of btu s are saved with block off plate as it keeps heating much longer... helps keep the stove warmer, you'll feel the bricks very warm and if you go up some more bricks they'll be cold

 

[chuckiep]

Bren582,
thanks for the reply. My installer told me the same thing. "No need for that. I've been doing thisw for over 10 years and never even heard of it." I asked him if he had heard about hearth net and he said "whats that?" I said 'how long have you been installing?' LOL.

 

[burntime]

I have had it both ways with and without the block off plate. My top plate was leaking as well. The difference is increditble It is a very bad mistake in my opinion to NOT do it. It is due to the laziness of the installer or in my case the initial ignorance. I asked the dealer and was told that it is not needed. Well, you can get to work on a big but a car is much easier The block off plate must put a third more heat in the house...and I have an internal chimney

 

[karl]

Craig has a burntime and btu calculator on here. https://www.hearth.com/econtent/index.php/articles/burn_time_calculator

It shows a stove putting out about 20% more heat than an insert for the same size fire box. No one has argued with his numbers, so you have about 20% more heat to try to recapture. Granted not all of the heat is lost up the chimney, some of it is lost through the wall of the fireplace; but that is what you have to try to recapture.

I would say block off plate and insulation.