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Calculate steam

Member Posts: 1,295
I’m replacing steam system with another one. Do I calculate the add a loop baseboard ? Can I use a taco switching relay to put the baseboard on priority ? Can I use the domestic tank for baseboard, radiant floor with a mixer and an indirect water heater. I’m thinking a small 20 gallon from peerless,

• Member Posts: 17,170
What what? First off -- size the boiler (unless the baseboard loop is a large fraction of the total heat load -- like at least half) for the EDR or the connected radiation. Keep in mind that by doing that you will have the "pickup" factor in the boiler power -- and that will almost always be ample to keep the baseboard loop very happy.

Now. By "domestic tank" do you mean the tankless heating coil in the boiler? Or by "domestic tank" do you mean a domestic hot water heater? Completely different problem. If you mean the tankless coil in the boiler, if may not have enough capacity to power to handle the combined other loads -- even though the boiler itself does. There are a variety of ways to do use the boiler itself, though -- this article: https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/ is as good a starting point as any for that. If you use the heat exchanger approach Dan talks about, which I recommend most enthusiastically, you essentially have -- on the other side of the heat exchanger -- a nice hot water system which can be handled quite conventionally.

There is no need to put the baseboard system on any sort of priority. Rather what is needed is an aquastat on the boiler, set to keep the boiler hot -- whatever is needed, but somewhere around 170 to 180 cutout with a 10 degree differential seems sort of normal. Wire it and the thermostat for the structure in parallel. That way if the structure is calling for heat, the boiler will operate as usual, but the aquastat will make it run occasionally if the thermostat isn't calling just to keep it hot for the heat exchanger to do its thing.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 10,374
Whatever load you add to the boiler as hot water load. baseboard, radiant and DHW should not exceed the boiler pick up factor as @Jamie Hall mentioned