Heat exchanger on steam boiler

Steamhead (in transit)

I think you're covered. But you want to set the HL on the exchanger a bit lower, around 160 or so. It's far enough away from the boiler that you want to set it a bit lower to keep the boiler from making steam when only the exchanger calls.

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Ironhead

Hi,

I am in the middle of a job in one of the suburbs just outside of Boston. Kitchen remodel, and the Owner wanted hydronic heat (she's an architect). Boiler is a gas-fired steam boiler by Utica. Someone had put a basement loop of baseboard off of it. They tied one leg of the loop to the lower gauge glass cock. I checked Utica's reference materials online, and found that there were no other ports on the boiler (say, to accommodate a DHWH). I decided to add a heat exchanger for my toe-kick, as well as to take the basement loop. I re-used the existing connections (1" tied into return, ¾" coming off gauge cock). I put a Grundfos three-speed circ on the steam side, and tried dialing it down slow. It sucked (or pushed) the water right out of the glass. Plus, I can only get my hydronic up to 120 d. F, as I am getting steam in the header. I am thinking about getting a welder out to weld a 1" coupling on, and taking my line off of the gauge cock. Or, option B, remove probe LWCO, install a MM #67 LWCO, and use that ¾" port for piping. Any ideas, comments, suggestions greatly appreciated.

Steamhead (in transit)

Don't even think

of using the sight glass tapping or probe LWCO opening for this. They're too close to the water line and if they suck air or steam, the pump will cavitate.

If this is a Utica PEG series boiler, there should be a drain cock in the rear. You can install a tee here, with the boiler drain on the run, and use the bull as the supply for the heat exchanger, routing the return into the same tapping as the return from the steam system. Since the sections on this boiler are assembled left-to-right instead of front-to-back, this arrangement will let the water flow thru all the sections and pick up more heat.

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Ironhead

Thank you. I will try that Tuesday, and let you know how I made out.

Steamhead (in transit)

Forgot to mention

If these zones have their own thermostats, you'll want to put an aquastat somewhere to keep the boiler from reaching steam temperatures when only the HW loop is calling. There's no really good place to do this on the boiler itself, so the next best choice is on the supply to the HX. Set it at 160 degrees or so.

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Ironhead

I have a high limit on the well of the exchanger. I also (because I am a paranoid S.O.B.) have two zones; original is all copper, and toe-kick I installed is done in pex. I have a three-way mixing valve feeding pex (to make sure it doesn't go above 180 d. F), and then I have a high limit set at 190 d. that will shut off circulator to that zone if it gets too hot (mixing valve fails).