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chuck172
Member Posts: **90** ✭✭

I'm trying to calculate how many zone valves I can put through a 40va transformer.

If I take the zone valve motor amp rating and multiply by 24 volts, divide that total into 40, that's the answer (right)?

Now I'm looking at a honeywell zone valve and it reads the following:

24vac 50 va pilot duty

120vac 4.4 amps full load

28.4 amps lock rotor.

Which number do I use?

If I take the zone valve motor amp rating and multiply by 24 volts, divide that total into 40, that's the answer (right)?

Now I'm looking at a honeywell zone valve and it reads the following:

24vac 50 va pilot duty

120vac 4.4 amps full load

28.4 amps lock rotor.

Which number do I use?

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## Comments

zone valve are you using. The numbers you posted seem like relay numbers not Honeywell ZV's. If memory serves me Honeywell ZV's use about .2 amps so you can use 5 of them with a 40 VA transformer.

If you are using a NEMA rated class II standard DC20-92 transformer you can exceed rating up to 200%.

90✭✭If a honeywell ZV drew .2 amps, .2X24=48

Wouldnt I be able to use 8?

233Would you be so kind as to show me how you calculated that? Or tell me what I'm doing wrong. The .2 amps is a 5th of an amp; 24 volts divided by 5 is almost 5, so each zone valve is drawing 5 va; 40 va divided by 5 va is 8 zone valves. There's probably a de-rating in there somewhere?

Alan

16.2 x 24 = 4.8 not 48

So a 50 VA transformer should be able to handle...

50 / 4.8 = 10.416 rounded to 10 zone valves

literature for their zone valves states 5 ZV,s per 40 VA transformer.

They also have a white paper they put out about 10 years ago that states that a 40 VA transformer can be run at 200% of capacity with only a small drop in voltage. This is how we can run three Taco ZV's with a 40 VA transformer as long as it is NEMA rated standard DC20-92 ClassII.For Taco which draws about 1 amp the math would be 1 x 24 = 24 VA per valve x 3 = 72 VA.

With the Honeywell ZV's at .2 x24 = 4.8 divided into a 50 VA = 10.416666 so I would imagine 8 to 10 would be okay with a 50 VA.