Looks Like I Have Unburned Coal in My Ash... HELP!

I recently installed a Harman Stoker VF3000 Boiler.. I seem to be going through coal quickly and it looks like unburned coal in my ash tub.. I have crunchy ash (maybe that is what is called fly ash I don't really know) with regular unburned coal mixed in.. I am very new to this coal burning thing.. Any help would be much appreciated! I will try to take a picture of the ash so all of you expert coal burners can help a newbie with getting a clue of what I am doing...
Thanks
Andy

That is normal, you will have a certain amount of unburnt coal in your ash, and sometimes clumps depending on how hot you are running it and how it is cycling. FLy ash is the light powdery stuff, the clumps, can be CLINKERS if fused together, normally only happens when burning really HOT.

have you checked and calibrated your draft with a gauge?

DO A search on Unburnt Coal,might slight adjustments, but sometimes it gets caught on the grate or doesn't burn correctly.

Too Much Unburnt Coal

Unburnt Coal

What;s your setting on the stove? ON TIME/OFF TIME aquatat setting, etc...

On time is 6 off time is 10, Aquastat is set to 180 with a max shut off of 190 because I am running PEX tubing and already over heated it and blew a line at 220... If I turn it any lower my temp drops to 140 and then my gas boiler turns on and I am trying to avoid that
Andy

Andy, if you just installed the boiler, it may just need some adjustments. There is some good information in this thread: VF3000 Installation & Operation Tips Also, there are a few VF3000 guru's on here that should chime in shortly.

In the mean time, can you show us a picture of the fire while the stoker is running? A picture of the ash would also be good.

Thanks for all your help, you have pointed me in the right direction!
Andy

Hi Andy

Six minutes on and 10 off is very high for a pilot time. I remember running about 1 minute on and about 12 minutes off back when I had my Mag. You do realize that the purpose of the timer is to run the stoker when the aquastat is not calling for heat. When the aquastat, calls for heat, the stoker and pilot blower run continuously till the demand for heat is met, then it goes back to the pilot mode feeding just enough coal to keep the fire going.

One of the tricks many people do here is to plug the pilot blower into a regular outlet so that it runs continuously. This cuts down the unburned coal considerably. You will always have some unburned, its just the nature of the beast.

BTW which Sparta are you located in? There is a Sparta here in Sussex Co NJ?

Good Luck

Bill

Bill, I am in Sussex County NJ, I have my Harman running stand alone feeding my gas boiler on the return lines and I have to maintain a 150 to 180 temp so when a zone calls for heat it goes through the gas boiler and then back to my coal boiler.. The aquastat only keeps the boiler from over heating. I did it this way because I would have to re-plumb my entire heating system with w dual pump and zones. So the way I have it running is just to keep the temp between 150 and 180, I jacked to off time to 12 and it seems to be okay that way also but if a zone calls for heat and it is in an off cycle it will take the temp down and the gas boiler comes on once in a while..... Any thoughts with the additional information...?
Andy

Hi Andy

You have the two boilers in series and have the coal boiler running essentially at a manual feed rate so that it feeds preheated water to the gas boiler and then the to the radiation. I don't think I would have done it that way. Without some form of modulation based on demand for the coal boiler you will either:

1. Have the coal boiler set so low as to not deliver as much heat as needed in really cold weather. You will lessen the risk of over temp doing this.
2. Have the coal boiler set so as to deliver a good portion of the heat during the cold weather, but have to then worry about over temps when the heat demand drops.

Why not use the aquastat to control the coal boiler like it should and set it to a temperature higher then the gas boiler, or just set the aquastat on the gas boiler to a lower setpoint then the coal boiler.

I think if you hit a really warm day without much of a demand for heat, your coal boiler will hit that high temp quite easily, and this with PEX tubing is especially bad.

What kind of house are you trying to heat? What was the capacity of the gas boiler? What kind of radiation do you have?

The Harman can deliver about 80 to 90K BTU, comfortably, much more then that and I think it would run out of steam.

I too am a Sussex Co resident, have been for the past 27 years. Not far from you in Sparta, maybe 20 to 30 minutes.

Bill A.

You have the two boilers in series and have the coal boiler running essentially at a manual feed rate so that it feeds preheated water to the gas boiler and then the to the radiation. I don't think I would have done it that way. Without some form of modulation based on demand for the coal boiler you will either:

1. Have the coal boiler set so low as to not deliver as much heat as needed in really cold weather. You will lessen the risk of over temp doing this.

2. Have the coal boiler set so as to deliver a good portion of the heat during the cold weather, but have to then worry about over temps when the heat demand drops.

Q. Why not use the aquastat to control the coal boiler like it should and set it to a temperature higher then the gas boiler, or just set the aquastat on the gas boiler to a lower setpoint then the coal boiler.

A. I have the temp on the gas boiler set to 140 and I have the Aquastat set at max of 180 on my stoker.. It sometimes gets over that but then the Johnson Controls will shut it down until it gets below 175.. then power will turn back on to the feeder and blower returning them to regular cycle.

I think if you hit a really warm day without much of a demand for heat, your coal boiler will hit that high temp quite easily, and this with PEX tubing is especially bad.

On a warm day it will get to the high temp quickly and stay there but the Aquastat and Johnson controls will keep it at the max temp. On a warm day I do back the feeder down or adjust the on / off time on the stoker control.

Q. What kind of house are you trying to heat? What was the capacity of the gas boiler? What kind of radiation do you have?

A. I have a split level house with 3000 square feet... Hot water base board and I think the gas boiler is about 110000 BTU

The Harman can deliver about 80 to 90K BTU, comfortably, much more then that and I think it would run out of steam.

I too am a Sussex Co resident, have been for the past 27 years. Not far from you in Sparta, maybe 20 to 30 minutes.

I have been in Sparta for 33 years and will most likely be here another 10 or so...

Bill A.

Andy I am new this year too. I also have a VF3K. Great boiler but worst setup manual and operating manual I have ever seen. You can learn a lot here . I will tell you that I worked at mine for a month until I really got it dialed in. I am running 2 on and 12 off. I too had a lot of unburned coal in my ash. One thing I found (which was not clear in the instructions) was that there is a lever under the fire grate that is used to clean the fly ash out. During operation this lever MUST be closed in the position perpendicular to the grate or to the flow of coal. This setting immediately increased my draft and raised my flames around 4 inches further and helped with the unburnt coal. I also learned to make adjustments very small and allow 12 hours or so before making more adjustments. It takes a while for the system to equalize to the new adjustments. Especially the feed rate. I am about 3 1/4 turns open. Mine will pop down to a 130 temp if all of my circulators come on at the same time but it will recover. Just give it some time. You will be happy saving $$$$ every day.

Sometimes unburnt coal is not coal....it's rock or slag. Sometimes anthracite is so hard it won't burn. I've never seen a coal stove, stoker or hand-fired that does not leave some coal unburnt. When I burned nut coal I used to pick it out of the ash and sometimes got as much as a half bucket of coal from 4 or 5 buckets of ash. I threw it back in the bin and tried again.