Coalgun- Puff backs & Explosions

I agree such a thread would be helpful. But more important why not ask the seller, AHS. They know the possible solutions. Let them be the creator of such a thread. It's their product and they should use all venues to support it. Including this forum.

Notice how AHS sales is noticeably absent from the forum after I put them on the spot about how tall a S130 with the new hopper was. That was a question you answered by measuring your new boiler. Why isn't the overall unit height on AHS's spec sheet?

I have had the puff back issue with AA's when I first started burning in them. There was no group 40 years ago to ask about the issue, no operators I knew of, but I figured it out VERY quickly. It is kinda like when you first learn how to make a car backfire. You know it is safe, but whomever hears it is scared to death. This is not something that happens often, and usually it will never reoccur. Hand feds, however can send a ball of blue flame out the loading door if you are too hasty opening it, or forget to open ash door vents. It is all very safe, no fires are caused, but it is fun to know a secret that can startle friends and family with.

If you have never heard an oil burner backfire from an fuel saturated combustion chamber, this is about the same deal. Gets your attention, and we learn not to set up that scenario again.....most of us learn, anyway.

Once again, it says to read the manual ALL THE WAY THROUGH before firing one up. The puff back is addressed, and if you have moved from a hand fed, you already knew about it from opening the feed door without adding some air to the combustion chamber first. It's not like propane or NG and the entire house becomes a missile traveling around the neighborhood.

Yanche wrote:I agree such a thread would be helpful. But more important why not ask the seller, AHS. They know the possible solutions. Let them be the creator of such a thread. It's their product and they should use all venues to support it. Including this forum.

Notice how AHS sales is noticeably absent from the forum after I put them on the spot about how tall a S130 with the new hopper was. That was a question you answered by measuring your new boiler. Why isn't the overall unit height on AHS's spec sheet?

Good point, this thread is in the AHS forum already, so they must be monitoring it. Some direct feedback from the manufacturer would be great.

In the "Troubleshooting" section of the manual, problem #9 is titled: "Coal Gas Ignitions (evidenced by an audible bang) during the off cycle", and the only answer to the problem is "Poor Draft", followed by this advice: "Assure .04" of water with a manometer. Increase flue height if necessary, or use an auxiliary power vent."

In the manual proper there is mention of allowing firing upon first start-up to continue for 2 to 3 hours before turning on the grate switch. It also mentions that during the off-cycle the sight hole cover must gap open 3/8" or more (though the reason given for this is to prevent over heating the unit during the off-cycle, with no mention of puff-backs). That's it.

Off topic, but in the five page "Installation Check List" flier I did see where there is an "oil auto switch over option" available. Great place for this to be mentioned. You have to already own the boiler in order to get the manual and this additional check list. Once you own the boiler it is too late to get this option. And there is no mention if this option is for an oil burner unit that is integral to the Coal Gun, or if it merely auto switches on your existing and separate oil boiler.

There is no mention of the proper positioning of the sight hole cover that is a small rotating plate within the off-cycle air supply flapper plate that itself is mysteriously referred to as the sight hole cover. I would naturally have thought that the sight hole assembly was the small rotating plate and the small hole that it uncovers, and the larger flapper port would be called something else. The manual is very poorly done. In several places (including the table of contents) it refers to the Coal Gun as the Coal Gum, and it has even trademarked the name Coal Gum no less.

The AHS manual also makes no mention of any requirement for the barometric damper to be configured as per the Axeman-Anderson recommended method. In fact the entire baro damper section of the manual is generic information from Fields. Nothing specific to the AHS. Perhaps what is needed is an AA manual for AHS users?

lsayre wrote:The AHS manual also makes no mention of any requirement for the barometric damper to be configured as per the Axeman-Anderson recommended method. In fact the entire baro damper section of the manual is generic information from Fields. Nothing specific to the AHS. Perhaps what is needed is an AA manual for AHS users?

You are correct there is no mention of it in the AHS manual. I can tell you though when I had my boiler back at AHS for modifications a few years ago, Jeff Gingerich and I were talking about the puff back condition. I told him about my A-A like baro installation. He was not familiar with it. I said it's in the A-A manual in the Appendix. He pulled a A-A manual off his bookcase and took a look. His comment was something along the lines of, "That's a good method and dang it a customer is telling us a better way to install our boilers".

I've made two changes to my installation: 1) Relocated my baro to the flue end -and- 2) Opened the door on the "sight tube flapper door." My explosions have now ceased...

Is this "door (or is it a window) within a door" supposed to be open or closed? How are you experienced AHS and AA owners running yours?

Based on my experience: I recommend opening the small rotating door on the "sight tube cover door." The allows air flow into the firebox while the boiler is firing; else, this air flow is cut off---hence the explosions. Apparently, the small rotating door is a relatively new modification on AHS boilers. I can't speak for our AA brothers and sisters.

lsayre wrote: How are you experienced AHS and AA owners running yours?

I have yet nock on wood , too see a ka-boom. I remember reading of some axemans putting a paper clip on the door to allow extra over fire air, and more so with smaller than pea coal. I always start out with ashes in the burn pot on a new burn, and for an outfire, I will manually shake all the unburned out. My door is completely close when running and doesn't have an extra hole drilled in it.

Thank goodness for this forum at least someone is listening and offering help.
After starting up my 130 in November, yesterday was my first "puff- back", not a loud one but none the less, she did it. I've been running with the little air bypass closed on the sight tube flapper up until that happened. Opened it all the way and hasn't done it since. I suspect that will reduce air entering up through the coal bed and will increase it's response time to a call for heat but with the light heating load on it this time of year, I don't think it's going to be a problem considering how it snickered at several -20℉ mornings in January.
My draft is minimal at .02 at idle and of course .04 after the ID fan gets brings the coal bed back to life.
That my 2¢ from page 1 of the learning curve.
I still like the d__ thing though

lsayre wrote:Is this "door (or is it a window) within a door" supposed to be open or closed?

I was told by Axeman Anderson (almost a quote): "Try it with the hole closed. If you never have a boom fine, but if you have just one boom, open the 5/8" hole & leave it open". They went on to say it has a lot to do with draft and the type of coal.

Axeman's did not have the hole until the late 70's or 80's. All the newer ones have it. I see AHS has added a hole. Three years ago they did not have one. I'm not sure if they suggested the paper clip trick or someone else. You could do that or punch a 5/8" hole in the door.

For me, the paper clip seems to work better (at reducing booms) than uncovering the hole in the inspection door. Also, it is important to run with the tombstone cover in place. I didn't do this at first, and the booms would sometimes end up bending the inspection door as it flew outward. With my paper clip and tombstaone cover in place, booms are now pretty rare (can't remember when I last heard one of any consequence), and I have fairly low draft at idle (.01-.02).

Have only heard mine boom once since firing it two years ago. My door lays away from the porthole a good 1/4" on the bottom when not running. I guess that's enough to keep the gasses moving. She slams shut as soon as the fan comes on though.

I wonder if leaving the 5/8" hole open all of the time impacts the overall efficiency of these boilers?