Taco 571-2 Wiring

[Gary in NJ]

I've been working on a large upstairs project for about a year. Yesterday I opened the valves for the hot & cold water to the bathroom - quite a good feeling. All of my plumbing is complete for the hydronic baseboard heating right to the boiler. As soon as I get the flow valve wired I'm ready to throw the final lever.

My existing setup was 3 Taco 571-2 valves (two for heat zones and one for domestic hot water). I have added a 4th Taco 571-2 flow valve for the upstairs zone. All four valves are next to one another. I am using a Honeywell RTH4300B thermostat for both the heat and a/c in this zone. The a/c is using four of the terminals on the thermostat.

There are three terminals on the flow valve. From what I can determine from the instructions, terminal 1 and 3 get connected to the thermostat and terminal 2 is connected to the transformer. There appears to be a 4th wire from the transformer that jumps across terminal 3 as well. I assume I can just jump the #2 & #3 terminals from the flow valve next to this new valve.

So I think the white wire gets connected to the W on the thermostat and runs to terminal #1 on the flow valve and the Red wire gets connected to the R on the thermostat and then goes to terminal 3 on the valve. Do I simply jump terminals 2 & 3 from the neighboring valve?

I'm sure this is simple...but I just want to get it right.

 

[hj]

Whether it is "simple or not" depends on HOW the rest of the system is wired. The thermostat SHOULD operate the zone valve, which in turn SHOULD turn on the burner and the circulator. BUT, the system could be wired for constant temperature and pump operation with the thermostat just opening and closing the zone valve. OR constant temperature with the thermostat also operating the pump.

 

[Sponsor]

 

[Gary in NJ]

OK, looks like I need to do a little more homework here. I'll take a look at how the circulator is wired. I have to tell you, whoever wired this existing system left a real mess. The connections at the transformer is a rats nest.

I'll trace the wires by color and see how this is wired.

 

[Tom Sawyer]

www.taco-hvac.com

Has the necessary wiring diagrams. It's too involved to explain here.
You have 4 zone valves so you either need to 24v 40va transformers or one 24v 60va transformer. Using a single 40va will burn the valve heads out. The easiest way to straighten out and simplify your wiring would be to get a Taco SR504 relay/zone valve controller. It's on their site. Using the SR controller solves your wiring and transformer issues.

 

[Gary in NJ]

I need a zone controller even though I only have a single circulator pump? Well, I know when to call a professional...now is that time.

 

[Gary in NJ]

I called TACO and spoke with customer service. The support tech (John) suggested that I could do one of two things:

1) Add a second transformer (as Tom suggested), or
2) I use a ZVC404-2.

Since I really don't like the rats nest of wires that I have right now, I'm going to go with the ZCV404 option.

Tom, thanks for putting me on the correct path.

 

[Tom Sawyer]

You are going to like it. It greatly simplifies and cleans up the usual rats nest of low voltage wiring. Tekmar and Argo also make similar products. If you talk to John again tell him he owes me one LOL

 

[Gary in NJ]

I finally got around to installing the ZVC404. What a straight-forward and easy job. The most difficult part (not that it was) was identifying which wires in the transformer rats nest were Zone 1 (living area) and which were Zone 2 (bedrroms). With that all sorted out (with a multi-meter) I removed all of the existing wires and started from scratch, making sure that everything was properly labeled for future reference. I checked all 3 heating zones and the DHW zone and they all worked. With 4 full baths in the house having the Priority switch for the DHW is a nice feature too.

 

[Tom Sawyer]

Hurray and hazzah

 

[arydant]

www.taco-hvac.com

Using a single 40va will burn the valve heads out. .

This is incorrect. Perhaps you meant to say that it would burn out the transformer.

On the TACO 571, terminals 1 and 2 are connected to a coil of nichrome wire that heats up a wax element. It draws .9A when you apply 24VAC across the terminals. Wire-wound power resistors are made this way and will only burn up if you run too much current through them.

Unless it is defective it should NEVER burn out with a 24VAC transformer. The TACO instructions specify a max load of 3 valves for a 40VA transformer. Additional loads will only cause the voltage to drop since the transformer core will saturate and be unable to supply the required current to heat up all the valves at once. This will not harm the coils since they would simply not get hot enough to melt the wax element.

In many cases, using a 40VA transformer with 4 zone valves would work just fine until all of your thermostats call for heat simultaneously. In that case, the system might get stuck in a perpetual "call for heat" and/or the transformer might burn up. TACO illustrates using additional transformers in that case.

These valves are pretty robust and hooking them up wrong won't damage them, but they can fail in other ways if not maintained. Corrosion can cause bad connections both on the terminals and on the internal switch contacts. The actuator can also get gummed up and freeze up the device. The area around a heating system is often damp and subject to corrosive gases so electronic and electro-mechanical controls see a lot of abuse.