Vermont Casting Aspen C3 - How hot should it run

[SpaceBus]

750-800 is totally acceptable for the hottest point on the exterior of the stove. Sounds like it's burning really well.

 

[wjohn]

I had a fire last night in mine. I reloaded on coals that I uncovered this morning, and shortly after the reload the center of the cooktop got up to a little over 750 pretty quickly, with the insulated spot between the cooktop and flue outlet being about 650. So far this is the hottest I have had things but we are supposed to get down into the single digits in a couple of days so I should be able to push it a little harder and report back.

 

[SpaceBus]

Do you happened to know how long it was at 750? Sounds like the stove did a good job managing on a warm reload.

 

[wjohn]

Do you happened to know how long it was at 750? Sounds like the stove did a good job managing on a warm reload.

Honestly I'm not entirely sure. I did not take temp readings before reloading, but I would guess the cooktop area was probably 150 to maybe 200 degrees tops. After I reloaded I watched it for 20 minutes or so, and it climbed to 750. It seemed to level off, and then started dropping more towards 700, so I went back to bed. The intake damper was maybe half open when I reloaded, so it would've been shutting down as it was heating up after the reload so that made sense.

I think I checked about an hour later and it was up around 750 again. So it could've been around 750 for about an hour, maybe an hour and a half? There's a possibility it could've been closer to 800 for a bit while I wasn't watching it. I am not concerned, personally.

 

[SpaceBus]

Honestly I'm not entirely sure. I did not take temp readings before reloading, but I would guess the cooktop area was probably 150 to maybe 200 degrees tops. After I reloaded I watched it for 20 minutes or so, and it climbed to 750. It seemed to level off, and then started dropping more towards 700, so I went back to bed. The intake damper was maybe half open when I reloaded, so it would've been shutting down as it was heating up after the reload so that made sense.

I think I checked about an hour later and it was up around 750 again. So it could've been around 750 for about an hour, maybe an hour and a half? There's a possibility it could've been closer to 800 for a bit while I wasn't watching it. I am not concerned, personally.

I wouldn't be either. Sounds like 700-750 is the design "setpoint" for the stove.

 

[wjohn]

I put some pretty dry mulberry on tonight and it really took off. It hit 855 degrees in the center of the cooktop and 760 degrees between cooktop and flue exit (insulated beneath). This lasted for 15 minutes or so. Things heated up enough that more paint cured and I got some stink, but I'm basically right at the high end of the EPA stovetop temps so I think we're still in good shape. Then it gradually settled down to 650-750 degrees.

Hopefully this helps some of you other guys/gals with Aspen C3s feel better. I verified my intake flap was closing. It was definitely closed when the stove was around 850 and I don't think it would be able to sustain that temp for too long, but I'll keep watching it for the next few fires here.

 

[wjohn]

Well, I hit 900 degrees F in the cooktop center last night for a bit. It's been in the single digits - low teens at night so this has been the first decent stretch of cold weather to push the stove a little. I'm surprised since my total flue length is on the short side per the installation manual. I'm going to call my dealer when they reopen and ask what they think about the temps, mostly so I can then call HHT (VC's parent company) and tell them I talked to my dealer, and see if I have any better luck than MikeGraz and EddyB did about getting proper info for acceptable stovetop temperatures.

This was a cold start where I was able to shut the door right after lighting the kindling and the fire just kept steadily building up. It never felt scary or wildy uncontrolled, but I definitely would've have been shutting the air down sooner if it had manual controls... Plenty of flames in the firebox, and the almost solid sheet of flames from the secondary air outlets was impressive. Even after the damper fully closed I would've reduced the air more, if I could, but that could only be done by reducing the size of the primary and secondary air holes once you hit that fully closed point. Exterior singlewall stovepipe temps 18" up were 490F max and typically more like 430F.

Do the fine folks of the forum think 900F is starting to get concerning?

 

[stoveliker]

To me that'd be borderline. As are the single wall pipe temps; you got near 1000 F flue gases inside the pipe...
I would try to avoid both - but this stove doesn't allow that.
I don't think something went wrong here (and if it did, you have a case for warranty repair or replacement...), but any higher and I'd be quite concerned.

 

[SpaceBus]

I would be installing a key damper.

Edit: your dealer may agree, but I can't imagine HHT ever verbally or in writing endorsing a key damper.

 

[wjohn]

I would be installing a key damper.

Edit: your dealer may agree, but I can't imagine HHT ever verbally or in writing endorsing a key damper.

The manual specifically states the stove "... is not approved for use with a flue damper." We can certainly debate the reasoning for that, but if I were a manufacturer, that's one of the first things I'd look for in the event I were trying to get out of any warranty claim or other liability, so I'm not even putting that option on the table.

What has me baffled is that I have 14.5' from floor to chimney outlet, vs. the 16' that the VC manual recommends. Out of that, I have ~6' of single wall pipe from the stove outlet to the ceiling, with back to back 45 degree elbows. So, I have three things there that should be somewhat reducing my draft over a standard straight-up 16' floor to chimney cap by the book installation. If anything, I should be having issues getting enough draft vs. too much for the design of the automatic air intake system. I can only imagine how hot things would get if I had another 1.5' of chimney outside, double-wall pipe inside, and no elbows.

I could also understand the need/desire for a flue damper if I had say 20' of chimney from ceiling on up in a multi-story house. It just doesn't make sense the stove should need one in my install, but I may be missing something. I'm open to thoughts and suggestions.

Does that logic make sense?

 

[SpaceBus]

Perhaps you live in a windy area and it's driving draft beyond what the stove was designed for. Does the manual have a draft specification? You can measure draft with a manomter and determine if intervention is necessary. Maybe there is a chimney cap for your system that can help reduce increased draft from wind. I can always tell when the winds are up just by watching the stove.

 

[wjohn]

Perhaps you live in a windy area and it's driving draft beyond what the stove was designed for. Does the manual have a draft specification? You can measure draft with a manomter and determine if intervention is necessary. Maybe there is a chimney cap for your system that can help reduce increased draft from wind. I can always tell when the winds are up just by watching the stove.

5-6 MPH when this occurred. Is that enough that it could cause excessive draft in such a short system? We do get 50 MPH winds now and then, but it's been pretty calm the last couple of days/nights (again, imagine what that situation would've been like in this 900 degree scenario!). I'm at about 1300' above sea level, for a little more background info.

The manual specifies minimum draft of 10 Pa/0.04" of WC. Max is 30 Pa/0.12" WC. I'll do some digging around in old threads on here to see if it's feasible for me to not spend too much money and get something that can accurately measure that.

Still, I am surprised that my setup would be causing problems. In my opinion it is hardly an outlier and should be on the conservative side (in this case - slightly less draft) of a pretty standard install.

I have had zero luck finding any spots around the door or gasketed joints between plates that suck smoke in. I checked again this morning just to rule it out.

I found some references of users with other stoves using magnets, HVAC duct tape, etc. to minimize the size of their intake openings. I'm toying with the idea of testing that on the primary and secondary inlet holes in the intake damper, just to see if it improves or changes anything. Not sure that would be a permanent solution but I might at least learn something.

 

[stoveliker]

No, that wind should not have been a problem.

Can you post pics of your set up (inside and chimney)?

Reading your situation indeed puzzles me. Unless you have an air leak someplace.

 

[wjohn]

I did call the dealer and he kind of went "Hmm" and said I certainly didn't hurt anything, but he wonders the same thing - is 900F repeatably okay to do with these stoves? What's the safe limit? Told me he was curious to hear what VC/HHT had to say as he didn't have an answer and apparently doesn't have direct access to a decent rep there that he can just ask. HHT's customer service is closed today so I will try later in the week.

 

[stoveliker]

Would it be more likely to get answers from VC/HHT if the dealer asked...?

 

[wjohn]

No, that wind should not have been a problem.

Can you post pics of your set up (inside and chimney)?

Reading your situation indeed puzzles me. Unless you have an air leak someplace.

Here's a link to my install thread showing the inside: Link
I will try to get an outside pic later but it is nothing exciting - about 4.5' of chimney sticking up from the roof, with adequate horizontal clearance to the outlet.

Since my install thread was started, I have disconnected the OAK per input from the forum, even though nobody can point me to any text, standard, etc. that actually states "thou shalt not place the OAK inlet above the bottom of the stove's firebox." I did - for testing purposes only - reconnect it at one point so I could use the closed blast gate to restrict air into the intake box of the stove, and it did seem to help slow things downs and temps were gradually dropping when I did this. This lines up with what some of the other Aspen C3 users have experienced earlier on in this thread.

I debated about posting the 900 degree question in here or in my thread, but ultimately decided to put it here as this thread is dedicated to the temps and we have several other Aspen C3 users in the loop.

 

[wjohn]

Would it be more likely to get answers from VC/HHT if the dealer asked...?

I kind of pushed him on that and like I said, he definitely wasn't giving the impression he had a direct line to anyone that would be any better than their general customer service number.

 

[stoveliker]

Hm. No issues stand out from the install.
(And warm air goes up. You want to make it physically impossible to have the exhaust gases go thru the OAK - hence the "has to be horizontal or go down " advice. I believe that's even in some (fire) code.

Stumped...

 

[wjohn]

Thanks stoveliker. I always appreciate having other sets of eyes see if I've missed something.

Really wishing I could have an engineer to engineer talk with someone at HHT. Then I'd know what stovetop temp is acceptable, and understand what range of cases they designed the air control system to be able to handle. To be fair I suppose those min/max draft spec numbers tell me something, and I could compare to what I get out of my setup, but the draft spec range should correspond to some sort of real life range of situations, I would think, which is going to account for some range of outside temps, altitudes, etc. at their target 16' chimney outlet height.

But I also know from experience you don't want every random customer bugging the engineers We'll see if my customer service experience is any better than the prior posters'.

 

[wjohn]

VC/HHT customer service claims that they do not have a max stovetop temp, nor a recommendation of where the stovetop temperature should be measured. They first gave a very canned answer saying there are too many variables (installation, venting, size of fire, type of wood, etc.). I countered saying none of those variables affect what the max recommended temp should be and asked them to reach out to their design engineering team. They came back saying the same thing again, and that they don't test and list it.

All I have to go off of is the highest stovetop temp I can find from the EPA reports - 857 degrees. I am still not able to find where it is measured. The EPA test report introductory pics may inadvertently indicate on the stovetop above the insulation blanket, between the cooktop circle and the flue outlet (see below). The center of the cooktop circle is always going to read higher than that location though because there is no insulation under it. In my experience it reads about 100 degrees higher than the spot between the cooktop and flue outlet. Either way 857 seems acceptable and would be conservative if measured above the insulation. Mine will hit 900 in the cooktop circle if I don't shut down the blast gate I have on the air intake. That's probably 800 above the insulation, so that would probably be acceptable if they are measuring above the insulation. If they are measuring at the cooktop then I am ~50 degrees above what was seen in the EPA testing and would be concerned.

I give them a D for customer service - no F rating, since they did at least respond. I do not at all believe that they would design a stove in recent history and not collect temperature data at different locations, and have temperatures they knew they needed to stay under. They have CAD at least, and an engineering department - this is not a guy in the backwoods with a welding shop building his own stoves and selling them to his neighbors.

Should anyone at VC/HHT be perusing the forums feel free to message me and improve my opinion of the company's customer service. If 900+ degree temps at the cooktop are perfectly acceptable then I would be happy as the stove would be performing as intended. If not something needs to be looked into given I have a pretty ideal install.

 

[Todd]

Try to PM Corie. He used to be an active member here and I believe he actually works for and designed the stove. I thought there was an old thread where he explained how they tested this stove for months burning it hot with 2x4’s with no il effects. Maybe search his posts or contact Begreen, I think he may have a contact for him. I PM’d him last year about the Dauntless, took him awhile to respond but he did answer my questions.

 

[SpaceBus]

What is going on with the white stuff on your flue connection? I wouldn't be too concerned about your temps since the cook plate is supposed to get that hot. When I still had the steel top on my cookstove it got up to 900f easily.

 

[wjohn]

Try to PM Corie. He used to be an active member here and I believe he actually works for and designed the stove. I thought there was an old thread where he explained how they tested this stove for months burning it hot with 2x4’s with no il effects. Maybe search his posts or contact Begreen, I think he may have a contact for him. I PM’d him last year about the Dauntless, took him awhile to respond but he did answer my questions.

Thanks, I did find that thread he had started a while back. I hate to pester folks, especially when their customer support should be doing their job. Like I said, if someone sees this and wants to message me, I'd be happy to have a conversation.

 

[wjohn]

What is going on with the white stuff on your flue connection? I wouldn't be too concerned about your temps since the cook plate is supposed to get that hot. When I still had the steel top on my cookstove it got up to 900f easily.

Those are pictures from the EPA testing report. I presume it's some kind of sealant to make 100% sure they have an absolutely airtight connection for measuring what's coming out of the flue.

Hmm. What's the highest you ever saw on your cookstove? Much past 900?

 

[SpaceBus]

Those are pictures from the EPA testing report. I presume it's some kind of sealant to make 100% sure they have an absolutely airtight connection for measuring what's coming out of the flue.

Hmm. What's the highest you ever saw on your cookstove? Much past 900?

I think the steel top hit 900-950 easily at the hottest point, but the glass top hits above 1000f. My Morso gets up to 800 sometimes, but I've stopped measuring STT and just go by flue temps now, and I don't measure anything on my cooker. The Morso has an insulated blanket over the whole length of the firebox, so I'm not surprised I have a bit lower temps despite having such a similar design.