New Wood Insert, Interior Chimney Makes Second Floor Bathroom Hot

[jbcnyc]

Hi all. New to the forum. I've searched around a bit and haven't seen this addressed. If it has been, my apologies.

I have a Vermont Castings Montpelier insert in my existing masonry chimney. We lined the chimney, and the liner is insulated.

Still, when we get it going, the chimney warms the walls that surround it upstairs pretty good. Maybe a little too good.

Wondering if I should be concerned that our insulated liner warms the chimney so much that the second floor walls and floor get warm/hot to the touch.

Any insight is greatly appreciated.

 

[Nick Mystic]

If you have an insulated liner it is doubtful that the liner is throwing off enough heat inside the masonry chimney to make a bathroom wall hot to the touch. Do you have a stop off plate installed above your insert in your fireplace? If not, that is how the heat is likely entering the chimney putting and putting off enough heat to feel it through the bathroom wall. Although for that to happen it seems you must have the bathroom wall right up against the chimney without the proper clearance. I think there is supposed to be a minimum of one or two inches between a masonry chimney and any combustible materials. If you do have an insulated stop off plate, then I don't understand how the chimney could be getting that hot.

 

[jbcnyc]

Thanks, Nick, for your response. Super helpful. FYI, here's the liner description from the installer:

Homesaver UltraPro 30' liner w/components and insulation blanket

To your other points:

1) I honestly don't know if I have a stop off plate installed, but that probably means I don't. (Sorry, I'm new to this.) A quick search gives me a sense of what it is. And it sounds like it might be a real good idea.

2) It's a great house from the 1920s, but we already know the chimney construction wasn't the greatest (which is why we had to get an insert instead of keep using the fireplace). So the clearance may not be up to current code.

Thanks again. Any other insight would be fantastic.

 

[KaptJaq]

As mentioned above, I would check on the block-off plate just above the insert. I would also make sure that the top cap is sealed. If hot air can get in from the bottom and out through the top a lot of heat is going through the space between your new liner and the old flue walls. That heat will warm up the old masonry chimney quite a bit. When I installed my liner I stuffed mineral wool in the gap between the liner and the old flue for the 5' the chimney extends above the roof line. Then I sealed the stainless steel cap to the top of the tile flue with silicone sealant.

I have the same insert with an un-insulated 6" SS liner in an internal masonry chimney. The external bricks of the chimney in the rooms behind and above the stove never get warmer than about 80°. Do you have an IR thermometer? How hot are you running the insert? Exactly how hot is the wall?

KaptJaq

 

[jbcnyc]

This is such great help. Many thanks.

KaptJaq -- I don't have an IR thermometer. Looks like I should get one. The magnetic thermometer the installers left says I don't go above 500F, but I'm learning from this forum not to trust the magnetic ones too much.

 

[KaptJaq]

This is such great help. Many thanks.

KaptJaq -- I don't have an IR thermometer. Looks like I should get one. The magnetic thermometer the installers left says I don't go above 500F, but I'm learning from this forum not to trust the magnetic ones too much.

Where did they place the magnetic thermometer on the stove?

KaptJaq

 

[jbcnyc]

Here's a picture -- right on the peak of the door.

 

[westkywood]

Here's a picture -- right on the peak of the door.

I've got a PE Super 27. I just put my IR Thermometer on the spot on my door where your thermometer is and it read 200 degrees cooler than my stove top. Place it on the top of the stove.

 

[KaptJaq]

Here's a picture -- right on the peak of the door.

To me 500° sounds a little hot for that location on the stove. Were you burning a really hot fire? I see some soot streaks on the glass near the latch. It should look more like the other side. Was the door completely closed and locked while you were burning? In the picture the primary air lever is in the closed position, was air leaking in between the door gasket and the frame?

Once the stove is burning that door should be completely closed and locked. If air is leaking in at that location the handle may need to be tightened. Do the "dollar bill" test. When the stove is cold put a dollar bill between the gasket and the frame, close and lock the door, then try to pull the dollar bill out. If it comes out very easily you need to adjust the handle.

KaptJaq

 

[mellow]

9 out of 10 installers do not put in a block off plate unless requested. At a minimum you can go to Lowes and buy some Roxul and stuff that in the damper above the insert to keep that heat in the fireplace.

I was actually surprised that my local Lowes now stocks Roxul.

 

[begreen]

Here is how to install a block off plate.

https://www.hearth.com/econtent/index.php/wiki/Why_damper_seal_is_needed/

 

[Jon1270]

I just put my IR Thermometer on the spot on my door where your thermometer is and it read 200 degrees cooler than my stove top.

Seconding this. Not only are cheap magnetic thermometers unreliable, but that's also the wrong place to put one. Unfortunately it's a little more challenging to measure temperature on an insert than on a freestanding stove.

Although for that to happen it seems you must have the bathroom wall right up against the chimney without the proper clearance.

In my last house (1930's construction, no fireplace or wood stove) the chimney *was* the wall. Plaster had been applied directly to the brick, with no intervening framing.

 

[glennm]

I have a Montpellier and I get readings in the mid 500's from that location using an ir thermometer