AA-130 Install...I'm back... Q:About flue and chimney

Hi everyone. Mark here from Niagara NY. I joined NEPA back in '08 when I bought an AA 130. I was readying myself for the overhaul and install, but then had a small house fire before I could get my AA130 installed. Long story short, we ended up moving down the road and I am just getting around to installing the boiler in our "new" old home. I am restoring it and rebuilding it as best I can, but I am pretty much a novice at all of this. I have been reading quite a bit online here at NEPA and I appreciate all the shared advice and wisdom---you guys do some impressive work!

I am going to have a lot of questions I suppose, and I would appreciate any help you might be able to offer very much. You were all a lot of help when I was learning what boiler to buy back in '08.

Well, here is the first of what may be many questions: I have read some posts regarding the AA flue/chimney set up. I have the manual, and I read about the 5" to T up to 6" with R draft control unit (I read this thread--[AHS S130 : Barometric Damper and Flue diameter question] by lsayre http://nepacrossroads.com/about19627.html) . My problem is that the chimney I have is built in such a way that the entrance where the T would go is 24" from the tile plane inside the chimney. Add to that some foundation that is in the way and I would say that as-is the closest I could get the T to the liner of the chimney is about 3 feet. Will this work OK? The AA manual calls for 9" from center of T to liner of chimney.

One other related question: Does it matter how long my horizontal run is from the top of the boiler to the T? The manual seems to suggest that it does not...just says use minimum of bends and an upward pitch. Where I would like to put the boiler places the smoke collar 12 feet from the chimney.

Here are some pics of the chimney in my basement. The cinder block to right of hole is base of second flue which is chimney for a fireplace in floor just above this area.

What do you guys think?

You'll be fine. As long as the hole into the chimney is higher than the top of the boiler. The idea is to have the barometric damper as close to the chimney as you can. The actual distance isn't all that important. Plumb that bad boy up & she'll work just fine.

Yup, what Freddy said.

When the AA's fan starts, it pushes a 'pulse' or 'pressure wave' of air up the flue. The flue has a certain amount of resistance inside, so it takes a certain distance for the 'pulse' to accelerate up to it's peak velocity. All the time the fan is also coming up to speed, eventually creating the steady pull of air through the coal bed, and pushing the exhaust up the flue.

When you get a manometer hooked up, if you hook it up just above the boiler breach, you will see a positive pressure for a second or two, soon followed by a more normal slight negative pressure [draft]. If you hook up the manometer near the chimney, the positive pressure is almost nil, it may go near zero for a moment, but the normal negative draft quickly returns

What you don't want is to have the baro located near the boiler breach where this positive pressure will cause exhaust gasses to be pushed out of the gaps around the baro's door. So with the baro located as far from the boiler as possible, the pressure pulse has converted to an air velocity increase, and the exhaust gasses just flow through the baro, and are pulled up the chimney.

So your placement as close to the chimney as possible will work just fine.

Looking forward to hearing that your AA is back in service.

Greg L

Thank guys! Nice to hear from you again...I spoke with LsFarm a couple of times and received several replies from Freddy as well back in '08. Thanks to you as well cabinover...

Anyway, couple more flue related question:

1. How about the length of the flue run---is 12 feet or so from boiler to chimney OK as long as I maintain positive pitch (1/2" per foot??)

2. How would I clean out the bottom of the chimney in the future? I have read that one is supposed to "cement" the pipe into the chimney entrance to prevent gases from entering boiler room and have a cleanout below that entrance, but that is not possible in this application. Can i construct a flue that is not too hard to take out every year and clean flyash out? Or would that not be "airtight" enough?

Mark, to your question on the 12' distance you will be fine as long as it is pitched upwards towards your thimble.

Even if you cement the pipe in the thimble it will still be easy enough to remove once a year for cleaning, then simply cement it back in. The fit of the pipe into the thimble should be very snug anyhow and the most the cement does is seal up any slight gaps for air tightness. Just be sure to follow Axeman's directions as far as the baro goes, as all above have explained.

Best of luck on your install. I just completed mine and it feels great to have it up and running. Would love to hear more of youe project. What will you do for a coal bin, what year is your Axeman, etc.?

Thanks,
Steve

markleo wrote:.........Anyway, couple more flue related question:

1. How about the length of the flue run---is 12 feet or so from boiler to chimney OK as long as I maintain positive pitch (1/2" per foot??)

2. How would I clean out the bottom of the chimney in the future? I have read that one is supposed to "cement" the pipe into the chimney entrance to prevent gases from entering boiler room and have a cleanout below that entrance, but that is not possible in this application. Can i construct a flue that is not too hard to take out every year and clean flyash out? Or would that not be "airtight" enough?

Our setup for the AA 260 requires about a 14' run of pipe to go from the AA to the wall. We have the same as you in that there is an 8" thimble in the wall for the chimney. We run 6" SS pipe from the boiler to the wall. The "T" with baro is right before it enters the wall. We installed an 8" to 6" reducer right at the thimble and cemented that in place. The pipe comes right out of the AA into a 90* elbow. Then a straight run to the wall. I do have a Dwyer Mark II permanently installed to monitor the draft.

We pull the entire run of pipe 3 times a year. At the beginning of the heat season around October, during the mid season based on coal useage and outside temps, and then at the end on the heating season, around the beginning of May. The pipe is pulled off the AA and disconnected where it enters the reducing ring. I try to shut down the boiler at a lower temp, like when it is near 140*. Then I pull the pipe, install a coffee can over the boiler outlet, and take it outside to clean it out. Before installing the pipe, I use the shop vac to suck fly ash out of the chimney. Note: we don't have a clean out for the chimney, just a well below where the pipe enters the flue. There may be a cleanout but if so, it was covered years ago. After vacuuming the flue, I reinstall the pipe and add some metal tape over the pipe connections. Total down time is 1/2 hour to 45 min. An AA 260 will take 2-3 days to go out completely. After hooking everything back up, don't forget to turn the breaker back on.........



Rick

Thanks for the feedback guys. Another question: Do I have to make the base airtight on the floor? Can I just make it level, or is it necessary to seal off all air from entering around the base of the unit where it touches the floor?

Also, should there be a rope seal (or other type) where the boiler unit mates to the base?

Thanks....Mark

Boiler mating surface to the base, yes, glue a ring of sealing rope down, to seal the joint.

Base to the floor, no, it's not required.. it will help keep the inevitalble ash dust and fly ash from spreading around, but there is a gap under the doors anyway, this is where the stove gets it's combustion air from: the gaps under the ashpan doors. So a small gap around the base doesn't harm anything.

Greg L