Steam Boiler

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hardcoalhardcore
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Post by hardcoalhardcore » Fri. Jul. 28, 2017 5:46 pm

Hi All,
New to the forum and new to coal boilers. The only coal heat I'm familiar with is hand fired stoves. My question is, can a hydronic boiler be converted to steam? I ask cause the house I bought has steam but its an oil boiler. I want to buy a used coal stoker boiler but mostly everything I see for sale is hydronic. Any input is appreciated.

Thanks


 
cabinover
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Post by cabinover » Fri. Jul. 28, 2017 6:30 pm

Pretty sure any Axeman-Anderson can do steam. Not sure about other brands. Someone way smarter than I will be along to help soon. Welcome to the club!

 
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StokerDon
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Post by StokerDon » Fri. Jul. 28, 2017 7:16 pm

All of the automatic feed (stoker) boilers that I can think of can do steam or hot water (hydronic). To convert from hot water to steam would be a matter of changing the controls and adding the sight glass.

There is another way to do this. If you have steam radiators they can be converted to hot water by plugging the steam vent, installing an air bleed, drilling and tapping a 1/2" hole for the return. Then run 1/2" PEX back to the boiler from each radiator.

You have more than 1 option.

-Don

 
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coaledsweat
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Post by coaledsweat » Fri. Jul. 28, 2017 7:43 pm

If the boiler has the H stamp it can run steam up to 15# IIRC. Doesn't matter if hand fired or stoker. Needs that stamp. Axeman, EFM , KEYSTOKER, AHS/ESHLAND to name a few. The difference between steam and water is the controls and plumbing to and from. Proper plumbing is critical with steam.

 
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Post by Pacowy » Fri. Jul. 28, 2017 8:33 pm

Need to plan carefully in any attempt to convert steam radiation to hot water. Heat transfer with HW is much lower than steam, so you immediately would lose around 1/3 of heating capacity.

Most Keystokers aren't H-stamped, but still are rated by mfgr for steam. Keystokers smaller than KA-6 are not rated for steam, and AFAIK some small coal boilers from other mfgr's are also HW only.

If the OP could provide input or output ratings from the oil boiler, it would be a good starting point for figuring out comparable coal stoker boiler options.

Mike

 
hardcoalhardcore
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Post by hardcoalhardcore » Fri. Jul. 28, 2017 9:23 pm

Its single pipe steam

 
Pacowy
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Post by Pacowy » Fri. Jul. 28, 2017 9:45 pm

That's fairly serious for a residential boiler. If you really use all of that power, that's about 315k btu/hr gross input (figure 28.5 lb/hr of coal) and 245k btu/hr gross output. In the EFM world, that's like a 700 running flat out (if you're lucky), or a 900 running with a bit of excess capacity. Among Keystokers, at least a KC-10, or a KD-12 if you want excess capacity. I'm sure the Axeman folks will chip in, but AFAIK that looks like an AA-260.

Mike


 
hardcoalhardcore
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Post by hardcoalhardcore » Fri. Jul. 28, 2017 9:55 pm

My house was built in the early 1900's. Still mostly plaster walls so probably no insulation. So I imagine that's why they installed such a hefty boiler. I just bought the place 2 months ago so I haven't gone through a winter yet. But it scares me thinking of all the oil this thing is going to guzzle. That's why I wanted to switch to coal. I emailed Keystoker and they suggested their K-8.

 
Pacowy
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Post by Pacowy » Fri. Jul. 28, 2017 10:18 pm

Roughly how big is the house, and does the boiler make DHW as well as steam?

I don't want to argue with Keystoker, but I would avoid installing any steam boiler that can't raise a positive pressure in the installed radiation.

Mike

 
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Post by hardcoalhardcore » Fri. Jul. 28, 2017 10:20 pm

House is about 2,200 sq ft. Yes the boiler has DHW

 
Pacowy
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Post by Pacowy » Fri. Jul. 28, 2017 10:50 pm

The DHW may be a big variable here. Depending upon the temp of your inlet water (pretty cold in winter) you can use upwards of 40k btu/hr of boiler output for each gpm of domestic water you need to heat to 120 (or so) deg. IIRC old-school shower heads often use over 5 gpm, so you might need a boiler that looks unreasonably large for a 2200 sf house to handle the combined load of heating and DHW. Something as simple as low volume shower heads might let you downsize the boiler somewhat, but it still would need to be able to carry the attached heating load (actual s.f. of steam radiation) plus a reasonable allowance for DHW.

Mike

 
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Rob R.
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Post by Rob R. » Sat. Jul. 29, 2017 6:19 am

hardcoalhardcore wrote:I can't get the pics to upload. Its an older EFM oil steam boiler.

Boiler # OBT-760-C3-W-S
Net - 760 Sq Ft Steam
IBR - 182,300 BTU/HR Steam
IBR Burner Capacity - 2.25 Gal/HR
Sizing a steam boiler is based on the amount of installed radiation. Trying to size a steam boiler based on the size of the house, or the size of the existing boiler can lead you down the wrong road. To do this correctly you need to measure the size of the radiators. Basically you determine if the radiator is a column or a tube type, then count the number of columns/tubes per section, the number of sections, and the height.

http://www.columbiaheatingsupply.com/page_images/Sizing%20Cast%20Iron%20Radiator%20Heating%20Capacity%20Guide.pdf

Once you have all the radiator dimensions, add up the total amount of EDR based on the chart I posted above. Stoker boilers have EDR ratings, and the manufactures will be happy to make recommendations. e.g. Keystoker already suggested their K8 to you - which has a "recommended load of 560 sq. feet of steam radiation".

I will have to get my old books out to check this, but I am pretty sure the standard recommendation for a long time was that the pickup factor included in the IBR rating (30%) was sufficient to provide domestic hot water for a single bathroom. For every bathroom over that, they suggest a small increase in boiler capacity.

Just as important as getting the boiler right is making sure all of the pipes are pitched correctly and the vents work properly. Generally speaking, the installer is much more important than which brand of boiler you pick.

Lastly - I shudder at the idea of running that monster EFM oil boiler through a winter with an un-insulated house.

 
cabinover
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Post by cabinover » Sat. Jul. 29, 2017 6:21 am

Pacowy wrote:The DHW may be a big variable here. Depending upon the temp of your inlet water (pretty cold in winter) you can use upwards of 40k btu/hr of boiler output for each gpm of domestic water you need to heat to 120 (or so) deg. IIRC old-school shower heads often use over 5 gpm, so you might need a boiler that looks unreasonably large for a 2200 sf house to handle the combined load of heating and DHW. Something as simple as low volume shower heads might let you downsize the boiler somewhat, but it still would need to be able to carry the attached heating load (actual s.f. of steam radiation) plus a reasonable allowance for DHW.

Mike
That being the case it would make a strong argument for an indirect water heater taking care of that large shot of cold water. Can you use one of these with steam?

 
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Rob R.
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Post by Rob R. » Sat. Jul. 29, 2017 6:26 am

Yes, but there are some special piping requirements and an expensive circulator is required. A big steam boiler can make a lot of hot water with a coil, so I would probably just run that and see how it does.

 
cabinover
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Post by cabinover » Sat. Jul. 29, 2017 7:03 am

Now I know, had no clue. Thanks Rob.


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