Zone Valve Information
Zone valve wiring varies with different manufacturers and different models. There are multiple ways to wire zone valves, but I suggest adding an external 24V transformer or a multi-zone relay for zone valve control. Do not wire zone valves to the boiler's existing 24V transformer unless the installation manual specifically indicates a method for incorporating the wiring into the boiler transformer. When adding external transformers, you must have a transformer rated at 24v and the proper VA (volt Amps).
Before we dive too deep into sizing transformers, you can use a multi-zone relay. Purchase the zone relay for the number of zone valves you have on your system. The zone valve panels will interconnect to accommodate a larger number of zone valves. This will make wiring much easier.
If you decide to tackle zone valve wiring, you will need the following information.
Some model zone valves can only have three on a 24V 40VA (most common transformer), while others support 12 zone valves per 24V 40VA transformer. You can buy a higher VA transformer to handle more zone valves if you decide not to use a zone valve panel. To size the transformer in VA, you need to determine the amp draw from the zone valve power heads you will be wiring. To determine how many amps a transformer can supply or what size transformer is required for the number of zone valves you are trying to operate is simple.
What does Volt Amps mean?
Volts/Amps is the amount of amps that can be drawn from the secondary windings of a transformer
To determine the number of amps available for zone valves, divide the VA rating by the transformer secondary voltage.
The formula would look like this
AA = VA/TS>
Where AA = Available Amps
VA = Volt Amps
TS = Transformer Secondary voltage
Example;
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
Example;
Add together the zone valve amperage. Let's assume the combined load is three amps.
3 amps x 24V = 72 VA transformer
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