I have a gas hot water boiler system with 2 zones. Zone 1 goes to radiators throughout the house and Zone 2 is for a den with baseboard heaters.
Zone 2 stopped working and I have began troubleshooting and had some questions. First I am not a HVAC specialist, but can use a meter and feel comfortable trying to at least diagnose the issue.
What I have been able to determine is that I believe the valve is opening. If the thermostat is on for Zone 2, the manual lever is loose and can not engage the motor. When it's off I can use the lever to engage the motor (plus if Zone 1 is on and Zone 2 thermostat is on hot water gets to the baseboards fine). What seems to not be happening is the trigger portion that powers the pump and fires the burners. It appears this valve has a switch built in for this purpose. Zone 1 has a similar valve but the terminals are on the outisde, so it appears the "ES" terminals are for triggering the pump an/or burner. However Zone 2 has wires coming out of the side so perhaps the terminals are on the inside, or it's just hard wired inside the case, but it has 2 red wires coming out which I am assuming are the same "ES" terminals just inside the pop top box.
On Zone 1 (the working one) these 2 red "ES" wires are 24 volts when thermostat is OFF, and when it switches on those 2 red wires drop to almost zero I believe.
Having not removed the cover of the zone 2 valve yet I have not yet metered those. Am I on the right track for tracing the problem? Is the switch portion replaceable or does the entire unit need to be replaced?
It looks like the Zone 1 valve is a "general close off" and Zone 2 is a "high close off". The part number of the Zone 2 valve that is causing the problem is VT2343G13Ao2AoF.
Any guidance would be greatly appreciated. I hope I have put enough information here to make sense of the problem.