AHS S130 Coalgun- Puffbacks & Explosions

dchartt wrote:sure would be NICE if AHS actually had two cents in all of this and backed their product up and maybe came up with some sort of recall and a way to fix

The new owners of AHS probably didn't know about this explosion issue before they bought Jeff's business. The new owners do now offer boilers that are safety certified, and that is why there is a tombstone cover over the inspection port where the explosions exhaust. That being said, and the fact that this is a problem with coal boilers and stoves overall, the new owners of AHS should help to offer a solution and or recall if they have solved the explosion problem.

All this being said, I am happy with the AHS 130 as a replacement for my expensive oil guzzling Columbia boiler. I have saved thousands of dollars since switching. I do want to have peace of mind that the boiler isn't going to puff back when I'm not home or sleeping in bed and cause a fire or detach a smoke pipe and cause a CO leak.

I have had some minor explosions these past three weeks since I've made the following changes:

1. Wired the ash grate motor to dump only when the fan is running
2. Lowered the thermo grate dump temperature to 110

There has been an improvement with the boiler performance and there are few unburnt coals in the ash pan. I agree with Yanche that a slower running fan motor after burn would help with the explosion problem. I feel there needs to be a combination of changes including the ones I have done to eliminate the frequency of the explosions.

I want to thank everyone who has been involved with this thread. We are working to find a safe solution without assistance from AHS.

Jeff Gingerich is no longer the owner, but I can personally attest that he most assuredly has not left the company, nor did he stiff the new owners by concealing anything from them.

BTW: Still no puff backs at all here, across straight Blaschak and a 50-50 blend of Stockton and Blaschak. I've yet to try the Stockton at 100%.

I just recently switched to Stockton and my booms came back

Have looked through all these comments... very interesting. We feel it is fresh coal on top of hot coals causing volatile gases for a long time.
We bought 4 ahs. 2 S130 2-S260 and sold several others to friends. We had one kaboom on s260 2 yrs ago, blew damper off and tombstone cover off. called jeff, added 7 ft st steel flue. Removed baro damper... none. This yr and last yr no major explosions , (also but -10 last night)... very cold up here. We few small burps. One guy we just bought a s260 for installed early nov. told me yesterday that it blew the baro damper, the tomb cover and the cap off the top off the stainless flue last week but it was during warm spell outside temps were in the 30's ...15-20 at nite..... I just went into our boiler room and set the sv at 130 and opened the peephole port on the firebox oval cover to see if anything happens in the next few days. we operated the boiler at 190 it may go to 210 after blower stops
Also s130 in machine shop had kaboom last yr blew the bar damper and tombstone cover off. But has short 24" flue and connected to a 40 ft high 12x16 brick chimmney. 2 baro dampers still too much draft as boiler would go to 240 on standby daft and overheat..(no dump) so much draft can't calm it as we have to keave the cleanout door open to reduce the draft..... so the not enough draft question seems???

RONO123 wrote:Have looked through all these comments... very interesting. We feel it is fresh coal on top of hot coals causing volatile gases for a long time.
We bought 4 ahs. 2 S130 2-S260 and sold several others to friends. We had one kaboom on s260 2 yrs ago, blew damper off and tombstone cover off. called jeff, added 7 ft st steel flue. Removed baro damper... none. This yr and last yr no major explosions , (also but -10 last night)... very cold up here. We few small burps. One guy we just bought a s260 for installed early nov. told me yesterday that it blew the baro damper, the tomb cover and the cap off the top off the stainless flue last week but it was during warm spell outside temps were in the 30's ...15-20 at nite..... I just went into our boiler room and set the sv at 130 and opened the peephole port on the firebox oval cover to see if anything happens in the next few days. we operated the boiler at 190 it may go to 210 after blower stops
Also s130 in machine shop had kaboom last yr blew the bar damper and tombstone cover off. But has short 24" flue and connected to a 40 ft high 12x16 brick chimmney. 2 baro dampers still too much draft as boiler would go to 240 on standby daft and overheat..(no dump) so much draft can't calm it as we have to keave the cleanout door open to reduce the draft..... so the not enough draft question seems???

Definitely its fresh coal on top gasing off in combination with the ashing rate introducing to much fresh coal too quickly because its gravity fed, and the fan causing a vacuum and then suddenly stopping and releasing the door quickly and lots of fresh air mixing with gas.

So slowing down the ashing, opening the small hole helps. If somehow the fan could idle down slowly it would help and maybe a tube that would extend from the main flue out to the corner by the peep hole so gases would get sucked into the flue instead of accumulating.

I can simulate it anytime by ashing at 130 instead of current 120.

In my opinion what's needed is a way to provide additional over-the-fire combustion air. There is just not enough margin to assure with all operating conditions and coal volatility variations to preclude puff backs. Several possible solutions likely exist but all would require additional hardware. Unfortunately AHS has not acknowledged there is a continuing problem and has only made minor improvements. Improvements that do not address the real issue, but only attempt to reduce the damage done. For example, the bar across the damper door was an improvement over the original free to swing anywhere flapper door. The tombstone cover was an improvement on it. Both these improvements acknowledge there is a problem. It's a margin problem. Yes under the right set of adjustments and coal it will work without puff backs. But not for all. Until combustion gas concentration measurements are made at various places in the boiler it's only a guess what's really happening.

Yanche wrote:Unfortunately AHS has not acknowledged there is a continuing problem and has only made minor improvements. Improvements that do not address the real issue, but only attempt to reduce the damage done. For example, the bar across the damper door was an improvement over the original free to swing anywhere flapper door. The tombstone cover was an improvement on it. Both these improvements acknowledge there is a problem.

I agree with Yanche that AHS knows there is a problem with the boilers and have made some changes to improve safety. They have not solved the puff back problem but WE have reduced the frequency by making changes to the operation. I have reduced the frequency of the puff backs by:

1. The ash grate motor only runs when the fan is running
2. Reducing the ash dump temperature to 110

Yanche's idea to have the fan speed reduced for a period after reaching the operating boiler temp is a great idea. That would remove the volitile gas before it ignites. I don't have any idea how to do this but hope another forum member has a plan.

I'm having booms at a rate of one every three days and that is an improvement from daily explosions.

I've been wondering how many AHS owners use a true 90* elbow for the first turn out of the vent collar?

I have seen where some have opted for a Tee instead for the first turn, to allow for convenient clean-out access.

I also wondered if the extra volume of a Tee and the added turbulence inside compared to a 90* was a contributing factor to puff-backs.

So many variables...

McGiever wrote:I've been wondering how many AHS owners use a true 90* elbow for the first turn out of the vent collar?

I have seen where some have opted for a Tee instead for the first turn, to allow for convenient clean-out access.

I also wondered if the extra volume of a Tee and the added turbulence inside compared to a 90* was a contributing factor to puff-backs.

So many variables...

I only have Tees, and I have yet to have a puff-back.

McGiever wrote:I've been wondering how many AHS owners use a true 90* elbow for the first turn out of the vent collar?

I have seen where some have opted for a Tee instead for the first turn, to allow for convenient clean-out access.

I also wondered if the extra volume of a Tee and the added turbulence inside compared to a 90* was a contributing factor to puff-backs.

So many variables...

No T here just a 90. I can easily simulate large puff backs. Just let your hopper go out, the ashing and blower will keep going on a call for heat. Then when the rocks are glowing and the ashing has left the chamber half way empty down dump in a full load of coal, smoother the fire, at the next call for heat stand back.

This can happen anytime the hopper feeds too much because it ashed too much due to low demand followed by spike in demand. Warm days cold nights. or ash too much and allow for too much room in chamber and lots of fresh coal.
The strong blower intensifies it by creating a vaccum and then stopping quickly and introducing fresh air to the area.
What I still don't understand is why its not sucking out the gases or are they build up too quick?

I just looked through all nineteen pages of this thread and could not find a single picture of the fire in one of these exploding boilers. Could one of you take a pic of your exploding boiler's fire after it's had a hard run (and preferably prior to ashing) and post it?

In order to simulate what I described I have too wait until the hooper is empty. But its pretty much solid lava color, not many blue ladies.
Once you load the hooper you see nothing but black.

So im thinking that sometimes the ashing takes long to stop because the fan is cooling the sensor, a thick layer has developed due to low demand, then it ashes for quite a bit and too much fresh coal is gravity feed all at once smoothering the fire.

Im also wondering if someone without the thermocouple/pid controller has puffbacks.

I do not have the thermo-ash controller. I have the grate timer control. It's a 10 minute cycle timer that only runs when the blower is running. Typical setting is 1-1/2 to 2-1/2 minutes. I have had puff backs. Like others I have made changes to reduce the number. I had AHS install the tombstone. It helped.

I changed my flue pipe to eliminate any tees or 90 deg turns. I do have two adjustable 90's, both as straight as possible. I use 5" stovepipe into the concentric 6" baro as shown in the A-A installation manual. It helped. What's important about the concentric baro is it prevents a damaged baro when a huge puff back occurs. Just look and the design and you will understand why. The puff back is directed into the chimney. Yes, the baro door does swing but not violently.

I still get really minor puff backs. Like others have said it occurs when the combustion blower shuts off. Clearly, it's the sound of combustion gases igniting. It's not much of a puff back, the flapper door does not slam into the inside of the tombstone cover.

My opinion is there is insufficient over-the-fire air, perhaps under all conditions. I say this because of my frequent sulfur smell from my chimney. I suspect the sulfur gases being outgassed are not burning. The entire combustion path begs for an engineering measurement of what's really there. Lacking that, it would be an interesting experiment to add combustion air above the fire, perhaps with an air pipe.

You think burning nut would be better more air?
or buckwheat less air?

or no effect?

where would you put the pipe?

anyone having explosions while the fan is running and furnace is in the middle of a call for heat? This is when most of mine occur, I have recently lowered my ashing temp and raised operating temp and the explosions have minimized, 124 ashing 175 operating temp