In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
I have a 7 year old heating system. The boiler is Buderus oil G115 with logamatic and 60 gal tank. 5 zones of heating all valves the main pipe is 1 1/4" copper with 3/4" zone valves. The problem I am having is old ZVC506 yellow light are on dim when no t stat is calling and old valves are Taco ESP (black heads) are not closing all the way. So I change out the Taco ZVC506 box with new Taco ZVC506 and light are off like it should be. I got a call back 2 days latter and valves are doing the same thing not closing off all the way. I change all the Taco ESP heads out with new Taco Zone Sentry heads. I got anther call that same thing is happening to 1 zone not shutting off all the way. I change out the valve and head with Taco zone sentry. Same thing is still going on.
On the main there are 3/4" Ball valves before the zone valves. So I found out if I pull off head just past its lock down I can spin head around with a finger (360) no problem. As soon as I open ball valve with other zones on and house pump pumping (Taco 007) the valve locks up. I shut off ball valve and work it back and forth frees up and I can spin it around free again open valve it locks up.