Jotul C550 Block Off Plate

[Orion 4343]

Hi All,

I had a Jotul C550 installed in 2017 and I've been heating my home with it as much as possible; typically 4 cords a winter. I have a 20' external chimney. Stove drafts well, sometimes too well. My home is 1900 sq ft colonial and on a winter day that's in the mid-20s, I can keep the first floor at 68-70 and the upstairs will be at 62-64. I am OK with this, but I am wondering if i can get more heat out of this thing.

When this unit was installed iI had an insulated liner installed as well, but no block off plate. At the time I was new to stoves and didn't know to ask for one. I do know that Jotul does no require a block-off plate as long as the liner is attached at the top, which it is. My question is, is it worth the effort of installing a block off plate? How much warmer would the house be? I know this is a loaded question, lots of variables, but would I notice a difference? Am I expecting too much from this stove?
Attached is a picture of how the stove is connected to the liner, shroud removed. I think i have enough room to install a block-off plate without removing the stove. Possibly put a plate 4-5" above the stove jacket.

Thank you for your time.

Andy

 

[begreen]

There was a homeowner with the C550 that complained about it not heating the home very well. After ascertaining that the wood supply was dry and the insert was properly run, the conclusion was to try a blockoff plate. We heard back from her a while later. She said it made a very big difference in the heat output. I'll see if I can dig up the thread.

 

[Orion 4343]

begreen,

Thank you. forr looking. I am generally happy with it, It saves me a ton of money not running the heatpump all winter. Generally, the heat pump wont run on a average cold day, high 20s. If if gets into the teens, then my heat pump kicks on at the end of the burn cycle. Just trying to ascertain if a block off plate might make things even better.

 

[begreen]

How tall is the liner on this insert? If it is very tall, the issue could be too strong draft.

Is the fireplace interior or on an exterior wall?

 

[Orion 4343]

The fireplace is on an exterior wall. My guess is 20' of liner. Attached a picture of chimney from outside. This stove runs hot, I have aired it down fast, used bigger splits, and packed it tight. I've gotten a lot better at controlling it, but every so often i have had it glow dull red on top.

 

[begreen]

At 20 ft, the draft shouldn't be too big an issue. Is the blower running when burning?

Yes, the back of the fireplace has a lot of exposure to the elements. In addition to the block-off plate, consider slipping in some Roxul or Kaowool insulation behind it if there is room. It looks like there might be just enough room above to squeeze in a 2 piece plate without removing the insert. Send the kids out of the house to avoid singeing their ears. Definitely make a cardboard template first.

 

[Orion 4343]

I will try a block off with some insulation. Last question. Will the block off plate effect draft in any way or make the actual stop top temp hotter?

 

[Orion 4343]

And yes, the blower is always on.

 

[begreen]

The plate shouldn't affect the draft but the insert body will get a bit hotter. If it is hard to control the stove, a draft damper could be added.
Note that this is a new owner in the thread below, so there is some user learning here too.

Jotul 550 Rockland Comments

In the meantime I've installed a damper in the flue just above the stove. I considered devising some kind of linkage to operate the damper from the side, but this approach was the simplest, and it has a clean look. Yeah, it was a scary thought to drill a hole right through the face of the cast...

www.hearth.com

 

[Orion 4343]

Begreen,

Got the block off plate installed this weekend. That was a real chore! Packed some Rockwool above the plate but there was not much room behind the stove, so I left it uninsulated. Just waiting on some Rutland RTV; couldn't find that near me. Now just need to wait a few months to see how well it improves the heating. For those that are interested, I will report back in late October or so. Begreen, thank you for your help.

 

[begreen]

Regular silicone adhesive caulk is fine for the perimeter of the plate. Don't use RTV against the liner. It's not rated for the high heat on the liner and may stink a lot. If the gap around the liner is large, use some stove door rope gasket to fill the gap. For caulk, use something rated for higher temp service like Mil-Pac sealant.

 

[Orion 4343]

I did use rope gasket around the liner as my gap was a little bigger than I would have liked. Is the RTV OK for the perimeter? I do have some All purpose GE silicone but it seems to only be rated for 400 degrees.

 

[begreen]

GE Silicone II is good for the perimeter. It will be fine there but if you want to use Rutland RTV that's ok too. It's only rated at 100º higher. The bricks won't get that hot.

 

[Orion 4343]

OK thank you. What I have is GE Silicone I which seems to not be the right product. I will just wait for the Rutland. Thanks again.

 

[skidawgz]

Very curious about the update on this plate and heat output!

 

[Orion 4343]

I don't want to get too excited yet, because it's just the beginning of the burning season, but so far I am seeing a significant increase in heat out put. The stove gets hot faster and stays hot longer. I am getting the house warmer faster and its staying warmer. I am curious about how well it does on the cold days. So far here in SE PA its been cold over night, but still warming into the 50s during the day. I have been making one fire in the morning. which gets the downstairs to about 71 from 65. The I let it cruise the rest of the day. I will give another update when it gets colder.

 

[skidawgz]

I'm in SE PA too (Philly). Did you DIY the install?

My stove was installed just this past April and it is my first burning season. Took the surround off and confirmed no block off plate for mine. I am capable but nervous to mess with the stove to liner coupling.

 

[Orion 4343]

I did do the install myself. There are a lot of good tutorials on this website that show how to do it. I bought the galvanized sheet metal from Lowes and bought a cheap metal brake from harbor freight. You do not need to mess with your stove to liner coupling. You're simply making a sheet to block off the giant gaping hole letting air up around your liner. You will attach it to the brick inside the fireplace and most likely the steel lintel at the front of the fireplace. Like others have said, make a template from cardboard, that's key.

 

[skidawgz]

Thank you so much! I forgot how abundant this forum is with resources. I'll follow this guide and give it a try soon.

 

[mellow]

If you can, even a piece of cement board behind the insert will be a big help, all that heat goes to the masonry on the back.

Finally got around to insulating my fireplace

Been able to run for a few days straight with the cold temps, I really do not see that much difference in everyday operating, where I see the difference is in how much longer the fan stays on because the insert stays warm longer and I now have large coals in the morning after an overnight burn...

www.hearth.com

 

[djc550]

I did do the install myself. There are a lot of good tutorials on this website that show how to do it. I bought the galvanized sheet metal from Lowes and bought a cheap metal brake from harbor freight. You do not need to mess with your stove to liner coupling. You're simply making a sheet to block off the giant gaping hole letting air up around your liner. You will attach it to the brick inside the fireplace and most likely the steel lintel at the front of the fireplace. Like others have said, make a template from cardboard, that's key.

Could you share a picture of the final block off plate? What temperature difference did you see in your stove? I have stuffed as much as possible insulation up the chimney.

Like you, I have lots of space behind the stove. Is it OK to put insulation between the stove and the outer chimney brick wall ?

My challenge is having a 22’ chimney and with the stove fully closed off, it’s gets up to over 800F. (Side note: I have a magnetic thermostat in the same location as you, on top of the firebox where the air returns. I found using WhiteEx, I was able to mark 400, and 600 which allows me see the temperature and the numbers on the thermostat cannot be read when it’s in there).

 

[mellow]

Could you share a picture of the final block off plate? What temperature difference did you see in your stove? I have stuffed as much as possible insulation up the chimney.

Like you, I have lots of space behind the stove. Is it OK to put insulation between the stove and the outer chimney brick wall ?

My challenge is having a 22’ chimney and with the stove fully closed off, it’s gets up to over 800F. (Side note: I have a magnetic thermostat in the same location as you, on top of the firebox where the air returns. I found using WhiteEx, I was able to mark 400, and 600 which allows me see the temperature and the numbers on the thermostat cannot be read when it’s in there).

You want an air gap between the insulation and the stove, and keep in mind that if you use Roxul it has fibers, hence why I suggest using concrete board as an insulator, however if you have space you can stuff roxul BEHIND the concrete board so it is encapsulated.

I would suggest using a thermocouple and use the exhaust temps rather than STT. Exhaust temps are more meaningful.

 

[djc550]

Super helpful - thank you.
It’s clear to see that the insulation installed at time of the C550 install has lots of gaps.

 

[Orion 4343]

Unfortunately I did not take any pics, but if you do a quick search on this site for block off plates there are lots of examples. Mine is very similar to what you will find.

As for the temp you are seeing on the stove top, the block off plate wont help you much with that. I've struggled to contain this stove and I will share what the typical procedure I use for lighting this thing off. When loading on a bed of coals I stack about 5 splits E/W and then I grab a couple short splits and load some N/S to get a good amount of firewood in. I have the air slider fully to the right at this point. When the fire gets going and you can see that the flames are licking up towards the baffle, I put the air control slider to the middle. I might do this in 2-10 mins after the load of wood goes in, just depends on how fast the fire gets going. At this point the flames recede a bit. When the flames begin to lick back up to the baffle again I close the air down almost all the way, maybe leave the slider 1/8" open. Let it go this way until secondary's have kicked off and STT is about 500, then air it down the rest of the way. If I do this, peak temps are about 700. Your goal should be to air it down as fast as you can without snuffing out the fire. Put the fan on high, or medium high and enjoy.

One other thing that helped. I put a small machine screw in one of the holes in the primary air doghouse. It helps keep the stove from going nuclear.

 

[begreen]

Here is a resource on the topic

Block-off plate construction

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...

www.hearth.com