48 volts across Taco 571 pins?

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Old 12-12-14, 06:23 PM
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48 volts across Taco 571 pins?

Just re-wired my 3 zone system to configure it to use wifi tstats (added Common) Schematic is below. I get 48V+/- between 571 pins 1 and 3 when there is a call for heat on t-stat. Is this correct?
Name:  1201 Zone Valve Wiring Schematic-Corrected.jpg
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Old 12-12-14, 06:42 PM
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Correct? it could be...

What I mean is that there really is no 'correct' between 1 and 3.

What you are reading between 1 and 3 is the SUM of the transformer in the aquastat and the external transformer.

If you swap the wires at T and TV you will see ZERO between 1 and 3.

This is because swapping those wires will place the transformers out of phase with each other and the voltages will not add, they will cancel each other.

BUT, it simply doesn't matter... either way is fine. It won't hurt anything.



You should read 24VAC between 1 and 2 when the thermostat is calling the valve to open, zero volts when the thermostat is not calling.

24VAC between 2 and 3 when there is NO CALL for heat (all valves closed).

ZERO volts between 2 and 3 when any one of the three valves are calling.

As long as you never see 48 VAC between 1 and 2, or between 2 and 3, you're good to go.

The wiring diagram is correct.
 

Last edited by NJT; 12-12-14 at 07:40 PM.
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Old 12-12-14, 06:58 PM
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Thanks a million NJ! I'll actually be able to sleep tonight.
 
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