AHS S130 Coalgun- Puffbacks & Explosions

Nice photo of the spring modification. Thanks!!!

I absolutely have no problem with your support of the fine folks at AHS, and they know it, too. Firstly, we ALL need to be safe; the rest of the politics can wait for someone who really cares. I just noticed Pete's post, and I would advise him the although the spring is working fine for him, I STILL recommend that the door be free to travel and only be sucked into the observation door by the unit blower. With the AHS, I also strongly recommend that the factory hopper cover of one of equal quality be in place at all times. When a call for heat occurs, the blower pulls it's air supply from the ground level, and should not be allowed to get air from the hopper....ever. If any of you with AHS's are operation without the cover, I suggest you change that policy very soon. I also do not feel that the fire level needs top be that high in an AHS, but if it works for you, that is terrific. It is very hard to make a definitive set of perimeters for every situation. Waaaaaay too many variables. Kinda like making your own situation fit the safe usage model the Manufacturers suggest. In the end, its all good, as long as it works and is safe.

You're exactly right about the flapper door. The reason I modified mine was to get the door to start to open just as the blower turns off but yet shuts immediately when the fan starts. As the fan comes to a stop the door opens the full amt. That is critical. Yes there are many variables and I happened to hit on what works for me. I think some took this modification as cure all and that's not what I intended as I clarified in one of my posts. Anyway this sight a lot of talent and great conversation.It's helped me out a lot with all the info. Good luck to all and as you said, be safe.

I wonder if a small solenoid setup to go off when the fan stops would have enough power to pull the door open?

I believe that Freddy's solenoid, relay, and timer "anti-boom" device on his AA-130 forces the flapper door to open 5 to 10 seconds before the fan is allowed to shut off. His testimony indicates that it solved his puff-back problems.

lsayre wrote:I believe that Freddy's solenoid, relay, and timer "anti-boom" device on his AA-130 forces the flapper door to open 5 to 10 seconds before the fan is allowed to shut off. His testimony indicates that it solved his puff-back problems.

I seem to remember that he made an ashing adjustment at the same time that he installed that anti-boom contraption.

Rob R. wrote:

lsayre wrote:I believe that Freddy's solenoid, relay, and timer "anti-boom" device on his AA-130 forces the flapper door to open 5 to 10 seconds before the fan is allowed to shut off. His testimony indicates that it solved his puff-back problems.

I seem to remember that he made an ashing adjustment at the same time that he installed that anti-boom contraption.

Good recollection. Ashing adjustment alone solved mine. Where is Freddy when we need him?

lsayre wrote:Where is Freddy when we need him?

Ohhh, I'm right here, and have read all of this, day by day. I just don't have much more to add. Anyone that reads page one of this 50 page post will read of my anti-boom device. I still use it in the Spring & in the Fall. Once weather gets cold enough to make the boiler run often it's not needed. I have never had an explosion while it's been turned on. The only issue I think is it's sound. The solenoid is very quick and makes quite the clank when it actuates. I have been thinking lately that a screw on a servo motor would do the same function and be silent. It really doesn't matter that the door opens instantly, it just needs to be opened for 10 seconds before the fan shuts off.

Amazingly after years of use it has never needed repair or adjustment. Here's a couple of pics. A long time ago I offered the idea to AHS for free but at that time they declined.

Larry's comment about using ashing control solving his issues is a very relevant one. Larry is very good at finding the answer to issues ,and that may be a gift. I also should mention that any boiler that has a draft inducer running prevents this issue also. Not that you need one, just saying it has been an unexpected benefit. Whatever works is the best solution path, and ferreting out that info will be helpful. The guys and gals at AHS are more than willing to help resolve setup and operational issues, and if we all work together on this one issue, I know everyone will be a winner. Each and every machine has its quirks, and like cars, no two see to occur at the same time, in the same circumstances........so troubleshooting can be frustrating.
Last night I was frustrated at the length of time it has taken to get there. I sent a few PM's later to take responsibility for being 'short' with some fine folks.....please know I mean it!!! If I could be in Chambersburg for a week, I'd be there, but too many calls about neglected heating equipment. Think about the fact that many of us are using equipment built in the 50's and 60's and it works as well today as then......I, for one would sure like to be driving a 55 or 57 Chev (or perhaps a Cameo P/U), and have it as dependable as the same era boilers are....a Chrysler or a Desoto.......dual quad Hemi's from the factory.......another day.....

Desoto---now that's what we're talkin about

Room for two in both front AND back seat. Somehow I'll bet many will remember that fondly!!! Try that in your Scion or Beemer!!! Then there was the GMC Surburban for the kids who had to 'sprawl'. All good!!!!! Might have been some huffin' and puffin', but no puff backs!!! Saw a Chrysler Imperial the other day on a side street in Manchester......looked as big as a deuce and a half! A different time......

whistlenut wrote: any boiler that has a draft inducer running prevents this issue also.

Not necessarily so! My AHS buddy installed a draft inducer last year per AHS suggestion. It helps,some, but he told me it still has the occasional puff, then this Fall he had a boom that took out his barometric damper. No one was home to hear it. He came home to find the baro door folded and across the room.

It sounds like there are some variables that interact in a very specific way to create the "boom".

My thought has been that draft really doesn't play as big a part in this issue as it gets credit for.

Think of it this way...If/when the rapid production of (excessive) potentionally flammable gases which are UNable to be ignited for lack of oxygen and/or ignition source ...and these same gases continue being drawn through double pass internals of boiler to next be expelled out of the breech into stove pipe then next passing by the baro damper and finally heading upward through the chimney to the 'out of doors'.
Now... at end of firing cycle when flapper opens you now have the oxygen...then if/when fuel to air ratio gets satisfied it only then depends on how long of the delay that an Ignition Source might happen,
Question is...What quanity of those gases and what distance did those gases travel before it ignited into explosion?

This senerio is not slowed or stopped by increasing the draft but it will sure add a good amount of the defient oxygen for an explosion. And it is a way more violant of an explosion if gases ignite all the way from the boiler and into the chimney at once .

It seems like 'the perfect storm' of variables has to occur.....in any event, it is difficult when it won't replicate itself for everyone. Sure beats the hell out a propane 'puff'. Perhaps Freddy can get the guy who makes SS and copper chimney tops over near Rumford to make an industrial strength baro, and get Fields to certify it. A mini Seabrook 2.... The fly ash is the biggest mess maker, and we don't talk about the type of coal, but have to understand it can happen with any source. Larry was kind enough to send us this cold blast, and no tornados.....and hopefully Ohio is warming up a little. In the meanwhile, I hope we can close off this 50 page plus series of posts. The very good news is that no one has been injured.

One wonders about the volatile gases reaching the LEL (lower explosive limit) like some chemicals, and below of above those levels we seem to be safe. Type of chimney and location are important if not critical. If you test run a boiler sitting in a driveway, with no chimney, bet you can't make it go puff, boom, or whatever.