Over Heating, Inefficient Burning, Outfires and Lots of Partially Burned Coal in AHS 130

1. inefficient burning--As suggested in some other threads and in the AHS manual the start up procedure is important to getting the full column of coal burning. AHS recommends starting the fire when there will be an extended demand to keep the boiler firing. I use heating my swimming pool as the extended demand when I start the boiler.

2. overheating--I have had that problem and I traced it back to improper draft control. I have found that my AHS-130 will overheat with draft at .04+. Since I readjusted the draft to ~ .035 I haven't had overheating. But I note you said your draft is very low--and that is inconsistent with overheating. Where are you measuring the draft and are you confident in the instrument you are measuring the draft with? As noted be several posters zero draft is simply inconsistent with a 38' interior chimney in good condition and properly sealed smoke pipe/cleanout.

3. outfires--there is a very long thread about "puff-backs" with the AHS and one of the lessons of that thread (in my view) is that control of the proper height of the fire is very important to the proper operation of the AHS boiler. The fire height is controled by the ashing control--raising the set value (SV) moves the fire down and lowering SV moves the fire up. In my experience you should be able to see glowing coal well after the boiler has fired if the fire is at the appropriate level. There is more extensive discussion of the appropriate fire level in other threads and I suggest you read them.

4. In my experience a timer is not necessary to keep the fire buring for at least 24 hours.

5. I second the comment about trying a different coal if all else fails.

6. A final thought is to just raise the question about whether one or more of the controls is not working or is seriously miscalibrated.

Good Morning Everyone, First off I would like to thank everyone who has taken the time to consider my situation and shared their knowledge with me. I haven't responded before this as I started a framing job an hour and 40 minutes from my home and have put in a couple of 13 hour days. Kind of dragging this morning. I will try to answer a few of the questions asked on here. I checked my expansion tank and my plumber went from a Extol 30 to a 60. Obviously that will need to be changed out. I have sealed off my clean out door completely but before I did that I recalled that I generally light a fire in there to warm up the chimney before lighting the boiler. I have to use a torch to light it as the draw is strong enough to keep blowing out the matches. This would lead me to believe that I have a decent draft. My manometer is install between the boiler and the barometric damper, is that the correct location? When we set it up we made sure it was set up perfectly level so I assume the calibration is right but don't understand the poor readings when I can feel the draft at the clean out which is 55 inches below the boiler vent pipe. I do not know if any of my Aquastats are malfunctioning and would not know how to check them if they were short of replacing each one at a time. When I start a fire I run the hot water down until it is cold and turn the 2 thermostats up to 70 degrees at least. I have a boiler mate hot water tank piped in with my oil boiler. I let the unit run for 3 to 4 hours before I switch the grater to the on position. I re lite the fire the day I sent out my original post and it was out again by 10 pm that night. When I looked in the inspection hole I had a beautiful red glow after the initial start at about the 3 hour mark. As far as my coal is concerned we get it by the TT load. I get pea and the others in my group get nut. They all have hand fired stoves and they all love the coal. Complete and hot burns. Does it make a difference that I have a stoker type boiler?? I have about 3.5 tons in the basement so I would prefer it not be the coal but that might be the easiest solution. Unfortunately, the local supplier has nothing in stock for me to try a different brand. I am running Centralia now but could get a load of Blashack in the fall. I could mix the two during the winter as it will burn continuously when there is more of a consistent need for heat. If a timer would solve my particular problem then I would go with one but it seems like some guys get by just fine with out one. The one Vermontday uses sounds like an amazing unit that can leap tall buildings and might just fit the bill. So that is my story , does this additional information help you to narrow things down a bit? I hope so. Thank you all again for you help. It is much appreciated. Ken

With the chimney cleanout sealed...
Has the Manometer shown an improvement in draft...
If the draft is still lacking cover the Baro...
it too can be a leak and reduce your draft...

Rob R. wrote: Do you have sufficient make-up air available to the boiler? If the house is tight, you may need to crack a window in the boiler area.

Maybe I missed it, but I don't think you answered my question about make-up air. It is very important...every try to suck air through a beer bottle? With the windows & doors closed, bathroom fans on, and the dryer running see what your draft gauge says and check for draft at the inspection door on the boiler. You may also need to cover the baro in warm weather to preserve draft.

You posted that the SV of the thermo-grate control is 120. This is different from the AHS manual recommendations and may be a cause of your problem with outfires.

While the AHS manual doesn't provide much information about the importance of the correct heighth of the fire and the results of a fire that is either too high or too low the Axeman Anderson manual does discuss this issue and attributes a fire that is too high to causing outfires. It also attributes puff-backs to the fire being too low.

There was extended discussion of this issue in the thread "AHS S130 Coalgun- Puffbacks & Explosions" and relevant extracts from the Axeman Anderson manual are posted there.

Here is the specific page from the Axeman Anderson manual that talks about effects of fire height:

Bob, I was digging through all of my coal-related stuff looking for the AA manual...I had a vague memory that it talked about this. Thanks for posting it.

Ken, if you are seeing a bright red fire through the inspection door it sounds like the fire is indeed too high.

I ran all winter with my SV at 130 degrees, and when it turned warm I dropped my SV to 120 degrees. The units all seem come from the factory set at 140 degrees, but the manual recommends 130 degrees as the standard and an SV of 120 degrees for warmer weather.

Hi guys,
Rob,My basement is far from air tight, I have a door I made at one end and it has a 1/4 inch gap all the way around it, I have a window open and I have a pipe directly at the bottom of the boiler with fresh air just for the unit. I have my SV set at 120 like the manual says to run in the warmer weather but I have the glowing red coals through the observation port when the unit is running. I will move it up to 130 and see if that helps but Isayre is running his at 120 now without incident. I am going to try and re fire it tonight as we are just about out of oil. I will increase my SV to 130 and block off my damper and see if this improves things for now. I will talk to my plumber about a larger expansion tank but the outfires are taking precidence for the moment. Do you think my aquastats are set to and acceptable level? I will keep you posted, thanks again, Ken

The calibration and performance of thermocouples can vary. Adjust your ashing control so you have a layer of unburned coal on the very top of the fire column, with burning coal visible between the unburned pieces. If you get puffbacks, reduce the ashing temperature.

Aquastat settings sound fine.

all my problems went away when I dropped my ashing down to 110 with a 8 deg. diff...and dropped my op. temp from 180 to 160 and even 150 in the warmer weather, I have no partially burnt coal or outfires and my boiler goes all day in 80 deg. weather without firing...I know every setup is diff. and so on and so forth...just giving you my settings if you wanna give her a whirl, my biggest simplest adjustment was my ashing temp drop, it changed everything as far as burning a lot of coal and unburnt in the ashes

Rob R. wrote:The calibration and performance of thermocouples can vary. Adjust your ashing control so you have a layer of unburned coal on the very top of the fire column, with burning coal visible between the unburned pieces. If you get puffbacks, reduce the ashing temperature.

Aquastat settings sound fine.

I agree with Rob on this.

Do not be concerned so much about a certain number setting or matching someone else's number...do it by what position the fire is in when viewed through the view port.

Another thought on outfires, even with the best chimney draft, the combustion air needs to come up through the ash from grate level on AA and AHS units.

With that said, draft/air will take the path of least resistance.
Burning a coal higher in ash can restrict air on even a unit with induced draft, as it will block or plug the spaces that the air needs to pass up through to re-ignite the dormant red coals perhaps near 12" above.
This likely would also be a cause for excess un-burnt coal in ash pan and since the ashing controller never gets to sense the fire position/temperature it keeps on ashing to no end causing high daily coal use.
If ash is restrictive enough, the air/draft from below will be reduced and the air will come from anywhere it is less restrictive. Anyone who has had their hopper on an ASH run empty or an AA auger exposed in the bin knows this...the fan will pull air down through hopper or up through hollow auger, and little if any air up through from the ash grate area.

It sounds like this supply of coal worked well during the colder seasons higher boiler loads and is only a problem when latter experiencing the lighter boiler loads.

My .02 cents, "You really need to get a few bags/buckets of a different coal to see what a difference that will make".
Making a whole lot of adjustments/changes would not make up for a draft problem which may not be a chimney problem.

I would check that manometer...a little light suction should prove tube is clear and poke a bit into flue fitting.

Well I re llite the boiler 2 nights ago and it is still going. I increased the ash temp to 130 as suggested to get the fire lower, this must have worked as I can not see any fire unless the blower is on. I covered the barometric damper and sealed all my vent pipe joints with aluminum tape, I now get a reading of at least .01 and as much as .035. The boiler while still lite is screaming through the coal maybe 80 pounds a day a lot of which is either not burnt or only partially burnt. I have found 2 different sources for coal so I am going to pick up half a dozen bags of each and see if that makes a difference. So to review, I have make up air, I have a draft although not .04, my ashing temp is at 130 with a 5 degree differential and my operating temp is at 170. I will check my manometer to see if there are any partial blocks. Any other thoughts? Thanks guys.

I don't understand why AHS suggested a differential of 5 degrees rather than the "normal" 10.

I am also still puzzled by your low draft given the description of the chimney.

If you continue to get lots of unburned coal but no outfire I suggest trying a SV of 125 and DIF of 10 to see if the situation improves.

I am running a 5 degree differential because Darren over at AHS said that they feel this is more efficient and it is how the new units are calibrated before they leave the shop. I have set my ashing at 130 since Sunday night with the 5 degree differentialit was at 120 leading up to this point. Upon the initial firing I had a really good bed of red coal going. Since then I know I have a fire but I can not see any red in there even when the blower is running. It looks dead. Temps say otherwise. I am dropping 80 to 100 pounds a day through it and I am getting mostly unburnt or partially burnt coal in my ash pan. I picked up 6 bags of Blaschack today, I am going to let my hopper run low and re fill with that and see if there is any difference in performance. I checked my manometer pipe and tube, both are clear. I have a draft of .02 now which is an improvement. If I am home tomorrow due to bad weather I am going to open all the windows and heat the great outdoors and see if I don't have a decent base fire going. The last thing that Darren mentioned to me was to re wire the asher to the blower so it only runs when the blower does. Lastly, I still have my old Extrol 30 if I have my plumber run that as well as the 60 I have now would that be sufficient amount for expansion or do I just need to go up to the 105? Thanks yet again, Ken

You need to know how many gallons of water your system holds to properly size the expansion tanks.

However, hooking up the 30 with the 60 in parallel would not hurt anything and will cost little to try if you have the room.