Indirect DHW with radiant floor on reset

Michael Oliphant

I have a 4 zone (4 circulators) radiant floor system on outdoor reset (Tekmar 253) to which I would like to add DHW. I was thinking about accomplishing this by putting the DHW tank on a primary loop and adding a secondary loop which would branch off to the radiant circulators as shown on pg 172 of Dan's book, Hydronic Radiant Heating. The branch to the circulators would be between a two-way valve (controlled by outdoor reset) on the supply side of the secondary loop and a balance valve which is on the return bypass side of the secondary loop. My thoughts are that this would be the cheapest and simplest method and works well with the boiler I have which is a modulating boiler, but does not take input from a reset control - it just wants to work to a set point. So, I can make the set point 160 deg and mix the radiant supply to the right temperature.

What I don't know is what a two-way valve is and who makes ones that can be controlled in this manner. I would also be interested in knowing if there are any piping size issues or can I just continue in the diameter of piping on the primary loop (3/4").

Thanks very much

Constantin

I'm a mere fellow homeowner...

...so discount appropriately.

Putting the IDWH on a primary loop is a classic solution. However, as Siggy pointed out at ISH in Boston, it might make sense to put the IDWH on a loop paralell to the rest of the system, with its own pump which is completely separate from the pri-sec part of the system. The rationale being, why energize a pri-circuit pump when you're only heating water in the summertime?

As for your boiler, you state that it modulates to a set temperature. One solution could be a motorized 4-way valve