Transfromer trouble

pappy

I'm using Taco 571-1 zone valves to split whole house heating system into 4 zones. I'm using 3 valve and letting the 4th zone (that is the coldest area) heat when ever the others call for heat.

My problem is the control transformer (the Thermostat to #1 & #2 terminals) keeps frying? I checked all the wiring and even had a friend check it as well? I'm using a Taco transformer so I know I have the right one. I even used an old 24 volt door bell transformer but I knew that one was a goner as soon as I flipped the switch.

billtwocase

are you using

a 50 VA transformer? Pics or diagram of your wiring will help. It is not right. I would leave the cold zone open manually with no wires on it. If your step down is frying, then the wiring is not right. 

icesailor

Transformer problems:

You can't do that. Every zone valve must have a thermostat. You can only run three Taco 571 zone valves, And you MUST use a 24 volt, 40 VA transformer on the three, If you use four, it MUST be a 60 VA. I don't know how you are trying to wire the fourth zone valve with the other three but you may have fried the heat anticipators on the thermostats and/or you may have almost 2.0 amps going to the power heads. They fry because the coil around the wax motor gets too hot and if it is cycling too fast, fries the coil or the wax runs out. They are very rugged valves. You must be doing something really bad to have them blowing like that. I've installed 571's for over 30 years ago that are still going. The ones with the green heads. Not many but a few.  

furnacefigher15

ocesailor

I think what he means is the 4th zone has no valve, and just heats anytime the boiler runs.



About the transformer, check the voltage output when all zones are calling and compare to just 1 valve, then 2 valves, then no valves.



I suspect if the VA is too low you'll see a voltage drop with the 3rd valve.



Also, Taco may not have taken account for whatever load the boiler itself is adding (gas valve, pump control, etc...)



If the transformer burns out immediately, you have a short of some kind. (pinched wire, bad thermostat, grounded, etc...)



Also, do yourself a favor and get a inline fuse rated at 3 or 5 amps (automotive style works well) to keep from replacing transformers, until the trouble is pinpointed.

icesailor

Transformers:

24 volt, 40VA transformers are the correct transformers for 3 Taco 571 valves. Each head draws .09 amps. A 40 VA transformers wired to 4 valves will open the first three to call but not the 4th. When one of the first three closes, the 4th will open.

The 24 volt, 40VA transformer is there to power the wax motor coil and operates through #1 and #2. The 24 volt power in the control being operated by the end switch, #2 and #3 are only common through #2.

He has a wiring and/or power issue. I hardly have ever had to change a transformer. Power heads more often but it isn't common.

If they are old valves, and have the nasties under the power head, they may be hard to push down. They may be leaking. Nasties on the plunger will make it hard for the wax motor to push the plunger down.

I usually replace the valve guts with a new valve and a new plunger and power head. They are easy to replace and I don't change the body. It's easiest to do that. If you want to know how, ask. It's easy.  

A doorbell transformer isn't usually 40 VA.

Mark Eatherton

How many conductors do you have going to the stat?

You will need a minimum of three, possibly 4...



If you have the right number of wires, then we can talk turkey.



If not, then you either need to go back to a conventional 2 wire thermostat or pull more conductors...



ME

billtwocase

ice is right

A door bell transformer is usually about 18 volts. You should have a 50 VA for the 4 zones. Like Ice, I replace the valve and seat when they are leaking or sticking, and more important, like Honeywell, etc, I disassemble the valve, sweat in the body, and reassemble when cool. That rubber don't like that kind of temps needed to melt solder. Somehow the transformer is dead shorting, possibly at #1 and #2 on the power heads. Do you need a wiring diagram for those Taco's?

Big Ed_4

transformers

Buy the better transformer with the built in circurt braker , they start installing them on the better 50VA and above ,it would save you money until you find the short . Or instal a three amp car fuse in line with spade conectors . Posted zone valve amp draw x number of zone valves x 24V would equal the least amount of rated VA needed and going larger is better ...

icesailor

Number of wires:

You can have 300 wires going to the thermostat. But you only need two wires on a Taco 571 Zone Valve. The 24 volt transformer is wired through the transformer to the #1 and #2 terminals on the power head but runs through the thermostat which acts as the switch. If you have a 3-wire to the thermostat, you only use two wires. Usually red and white. You tuck the green. At the power head, you usually just tuck the green and use the red and white. Most use red on top, white in the middle and green on the bottom with the green and common white going to the TT terminal on the control.

They may make a 4 wire Taco power head but I have never seen one or used one. Any electronic thermostat I have ever installed only used the red and white for heating control. Whatever was done for cooling, I am mostly clueless about. I have a hard enough time dealing with the heating end of it.

icesailor

Zone Valves:

Bill,

To keep my head from hurting, here is how I change valves.

No matter what you do, you can never un-solder a 571 zone valve unless you cut slots in the bottom of the valve. So you must boil the water out of the pipe. As soon as you try to get the body off, more water shows up and cools the body.

Take the power head off and take a big pair of pliers. One end on the bottom of the body and the other end on the plunger. Squeeze the plunger down and compress the spring. Unscrew the plate holding the plunger in place and ease the plate and plunger up until the spring is relaxed. Pull the guts out. I grease the new plunger assembly and grease the screws with SuperLube synthetic grease because it doesn't wreck O-rings. Put the new plunger and plate back and clamp it down again with pliers. You can hold the plate and plunger down with one hand while you put the screws back in. You just turned a three hour job into an hour. The power-head alone is almost as much as the whole valve and the plunger and power head as a repair part is far more than the complete valve which is heavily discounted. The new valve body goes in the brass scrap barrel. I charge for a new valve. Because that's what they got.

If you have the time and the valve is working, but leaking, squirt Kroil (www.kanolabs.com) on the screws and let it sit for a day. They have almost always come out for me. If the plunger is sticking through the hole in the top of the hold down plate, squirt some Kroil in it. Operate the plunger with the big pair of pliers until it works easily. Once operating easily, put Never Seize in the hole when the plunger is down. It will usually work after that. You can come back another day and do a complete repair if you must.

That's how I do it. If the screws won't come out, you have to change the whole valve body. The only time I have had to do that though is when I can't get the power head off because it is rusted in place.

It works for me.

I have never seen a case where a 40 VA transformer didn't operate 3 571 zone valves properly. A 50VA or 60VA will work fine but it takes a 60VA transformer to operate 4-571's.

Harvey Ramer

I was in a similar situation recently.

I wired a transformer with 2 taco power heads and 2 thermostats and it went, poof...

It was a bad transformer. Sometimes this happens. I put a new one in and it works perfectly.

Check the voltage coming in on the line side. If you are wiring it up to 120V make sure you have at least 120V but not more than 125V. Likewise if you are connecting it to 240V make sure you have at least 240V but not more than 248V. Usally you would use the same common on the transformer for either 120V or 240V.

Check the voltage on the output, should be in the range of 24V to 28V.

On the TRaco power head your dry contact end switch switch should be between terminals 2 and 3, that will connect to the t-t on you boiler or pump relay.

If you have to seperate transformers in your system you can cross one leg without causing any damage. If you cross both legs your transformer will go poof...

Tim McElwain

For 3 TACO

571 zone valves you need at least a 40 VA transformer. It should be a NEMA (National Electrical Manufacturers Association) rated class II Standard DC20-92 transformer which can operate at 200% of capacity so it will give out the equivalent of 80 VA (80 watts) with a slight reduction in voltage say around 22 to 24 versus your normal at around 24 to 27 volts. If you did the math a TACO ZV uses about 1 amp to operate multiply that times 24 that is 24 watts (VA) per head times three would give 72 VA.



Now the other thing you have to watch out for other than using cheap transformers (non NEMA rated) is the correct polarity on the primary of the transformer making sure 120 Volts hot goes to the black wire and neutral white wire has "0' potential. On the secondary side if you are parallel connecting two transformers they must be in phase "R" wired to "R" on the other transformer and "C" To "C". Then from "R" you go through the thermostat to terminal "1" on the TACO ZV and then "C" to "2" on the zone valve. Then from "2" and "3" you go to "T" "T" on the relay or "T" and TV" (depends on the relay). If you have a relay with "T", "TV" and "Z" then you can get 40 VA power from the transformer relay. Wiring as follows "Z' to the thermostat then to "1" on ZV; TV goes to "2" on ZV and "T" to "3" on ZV.



DO NOT USE CHEAP TRANSFORMERS!!!!



Maybe this will clear up your problem.