Coal burning, city girl style

 
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coaledsweat
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Post by coaledsweat » Fri. May. 10, 2019 5:23 pm

Power vent the oil boiler and put a coal boiler on the chimney. Comfort and no chimney issues with 100% backup.

 
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CoalJockey
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Post by CoalJockey » Fri. May. 10, 2019 10:05 pm

Pull the 6” liner out and leave the 8” out of the question as well. That is of course if your still planning to go coal... stainless chimney liner + sulphuric gasses = trouble.


 
bksaun
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Post by bksaun » Mon. Sep. 16, 2019 12:08 am

get a different girl!

 
Pacowy
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Post by Pacowy » Mon. Sep. 16, 2019 11:57 am

I think here the girl may have a point that the current stove installation is aesthetically kind of....lacking. Is there some kind of local requirement for the shield all over the wall? I think the LL website only calls for 2" clearance behind the plane of the back wall of the hopper on a top-vent unit. And there have been many threads addressing ways to control fly ash and coal dust, esp. when such stoves are used in finished living areas. With a little attention to such details, the stove might be less offensive.

That said, I'm all in favor of a coal boiler. We used to make steam for a big house and DHW for a family of 8 using an EFM 900 w/a DHW coil. Ok, so that was overkill, but with steam it is essential that boiler be able to carry all of the radiation load to which it is attached (from memory, required gross output = 1.33x(sf radiation x 240 btu/hr/sf)), plus a reasonable allowance for other loads, like DHW. To check your work on sizing, compare your estimate of the capacity you think you need to the rated output of the existing oil boiler.

You should be able to use any suitably rated coal boiler that fits down the stairs and for which your ceiling height permits use of a vertical riser to a point at least 24" above the waterline. With a drop header, the header itself can be placed below that level (using a couple of elbows), but still should be above the boiler.

Continuing to overtax my memory, an EFM 520 boiler head is a little under 26" wide, so you might need to pull the door jamb to get that down the stairs. Historically they were rated at 166k btu/hr gross output, which is 1.33x520x240. In other words, for the benefit of absent-minded or arithmophobic plumbers, the name of the boiler indicated the sf of installed steam radiation load it was rated to carry. Nowadays you can find a higher rating on the same boiler, but if you read the fine print it assumes you can get an orderly burn of rice coal on 9 or 10 teeth of feed, which has proven to be elusive for most users in practice. The old school ratings correspond to a functional max of 8 teeth, or 20 lb/hr.

I agree with the suggestion that you're best off to use the original masonry flue (with no metal liner) for the coal boiler, and powervent the oil boiler. If you keep the oil boiler you could use a non-DF 520, which has a little more heat exchange surface than the DF, and could provide a little more oomph for steam.

I'll defer to other members regarding the suitability of AA-type units. A low ceiling height could get in the way of tall units like Keystokers and old Yellow Flames. If you would consider older units, I know Wagner used to make short and narrow units (long from front to back) that might fit your situation.

Mike

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