3 Wire \"powered closed\" Thermostat wiring and thermostat options

Bart Vaio

I was call out to a service call where the gas control had failed. I replaced the control and on a call for heat the (fifty year old) zone valves will open and close in a non stop cycle. The motors basically slowyly spin powering then unpowering the pump relay/gas control with 24v severely short cycling the system endlessly till the call for heat is over. After a little prodding the owner told me that his painter had replaced the stats after painting the inside of the house. Bottom line is this, on a call for heat red wire needs to close circuit to green and the valve will open and when the call ends that circuit must open and the red wire must close to white wire to power the valve closed. If the valve is not powered closed the boiler will continue to run. Do i need special stats for this or do I have to tear all the zone valves out and start over. The only references i can find spec a w/r 1f35 3wire water valve thermostats, is this my only solution?
http://www.white-rodgers.com/wrdhom/pdfs/instruction_sheets/0037-2304.pdf

Bart

Bart Vaio

SPDT Thermostat

I guess this would be refered to as a SPDT t-stat, Has anyone used or could you use a Honeywell T651a for this?

Rocky_3

Any three wire thermostat will work

As long as you have a "#4, #5, and #6" terminal on the thermostat. #4,5, and 6 terminals on the zone valve has to have the same wire connected to the corresponding thermostat terminal. IE: #4 zone valve terminal has a red wire on it. The #4 terminal on the thermostat has to have the same red wire on it (providing of course there is no splice in the wiring between zone valve and thermostat. A simple continuity test will tell you if you have the same wire). Likewise with the #5 and #6 terminals on the zone valve. Just for convention, because it is easy to remember when we wire them in, we use red, white and blue to correspond to 4, 5, and 6. A White/Rogers 1E35-910, or a 1F35-910 depending on vertical or horizontal mounting preference works great. Also, make sure the 24 volt transforer is of sufficient strength. I once had the same problem as you, and after way too long trying to figure it out, I found the home owner had installed a new 24 volt transformer, only it was a 10va doorbell transformer, not a 40 va. Caused the zone to go round and round.
Hope this helps,
Rocky

FredR

Perhaps the painter reinstalled the stats incorrectly. I believe some of those earlier stats, W was the common. Have you rechecked his wiring?