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General question: do you need a tankless coil to connect FHW boiler to indirect DHW?
I only ask because sometimes I see existing FHW w/indirect systems where the tankless coil is piped to the heat exchanger in the indirect DHW tank... and other times I just see an extra heat supply zone that's piped into the indirect tank.
In what cases would you want a boiler w/tankless coil piped into indirect tank, vs when you can just pipe another heat supply zone into the indirect tank?
How about when your existing FHW boiler has tankless coil piped to indirect - must the new boiler have a tankless as well? Sometimes cheaper to get a new FHW boiler without the tankless coil; also can get better AFUE on some models without a tankless coil.
This is a very general question. Any and all responses from professionals and experts will be very much appreciated!