We are rebuilding our home with Hydro air- we have 3 zones 1 for Waterheater, 2nd for 1st floor and 3rd for 2nd floor. ThE HVAC installed the air handlehandler and thermostat, the plumber did the boiler, and the electrician hooked up the TACO control and all the wiring. Issue: the zone valve stays open on the 1st floor and when control by our Nest thermostat, it doesn't push hot water through. Intermittently, heat comes o . But the zone valve stays open da and night.
Of course they all point fingers at each other and weeks go by and problem still exists.
Not sure if it's the thermostat, the wiring, or a stuck zone valve.
No one wants to trouble shoot and just want to play the blame game.please help.

The first thing you need to do is disconnect the wire from terminal 1 on the zone valve. Wait a few minutes & try to move the lever. If it moves easily, the valve is stuck open. This will tell you if the problem is mechanical or electrical.
If determined to be electrical, reconnect the wire, disconnect the thermostat & check the valve again. If the valve stays open, the problem is somewhere between the stat & the valve.

With all due respect to the electrical trade; most electricians are lost when it comes to low voltage controls.

Thanks so much for the ququick repsonse! The lever as in the automatic--max on the zone valve? Sorry I am so ignorant on these things. Figured that's why we pay the trades big money to do their jobs.

Does the zone valve look like this?
571-2 - Taco 571-2 - 3/4" 571 Sweat Zone Valve (http://www.supplyhouse.com/Taco-571-2-3-4-571-Sweat-Zone-Valve)
If so, I mean the lever on the left.

No. It's a silver box with lever going left to right. http://www.homedepot.ca/wcsstore/HomeDepotCanada/images/catalog/15567.V8043G1216_4.jpg

Ok, That is a Honeywell zone valve. If the lever moves easily nearly the whole width of the slot, the valve is open. Instead of removing a wire from terminal 1 as stated in post #2, disconnect one of the yellow wires. Otherwise troubleshooting is the same. If we haven't found the problem after this, we can go on but let's do the easy stuff first.