zone valve stopped working, voltage always at taco 571

addotson

Hello -



Well this morning has been fun trouble shooting.  Our upstairs zone stopped working via thermostat yesterday.  The powerhead on the Taco 571 allowed me to put it into manual but it didn't seem to open all the way so I purchased a new one.  Installed and still no thermostat control of the valve.  Unlike the other zone, regardless the status of the thermostat there is always voltage on the wires leading to the zone valve.  With the thermostat plugged in (I have digital white rogers thermostats) there is 26.2V with the thermostat unplugged from the wall there is 20.3V.  The other zone has 0V when the thermostat is not requesting heat and about 25V when it is. 



We still can get heat when I push the lever from auto to manual upstairs so I am currently the thermostat...



Any help is greatly appreciated!  Thank you in advance.



Aaron

STEVEusaPA

did you.....

make sure no power was going to the taco head (everything off, thermostat not calling for heat) when you hooked the wires back up to the new head?  If not, you may have fried the new one.  When you say it didnt open all the way, do you mean the lever wouldnt go all the way to manual, or the lever did, but the pipe is hotter on one side of the zone valve then the other?  You should only move the lever with no power to the valve head (thermostat not calling for heat).

If you take the thermostat off the wall, and didnt already fry the head, use an insulated jumper across the two wires AT THE THERMOSTAT ONLY.  If the zone valve opens, it's the thermostat.  If it doesnt, could be other problems.  But make sure you turn all the power off before moving the lever (power off to the transformer, other controls, and thermostat not calling for heat).  

addotson

continued issues...

I did not measure voltages when i installed the new powerhead I just turned off the thermostat.



At this point the thermostat wires are disconnected from the powerhead and the thermostat is removed from the mounting plate on the wall. The thermostat wires which are to plug into the powerhead currently have a voltage of 20V. I reinstalled the initial head as at this point I think there is another issue... sadly this head's valve handle is soft at the top and hard at the bottom but it still opens and thus heat is still flowing to the second floor.



What does voltage on the thermostat wire mean? when the thermostat on the bottom is not requesting heat the voltage at the powerhead is 0V.



Should I still try to jumper the thermostat?



-Aaron

addotson

voltages

OK... I am concerned at this point that the wires going to my upstairs zone thermostat have shorted. Here is what I have...



At the Thermostat I have white wire in W/E and a red in RH with a jumper from RC to RH. When I measure the voltage from W/E to RH I read about 2V with the thermostat off. When I go to my boiler where I have the two leads which should be attached to my Taco 571 zone valve, measuring the voltage from white to red I measure about 24-26 volts (this is about the voltage output by the transformer mounted on the outside of my boiler). This is with the thermostat controls off the wall. I am guessing something is wrong here as I know when the lower zone is not calling for heat there is no voltage on the wires that go into the Taco 571 zone valve. My lower zone is currently functioning on a different thermostat wired the same at the thermostat and to the zone valve. I know where the wires from the transformer and the zone valves meet in a junction box which then wires head into the house to what I am assume is the thermostats.



Any suggestions on how to proceed? I have a heater guy schedule to come out next Friday (over a week away) but I would personally like to fix this. Should I just wire up a new upstairs thermostat with new wire and try it out? Anything else I can check so I can get some extra help troubleshooting?



Thanks again!

addotson

voltages

OK... I am concerned at this point that the wires going to my upstairs zone thermostat have shorted. Here is what I have...



At the Thermostat I have white wire in W/E and a red in RH with a jumper from RC to RH. When I measure the voltage from W/E to RH I read about 2V with the thermostat off. When I go to my boiler where I have the two leads which should be attached to my Taco 571 zone valve, measuring the voltage from white to red I measure about 24-26 volts (this is about the voltage output by the transformer mounted on the outside of my boiler). This is with the thermostat controls off the wall. I am guessing something is wrong here as I know when the lower zone is not calling for heat there is no voltage on the wires that go into the Taco 571 zone valve. My lower zone is currently functioning on a different thermostat wired the same at the thermostat and to the zone valve. I know where the wires from the transformer and the zone valves meet in a junction box which then wires head into the house to what I am assume is the thermostats.



Any suggestions on how to proceed? I have a heater guy schedule to come out next Friday (over a week away) but I would personally like to fix this. Should I just wire up a new upstairs thermostat with new wire and try it out? Anything else I can check so I can get some extra help troubleshooting?



Thanks again!

billtwocase

Check

Did you take all the wires off the power head? I would put them back on to start. Make sure it is wired exactly like the other zone. You probably need a new power head. You should have voltage at #1 terminal if the thermostat is calling for heat. #2 terminal is the ground from the step down transformer, and along with #3 terminal, connect to "TT" in your control. It's possible, but not likely that the heads can not depress the valve/seat inside of the zone base due to it jamming up.