primary secondary -- pumping upstream

don_185

Why would you need a mixing valve other then using it as a safety.

If the control is controlling floor temps what the harm at feeding alittle 180 into the secondary after a call for domestic.

You always want the secondary to be smaller or match the primary pump.If not, you will turn your return tee into a mixing valve.

tomg

secondary pump suction is downstream of the outlet

i'm verifying operation of a prim/sec boiler control. seems to work, but the radiant floor heat circulator sucks /downstream/ and discharges back upstream to the primary circuit. seems like a mixing valve is the proper thing to do, but is this a viable alternative? don't see it in dan's book!
also piped on the primary is an indirect water heater. the boiler is modulating/ 180F setpt for DHW and 100F for floor heating. secondary circulator is smaller than primary -- 1/25 hp vs 1/8 hp i think.
any thoughts or resources on this? thanks much!

tomg

for temp control

actually, by pumping backwards they are using the return tee to mix -- the return mixes with primary and then is supplied to the secondary. Seems like with this setup there is no temperature control -- starts out very cool (cold return water) and gets very warm if the dhw calls (which it does frequently -- this is a restaurant).

does anyone else pump backwards on their secondary?

Charlie from wmass

Yes viega mixing stations http://www.viega.net/5144.html cut and paste this link for their page.