Taco ZVC404 and 4 Taco 571-2 zone valves

russiand

I think this topic has been discussed before but I have a question still. Taco says that a 40amp transformer can only handle 3 of their 571 series zone valves. The ZVC404(regular) comes with 40amp transofrmer and yet it claims to be able support 4 valves at once. What gives? Am I asking for trouble attempting to run 4 zones with this controller that may potentially have all of the 4 valves on?

Tim McElwain

You mis read the instructions

It says "Number of Zones" 4 with priority, that means 3 zone valves and one domestic hot water zone. By the way those are not 40 amp but 40 VA which is volt amps or actually watts. So it is a 40 watt transformer which can handle 3 Taco ZV's. The reason it can is that it is a NEMA (National Electrical Manufacturers Assoc) rated Class II Standard DC20-92 transformer which is used which can run at 200% of capacity.

bill_105

Missing fine print?

 You can use any brand of ZV you want. I think 570's on all, but you better have that priority switch turned on.

If #4 was for DHW I wouldn't use that slow opening ZV anyway.

Mark Eatherton

Priority optional...

Tim, the priority setting on those controls is optional, which means it is entirely possible the transformer would be seeing the load of all four heat motors at the same time. I think the saving grace is that the valve only draws that much amperage when it is initially opening. once opened completely, it pulses power to the heating element.



As you said, the transformer is rated for 200% load factor (intermittently) and worst case, if the VA is weak, the opening time of the valves is extended, but will eventually open.



I have run 40 watt transformers at 150 % of their rated capacity for long periods of time in the lab on a radiant window, and it didn't fail, but boy did it get HOT. You could smell it across the room :-) When I wired two 40 watt xfrmers in parallel, the smell went away, and the transformers cooled way down.



Tacos ZVC 406 has two 40 va xfrmers wired in parallel. Each heat motor operator draws 1 amp, of 24 watts during opening, then momentarily while it is open.



Taco is not the only manufacturer of heat motor type of operators.



ME

russiand

If one were to use a zone valve on a DHW zone which one?

Is the EBV from Taco a better choice than the 570. Just how slow is 570 to open?

Mark Eatherton

Minutes as opposed to seconds...

and a BIG difference in amp draw...



ME