My S260 Had Two Puff Back/Explosions Last Night!!!

My S260 had two puff back/explosions last night; with, the second one being HUGE! The explosion scared the hell out of me, my wife, and my three kids. Going down to the basement after what sounded like two shotgun blasts, I found my boiler room full of soot, smoke, and CO. The explosion (probably the second one...) blew the sight tube cover across the room; and, my type M baro right out of it's receptacle. Luckly I was able to put the type M back together (it was blown out of it's "tee" across the room); and, got it working properly again.

I had a few small puff backs with the S130; but, nothing like this. I realize unburned coal gas volitiles cause this problem; but, how can I prevent this from happening again? A small puff back in one thing; but, this was crazy.

My flue arrangement is exactly like the one depicted in the CoalGun manual page 5. Figure 1. with the horizontal runs, tee connections, and type M baro. Luckly I have 3 to 4 screws and high temperature tape holding every exhaust pipe seam together.

I have excellent draft of 0.04 to 0.06" of water as measured in real-time with my Dwyer Mark II manometer; with, the type M baro keeping draft steady. NOTE: I just cleaned/vacuumed the horizontal run last Monday, 10/10.

Could the root cause of the explosion be the sight tube cover being out of adjustment; i.e. not opening fully after the fan stopped running? BTW: I have the little rotary door "open" allowing 100% air flow to the coal bed. With the S130, this minimized small puff backs I was experiencing. Should the rotary door be kept 100% open; or, do I need to play with this adjustment too?

I've been running/boiling since Saturday 7/30; and, I've probably burned about 3 tons of coal. Do I need to pull the fan assembly and clean out the cyclone funnel and swirl chamber?

watkinsdr wrote:I've been running/boiling since Saturday 7/30; and, I've probably burned about 3 tons of coal.

That's alot of coal for this time of year, 2 1/2 months . As far as the cover not opening fast enough, I would not think that would help, more the other way, once some fresh oxygen hits the unburned gasses, and a flame, = disaster. Might it be it's not getting enough oxygen to burn them off in the first place( but you say the port hole window is open). Is the house very AIR tight, not enough make up air ?

You're right: that's a lot of coal. I was heating a 22x44 in-ground pool... Fortunately the pool gets closed tomorrow 10/19.

While only making DHW the S260 was pretty frugal with coal consumption; but, while heating the pool, she'd burn coal like crazy---I stopped counting the 40 lb bags I dumped into the hopper. It was way cheaper than propane...

I have a window open in the basement allowing plenty of "make-up" air---the boiler/flue isn't starving for air.

I'm stumped.

I'm going to shut the beast down and thoroughly clean her this weekend.

Wish me luck.

AHS contacted me and confirmed the sight tube flapper door adjustment is probably the problem. They recommend adjusting the flapper door away from the boiler another 3/8 inch; and, keep the rotary door 100% open. AHS also indicated the boiler will work fine if the flapper doesn't completely seal against the sight tube while the boiler fan is operating. I'll post results. I hope this helps!

I only ever had one boom in my 2 years. And I know why, new fire, and I did not have the burn pot filled, fresh coal on top and It was satisfied for heat, so I figure I'll fire it back up, fan comes on and off right after it stoped with fresh coal added, and one heck of a mess , blew the baro open the opposite way it turns. Be careful with a new fire and fresh coal on top of hot coal, needs time to burn off the gasses.

Check the bracket on the ash sensor, if it get bend out of wack it allows to much coal on a recharge. I know of one that blew the top off the chimmey and it landed on the hood of the wife car! Not a happy husband.

watkinsdr wrote:AHS contacted me and confirmed the sight tube flapper door adjustment is probably the problem. They recommend adjusting the flapper door away from the boiler another 3/8 inch; and, keep the rotary door 100% open.

What clearance are (were) you using before?

watkinsdr wrote:My S260 had two puff back/explosions last night; with, the second one being HUGE! The explosion scared the hell out of me, my wife, and my three kids. Going down to the basement after what sounded like two shotgun blasts, I found my boiler room full of soot, smoke, and CO.

Good thing the girls already got to experience the warm pool...if this had happened on day 1 it may have not gone over well. Reminds me of my first week with my Hitzer 82 stove, I got such a huge puffback from that stove that while I was outside dumping the ashes I witnessed a monster ash cloud blow out of the chimney. When I got back in the basement there was ash everywhere and my wife was up in the kitchen yelling "What the f*ck was that!!??".

Consider a field controls combustion air supply, aka "fan in a can". Turns on when the blower turns on.

How big is the pool? Swg? what type heat exchanger?

I am very familiar with the "Big Bang" and while a serious issue once in a while, it surely will get your attention. it is a secondary air issue, and the suggestions that have been posted are the answer.

Too much fresh coal and too little air.....kinda like operating at the 'lower explosive limit' for coal gasses. If you we standing there at the time of the POOF, you would need new shorts, but a little more experience and you won't ever see it again. The Hand Fed guys know this all too well. Lots of fresh coal, small fire,.....bad timing on opening the door to check on the fire and you might be on your fanny 10 feet away wondering what the heck happened. Don't be alarmed, Dewey, you will master this dilemma. Get the bulk delivery with Black Diamond Doug yet?

whistlenut wrote: If you we standing there at the time of the POOF, you would need new shorts

Aint that the truth My son and I were there when it hapened, soot,fireball and kabluueeee. My son thought the house was on fire. Hope it never happens again.

If that ever happens at my house my wife will never let me fire the boiler up again!!! Good luck Dewey