I had a new hydronic heating system installed 2 1/2 years ago and have had 4 zone valve failures to date. The system has a NTI Trinity boiler and 3 zones using Taco 571-2 zone valves connected to a Taco 4 zone control module.
3 of these failures were the power head. The small plastic 'switch lifter' melted loose and allowed the heater to run continiously till it burnt out. The other was a cracked bellows on the valve stem allowing water to leak. I checked voltage to the valves at various times and it's been between 24.5 to 27 volts.
I'm wondering if others have had this trouble with these valves. Is this common, or could Taco have had a bad batch or parts? Or should I consider replacing these with a different valve. Any recomdendations for a reliable valve?