EFM stoker won't heat up

 
todapark
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Post by todapark » Mon. Mar. 15, 2021 4:55 pm

I have a friend that has an older EFM coal stoker that was running constantly. It is an older unit no nomenclature tag so not sure of the model, it has a 10 inch round view door for checking the burner, it has a 55 gal drum for a hopper with auger feed and the typical blower fan on the other side from the hopper. It uses hot water for heat and a hot water coil that is bolted into the back of the unit. Now here is the problem, it will not come up to temp, maximum temp on the top mounted water temp gauge will never go above 140f, we installed a newer digital readout aquastat from Honeywell and it displays the boiler temp and it matches the temp reading on the aforementioned top mounted analog gauge within 2 degrees of each other. We adjusted the feed and fan over a week of trying and fire pot looks good, ashes are burnt nicely no unburned coal in ash bucket. I even closed the valve below the recirculating pump so no water was cycling thru the boiler and the darn thing will not go above 140 on the analog gauge or on the aquastat readout, the aquastat is installed on the back of the boiler. We bled the system, house is all radiators , I even loosened the top mounted temp gauge in the boiler thinking maybe there was air trapped in the boiler but no air came out just water. Here are a couple additional clues, if I adjust the fan above 4.5 I can see the flame in the burner get higher, it is just licking the top the boiler plate however any additional increase in fan air causes the gases to start seeping out of the top of the hopper (not good I know), any help or suggestions will be appreciated, why wont it heat above 140f, oh yea using anthracite, this problem has me puzzled. also just so the unit would not run constantly until the problem is solved I had to turn the aquastat setting down to 139h and 119L from their usual 180 and 140 settings, any suggestions anyone?


 
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Post by coalmanjoe » Mon. Mar. 15, 2021 5:52 pm

My first guess would be your aquastat is bad. If you are comfortable with basic wiring you can disconnect the wire going to the motor from the aquastat and hot wire the motor to let it run continuously-----if the boiler temperature exceeds 140 degrees I would certainly think it is the aquastat. There are some very knowledgeable individuals on this forum so I will waiting to see what they have to say.

 
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Post by StokerDon » Mon. Mar. 15, 2021 7:11 pm

Welcome Tod, That's a pretty good puzzle!

Let me see if I understand this. Digital readout and mechanical gauge never go over 140. Stoker runs constantly and the boiler never goes over 140. Aquastat was replaced and the system has no air in it. Still the boiler temp won't go over 140.

What feed rate are you running? What are you heating with this boiler? Have the plates or tubes been cleaned this century?

-Don

 
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Post by todapark » Mon. Mar. 15, 2021 7:49 pm

You got the issues correct,new aquastat, new 9' exhaust pipe new timer and new recirc pump (Taco), single zone , the stoker was cleaned this past summer, walls and sides were scraped and back exhaust area plates were wire brushed, holes in the fire pot pedals all seemed clear of debris and no breaks, its's an older model EFM , tried multiple feed settings from 3 to 7 teeth over a week with allowing for 24 hour settling in time and each time boiler will not go above 140f while running constantly, it is just heating hot water in the boiler for a half row home w all rads and the hot water for personal use . I'm guessing and grabbing at straws (yes I know) that there may be something clogging the airflow as I said any fan setting above 4.5 and it starts pushing fumes out the hopper, the clean out lever works and does get some fine sediments in ash bucket when opened, while the guy is using anthracite, he is using the cheaper bank coal vs vein coal and it is dirtier with more fines, the sized used is pea, but he said it used to run at 180 last winter, anyway I've seen a lot of coal stoker problems and never been as flummoxed as with this one, tomorrow I will try to get some pics of the unit, inside the burn area and the fire when running, at the base of the issue I believe we are just not getting enough heat out of the burn pot but why?

 
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Post by franco b » Mon. Mar. 15, 2021 8:02 pm

I would try a sample of another known good coal.

 
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Post by nepacoal » Mon. Mar. 15, 2021 8:23 pm

Pea size coal in a residential EFM? That doesn't sound right... And might be why you get exhaust out through the auger tube and your barrel when the air is increased...

 
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Post by Rob R. » Mon. Mar. 15, 2021 8:26 pm

Sounds like crap coal to me.


 
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Post by Holdencoal » Mon. Mar. 15, 2021 8:35 pm

Did you make sure the water feeder wasn’t stuck open? It’s always running never getting hot, sounds like a lot of cold water is getting in.

 
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Post by todapark » Mon. Mar. 15, 2021 8:41 pm

water feed regulator seems good , pressure gauge sitting at approx. 18psi, coal used is rice some call it pea

 
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nepacoal
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Post by nepacoal » Mon. Mar. 15, 2021 8:45 pm

todapark wrote:
Mon. Mar. 15, 2021 8:41 pm
water feed regulator seems good , pressure gauge sitting at approx. 18psi, coal used is rice some call it pea
Rice sounds better! Pea is two sizes bigger.

 
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Post by McGiever » Mon. Mar. 15, 2021 9:34 pm

Better know that the chimney is clear...shouldn’t be pushing exhaust out thru the hopper.
Some have found dead birds or birds nests...then there is always the fly ash build up to contend with...

 
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Post by Scottscoaled » Tue. Mar. 16, 2021 2:53 pm

I don’t remember the fire reaching the top on mine. Almost like you have a load of Bit. Where did you get the coal?

 
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Post by Scottscoaled » Tue. Mar. 16, 2021 2:56 pm

Show a pictere of the flame if you can

 
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Post by todapark » Wed. Mar. 17, 2021 3:15 pm

Tried some new good vein coal today and same thing, won't heat above 140f no matter how long I leave it run, even with the domestic hot water feed valve closed, the boiler water feed valve closed and the valve below the recirculating pump closed. Person doesn't want it shut down until warmer weather hits. I'm now thinking there is a break, crack or something down in the fire pot between the auger feed pipe and the blower fan pipe as the darn thing keeps pushing fumes up through the 55gal hopper when the fan is set anywhere above 4 even if I hold the 10inch round front view door open while it is running, no fumes come out front door when held open but does come up through hopper. Chimney is newer and is clear and stovepipes are new and clear. When warm weather hits, am going to pull the fire pot out and see what I can find, will update post when I find the problem.

 
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Post by nepacoal » Wed. Mar. 17, 2021 4:07 pm

Perhaps your motor is running backwards... Has it been recently replaced? Some of the replacement motors used need to be reversed for the EFM.


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