Zone Control Wiring

Alan (California Radiant) Forbes

Everyone has their own way of wiring, even on a controller where they provide you a terminal for every wire. This installer sent 24 volts (both "R" and "C", large red and blue wires) directly from the transformer to the thermostats and then a return wire from the thermostat to the "W" terminal.

EdTheHeaterMan

Was there a picture to go with this?

Alan (California Radiant) Forbes said:

Everyone has their own way of wiring, even on a controller where they provide you a terminal for every wire. This installer sent 24 volts (both "R" and "C", large red and blue wires) directly from the transformer to the thermostats and then a return wire from the thermostat to the "W" terminal.

Otherwise, It sounds like R to R w to W and C to C is what you would expect.
Makes more sense with the photo.

Big Ed_4

Someone thought they can wire a nest

hot_rod

Looks like an additional relay involved also 
Does it work?

Big Ed_4

Maybe but why .... It would be simpler to rip the board out and hard wire

STEVEusaPA

Looks like they just basically mimicked what it looked like when it was wired without the zone control.

Alan (California Radiant) Forbes

hot_rod said:

Looks like an additional relay involved also 
Does it work?

Not a relay. It's just a toggle switch for those who prefer toggles to unplugging a cord.

This was installed by a company in California, early on in hydronics who were very good at marketing. They used large water heaters for DHW and radiant (via a HX), homemade expansion tanks, non-barrier tubing, non-ferrous pumps, no remote manifolds (all home runs to the mechanical room)..........

mattmia2

Are you sure they didnt burn out some part of it

EdTheHeaterMan

Has this ever worked before the Nest Thermostats were installed? I think they used the correct T terminal for the W. And R is R where ever you pick it up from. Same for C... C is still C where ever you pick it up from.

Looks like there is custom wiring in order to confuse their competitors. Kind of a guarantee that the customer comes back to the original installer for service. "If the competition can't figure it out, then I guess we need to call the guys that installed it"

Sounds like Weil McLain parts. Can't use lower price generic off the shelf parts, Must use the Weil McLain part number or it won't work.

Alan (California Radiant) Forbes

There are no Nest or other wi-fi thermostats; simple setback ones that are not power stealing. Some installers like to power thermostats with a "C" wire so you don't have to change the batteries so often.

Big Ed_4

I would recommend fusing the transformer