Upping Heat Output

Upping Heat Output

PostBy: crazysteamer On: Tue Jul 06, 2010 10:13 pm

OK, dumb question.

My Reading is running combustion fans (full time, after-market 66 CFM rated Grainger units with external air).

What happens if I put on fans that run 100+ CFM?

Other than the obvious...more heat...the considered possibilities are:

1> blowing coal off grate
2> too high a temperature in furnace area, melting / warping things
3> Everything goes as planned, and I can up the output air temperature by 15-20 degrees by being able to feed more coal.

Last winter (my first) was just fine, but there were a couple of days when it was really cold out and the furnace ran pretty much non-stop to keep up. I would like to actually have just a bit of excess capacity so that the furnace can actually cycle once in a while. It's a BIG house for the furnace.

Anybody 'been there done that'?
crazysteamer
 
Stove/Furnace Make: Reading
Stove/Furnace Model: Susquehanna

Re: Upping Heat Output

PostBy: 2001Sierra On: Tue Jul 06, 2010 10:20 pm

I am thinking feed rate is where the btu's are. If the feed rate is increased too much coals fall off the grate before being consumed. The combustion fan helps maintain the static pressure of the burn chamber as well as combustion air. Increasing the combustion air puts the system out of designed output. Kind of like a blast funace. This is my opinion for what it is worth. I have replaced my Keystoker combustion fan with a Grainger ball bearing unit trying to lower the fan noise. This has helped but I also used a high end manometer to verify proper combustion chamber pressure.
2001Sierra
 
Hot Air Coal Stoker Stove: Keystoker 90 Chimney vent
Coal Size/Type: Rice
Other Heating: Buderus Oil Boiler 3115-34
Stove/Furnace Model: Keystoker 90 Chimney Vent

Re: Upping Heat Output

PostBy: Wood'nCoal On: Wed Jul 07, 2010 7:05 am

You can try a higher CFM blower for the combustion air, however it has to be done correctly. You need to take over-fire draft readings with a manometer. If you increase the combustion air too much you'll end up pressurizing the inside of the stove. There should always be negative pressure (draft) inside the stove. Some stoves have an adjustable cover over the fan's air intake for this purpose.
Wood'nCoal
 
Stoker Coal Boiler: 1959 EFM 350
Hand Fed Coal Stove: Harman Magnafire Mark I
Coal Size/Type: Rice and Chestnut
Other Heating: Fisher Fireplace Insert

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Re: Upping Heat Output

PostBy: WNY On: Wed Jul 07, 2010 7:30 am

I ran a higher CFM combustion fan temporary while I got a replacement and yes, it gives you a bit more heat, but the clinkers were terrible, it was TOO HOT, the coal fused together and made lumps. Plus you could warp your grates. Just my 2 cents.
Like they said, make sure you monitor yoru Draft, if you put too much air into the stove, you need to be able to exhaust it out your chimney.
WNY
 
Hot Air Coal Stoker Stove: Keystoker 90K, Leisure Line Hyfire I
Coal Size/Type: Rice
Stove/Furnace Make: Keystoker, LL & CoalTrol
Stove/Furnace Model: 90K, Hyfire I, VF3000 Soon

Re: Upping Heat Output

PostBy: crazysteamer On: Wed Jul 07, 2010 7:32 am

I had assumed (you know how that is), that it would be a given that with more air, I would crank up the feedrate accordingly. Sorry about that confusion.

Pressurizing the chamber is something that I had not considered, since on big boilers, this is handled with a draught fan, which isn't the case here (unless I want to put in a power vent)....

Hmmmm.....need to consider this as a possibility....

I have plenty of natural draught with my stack, but have not been specifically monitoring the chamber reference.

Perhaps just keeping the heat IN the furnace would be as beneficial....
crazysteamer
 
Stove/Furnace Make: Reading
Stove/Furnace Model: Susquehanna

Re: Upping Heat Output

PostBy: Wood'nCoal On: Wed Jul 07, 2010 8:17 am

Burning with too much draft will send heat and money right up the chimney, sort of negates the whole idea! You need around -.04" WC draft in the smoke pipe and around -.01" to -.02" WC draft over the fire, if I recall correctly.
Wood'nCoal
 
Stoker Coal Boiler: 1959 EFM 350
Hand Fed Coal Stove: Harman Magnafire Mark I
Coal Size/Type: Rice and Chestnut
Other Heating: Fisher Fireplace Insert

Re: Upping Heat Output

PostBy: LsFarm On: Wed Jul 07, 2010 8:26 am

On those few days that the heat output was not adequate, and the stoker ran at full capacity, was the fire on the grate all the way to the end, maybe with a 1/2" of dark ash at the end? If not you can increase the feed slightly to increase the area of burning coal.

As Dave [WNY] stated, adding more air will increase the heat, but probably cause clinker formation. Not something to have to deal with, or be surprised by. A clinker that doesn't fall off the grate, blocking the fire up behind it,, well it will make a mess, possibly cause an out-fire, or cause a back up of the fire too high on the grate.. none of these are what you want to experience.

On those really cold days, did your barometric damper work adequately? Did it keep the draft in the flue under control? A lot of heat, coupled with a very cold temperature will cause your chimney to have very strong draft.. if the draft is too strong, it will pull a lot of the heat out of the stove, dropping the stove surface temps, lessening the heat available to heat the house.. I'm assuming you have a barometric damper..

Did you monitor the surface temps of the stove and flue pipe?? You need real numbers if you decide to experiment.. otherwise the variables of weather conditions will totally confuse any possible results, and make the experiments just guesses as to whether they are an improvement or not.

Hope this helps.

Greg L
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: Upping Heat Output

PostBy: Wood'nCoal On: Wed Jul 07, 2010 4:53 pm

You need real numbers if you decide to experiment.. otherwise the variables of weather conditions will totally confuse any possible results, and make the experiments just guesses as to whether they are an improvement or not.


My thoughts exactly!
Wood'nCoal
 
Stoker Coal Boiler: 1959 EFM 350
Hand Fed Coal Stove: Harman Magnafire Mark I
Coal Size/Type: Rice and Chestnut
Other Heating: Fisher Fireplace Insert

Re: Upping Heat Output

PostBy: coal berner On: Thu Jul 08, 2010 2:34 pm

He will only have clinkers if he is burning red ash coal not everyone burns red ash coal .
White ash coal will not clinker it will Just produce more fly ash.
coal berner
 
Stoker Coal Boiler: 1986 Electric Furnace Man 520 DF
Stove/Furnace Make: Electric Furnace Man
Stove/Furnace Model: DF520

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