Zone Valve Wiring

Zone Valve Information


Zone valve wiring varies with different manufacturer's and different models. There are multiple ways you can wire zone valves but I suggest adding an external 24v transformer or a multi-zone relay for zone valves. Do not wire zone valves to the boilers existing 24v system. When adding external transformers you must have a transformer rated at 24v and the proper VA (volt Amps). If using a multi-zone relay you buy a relay for the amount of zone valves you are running.

Some model zone valves you can only have 3 on a 24v 40VA  (most common transformer) and others is 12 zone valves per 24v 40VA transformer. You can buy a higher VA transformer to handle more zone valves. To size the transformer VA you need to get the amp draw off the zone valve power head. To determine how many amps a transformer can operate or what size transformer is required for the amount of zone valves you are trying to operate.

What does Volt Amps mean?

Volt Amps is the amount of amps that can be drawn from the secondary windings of a transformer.

To determine the amount of amps available for zone valves divide VA rating by transformer secondary voltage.

The formula would look like this

Where AA = Available Amps

VA = Volt Amps

TS = Transformer Secondary voltage


A 24v 40VA transformer you would use the following formula

40VA divided by 24V = 1.6 amps

A 24v 72VA transformer would be

72VA divided by 24v = 3 Amps for zone valves

To determine required transformer volt-amps, with known amp draw multiply amps x secondary voltage (24v).

The formula would look like this;

VA = A x TS


VA = Volt Amps

A = Amp load

TS = Transformer secondary voltage


Add together the zone valve amperage. Let’s assume the combined

is 3 amps.

3 amps x 24V = 72 VA transformer

If wiring Taco 3 wire zone valves into the new US Boiler IQ control see this wiring
diagram and use caution to not cross the 24v polarity.

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