Hearthstone Morgan 8470 Insert - Trouble Getting up to Temp

[triangle]

As far as wood stoves go, i'm somewhere within beginner to intermediate. I've got 2 hearthstones, a heritage (beautiful nice one) and the Morgan insert.

The heritage absolutely cranks out a tremendous amount of heat. I've done basic stuff like cleaning them, replacing the gaskets/cement, etc, and a little masonry work replacing the chimney cleanout.

However I can't seem to get my Morgan insert to really crank. I've only gotten it up to 350 degrees or so, so the heat output is definitely lacking. The baffle seems in place. I replaced the gasket around the main stove unit, but I see discoloration from what I think is cold air getting in the glass pane.

That's my last idea here is that the air coming in from around the glass (there is a secondary gasket esque fiber that surrounds the glass) is simply getting sucked upwards and out the chimney.

I've included a picture.

Anybody deal with this issue?

 

[nortcan]

Are all the screws all tight?, If OK, did you made the dollar bill test for the door gasket ? Can you post a not so close to the stove photo?

 

[bholler]

As far as wood stoves go, i'm somewhere within beginner to intermediate. I've got 2 hearthstones, a heritage (beautiful nice one) and the Morgan insert.

The heritage absolutely cranks out a tremendous amount of heat. I've done basic stuff like cleaning them, replacing the gaskets/cement, etc, and a little masonry work replacing the chimney cleanout.

However I can't seem to get my Morgan insert to really crank. I've only gotten it up to 350 degrees or so, so the heat output is definitely lacking. The baffle seems in place. I replaced the gasket around the main stove unit, but I see discoloration from what I think is cold air getting in the glass pane.

That's my last idea here is that the air coming in from around the glass (there is a secondary gasket esque fiber that surrounds the glass) is simply getting sucked upwards and out the chimney.

I've included a picture.

Anybody deal with this issue?

View attachment 273573

First off how is it installed? What is the height of the chimney and what size liner?

 

[triangle]

First off how is it installed? What is the height of the chimney and what size liner?

so it's inserted into an old fireplace, with a stainless steel lined pipe vertical that goes straight up and directly through the roof.
it has a fantastic draft and is very easy to light.

the chimney height i'm not 100% sure on the exact measurement, but whatever a standard 2 story building's chimney height - it's that.

 

[triangle]

Are all the screws all tight?, If OK, did you made the dollar bill test for the door gasket ? Can you post a not so close to the stove photo?

yeah the screws are certainly tight. i noticed one of the screws is snapped off from previous maintenance. it still screws in, but it buts up against the rest of the screw further in (the screw is in 2 pieces each with threading).

i will try out the dollar bill test.

 

[triangle]

I can't seem to edit the original post, but one thing to note:

I recently replaced the inner gasket on this stove, in attempt to try and improve this temperature situation. it did improve, but only mildly. the peak temperature went from maybe 325 -> 350. this temperature is being read by one of the sit on top magnet thermometers that has the moving needle.

 

[triangle]

> and what size liner?
the liner looks about 6" diameter.

> did you made the dollar bill test for the door gasket ?
so there is some friction, but I can still pull the bill out fairly easily.

So I think I might have figured this out.

When I had replaced the gasket, I had matched the gasket that was present in the woodstove (1/4"). The previous homeowner to me was a 'jack of all trades' but more realistically he did a lot of things improperly.

I did some more online digging (including on these forums), and the Hearthstone 8470 Insert looks like it actually takes a 3/8" gasket. So I thought I was playing it safe replacing the same size gasket, but turns out I was just replacing it with another undersized gasket.

I'm assuming that's my problem. Of course, the local shops around me are out of 3/8" gaskets but amazon will have one here on Sunday.

I'll update this thread once I have confirmation whether or not this fixes things!

 

[nortcan]

> and what size liner?
the liner looks about 6" diameter.

> did you made the dollar bill test for the door gasket ?
so there is some friction, but I can still pull the bill out fairly easily.

So I think I might have figured this out.

When I had replaced the gasket, I had matched the gasket that was present in the woodstove (1/4"). The previous homeowner to me was a 'jack of all trades' but more realistically he did a lot of things improperly.

I did some more online digging (including on these forums), and the Hearthstone 8470 Insert looks like it actually takes a 3/8" gasket. So I thought I was playing it safe replacing the same size gasket, but turns out I was just replacing it with another undersized gasket.

I'm assuming that's my problem. Of course, the local shops around me are out of 3/8" gaskets but amazon will have one here on Sunday.

I'll update this thread once I have confirmation whether or not this fixes things!

Good, if possible use HT silicone for the new rope gasket, just a small layer in the cleaned gasket channel is a lot better than the liquid cement, the liquid cement coming with the rope gasket tends to soak the gasket and that cement becomes as hard as cement so the gasket may become cement hard at some points. The HT silicone on the opposite stays soft and makes a better seal, it worth the price to make the best job first time...

 

[triangle]

the HT silicone i'm finding says max temp 500. Is that OK? When my other stove cranks it goes to 550.
I've never used silicone for binding the gasket in place, but I like the idea.

is the 500 stuff fine or is there an extra special type of HT silicone I need to find?

 

[triangle]

i've found the 600 degree silicone. that should be sufficient

 

[triangle]

alright. Managed to get my hands on the 3/8" gasket. a couple observations:

* the amazon gasket arrived early (midwest hearth) 3/8"
* the rutland gasket I picked up from ace HW 3/8"
* both are graphite coated fiberglass
* they are not the same width, although they are both marked as 3/8" - I'm assuming one is high density and the other low density? one is more compressible.

I installed the "larger" rutland gasket, and now the stove passes the dollar bill test with flying colors. super tight. door is noticeably more difficult to close.

burn time has been extended with the gasket installed, and the burn seems healthier. temperature peak has not risen, but I also did some more disassembly and cleaning of this unit and found out where I'm putting the temp gauge is actually a floating encasement, and not necessarily the top of the cast iron box for the stove. So it may not be providing the most accurate temp measurement.

as for the glass discoloration - I still see it around some edges. Since I did the gasket install with HT silicone as recommended, I'm considering putting a small bead around the outside glass border, spraying with some alcohol (without a fire of course), and wiping/pressing it in to see if it will mitigate this last issue.

would you guys consider this a hack?

one last enhancement I think I need is some type of heat shield for where the liner goes up into the chimney. there is insulation there, but I've seen some installations have a reflective barrier to help retain heat - an issue I think I also have. I forget what it's called here, but i may fabricate something for that.

 

[moresnow]

Search "block off plate" here. Should give you some ideas. Heck of a blaze you have going in that pic! Nice.

 

[begreen]

Here's an article on block-off plate installation. There are also several new threads on the topic.

Make a damper sealing block-off plate

How to make a block-off plate A block-off plate is particularly helpful with inserts installed in fireplace on exterior walls with exterior chimneys. Without one, the flue liner (which should be insulated) and the stove will try to heat the mass of masonry that is exposed to the outdoors...

www.hearth.com

 

[triangle]

block off plate, that's exactly it. that's what I need.

thank you guys for the links.

 

[triangle]

Search "block off plate" here. Should give you some ideas. Heck of a blaze you have going in that pic! Nice.

heh its basswood, so it goes very, very quick. i have a lot of shagbark hickory that's about ready. I've been burning basswood on the off season a bit when its not dreadful outside. extremely easy to start fires with so i may keep it around a bit.

its crazy comparing the two. they are literally opposite ends of the spectrum for weight and BTU output.

 

[triangle]

Alright, well I always appreciate summaries / lessons learned when I come to forums like this. So I just wanted to take a moment and pay it forward from what Ive learned in the past couple weeks.

1. Do NOT assume your woodstove has the correct gasket size in it, if you have difficulty getting up to temp. Look it up from an authoritative source.
2. Seal with HT silicone over cement. Flexibility is better, and you can also use it on the woodstove glass door.
3. Temp gauges placed on the woodstove may not show a completely accurate number - this is especially true if your stove has a floating encasement around the actual cast iron stove as the Hearthstone Morgan 8470 Insert does.
4. Block off plates are probably the #1 cause of heat loss from woodstove inserts. Assuming your climate has snow, does the area around your chimney melt quicker than the rest of your roof? You want to heat your room/home not the masonry, It may even be worth building a reflector for behind and on the sides of your stove.

So for now I've solved 1-3, but still working on the biggest culprit, #4.

A big thank you to everyone who responded in the thread.