Super high stack temps!

Mr.Ark · Post by **Mr.Ark** » Sun. Mar. 17, 2019 8:12 pm

Hello,
I have posted a few times here and I’m trying to get the coal thing down in my dual purpose wood/coal boiler. I have tried a few different sizes and brands of coal with mixed results. I am now burning some blashchak pea size coal. I was told that pea size as opposed to but or stove would burn slower. I was trying to get a slower more complete burn and less clinker.
So far my take on this coal is it’s MUCH higher in volatiles. It really stinks like sulfur compared to Lehigh nut coal. Is that because of the smaller size?
I also just observed a 550-600 degree OUTSIDE pipe stack temp just up from the boiler exhaust. That is as bad as a raging wood fire!! Talk about wasting heat. I taped off half of my forced draft fan inlet to choke the air way back.
Are these temps just way too high or is it just because of the initial volatile burn from the 3-4 shovels that I just put on the fire??

Post by **coaledsweat** » Sun. Mar. 17, 2019 8:15 pm

Do you have a manometer or know what your chimney draft is?

Mr.Ark · Post by **Mr.Ark** » Sun. Mar. 17, 2019 8:44 pm

coaledsweat wrote: ↑
Sun. Mar. 17, 2019 8:15 pm
Do you have a manometer or know what your chimney draft is?

No I don’t.
It’s a sealed unit with forced draft from a fan with a sealed flapper when it shuts off.
It’s an interior 8” chimney that’s about 2 stories tall plus up through the roof.

Post by **StokerDon** » Sun. Mar. 17, 2019 9:34 pm

Anthracite Pea sized coal is a good bit smaller than Stove size, so, yes it should burn slower. Typically, hand fired anthracite boilers don't use a "forced draft blower". The Pea coal bed would be much more dense than the Stove coal bed, it is possible that the blower is getting your coal bed too revved up.

You should invest in an inexpensive draft gauge. It's always a good idea to know what the chimney draft is when things go wrong.

-Don

Mr.Ark · Post by **Mr.Ark** » Sun. Mar. 17, 2019 11:28 pm

StokerDon wrote: ↑
Sun. Mar. 17, 2019 9:34 pm
Anthracite Pea sized coal is a good bit smaller than Stove size, so, yes it should burn slower. Typically, hand fired anthracite boilers don't use a "forced draft blower". The Pea coal bed would be much more dense than the Stove coal bed, it is possible that the blower is getting your coal bed too revved up.

You should invest in an inexpensive draft gauge. It's always a good idea to know what the chimney draft is when things go wrong.

-Don

I’m pretty sure the opposite of what I wanted to happen is happening.
I was told the stove coal will burn faster because it’s more open to air flow and the small stuff will burn slower because it lets less air through.
I was a little skeptical with that idea but went along with it.

It seems to burn super hot and fast much the way wood kindling would instead of a firebox full of unsplit round.

Post by **coaledsweat** » Mon. Mar. 18, 2019 10:44 am

You are giving heat up to the outside because of an excellent chimney and forced draft. You need a barometric damper to control the draft and it should probably not exceed -.06. I'll wager yours is twice that. Post up some pics of the install and controls and our resident wizards will have answers for you.

Post by **Rob R.** » Mon. Mar. 18, 2019 10:53 am

I was told the stove coal will burn faster because it’s more open to air flow and the small stuff will burn slower because it lets less air through.

All other things equal, that is true.

CoalisCoolxWarm · Post by **CoalisCoolxWarm** » Mon. Mar. 18, 2019 11:43 am

Are you talking about a power vent, draft inducer, or combustion fan?

They could each meet your description but function quite differently.

McGiever · Post by **McGiever** » Mon. Mar. 18, 2019 11:55 am

As reported elsewhere...Sealed burn chamber and the combustion fan is only inlet in for burning of either his wood or coal.

OP Was considering adding on a bimetallic chain damper in lieu of the forced draft.

Moderators need to merge his 2 topics into 1.

CoalisCoolxWarm · Post by **CoalisCoolxWarm** » Mon. Mar. 18, 2019 12:09 pm

Thanks for that info.

Sounds like way too much air from that blower.

Do you have a round opening on the side of your fan? Can you get a pic?

McGiever · Post by **McGiever** » Mon. Mar. 18, 2019 12:39 pm

Mr.Ark wrote: ↑
Sun. Mar. 17, 2019 11:25 pm
This is a sealed firebox. There is no other way to let air in without some fabrication of the boiler.
What I’m trying to figure out is how much of a volume of air is needed for the given btu output.
More air or less air will control the burn rate.
Right now I’m experimenting with closing off some of the air because I think the fan is running the coal too hot.

His other thread discusses his attempts at partially blocking off the fan intake.
But even then with fan cycle off the inlet hole then becomes 100% sealed shut until next heat cycle call.
With the heat cycle call it's a blast of air from forced fan on the 150-200 lb. charge of glowing coals...that's even 10 times the size of what AA/AHS_260 does...WOW!!!

Natural Draft with 'feathering' or modulating control is best fix for tighter control...
Since this a boiler a Samson Valve would serve this best. https://www.samson.de/document/e05300en.pdf

CoalisCoolxWarm · Post by **CoalisCoolxWarm** » Mon. Mar. 18, 2019 3:50 pm

Wow, never saw one like that. No air at all?

Mr.Ark · Post by **Mr.Ark** » Tue. Mar. 19, 2019 12:37 am

CoalisCoolxWarm wrote: ↑
Mon. Mar. 18, 2019 3:50 pm
Wow, never saw one like that. No air at all?

The boiler is the same as a Royall 6300 that is currently made. I think there is some good pics on there website.
It is a sealed unit that starts a fan when it needs heat.

Mr.Ark · Post by **Mr.Ark** » Tue. Mar. 19, 2019 12:38 am

CoalisCoolxWarm wrote: ↑
Mon. Mar. 18, 2019 11:43 am
Are you talking about a power vent, draft inducer, or combustion fan?

They could each meet your description but function quite differently.

It’s a combustion fan.