Vermont Casting Aspen C3 - How hot should it run

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MikeGraz

New Member
Oct 31, 2021
15
NY
Just installed a VC Aspen C3. With a full load of wood the stove seems to run very hot. The Center of the cook top area measures over 750 Degrees ( limit of my IR thermometer) The rest of the cook top is measuring 700 - 750. Have about 20 ft of stovepipe with 2 90 degree bends. Have the outside air intake installed. Wood is stored outside and does not seem overly dry. Did not have this problem with my previous stove, on which I could control the air intake. I have only loaded the stove up twice. Now I am only burning small fires and I am afraid to load it up, if its not controlling.

Any idea if these are normal temperatures for this stove ?

I contacted VC and asked if they could tell me what temp range the thermostat should control the stovetop to. Instead of answering, they referred me back to the dealer. Sent the dealer an email and never heard back from them. Not happy with VC customer service
 

begreen

Mooderator
Staff member
Nov 18, 2005
94,575
South Puget Sound, WA
The stove has no user air setting, it's thermostatically controlled. The only user control is to load less wood and thicker splits. A key damper could be added to the stove pipe for a bit more control by reducing draft.
 

MikeGraz

New Member
Oct 31, 2021
15
NY
The stove has no user air setting, it's thermostatically controlled. The only user control is to load less wood and thicker splits. A key damper could be added to the stove pipe for a bit more control by reducing draft.
Thanks for the reply, that is essentially what I am currently doing and I do have a damper in the flue.

What I am trying to figure out is if the thermostat is working correctly or is it allowing the stove to get too hot. It seems like VC would have some design parameters for the thermostatic control or at least a recommended temp range for the cast iron. I have not been able to find either.
 

begreen

Mooderator
Staff member
Nov 18, 2005
94,575
South Puget Sound, WA
Agreed. One would expect that the dealer would have a service bulletin on how to check this. I am not sure if the thermostat can be calibrated in the field. Wish I had one of these stoves for some testing and exploration. corrie is this an expected stovetop temp for this stove?
 

SpaceBus

Minister of Fire
Nov 18, 2018
7,042
Downeast Maine
How long did it peak at 700-750 df?
 

MikeGraz

New Member
Oct 31, 2021
15
NY
How long did it peak at 700-750 df?
Once I saw it getting this hot I shut the damper down. Was probably at 700 - 750 for about a 1/2 hr.

Once you get a good bed of coals it burns nice with one or two pieces of wood, but seems to want to take off if you load more. Until I have more time to "play" with it, I'm afraid to load it up, especially overnight when I won't be monitoring it. With the auto control I was hoping to be able to load it up and forget about it.
 

EbS-P

Minister of Fire
Jan 19, 2019
3,011
SE North Carolina
Another user posted a picture looking in to the rear air inlet and you can see the flap and the chain that pulls it open, appears that gravity closes it. Se if you can take a picture to verify that everything is there and looking ok. With a cold stove the flap should be pulled up. Allowing more air in and as it heats the spring it expands and allows the air control to close over the inlet. Now this is all conjecture from the one picture and the diagram on the website so take as an option not fact.
 

SpaceBus

Minister of Fire
Nov 18, 2018
7,042
Downeast Maine
Once I saw it getting this hot I shut the damper down. Was probably at 700 - 750 for about a 1/2 hr.

Once you get a good bed of coals it burns nice with one or two pieces of wood, but seems to want to take off if you load more. Until I have more time to "play" with it, I'm afraid to load it up, especially overnight when I won't be monitoring it. With the auto control I was hoping to be able to load it up and forget about it.
It's pretty normal for a stove to peak at 700-750f for a bit. That's the nature of wood heat. Close the stove pipe damper sooner if you want to stretch the burn out a little bit and smooth that peak. You have a ton of draft, most stoves are designed around little single story low pitch ranch homes.
 

MikeGraz

New Member
Oct 31, 2021
15
NY
It's pretty normal for a stove to peak at 700-750f for a bit. That's the nature of wood heat. Close the stove pipe damper sooner if you want to stretch the burn out a little bit and smooth that peak. You have a ton of draft, most stoves are designed around little single story low pitch ranch homes.
Thanks for all the responses .

I did try to look at the rear air inlet, but with the cold air intake installed, its hard to see the flap and I can't tell if its closing all the way.

Good to know that 700 to 750 short term is OK. Old stove never ran over 600 or so.

Once I figure out how much to load and when to start closing the damper, I'm hoping the stove will work well for me. Just not what I expected in terms of "load it and forget it". Definitely going to have a learning curve .
 
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SpaceBus

Minister of Fire
Nov 18, 2018
7,042
Downeast Maine
Thanks for all the responses .

I did try to look at the rear air inlet, but with the cold air intake installed, its hard to see the flap and I can't tell if its closing all the way.

Good to know that 700 to 750 short term is OK. Old stove never ran over 600 or so.

Once I figure out how much to load and when to start closing the damper, I'm hoping the stove will work well for me. Just not what I expected in terms of "load it and forget it". Definitely going to have a learning curve .
Once you figure out how it likes to run it will probably turn into load it and forget it. My manual draft stoves are like that. I babysit for 20-30 minutes and then I can walk away and do whatever.

Edit: You will also find that the draft gets even more intense as it gets colder. Good that you are getting on top of this in milder weather.
 
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EbS-P

Minister of Fire
Jan 19, 2019
3,011
SE North Carolina
I would experiment with fixed damper settings for the whole burn. The stove was designed to run with out one. You may, by opening the damper at startup be getting a burn rate faster than intended (sounds like you don’t have insufficient draft). Once it takes off the outgassing has started it’s harder to slow down.

I would pick a damper position that you had when burning a full load halfway through that load and leave it there and try to start a top down fire with the damper in that position. Leave door crack a few minutes then close it and see what happens. Not the time it takes to get rolling secondary combustion and the stove top temps when that happens and what it gets up too. Reload and see how it burns.

If you don’t get good results open or close the damper some and try again. The goal being, find a damper setting where you don’t have to touch the damper and let the C3 system control the stove for you.

Flame patterns should show that the air control is working. Secondary combustion should be dominant flame with the C3 automatic air closed all the way.

Just some thoughts and ideas.
 
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begreen

Mooderator
Staff member
Nov 18, 2005
94,575
South Puget Sound, WA
Like spacebus, it took some tries with our F602 before we came up with the right combo of air control and pipe damper. The stove would willingly and quickly go up to 700-800 on the stovetop. The final method we ended up with was closing down the stovepipe damper all the way once the fire was well established. The damper never closes off all of the flue. Then, let it equalize for a minute or two, then closing down the air almost all the way, until it was just open a hair. That gave us the longest burns and a stovetop temp in the 650º range. And the stove only had a 10' flue.
 

MikeGraz

New Member
Oct 31, 2021
15
NY
Thanks again for the inputs. I will try various damper settings, and let the thermostat do its thing. I am encouaged because the stove throws out a lot of heat for a small unit. Will let you know how it works out
 
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wjohn

Member
Jul 27, 2021
213
KS
I had my largest fire yet (still not that big) with my Aspen C3 tonight and with the rear 1/3 of the firebox full of short locust and mulberry chunks, the center of the cooking surface got up to ~650 degrees about 90 minutes later, and then gradually declined.

I do agree it is crap that their customer service couldn't get you a max surface temp value. The fun of big companies... Usually the people who have the info like that are super helpful; it's just getting to them that's the painful part.
 

wjohn

Member
Jul 27, 2021
213
KS
Also forgot to mention my floor to chimney cap height is about 14.5' and VC states something along the lines of any deviation away from 16' could affect performance. Sounds like you have more pipe but those 2 90s should knock it back down some. With your damper you should be able to dial it in, I would think.
 

MikeGraz

New Member
Oct 31, 2021
15
NY
Last night I ran it with 2 pieces of wood, firebox about 1/3 full. I loaded the wood when the stove was full of coals and shut the damper. Even with the damper shut, the center of the cooktop reached 725 degrees about an hour into the burn, then declined from there. I am going to have to try a full load and see if it burns hotter. I can always go out and block the OAK to shut it down.

I have about 20 ft of pipe, most of it is outside the house. Also has 2 90s, so I thought it would not have that much more draft than a straight 16 ft, which is what VC designed and tested the stove with. I just wish I could find out what temperatures the stove ran during their testing.

VC states that a draft over .12 WC can cause short burn times and overfiring. I guess I am going to have to get a manometer and check the draft. I find it hard to believe that with the damper closed I would still have too much draft, but I guess its possible.
 

SpaceBus

Minister of Fire
Nov 18, 2018
7,042
Downeast Maine
Some people need two key dampers to get the draft manageable. So far things sound like they are working well, despite the high draft.

Don't feel bad that the company couldn't tell you how hot is too hot, I tried to ask the Morso customer service the same question when we first got our stove.
 
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wjohn

Member
Jul 27, 2021
213
KS
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stoveliker

Minister of Fire
Nov 17, 2019
5,242
Long Island NY
Does that mean that it is safe to always hit that temperature...? Testing is a one-off procedure...
 

wjohn

Member
Jul 27, 2021
213
KS
Does that mean that it is safe to always hit that temperature...? Testing is a one-off procedure...
I am curious to see the forum's thoughts on this.

I will not pretend to be a stove industry expert, but from a general product liability perspective, I would not want to have to defend a manufacturer in this situation:

1. EPA Certification achieved and documented with above linked test report.
2. Stove top temperatures of 800-850 degrees reached and documented in above test report.
3. Manufacturer tells consumer "No, don't ever let it get up to 800-850 degrees during operation" AKA "Don't operate stove in a manner consistent with what was documented to achieve EPA compliance."
 

Todd

Minister of Fire
Nov 19, 2005
9,654
NW Wisconsin
What does the temps look like between the cook plate and flue collar? I know my Jotul 602 can easily hit 800+ on its cook plate and it was recommended to me to take stove top temps between it and the flue collar and it was about 150 less than the cook plate. What is the Aspen cook plate made of? Is it similar to the 602?
 

begreen

Mooderator
Staff member
Nov 18, 2005
94,575
South Puget Sound, WA
I wouldn't do 800 or 850 with anything other than welded steel
Cast iron is tough, it just doesn't like thermal shock. Cast iron car and truck manifolds can get much hotter. Our F602 has seen 800º several times, though I try to keep it more in the 700º range at peak.

@MikeGraz what is being used to measure the stovetop temp now? Did you get a new IR thermometer with a higher reading temp range?
 
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MikeGraz

New Member
Oct 31, 2021
15
NY
Thanks for the link to the EPA report. Interesting reading. I saw that the temperatures listed are FB top. I was not sure if that was the surface temp of the box

The cook top surface is the same as the rest of the top, cast iron, but appears to be thinner inside the cooking circle. The inside of the cooking circle normally runs 50 - 100 degrees hotter than outside of it

I am using an IR thermometer that goes up 750. When i had the stove fully loaded, inside the circle read "Hi", indicating it was over 750. Outside the circle was measuring around 750.
 

wjohn

Member
Jul 27, 2021
213
KS
Good points about the location. They don't give the FB Top location (I am making a possibly dangerous assumption that FB Top = outside top surface of the firebox). I may be seeing wiring to a thermocouple between the cooktop and the pipe outlet in some of the pictures but you can't tell for sure.

The area where the cooktop is does not have insulation underneath it. You can see this in the illustrated parts list at the end of the manual - there's a sort of semi-circular cutout for the cooktop circle. The rest of the cooktop has the insulation underneath it and does not get quite as hot. I don't know if or how much the thickness of the cast iron differs between the cooktop circle and the rest of the stovetop.

If they were seeing 850 on top outside the cooktop, then your 750 outside the cooktop looks pretty good. If they were seeing 850 in the middle of the cooktop then you could be in about the same boat.