Gas wet-base boiler suggestion

steve_173

Does the dual wet-base boiler payback long term? I'm estimating a 5% efficiency gain due to the wet base. The power burner adds some more over atmospheric, lets say 2%. Then the dual boilers add perhaps another 5%. Conservatively, I'm guessing 10% gain is a safe bet versus one larger atmospheric boiler. Does that sound reasonable?

Regardless, there is slightly larger upfront purchase and installation costs plus maintenance costs to overcome. The payback should be reasonable, except for the deals through the gas company on the atmospheric boilers.

steve_173

I'm looking for gas wet-base boiler suggestions. I need about 740 sq ft of steam. Smith G8 is too small and a 19A is too big (I think).

I want wet base for efficiency and the option to go back to oil in the future.

Steamhead (in transit)

How about

twinning two G8 boilers- say a 3-section and a 4-section?

Then you can drop out the smaller one with a Vaporstat once the pickup factor has been satisfied, and save a bunch of fuel.

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steve_173

How does the sq ft of steam add? Just regular addition? On the G8, a 3+4 is 283+413=696 and a 3+5 is 283+525=808. In my case, I think I would have to do a 3 section and 5 section.

Will just any plumber know how to do this? I would guess that it needs a larger footprint than just a single boiler. What about the chimney being too large when just the smaller boiler is firing? Which would fire first? larger or smaller boiler?

Once the pickup is satisfied won't both boilers just shut off?

How common is it for the 1.33 factor to be inadequate in an older home? Should I try to measure all the piping runs and get the EDR of the piping?

Are insulated valves on the radiators worth the cost?

Thanks.

John_173

Check out these recent threads

Actually, here is the more recent, which in turn refers to an earlier one.

If my hot link doesn't work, copy & paste this:

http://forums.invision.net/Thread.cfm?CFApp=2&Thread_ID=53683&mc=10

It sounds like we're in the same fog of learning. I wish you well.

The dual boiler solution really appeals to me. I'm still not certain I'll be able to pull it off (height restrictions, perhaps). I must say "not any plumber" will be able to do this work. It'll take a pro with steam knowledge.

Unknown

regular addition is fine.

Run both boilers together at start-up, and when you hit the max pressure that it takes to get steam into all of the radiator vents, use a vaporstat to shut off the smaller boiler. Use a second vaporstat, set a little higher to shut off the bigger boiler. Do it all with steam pressure, to keep it simple. There's other ways to stage them. Use your thermostat to operate a standard 845 relay, with each contact set controlling one boiler thermostat connection.

The chimney is a valid concern. The fuel gas code has tables that take height, connector rise, etc. into consideration. He'll have to use those.

The near boiler piping is critical, and make sure that he understands the choices that he has to make in piping it. We can help him make the choices.

Insulated valves make no sense to me. They're in the room with the radiator. They help heat the space.

Noel

Unknown

If you use two boilers, atmospheric almost doesn't make sense.

No way to stop the airflow up through the off boiler without beating a vent damper to death.

Power burners make the most sense to me.

Noel

steve_173

I am comparing two smaller wet-base to one larger atmospheric.

Unknown

I think

The two wet base boilers will use less fuel, if the rest of the system operates properly.

Noel