we have a (school) client with a 60s vintage H.B. Smith 340 Mills Series 34, 12 section boiler, gas-fired, hydronic, from which the capacity plate has been removed. Anyone out there with yellowed catalogs?
It's not a 350; the casting clearly shows "340 Mills" and under that, "Series 34." I found an old catalog that lists a Series 34, but it's hand fired; I don't believe that this boiler was ever run on coal. The gross output rating for a 340-W-12 (hydronic) is listed as 9,720 MBH, but that's 'way too much for the building that it serves. The page also lists the firing rate as 13.1 gph, or about 1.8 MMBtuh in. If I can figure out how Mr. Smith got 9.7 MMBtuh out with only 1.8 in, I'll retire.
The net output of that boiler is 1,109,600 BTUs. A Smith 28HE -6 setion would match the BTU load nearly identically, but if this is a steam application I would also watch the steam capacity of the boiler.
The 28 HE boasts efficiency of nearly 85% on that sized unit, so the payback would be relatively quick.
Smith Boiler / Mestek
Hi Bruce. The 340-W-12 was rated to produce 1,458,000 BTU/Hr. when fired at an input of 13.10 GPH of #2 oil with an oil heat value of 140,000 BTU per gallon.
Maximum water working pressure was 40 PSI.
As stated by Guy, Net Water was 1,109,600 BTU/Hr.