Stack Temperatures Hand Fired Stoves

skobydog · Post by **skobydog** » Tue. Dec. 17, 2013 2:28 pm

Would it be abnormal to see a 600 degree (internal probe thermometer) temperature on a coal stove?

I ask because I noticed the other day (and today) that my stack temperatures shot up to 600 degrees (internal probe thermometer appr 24 inches above stove and MPD closed) when the stove was given some air. This is the Hitzer with the automatic damper on the back so it adjusts the air automatically. I could hear the flames going up the stove pipe. Maybe I just never noticed it because I'm not always here.

Normally my stack temp sits a bit under 200 degrees. Maybe I just never noticed the stack temp rising that high before as I'm not always home to see it.

Is this is a normal stack temp for a hand-fired stove? Thanks

wsherrick · Post by **wsherrick** » Tue. Dec. 17, 2013 5:43 pm

A 600 degree stack temperature is really, really high.

EarthWindandFire · Post by **EarthWindandFire** » Tue. Dec. 17, 2013 5:56 pm

If everyone had a 600 degree stack temp, we would melt the polar ice caps and send Santa's workshop crashing into the Arctic Ocean.

Anything above 350 degrees would be unacceptable.

fastcat · Post by **fastcat** » Tue. Dec. 17, 2013 6:10 pm

That temp is normal to see with the Hitzer when running a little higher temps in the stove due to low outside temps. Mine has been doing the same thing. Myself I'm not worried about it because it is only for a short time till the flapper closes.

mmcoal · Post by **mmcoal** » Tue. Dec. 17, 2013 6:17 pm

My 50-93 does the same thing. It doesn't happen all the time, but I do get 500-600 degree stack temps after a shake down once in awhile. For me once it spikes, it usually calms down within about 15-20 minutes. It also doesn't matter whether I have my MPD is open or closed either. I think sometimes the new coal igniting right after a shake down starts to rage a little too much before the stove temperature raises enough for the bi-metal damper to respond and close. At least that's my thought on it.

skobydog · Post by **skobydog** » Tue. Dec. 17, 2013 6:46 pm

mmcoal wrote: It doesn't happen all the time, but I do get 500-600 degree stack temps after a shake down once in awhile. For me once it spikes, it usually calms down within about 15-20 minutes. It also doesn't matter whether I have my MPD is open or closed either. I think sometimes the new coal igniting right after a shake down starts to rage a little too much before the stove temperature raises enough for the bi-metal damper to respond and close. At least that's my thought on it.

Looks like you and fastcat have had the same experience with this stove.

What you described is exactly what happened today. I shook down the stove. A short time later (not sure how long) the stack temp spiked for a number of minutes until the back flapper closed. Then within 20-30 mins the stack temp dropped back to around 200 degrees and stayed in that range.

When I opened the flapper again shortly after there was on spike in the stack temp. Like you said, I guess it's just the new coal being introduced at that time.

I suppose it doesn't happen all the time because the back flapper isn't always open after shaking.

JohnnyV · Post by **JohnnyV** » Tue. Dec. 17, 2013 6:53 pm

I believe that is normal. It is only temporary, until the flap closes.

skobydog · Post by **skobydog** » Tue. Dec. 17, 2013 7:10 pm

JohnnyV wrote:I believe that is normal. It is only temporary, until the flap closes.

I'll have to experiment over the next couple shake downs. If I can replicate it then I'll know. I'll purposely keep the flapper open and then closed to see.

I'm still with this stove and would like to make sure for piece of mind while I'm at work.

Keepaeyeonit · Post by **Keepaeyeonit** » Tue. Dec. 17, 2013 7:30 pm

Skobydog,I have a thermometer 2" above the stove outlet and a thermocouple at the same level to check flue gas temp and at shake down/reload I see 500* pipe and 700* to 800*(1000* was the max I ever saw but the pipe never got above 550*) gas temp but thats for a very short amount of time.During normal use with the stove above 500* the pipe is 350* or so and the gas temp is 400*, the pipe is 145* 6' from the stove and after the baro.Keepaeyeonit

skobydog · Post by **skobydog** » Tue. Dec. 17, 2013 9:43 pm

Keepaeyeonit wrote:Skobydog,I have a thermometer 2" above the stove outlet and a thermocouple at the same level to check flue gas temp and at shake down/reload I see 500* pipe and 700* to 800*(1000* was the max I ever saw but the pipe never got above 550*) gas temp but thats for a very short amount of time.During normal use with the stove above 500* the pipe is 350* or so and the gas temp is 400*, the pipe is 145* 6' from the stove and after the baro.Keepaeyeonit

Because I am using double-wall stove pipe I am using a probe thermometer.

Would I be correct in assuming a probe thermometer would be closer to the thermocouple vs a magnetic stick-on stove pipe thermometer?

2001Sierra · Post by **2001Sierra** » Tue. Dec. 17, 2013 9:51 pm

My old Buderus never exceeded 300 degrees, 59000 BTU stove rated.

oliver power · Post by **oliver power** » Wed. Dec. 18, 2013 4:29 am

OK, here's what's happening; If you have a good hot fire at tending time, no problems. Your stack temp may, or may not rise. If it does rise, it wouldn't be much (Example: 25* - 50*) ,then settles back down. Now, if your fire is low at tending time, the first thing you need to do is shut the fan off. You don't want the fan taking any heat off the mass of the stove. As you loose heat off the mass of the stove, the back flapper door will open wider, and wider. Once the fire gets going, it has to heat the entire mass of the stove back up, till the flapper door closes again. By that time, you have a roaring fire, and way higher stack temps than you should. The flapper door acts like a mini ash pan door being left open. The stove runs away on you. Stack temps surge. You loose control (not good). I wouldn't except these high spikes in stack temps as "Normal". The secret is not to loose the stoves heat mass. Also, should the fire be low; it should be built up a little to a time (as if starting a fresh fire), till you have a good hot bed of coals to start with. Because the fan is off, the mass of the stove is heated back up. Or at least rapidly heading in that direction. Only then, the hopper should be topped off. And yes, you're correct about many people not seeing this happen, as off to work they go. All the while, never knowing how close they are to having a house fire Every Day.

Keepaeyeonit · Post by **Keepaeyeonit** » Wed. Dec. 18, 2013 7:02 am

Skobydog,OP brings up something I forgot your stove has dial-a-temp so your tending routine is going to be different then mine.The other thing is not tending the stove and running out the door, I leave myself 25 to 30 minutes after a reload to make sure that everything settles down before I leave the house.Keepaeyeonit

coalkirk · Post by **coalkirk** » Wed. Dec. 18, 2013 7:25 am

If you are using an internal probe thermometer you need to make sure the probe cannot "see" the fire in the stove. If it does you are getting a radiant effect on the probe instead of measuring the stack temp.

bksaun · Post by **bksaun** » Wed. Dec. 18, 2013 7:33 am

Big difference between an internal temp and an external magnet temp, 600 was normal for my hitzer, I used a grill thermometer so it measured the internal temp, also had a magnet type beside it and the temps were 175-200 degrees different when running on high.

We need to compare apples to apples here.

Bk