Long time lurker, 1st time posting...
I have an older style TACO zone valve (black case) controlling the hot water heater (ESP 100c2-1 dated 01-03) - gas furnace <10y/o. Worked fine until about a month ago when it wouldn't shut off. Since then, its either been running continuously or I have to manually turn it off and on (rotating button on powerhead). I checked the voltage from the transformer - ~24v AC, checked the thermostat on the waterheater for both the hot and cold conditions - ok. I know everything operates fine because when its on, there is hot water and when its off for an extended period of time, there isn't. The problem its that it doesn't operate in auto mode.
Spoke with the plumbing supply counter guy who informed me the older style TACO zone valve heads had a very high failure rate and were redesigned. The new powerheads are green, so I bought a replacement head (ZA024Q4A1) - not the valve. Checked the wiring (swapped wires for the w/y and c connector as they were opposite that of the older style), installed and turned on power. The new valve will not power up (green LED is off). Tried to manually turn the valve with the button, it rotates 90 degrees but the furnace does not come on. Reinstalled the old TACO head, works fine in manual mode. I noticed that the old and new heads both have the same size valve sprocket on the back so the valve itself is turning.
My questions: Is the new designed TACO head not compatible with the old valve even though it fits? Is the new head faulty to begin with? Is there a better replacement for the old style TACO powerhead?
I have pics of the heads if needed. Any help would be appreciated. thanks - Paul
EDIT: Here is a pic of the old valve:http://smg.photobucket.com/albums/v626/ppap/?action=view¤t=valve.jpg
On the new valve, the green light never goes on.