Boiler Replacement- Circulator placement on radiant floor zone

heidleml

My technician installed a zone circ on the hot supply to the mixing valve instead of on the mixed side. Customer is not getting adequate heat and my tech says it will be pretty difficult to get the circ on the mixed piping. He said he can move the circ to the return side as it comes back to the boiler. I understand pumping away etc. and that this isn't ideal, but any reason it won't work?

Other zones are pumping away to high temp and working fine.

Jamie Hall

Last i looked the circulator has to be pulling from the mixing valve...

heidleml

so return will do the trick

Jamie Hall

Maybe. If it's before the connection back to the mixing valve. It's not ideal, however, as the pressure at its inlet will be low -- and maybe too low for long life for the pump. Surely there is enough pipe work somewhere between the outlet from the mixing valve and the beginning of the loops? A pump isn't all that long. Someone is not thinking.

HomerJSmith

One should pump away from the mixing valve (the mixed port), but not everyone does what they should do.

hot_rod

Any 3 way mixing valve, manual or thermostatic, has 2 inlet ports and 1 outlet or mixed port.
To work properly and adequately you need to flow out, or pump out of the mixed port. That allows flow to enter the H&C port, blend to the appropriate temperature.

I doubt you will get a consistent or accurate temperature pumping into either inlet port.
Depending on the design of the thermostatic cartridge inside the valve could lock up or close off one of the inlet ports if you are pumping into it. If it is a ASSE 1070 valve, it is considered a scald guard type and will fail to mix. There is both a pressure and temperature component and acceptable range on 3 way thermostatic valves. An ASSE 1017 may flow, but will not mix properly.

I’d come up with a way to do it correctly. It’s the reason the ports are labeled🤔

Now different brands of mix valves have different port locations. You should have H, C, and mix.
Some valves may have A, B, and AB