Boiler Suggestion

S Davis

What would you guy's use?
High mass cast iron rads in three story apartment building with a load of 650,000 Btu and DHW production this load is now powered by a 340,000 Btu AO Smith with a 200gal storage. by the way these numbers are output.

S Davis


Apex Radiant Heating

Big Ed

A few smaller ones

A modular boiler arrangement. Assuming hot water system?

S Davis

System

Yes it is water system.

S Davis

Apex Radiant Heating

Constantin

Assuming the actual heating need is 600kBTU,

I would stage this across two modulating gas boilers. Pick different sizes like a M199 and a M399 and you have an incredibly wide range of BTU inputs (40kBTU-600kBTU). Combined with a Vision control package, you have redundancy, OR, and very attractive fuel savings.

Naturally, I would also throw in a Vitodens combo thus have several price points and options for them to chose amongst.

If oil is a possibility, I'd also stage multiple smaller boilers to better take advantage of OR, modulating water temperatures, etc.

BTW, your description confuses me. How is it possible for a house with a 650kBTU design-day loss to be heated by a single 340kBTU boiler?

Uni R

340

The 340K would be dedicated DHW.

Constantin

Aha...

Well, in that case, we'd better cover the building load and then add some.

You could do something very elegant like a four 200kBTU Vitodens' system with a cascading controller. Or, you could install a 200kTBU Vitodens for the first 200kBTU, followed by a VSB-13 (438kBTU) Vertomat for anything higher.

At a lower price point, four M199's or two Munchkin M399's combined with the Vision 2 system should also work great.

Combine any of these combinations with some intelligent piping to the heating system and you should have comfortable heat and a IDWH that "never" runs out of hot water. At 800kBTU input, the better IDWHs will produce over a thousand gallons of hot water per hour... For example, the Ergomax E109 has a continuous rating of 1379 Gallons/hour at 110°F rise. That's 23 gallons/minute...

The great thing about cast iron rads is the thermal flywheel they create... which leaves you more time to make up hot water as its needed for the DHW system.