How quickly does the stove warm up?

[begreen]

Recently the question has come up about how quickly a stove of large mass can get up to temperature. It's finally getting cool here so I decided to time some fire starts. I noticed last night with a cold start that the stove warmed up pretty quickly, but didn't time it. This morning I did watch the clock. This first timing was with a slightly warm stove from last night's fire.

Temp this morning was 40F. We had a medium sized fire last night, but only cold coals this morning when I got up. The stove was still slightly warm to the touch, maybe about 110F. I put in 5 doug fir splits with a chunk of super cedar. The dry wood took off immediately. 11 minutes later the stove top was at 300F, heat was radiating from the glass and I turned the air down to about 1/4 open. Secondary combustion was present and active. At 20 minutes the stove top was 425F with good secondary combustion. I added one more split to the middle to even out the load. At 30 minutes stove top temp was 510F. Good heat was convecting off the top and the front was quite radiantly hot. At 60 minutes the stove was close to cruising temperature of 625F. It might creep up to 650F. Air was turned down al little more to 1/8 open. Living room temp was 71F, house temp in the hall at the thermostat was 69F.

I'll do this test again with a stone cold stove for comparison.

 

[Poindexter]

If you are a regulated burner it looks to me like 20 minutes to good secondary combustion should keep the PM2.5 police off your front porch.

 

[Highbeam]

If you are a regulated burner it looks to me like 20 minutes to good secondary combustion should keep the PM2.5 police off your front porch.

He and I are regulated, as are all major Puget sound counties. Under 20% within 20 minutes or something like that.

This was a warm start though. Add time for a cold stove.

My non-cat got a burn last night from cold and within a half hour I was well past 500 degrees stove top temp. Non-cats are way faster to bring up to clean burning temp.

 

[begreen]

This test encouraged me to try a dead cold startup next. There were no hot or glowing coals for this start. The two things that helped this fire take off quickly were - dry wood and supercedar. I started the fire with full-sized 6-7" splits in the tunnel of love config with one sliver of kindling on top of the 1/4 chunk of supercedar in between the two splits. Then on top was a 4" split at a slight angle to allow air and flames from the starter to ignite the top piece. Two other full-sized splits were placed on either side. Overall this is a medium sized fire once the additional split was added. Stove top leveled out at 650F and is cruising now at that temp.

 

[Woody Stover]

I'd think you'd have the advantage with the non-cat. Seems like a lot of heat can still get to the stove top of the non-cats in bypass mode. I have to think that cats are sending a greater percentage of heat up the open bypass; There's only the small cat opening to supply heat to the stove top, and flow is further restricted by the cat itself. I don't know how much quicker my cats can get to temp with a slightly warm stove as opposed to stone-cold, but it's probably more of a factor than it would be with a non-cat.

 

[bwells794]

I read the second paragraph in my mind as a scientist in a white lab coat, clipboard in hand, speaking into a miniature tape recorder... is that weird? lol

 

[begreen]

No bypass mode on the T6. Fortunately draft is strong enough that this isn't needed. What would be helpful to others would be this same test done on a non-bypass soapstone stove like the Mansfield.

 

[webby3650]

No bypass mode on the T6. Fortunately draft is strong enough that this isn't needed. What would be helpful to others would be this same test done on a non-bypass soapstone stove like the Mansfield.

With my Mansfield you could still sit on it after a good 30 minutes of ripping fire.

 

[Woody Stover]

My gut feeling is that the Mansfield will lag behind your plate-steel top a bit but nowhere near as much as my cat will. I'm waiting for the cat to fire off before I can really get heat to the stove top, and I'm looking at a half hour at least until I can do that. It's hard to measure the stove top temps on my steel/cast-box cats (Dutchwest and Buck 91.) The Dutchwest has about a 5/8"-thick cast chunk above the cat, which is slow to heat up, and there's no good way to shoot the temp on the Buck stove top.

 

[begreen]

Another big difference in my example from what others may see is the wood. Very dry doug fir burns hot and quickly. Someone doing the same test with oak or locust would likely get a slower warmup. Even when burning locust or madrone I always start up with a softwood like fir.

 

[begreen]

With my Mansfield you could still sit on it after a good 30 minutes of ripping fire.

Good to know. FWIW, I think you could do the same, for a brief time, on the trivet top of the T6. One could place their hand on it for a short while without pain.

 

[Woody Stover]

I've usually got some hotter wood on the top/front of the load, Tulip, Cherry or soft Maple. On both the cats I mentioned, the tip of the cat probe should give a good indication of the temps getting through the cat, and they are both slow to rise. The Keystone probe doesn't reach over the cat...

 

[Woody Stover]

The sides of my Dutchwest are getting hot probably as quickly as any non-cat would, so that's some heat into the room, maybe more than your T6 and my Buck which are losing some radiation into the jacket.

 

[begreen]

Yes, the sides of the T6 never get very hot. They currently read 200F with a dwindling fire and 475F stove top. The heat from the inner steel stove sides is much hotter and much of it convects up the air channel created by the cast sides to the top.

 

[Highbeam]

Very few non-cats have any sort of bypass anymore. That's one of the reasons they are so easy to operate. Just light the fire, close the door and adjust air intake. The very first wisp of cold smoke is running along the entire stove top between the front door and the flue outlet. Compare to a stove with bypass (like a cat) which shoots the smoke directly up the stack without warming the stove much.

I've had non-cat, non-cat stone, and cat stoves and the absolute slowest one to heat the room was the stone stove by a long shot. In comparison to stone, the cat stove is fast.

 

[webby3650]

Very few non-cats have any sort of bypass anymore. That's one of the reasons they are so easy to operate. Just light the fire, close the door and adjust air intake. The very first wisp of cold smoke is running along the entire stove top between the front door and the flue outlet. Compare to a stove with bypass (like a cat) which shoots the smoke directly up the stack without warming the stove much.

I've had non-cat, non-cat stone, and cat stoves and the absolute slowest one to heat the room was the stone stove by a long shot. In comparison to stone, the cat stove is fast.

My experience as well.

 

[Dairyman]

No bypass mode on the T6. Fortunately draft is strong enough that this isn't needed. What would be helpful to others would be this same test done on a non-bypass soapstone stove like the Mansfield.

Stone cold start tonight. 68° in the house 60° outside so not the best draft on startup.

Two ash splits & a small pine round on the bottom with two pine rounds & an oak on top. 1/4 super ceder broken into thirds two on top the other in front of the doghouse with a few pieces of kindling on top. 7:30 start.



7:40 flue probe at 600 stt 120. Shut the air to half. (I like to turn it down at around 500 but stuff happens.)



7:45 probe at 750 stt 170. Turned the air down to its sweet spot.



8:00 probe at 700 stt 360. Turned blower on at half speed. Still no change in room temp.

And at 8:15 the room temp had jumped to 73°. I didn't check the stove temp due to the blower being on.

 

[electrathon]

My main complaint with my stone stove is that it takes a couple hours to really get the stone that is fully cold up to temperature. The stone is like a super insulator keeping the heat out of the room, frustrating when you get home from work and the house is cold.

 

[begreen]

Stone cold start tonight. 68° in the house 60° outside so not the best draft on startup.
Two ash splits & a small pine round on the bottom with two pine rounds & an oak on top. 1/4 super ceder broken into thirds two on top the other in front of the doghouse. 7:30 start.
And at 8:15 the room temp had jumped to 73°. I didn't check the stove temp due to the blower being on.

Was this with the Mansfield? If so, that's an impressive liftoff for a big rock stove.

 

[Dairyman]

Was this with the Mansfield? If so, that's an impressive liftoff for a big rock stove.

With the Mansfield. That was probably the best start this year. Which surprised me considering the draft. Average with super ceders is probably 5 minutes slower. Classic top down start with paper and a lot more kindling this would be average for me.

 

[BrotherBart]

Want it hot at the front end, steel stove. Want it still hot at the back end,. rock stove. Kinda some physics involved.

I still believe the rocks waste too much heat up the pipe warming up, but that is just me. Since the dealer wouldn't sell me that too many years on the floor Mansfield I lusted for at a price I would't pay.

 

[webby3650]

Want it hot at the front end, steel stove. Want it still hot at the back end,. rock stove. Kinda some physics involved.

I still believe the rocks waste too much heat up the pipe warming up, but that is just me. Since the dealer wouldn't sell me that too many years on the floor Mansfield I lusted for at a price I would't pay.

I agree! I felt like tons of heat was being pumped out the pipe. That stone can only release a certain amount of heat, the rest goes up.
I rarely ever see a Hearthstone with a dirty flue either, I think it's because of all that extra heat in the flue. Owning one certainly helped me realize that I'm a steel stove kinda guy!

 

[Fastdonzi]

I'm learning that once the fire is ripping I can close the bypass about 1/2, then some heat is forced to take the Cat route and it'll heat the Cat and stove top faster.. I'll have to do a Timed start to see.. ( In my mind I think it helps )

 

[spirilis]

I agree! I felt like tons of heat was being pumped out the pipe. That stone can only release a certain amount of heat, the rest goes up.
I rarely ever see a Hearthstone with a dirty flue either, I think it's because of all that extra heat in the flue. Owning one certainly helped me realize that I'm a steel stove kinda guy!

A book I read on masonry heaters mentioned that in the early days of such developments in Europe, lots of ideas were tried, including clay stoves that were otherwise just boxes of fire surrounded by clay.... similar to a modern woodstove just made of ceramic, and that was the big conclusion - clay didn't "accept" the heat fast enough so a lot of heat still went up the flue. The answer then was to increase the length of the flue, eventually into weird contorted cross-flow or zig-zag designs so that enough heat could be extracted by the clay to make it worthwhile. Wonder if soapstone behaves similarly... wouldn't be shocked if it was. Metal just conducts and accepts heat so much faster. An eventual innovation was to use a cast iron "firebox" with ceramics outside of that to improve heat extraction so smaller masonry heaters could be built. (I do wonder how efficient they burned though...)

 

[Dairyman]

Want it hot at the front end, steel stove. Want it still hot at the back end,. rock stove. Kinda some physics involved.

I still believe the rocks waste too much heat up the pipe warming up, but that is just me. Since the dealer wouldn't sell me that too many years on the floor Mansfield I lusted for at a price I wouldn't pay.

With that in mind here's the back end report.

7:30 am: stt 125 with blower on low all night. Hottest spot on the sides was 175. House temp 71 and 59 outside.

Another successful load.

As far as wasted heat & flue temps go that would be my biggest complaint with this stove. But as web said the flue stays clean so at least its not a total waste. But strangely so far this year its been running a little cooler. Maybe the probe is going bad or the pine perhaps?