Thermal Mass not warming up why???

[Andy]

I have been burning in inserts for years. Had a Country Flame with catalyst that was my favorite but the catalyst required a fair amount of maintenance and cleaning so this time I bought a Clydesdale . Well the Country Flame was a great stove. Mega heat output. Good beefy door with heavy hinges. The Clydesdale looks great and is working fairly good. Couple of problems that might be install related and I want to get some opinions. First the stove was installed about a month ago. I insisted on the smooth stainless steel flue liner. About a 25 foot run on my rancher to the top of the chimney. So with every wood insert I have had, all have been put into an existing fireplace, after the stove was burning for a day or so the thermal mass of the brick and mortar would warm significantly. Not with the Clydesdale. The mass stay cool to the touch even after burning the stove hot for 5 days. Now when the installed the liner they told me I had to use the on liner insulation that attached directly to the liner and is netted on, about an inch or two thick since my flue was 12x12 and would require too much vermiculite to fill it. Was this the proper install? Is the lack of vermiculite fill allowing the heat in the stove mass to go up the chimney rather than heat the brick mass? Prior to having this stove installed I had several fire in the fireplace and the thermal mass definitely warmed very nicely. Any ideas?

 

[begreen]

Welcome Andy, it sounds like the insulation is doing it's job. A modern stove is going to try to deliver the maximum heat output into the room and not the surrounding masonry. The reason being, if this is an exterior chimney, that heat is heading straight outdoors.

 

[BrotherBart]

Here is the answer most find works to keep the heat in the fireplace and the living space.

https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/

 

[branchburner]

On your previous inserts, it sounds like you did not have a liner... were they six-inch exhausts that had stovepipe extending into your 12x12 flue, without any blockoff plate? I expect that even though the warmth of that thermal mass felt pretty good to the touch, a lot of that heat absorbed into the masonry was not truly useful heat (as it would be with a true masonry heater). By using the insert to heat more of your living space and less of your brick, you should feel warmer while burning less wood (assuming the stove is burning efficiently).

BTW, perlite is so darn cheap I can't imagine any flue requiring "too much" fill to insulate, as far as cost goes. Now, if it was sifting down into your living room, "too much" would be pretty easy to acheive!

 

[Andy]

On your previous inserts, it sounds like you did not have a liner... were they six-inch exhausts that had stovepipe extending into your 12x12 flue, without any blockoff plate? I expect that even though the warmth of that thermal mass felt pretty good to the touch, a lot of that heat absorbed into the masonry was not truly useful heat (as it would be with a true masonry heater). By using the insert to heat more of your living space and less of your brick, you should feel warmer while burning less wood (assuming the stove is burning efficiently).

BTW, perlite is so darn cheap I can't imagine any flue requiring "too much" fill to insulate, as far as cost goes. Now, if it was sifting down into your living room, "too much" would be pretty easy to acheive!

My chimney mass is inside the house, For a 2000 sq foot stove the Clydesdale sure falls short of heating the house (1400 sq ft. fully insulated with double pane windows)) . My issue is was the stove installed correctly. All of my stoves have had an insulated liner , poured in. My thought is if this stove only has the wrapped insulation around the liner that the heat of the stove mass which is out the rear of the stove as well as via the designed outlets (front, air vents) is actually being vented up and out of the chimney rather than heating the mass. I guess my first question is did the installers put in a blockoff plate just above the stove. Now that the install is done can they come back and install a blockoff plate if there is none and can they still pour in some perilite to salvage the lost heat. No matter how good the stove, there is still going to be heat loss all around the stove and this Clydesdale is just not putting out that much heat even though I know I am burning hot. ?????????

 

[Nick Mystic]

Hi Andy,
Your thinking on this is a bit backwards. If the installers did not install a block off plate then the likelihood is that your thermal mass of the chimney would be getting plenty warm. Certainly warmer than if you had a block off plate keeping the heat in the room and minimizing the amount making its way up the brick structure of your chimney. If you had poured in vermiculite with your previous stoves you must have had block off plates to hold the vermiculite in the chimney from raining down onto the insert. I suppose it's possible that the wrapped insulation on your liner is doing a better job of keeping the heat inside the flex liner preventing it from heating up the thermal mass you used to be able to use for a slow heat release after your insert cooled down.

I have a Jotul F600 freestanding stove sitting in front of my massive fireplace and chimney (8'x4' running about 20' tall inside the house - over 6000 bricks). I just now took some temperature readings off the stove and chimney: Stove = 400F, fireplace 24" above the opening = 225F. Even the backside of the chimney in the kitchen is reading 86F while the living room temperature is sitting at 72F. So, I can see why you are concerned that you are losing the benefit of all that thermal mass heating you had been getting in the past. Perhaps you should have forgone the wrapped insulation on your liner if your clay tile liner was in good shape and didn't have any cracks, which requires the insulation on the flex liner. I made a deliberate decision to do my install without an insulated liner for just that reason. I installed a block off plate with some insulation laying on top of it and I stuffed insulation around my flex liner for the top 4' or so of the chimney that is above my roof line. With an airtight top cap I seem to be trapping a good amount of heat to both warm the liner for good draft and bleed off enough heat to warm the thermal mass of the chimney for slow release later. So, if your clay tiles are in good shape I suppose you could consider pulling off the insulation if it is a big enough issue for you.

 

[branchburner]

My thought is if this stove only has the wrapped insulation around the liner that the heat of the stove mass which is out the rear of the stove as well as via the designed outlets (front, air vents) is actually being vented up and out of the chimney rather than heating the mass.

Now that the install is done can they come back and install a blockoff plate if there is none and can they still pour in some perilite to salvage the lost heat.

Sorry, I was thinking loose vermiculite/perlite, not the pour-in mix. But regardless, there should be a top plate that seals the chimney exit around your new liner. Along with a block-off plate at the bottom, that would create a dead-air space around the liner, whether it is insulated or not.

So if your liner was uninsulated, the dead air space (which is also itself a form of insulation) of the large flue might mean the upper part of your flue liner would run a bit cooler, producing more creosote and less draft -- that is the point of the insulation, to keep more heat in the pipe. But with an interior chimney, the difference alone between insulated, uninsulated, and poured-in flues should not make really major differences in the ability of a stove to heat a house.

The transfer of any heat to the chimney masonry -- and subsequent re-transfer into the living space -- is always going to be a relatively small portion of your productive heat output with a stove/insert (my center chimney keeps the upstairs center closet nice and warm, which is of no use to anyone but the cat).

Transfer of heat to chimney masonry CAN be a significant portion of heat loss, however, especially with an exterior chimney. Even with an interior chimney, if the insert has no blockoff then warm air can flow into the airspace around the liner. Since there is a top plate, the air does not escape, but it can be cooled by the cold masonry at the top of the chimney. That convection loop within your flue can transfer heat to the outdoors. But that transfer can be reduced by creating dead air with a block off.

In addition to adding the blockoff (if not there already) it might make sense to stuff mineral wool around the portion of your liner that is above the roof line -- this should reduce heat transfer by eliminating some airspace. But also consider, you may not be getting best results with the new stove because its burn technology is very different than the cat stove you had. When I run my stove too hot, for example, it means too much primary air is pushing a lot of heat up the flue... running my stove harder doesn't always mean my house is that much warmer.

 

[BrotherBart]

One thing about the Clyde is that it is all cast iron with soapstone lining in it. It will never toss the tons of radiant heat that a steel or regular cast stove does. And the sucker takes a long time to heat up because of the soapstone lining. Members have complained about the Clyde taking forevery to heat up and not getting hot enough only to later find out that it gives off heat for a long time after the fire dies down.

 

[begreen]

How are you loading and running the Clydesdale? Can you give us a rundown including the air control setting at the start, middle and end of the burn cycle?