Using steam boiler as backup

Al Letellier_9

Did you say an SGO-8...??? That's a lot of boiler for your heat loss. Why so big? No wonder you are considering another heat source. It may be worth lookin into getting the right size boiler in there and fixing the system properly.

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Peter Rothstein_2

Using steam boiler as backup

Considering converting my steam-heated (single-pipe) house to ground-source heatpump. Have in place a Unico high-velocity system for a/c retrofitted, have a bid (ugh) to convert it to ground-source heat pump. Heat loss shows 94K BTU @ -7f (location is central PA) and proposal is to put in a 5 ton system. Plan is to use boiler as backup for coldest days. What kind of issues may I run into with such fairly infrequent use of boiler (I leave it filled?)? Boiler is about 6 y.o. Weil-McLain SGO-8. Any input is truly welcome. Thanks!

Peter Rothstein_2

Yeah, SGO-8. That replacement is substantially smaller than the American Standard it replaced (I think that it was rated for 320K BTU). Could be that the heat loss analysis is off too, but the house is a 70 Y.O. cape cod with precious little insulation (well, lots in the attic, but the kneewalls are probably not insulated, and the sidewalls aren't. Regardless of what I do, insulation is also in the plans), and they probably ran the heat with the windows open when it was built.

I'm figuring that I'd be better off putting some of the money I'd be spending on oil into mechanicals that would get me off of petroleum.

Al Letellier_9

steam backup

If your heat loss is correct and you have a HiV system in place, I might consider making it your primary and adding a properly sized mod/con or small oil boiler and parting with that oversized beast. You didn't mention how you make your domestic hot water, but this might be a good time to improve that as well. You could use the new boiler to generate the backup heat and the domestic hot water. Don't know a lot about how efficient your geo heat pump would be or how cold it gets there, but I would seriously consider my suggestion. You might also be able to sell that SGO8 and the rads to help with the conversion. It's a great boiler and I've installed a bunch of them but it is way too big for the job.

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Steamhead (in transit)

Peter, do you know

how much radiation you have? How does it compare to your calced heat loss?

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Peter Rothstein_2

Yeah, the bid is to use the high velocity as primary with a ground-source heat pump (having to replace the air handler and coil to accomodate the new heat pump).

DHW is via a coil in the boiler, so our summer hot water bills have not been cheap. The "geothermal" will produce dhw as well- the bid has a second water heater (electric) in series for when the heat pump is not running.

I have been thinking for awhile about a propane demand hot water heater (which is, I guess, like a mod/con if I understand correctly) just to turn off the boiler in the summer, I suppose that that could be installed instead of the second electric tank heater- it'd just cost more.

I guess I'd be trading electricity (coal and wind, in PA) for oil, albeit at higher efficiency because of the ground source heat pump. Since it generally is never too much colder then the single digits or teens in the dead of winter, the SGO-8 would be idle most of the time.

I'm thinking around here, there's not much of a market for old steam boilers and radiators (most are under-window convector like units). Am I going to likely end up with a basement full of water as I heat up the boiler periodically?

Peter Rothstein_2

Boy- I'll have to check it out. It is probably significantly greater than the calculated loss, given that the original boiler was so large compared to the current calculated loss.