Taco 3 wire to Honeywell WF Thermostat troubleshooting.

Captbutch

I have been struggling mightily to get any thermostat working (including old school style) with taco 573 zone valve and head. currently the old school thermostat switches heat on regardless of set point.

The goal here is to connect a Honeywell RTH9585WF to the 573. Taco wants me to buy a ZVC 403. Not sure why that is necessary, but I will hear anyone out. Has anyone solved this exact issue before? Mind explaining it?

For an intro as I am new here I am in Maplewood, NJ.

I did some LL87 & 97 benchmarking work for an outfit called BES out of the five towns. Learned a lot on the job. Definitely appreciative of the dead men's podcast, and the lost art book and reference guide. Tried to get a job at Leonard Powers, but ended up spinning wrenches over at Subaru instead. Life is good. Jerry Lives. Glad for the help of this forum. Already learned more than I wanted to know about wiring the Nest to the ZVC.

Peace out everyone,

Kris

Captbutch

@Erin Holohan Haskell bumping this for response from Taco or other qualified professional.

EBEBRATT-Ed

See the attached wiring for the Taco valves. In addition you need a "C" or common wire to the thermostat from the transformer (the wire that connects to terminal #2 on the valve)

Maybe there is a reason that the valve will not play well with this thermostat & that could be why Taco wants you to use a relay. Can't give you any more information without knowing more about your system

Jamie Hall

Well now. If the old school thermostat switches the heat on regardless, there's something amiss. Probably not with the zone valves.

Consider. The Taco zone valves are about as simple as it gets. When the thermostat closes to ask for heat, the zone valve motor is actuated and the zone valve opens. When the valve opens, a different set of contacts makes and this, in turn, activates the boiler or a relay box or... whatever.

So the first thing to figure out is why the thermostat asks for heat regardless of setpoint. Bad thermostat? Shorted wires?

SteveSan

@Captbutch If you have any questions, please give Taco Technical Services a call during normal business hours Mon-Fri 8am-5pm EST 401-942-8000 just ask for Steve

Joe Mattiello

Has this been resolved? You will need to power the thermostat with C terminal, and explains why Taco tech support suggested using a ZVC panel to facilitate wiring. Let me know how you made out   

Captbutch

Has not been resolved. C wire exists. Thermostat will not operate off of C R W Y G alone.

Captbutch

Sorry that is redundant. GRWY is correct