Low votage boiler wiring

[Bruce Sr.]

need to wire two zone valves ,but only two t- stat wires from boiler each zone valve has four wires. Do i need to add additional trans former Thanks Bruce

 

[hbiss]

You do understand what the 4 wires on a zone valve are for don't you? Two are for the motor that opens the valve and the other two are from an end switch that provides a contact closure when the valve is fully open. These (from each zone valve) are usually connected in parallel then to the boiler control to turn the circulator and boiler on when any valve opens.

The thermostats simply control the motors of their respective zone valve. Whether or not you will need a transformer to power the circuits depends on whether you are using a zone control panel or not. A zone controller will have the transformer built in and will provide connections for the T stats, zone valves and circulator.

If you roll your own use a 24 volt transformer to power the two T stat/zone valve motor circuits so that if a T stat closes it will provide voltage to the motor leads of its associated zone valve. Then, as above, connect both end switch leads in parallel then to the TT terminals (where you would normally connect a single T stat if there were only one zone and no zone valves) on the boiler control.

In operation, the T stat will open the zone valve which causes the end switch to close and start the circulator and boiler.

-Hal

 

[infinity]

Some boilers have internal transformers large enough to run 2 zone valves. Personally we always use a external transformer for 2 or more zones. It makes future replacement easier and can allow for expansion of another zone in the future. When wiring multizone boiler you need to remember the simple formula, the t-stat control the zone valve and the valve controls the boiler.

 

[LarryFine]

I would imagine that one transformer can operate many valves as long as the don't operate simultaneoulsy.

 

[infinity]

I would imagine that one transformer can operate many valves as long as the don't operate simultaneoulsy.

That's true, but predicting whether or not that a few will call for heat at the same time is the tricky part.