Hi,

I have 5 electronic zones, each with a separate thermostat, running off a single circulator motor. Two of my zones were heating up way beyond the temperature set on the thermostats. I shut off the thermostats but the zones kept getting heat until I finally turned off the boiler. I've checked the zone valves in the affected zones and they seem to be operating correctly, i.e. there is resistance on the levers. What else could be the problem? Could the aquastat relay cause the issue?

Thanks,
Jeff

If this was occurring while other zones were calling for heat, you may have leak-through of the valves serving the over-heated zones.