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Apartment Building DHW
A small apartment building currently has an A.O. Smith Burkay 120,000 BTU boiler directly heating a 75 gallon storage tank (not an indirect) and the boiler needs to be replaced. That boiler doesn't seem to be made anymore and it would be nice to use the existing 6" flue rather than going high efficiency PVC up the side of the building. Any suggestions for a replacement boiler?
Since the Burkay has no storage, it's short which helps with the flue run. It's basically a copper heat exchanger sitting on top of a flame.
Two btu per sq ft for degree difference for a slab
Comments
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a copper tube boiler from Lochinvar, RBI, Raypack with a plate HX and use the existing tank. Similar to the EK system.
How old is the tank? EK builds the package to connect to any boiler.
No way to fish a mod con flex vent up the 6"
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
A.O. Smith has a 71 gallon 120,000 btu commercial water heater.
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htp makes some similar stuff too. with the cost of commercial water heaters, the htp stainless tanks are probably competitive now.
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you could probably do something with a tankless water heater and a circulator too. There are tankless models that are only 85% efficient or so that use a conventional vent if getting a direct vent outside is an issue.
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The Rinnai Demand Duo was built for hotel and apartments
High efficiency and endless water
How many units, how much DHW fo they need or want?
Tubs? Older high flow faucets?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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Laars Mini Therm JVS-125 has a 6" flue and sounds pretty similar to what you have going on with the copper HX. I have the JVS-100 in one of my buildings running baseboard for 5 units and a 120 gallon indirect, going on 7 years now with nothing to complain about.
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Hi, I think I'd start with a survey of the fixtures to see what could be done with the demand side. Once done, just possibly a light commercial tank-type heater could be piped (recirc?) to keep itself and the existing tank hot.
Yours, Larry
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Do they still make the JVS?
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab
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Whoops, looks like they call it a JX now. Actually mine may even be a JX? Heck, good question! But yes they definitely make a JX-125 with a 6" flue.
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what about running a load calc to see what what size system you need
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
Amazing @Alan (California Radiant) Forbes . I don't think I've ever seen that boiler before you started this thread. Today I show up at a house that air filters were owed from the maintenance, and what do I see in the basement?
This one is feeding a 119 gallon indirect.
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Laars JX series boilers gives a variety of BTU ratings to match your needs. Not to run it with street water, tho, lots of O2. Need a heat exchanger & two pumps.
If the current sys satisfies morning & evening hot water needs, go with what's there. You may be able to boost tank temp with a Caleffi Angle Mix valve. You may have to install a back flow valve and Expansion tank depending on regulations.
San Francisco is a temperate climate running a 4" vent into a 6" B-vent may not pose a buoyancy exhaust problem if 6" boiler venting isn't available. If the existing venting is round and a straight shot to the roof you could run a 4" thru it. I've done that. I've just supported the 4" with plumber's tape.
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Rinnai also makes something like this
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Owner will save electricity with storage heater. Do the arithmetic. You can save gas with tank heaters in series.
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i'm pretty sure ao smith still makes some ideration of that boiler, but likely doesn't meet ultra low nox requirements in the sf bay.. @HVACNUT i believe is on the right track. might make sense upgrading to a commercial water heater.. is there any wiggle on the 6" flue? seems like a wh might be simpler than using a boiler designed for space heating with some type of hx. The Ray Pak hdss copper fin is rated for dhw (pace stocks bronze headers fitted with ss pump and 150psi relief valve) and the flue connection is 4" (will likely need to add a barometric damper) lowest input is around 150k…
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back in the day almost every school I ever did service at had going back 50 years or more had an AO SMITH Barkay heater piped to an asbestos covered storage tank. I guess they held up pretty well, but I noticed they always seemed to short cycle a lot.
Seems that the smallest one they make now is 300,000 input.
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