BOOM!

Re: BOOM!

PostBy: lowfog01 On: Sun Mar 15, 2009 4:38 pm

So I'm back from Norfolk. While we were gone I had the stove on an idle. When we got back this afternoon (37 hours) I still had a red glow in the ash pan and plenty of unburned coal in the stove so I gave the fire 2 or 3 long pulls on the ash grates and opened the ash door. The house was 65*. I set my timer and over the next hour I periodically closed the ash door while opening the load door for a little while. I was trying to see if that eliminated or made a difference in the strength of the puff backs I'd been having. After about an hour the blue ladies showed up with a whoosh as I opened the load door.

It was sort of cool. It was significantly less powerful than I'd been experiencing but I think only because I had been periodically opening and closing the various doors. Maybe that's the answer when I'm reviving this stove from idle before a strong draft develops.

Someone suggested that maybe I need to clean the flyash out of the stove and my chimmey connector pipe but I just did that in late Jan. That was the first time since I got the stove 3 seasons ago so there was a lot of flyash then but I have a had time believing it could build up so much again in 2 months. Despite the fire burning Ok I am beginning to think I have an ongoing problem with the draft because I couldn't get the monometer to register and the fire has been sort of funky lately. I'll find out soon enough if the flyash was the problem as the heating season is coming to an end very quickly. :(

It's been a very good season for us and the many things I've learned are allowing me to already begin planning for next year. I hope everyone has a good week. Lisa
lowfog01
 
Hand Fed Coal Stove: Mark II & Mark I
Coal Size/Type: nut/pea

Re: BOOM!

PostBy: rberq On: Sun Mar 15, 2009 5:32 pm

lowfog01 wrote:It was significantly less powerful than I'd been experiencing but I think only because I had been periodically opening and closing the various doors.

I hate to rain on your parade, but I think you were just lucky in your timing. When the coal bed is reaching that critical point where the gas/air mix is close to ignition, a matter of a minute can make the difference between gentle whoosh and BANG. I recommend (just call me Mr.Know-It-All) that you NOT close the ash door before opening the load door when going through that revival process. Just closing the ash door can sometimes make the bang by suddenly making the mixture richer in coal gas and leaner in air. With the ash door still wide open, SLOWLY open the load door, then SLOWLY close it. Closing it too fast can also trigger a bang. Once you get flames that sustain themselves after you close the load door, then close the ash door but still with the spin draft wide open. Let 'er rip for awhile like that, until stove temp gets up to a reasonable number, then close the spin draft to a reasonable level.

That works well for me when loading new coal, and I'm sure it would work for reviving your fire. However, it's not very practical, because reloading a hot stove requires the door-open-close process for only a few minutes, whereas reviving after a long idle would require you to play with the doors for much, much longer. Sorry, I don't have a practical solution for your case.
rberq
 
Hand Fed Coal Stove: DS Machine 1300
Coal Size/Type: Nut -- Kimmel/Blaschak/Reading
Other Heating: Oil hot water radiators, propane

Re: BOOM!

PostBy: lowfog01 On: Sun Mar 15, 2009 6:52 pm

rberq wrote:
lowfog01 wrote:It was significantly less powerful than I'd been experiencing but I think only because I had been periodically opening and closing the various doors.

I hate to rain on your parade, but I think you were just lucky in your timing. When the coal bed is reaching that critical point where the gas/air mix is close to ignition, a matter of a minute can make the difference between gentle whoosh and BANG. I recommend (just call me Mr.Know-It-All) that you NOT close the ash door before opening the load door when going through that revival process. Just closing the ash door can sometimes make the bang by suddenly making the mixture richer in coal gas and leaner in air. With the ash door still wide open, SLOWLY open the load door, then SLOWLY close it. Closing it too fast can also trigger a bang. Once you get flames that sustain themselves after you close the load door, then close the ash door but still with the spin draft wide open. Let 'er rip for awhile like that, until stove temp gets up to a reasonable number, then close the spin draft to a reasonable level.


I don't mind a little rain if it's going to make my life easier. :) What you say has a lot of validity to it except I thought that the 2cd rule of a well burning stove was never have both doors open at the same time. Number one is never mess with a weak fire; revive it first. However, having the doors open one at a time isn't exactly working either so I will give your advice a try. From the looks of this week's forecast I'll be putting my stove to idle everyday so I'll be reviving it, too. Thanks for you input. I'd really like to get this cleared up before the season truly ends. Lisa
lowfog01
 
Hand Fed Coal Stove: Mark II & Mark I
Coal Size/Type: nut/pea

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Re: BOOM!

PostBy: franco b On: Mon Mar 16, 2009 7:04 pm

I don't think it is acceptable to ever get a puff back, which is a polite word for explosion and means that the appliance is being operated in a dangerous manner. Also it is being operated in a very innefficient way. Those gases are a perfectly good fuel and should be burned.

Everybody knows that if you are manually lighting a gas fired oven you turn on the gas and immediately apply the match. If you wait too long the gas explodes because too much has accumulated before ignition.

The same thing happens with a coal stove. A large load of unburnt coal that has been cooking for hours suddenly gets more heat and releases its gas all at once overwhelming the ability of the stove to pull it up the chimney due to low draft. If it then gets enough air it explodes. A wood fire under the same conditions smolders and smokes. The coal fire does not smoke but produces large quantities of Co and the stove that ran at 80% efficiency in cold weather probably gets about 60 or 70 percent.

In warm weather tend the stove more frequently and run it with a thinner bed so hot coals are visible all the time. Feed with smaller amounts. Any fuel burns best when burned in small quantities,very hot, as in coal stokers or pellet stoves.

So let experience be the guide and experiment with different techniques in warm and cold weather. Be aware that if it puffs it is not right. Just because a coal stove is capable of being throttled down and still burn does not mean there is not a price to pay.

Richard
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: BOOM!

PostBy: lowfog01 On: Mon Mar 16, 2009 8:13 pm

franco b wrote:So let experience be the guide and experiment with different techniques in warm and cold weather. Be aware that if it puffs it is not right. Just because a coal stove is capable of being throttled down and still burn does not mean there is not a price to pay.

Richard


I'm definitely experimenting with different techniques in the warm weather. I'm learning something new about burning coal everyday. I'll try to apply what you suggested in tomorrow's idle. We are forecasted to have a 40* overnight with a 65* daytime tomorrow before dropping to a 30* overnight and 40* high over the weekend. I like the cooler weather but hope the weather even outs soon. Thanks for the input. Lisa
lowfog01
 
Hand Fed Coal Stove: Mark II & Mark I
Coal Size/Type: nut/pea

Re: BOOM!

PostBy: rberq On: Mon Mar 16, 2009 9:10 pm

I like that idea, Richard, burning with a thinner coal bed in warm weather. I'm going to try it, too. I don't like to see zero flames, because I know all that good gas is going up the chimney unburned.
rberq
 
Hand Fed Coal Stove: DS Machine 1300
Coal Size/Type: Nut -- Kimmel/Blaschak/Reading
Other Heating: Oil hot water radiators, propane

Re: BOOM!

PostBy: lowfog01 On: Wed Mar 18, 2009 1:01 pm

rberq wrote:I like that idea, Richard, burning with a thinner coal bed in warm weather. I'm going to try it, too. I don't like to see zero flames, because I know all that good gas is going up the chimney unburned.


I have been burning a thinner coal bed the last couple of days per Richard's suggestion. It's going much better while burning at a slow idle. The stove room has been bearable to be in (the windows are open) and the rest of the house is comfortable. It hasn't taken nearly as long to refresh the fire for the evening and I haven't had any puff backs. I'll keep doing this until I end the season in about a week to ten days. While its 60* outside today, our temperatures are forecast to drop back to the low 30s for overnight and the low 50s for the high through the weekend. It's classic March weather for around here. Thanks again, Lisa
lowfog01
 
Hand Fed Coal Stove: Mark II & Mark I
Coal Size/Type: nut/pea

Re: BOOM!

PostBy: Jeddbird On: Wed Mar 18, 2009 4:42 pm

rberq wrote:I like that idea, Richard, burning with a thinner coal bed in warm weather. I'm going to try it, too. I don't like to see zero flames, because I know all that good gas is going up the chimney unburned.


The only time I actually see flames in warmer weather is when I reload the stove & want flames to burn off volatiles. Normaly, I keep the fire cool enough that it almost looks dead if I didn't read the thermometer. (which I keep between 120*-160* when it's warm out.
Jeddbird
 
Stove/Furnace Make: Dutchwest
Stove/Furnace Model: Federal

Re: BOOM!

PostBy: franco b On: Wed Mar 18, 2009 6:09 pm

Jeddbird wrote:
rberq wrote:I like that idea, Richard, burning with a thinner coal bed in warm weather. I'm going to try it, too. I don't like to see zero flames, because I know all that good gas is going up the chimney unburned.


The only time I actually see flames in warmer weather is when I reload the stove & want flames to burn off volatiles. Normaly, I keep the fire cool enough that it almost looks dead if I didn't read the thermometer. (which I keep between 120*-160* when it's warm out.


It's not just the burning of volatiles, but getting as close as possible to complete combustion of the remaining carbon.

If your stove is putting out half the heat as when you were running it at the sweet spot you discovered by experience in the cold weather, then common sense says you should be burning half the coal. I suspect you will find however, that you are using a bit more than half the coal that common sense would dictate. That cooler fire is not as efficient and is putting out more CO which accounts for the extra coal. Anything you can do to attain the ideal of a small hot fire will help. Thinner hotter bed and more frequent feeding of small amounts should help. With low draft and the need for low output it is a juggling act to find that sweet spot again with a low fire.

Richard
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

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