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Recirc DHW tankless + buffer Qs

rbphhc Member Posts: 125
edited March 6 in Domestic Hot Water
Guys, can anyone share a schematic for DHW buffer tank *with* recirc loop?

Looking for periodic refreshing of the 20 gal buffer *and* hot in the lines.

Return line is pretty short from last fixture to cold supply.

Assuming we want to tee into cold *after* the CK valve (B, not A).

Is there an ideal position for SS circ pump? In the return? Pre- or post- buffer? (1, 2, or 3?)

Thanks for any feedback.


  • Larry Weingarten
    Larry Weingarten Member Posts: 3,142

    Hi, A question. Does the buffer tank have some sort of backup heater, or is it strictly storage?

    Yours, Larry

  • rbphhc
    rbphhc Member Posts: 125
    edited March 29

    No heating element. Functioning as a buffer right now. Heavily insulated, and working great to even out the hot and cold spikes from the tankless HWH.

    Next job is to hook up the circ pump to a controller. Scavenged a PID and some SSRs from a different project, will see if they do the trick. That will make sure buffer stays up to temp (circulating through the tankless - 006e3 pump fire it easily).

    But the buffer tank is actually an indirect. NTI S20W. Wall mounted, 20gal. Planning to run a radiant in-floor circuit through the coil as well. So it will be more than a buffer at that point.

    Guessing we will keep the indirect at 140*f and run DHW with a mixing valve. The floor wircuit will also have a mixing valve to keep those temps at @90-100*f. Keeping temps that high should prevent a 'perfect storm of DHW plus radiant from drawing the indirect down too much.

    Fingers crossed. The tankless is a Rinnai 199kiP, so it has the firepower to put out a lot of heat quickly and recover that tank fast.