Hydrostat 3250 Aquastat & Taco ZVC406 Zone Valve Control Wiring

DIYCharlie

Possibly dumb questions, but here goes:

(System consists of six Taco Sentry zone valves/single circulator/no indirect water heating.)

According the diagrams as I understand them:

Power to the circulator is wired through the ZVC pump end switch and through the 3250 aquastat.
Does this sound right?

The "TT" wires run from the burner control to the TT terminals in the aquastat, and TT wires run from the "XX" isolated end switch terminals in the ZVC to the same terminals in the aquastat.
Again, is this right?

This is my second boiler install, to replace the first I did 30 years ago in our house. I'm a little rusty, but the ZVC is really the only thing that is new to the system set-up.

Thanks for any and all help,
Charlie

HomerJSmith

... TT wires run from the "XX" isolated end switch terminals in the ZVC to the same terminals in the aquastat.

Yup.

Power to the circulator is wired through the ZVC pump end switch and through the 3250 aquastat.
Does this sound right?

Nope. The aquastat provides the power to the circulator. The XX on the Taco ZVC activates the aquastat to turn on the boiler and start the circulator.
There are relays that can control a circulator, but in your case, the aquastat does that job.

Steamhead

@HomerJSmith is right. I'll add that the HydroStat can hold the circulator off for a few minutes so the boiler can heat up past condensing temperature, but that won't work if you power the circ from the ZVC.

HomerJSmith

All boiler condense at start up. It is sustained condensation that's the biggie.

DIYCharlie

So 120V to circulator would be routed either (a) as shown here, or (b) direct to aquastat?
Thanks again.

HomerJSmith

Read my post! You can do it thru the Taco, but I prefer to do it thru the aquastat. In a Primary/Secondary sys the sys pump contacts on the Taco would power the load distribution circuit pump and the aquastat would power the boiler circuit pump.

The TT on the Taco to the TT on the aquastat tells the aquastat to turn on the boiler firing and the circulator. You can choose how you want to do it.

DIYCharlie

O.K., let me admit I'm a hard case, slow on the uptake and all that bad stuff.
I guess what I am missing is what happens with the TT connections on the boiler relay (GeniSys 7505), which I perhaps mistakenly referred to as the "boiler control" earlier. Are they simply not used?

Thanks for your patience.

HVACNUT

TT gets jumped on the Genisys. It should have 1 leg constant 120 volt to power the Genisys, and then 120 volt from B1 on the Hydrostat to limit on the Genisys. So switching is line volt. By jumping the 24 volt TT circuit, the burner is ready to go once B1 is energized.

DIYCharlie

Thanks all.

EdTheHeaterMan

To add to the confusion:
This set up is for a system that may have primary/secondary piping design or some other design where there is more than one circulator. The boiler control (Hydrostat 3250 in your case) might operate the boiler circulator, while the ZVC would operate the system circulator. You have only one circulator pump, so you would not use the ZVC pump switch relay.
Hope this adds to your confusion, or at least makes things clear as mud.
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DIYCharlie

Starting up the system now and having a couple of problems. Boiler starts up w/o any t-stats calling. When I turned one up, the boiler shut down. I then changed some wires around on the 24V circuit to what I think is right, and now I get fuse blow on the ZVC. Attached is the 24V wiring. Do I have my wires crossed? XX End Switch on ZVC T-stat side is wired to TT on Hydrostat and the T-stat terminals are jumped at the burner control, per above advice. THANKS again.

HVACNUT

Wrong thermostat. You're sending 24 volts via Y to common creating a direct short when the thermostat is turned below indoor temperature. 
Remove the wires from C on the thermostat terminals on the Zone panel and from Y at the thermostats. 

DIYCharlie

Yeah, it hit me a little while after I posted. I had done what you say and got it working correctly.
Thanks for the reply.