MODULAR VS. TRADITIONAL / SIZING STEAM BOILER

OleTwoPiper

I'm working on an oil to gas conversion on a 28,000 SF converted loft to residential building in Brooklyn, NY.
Currently there is a Smith 28-6 1M BTU boiler in place
Connected load is 2,100 EDR.
In looking at a new gas burner, it became apparent that the 1980-era boiler was greatly oversized and that a new properly sized boiler would be advantageous. Hot water is handled by a separate gas hot water heater.

Any thoughts on whether two or three smaller boilers (Slant fin Caravan, etc.) is more advantageous vs a single larger boiler?

Can anyone recommend a boiler model which is cost efficient and properly sized for the building?

vaporvac

Thanks for the shout-out @Hatterasguy ! @OleTwoPiper , feel free to take a look at my old posts when I was figuring out what to do with my 1,466 edr system. The resounding professional opinion was twinning. I'd go with the tr60 rather than the Caravan boiler. Sf actually heated their building with the intrepids and gas conversion burners, caravan-style. Twinning isn't as difficult with hind-sight! it's obvious to me now, but a careful reading of their specs make it apparent. You have to ask for a gas I&O however, as they don't include that. You do not have to isolate the boiler as often suggested because you will be using one or both throughout the day. the WB boiler also has smaller stand-by losses. Take a close read of the following pdf for more great info on gaining efficiencies through system design: http://forum.heatinghelp.com/discussion/154223/increasing-steam-efficiency-wm-pdf#latest

Feel free to ask away! I love talking about my little set-up. I researched it at the wazzoo and couldn't be more pleased with how it functions. Colleen

OleTwoPiper

Thanks for the suggestions @vaporvac and @Hatterasguy . Few questions:
- Can Slant Fin help design the system with proper install drawings or is there someone else you recommend?
- What kind of boiler controls are you using? (there is currently a Tekmar 279 steam control with indoor and outdoor sensors)
- Any other anecdotes you think would be helpful to know regarding this setup?

OleTwoPiper

In furthering the analysis, a few issues came up:
- Slant Fin doesn't make an Intrepid system with gas burners. The TR's can be bought in pieces and then installed with a gas burner a la carte, but no warranty across the whole system.
- Because there isn't a tested system, it wouldn't pass New York City code.

As a result, it was suggested to use a Caravan modular system instead. (also we realized that there were a few extra radiators in a roof tank room that weren't in the original 2100 EDU calculation, so we are working with 2300 EDU now. (2) TR-70
s would have worked instead of (2) TR-60's.

Possibly GXHT900EZ

What do you think of the above? What do you think is the difference with two Caravans vs two Intrepids?

Also, in your setup, did you use the Slantfin SC Controls or manually fire through adjusting pressuretrols?

@vaporvac
@Hatterasguy

OleTwoPiper

Thank you @Hatterasguy .

Does anyone else have experience with modular boilers for a system size of 2300 EDR? (whether Slant Fin or other brands)

Also, if we install a modulating gas burner, does that negate the benefits of the modular boilers and therefore a single traditional boiler is just as good?

vaporvac

I'll write tomorrow when I have a bit more time. I got the same runaraound at first, but when I wxpressed my reasoning they said it was absolutely correct. (I knew it would be because the folks here first suggested it.) Jstar and steamwhisperer ( I think) have often used this set-up, switching between the Smith g8 (no longer available?) and the Intrepid. I chose the Intrepid due to great customer service and tech support, availability and price. I bought them through Karen @ simplyplumbing.com as was suggested by a couple of folks on this site. I also got my Riello g400 burners there. I'll discuss your prior warranty concerns tomorrow.

nicholas bonham-carter

That boiler is certainly oversized, but not so much that a 2 stage gas burner couldn't handle the required down-firing. Is the old one leaking?
When it does, then the gas gun could be used on the replacement.
Twin boilers would certainly be better, but more expensive, however more easily installed, especially if you used three pre-assembled ones, piped into a common large size drop header.
For control strategies, all the boilers could fire in unison, upon a call for heat. As the pressure rose to a few ounces, the lead boiler would be cut off by the vaporstat, leaving the remaining two to carry the load.--NBC