Boiler with Zone Valves Won't Come On - Bad End Switches

Make:  All

Model or Series:  All

Type:  Gas Boiler

Problem Description:  No heat

Observed Symptoms:  All thermostats calling for heat but pump doesn't run & burners don't ignite.

Solution:  Found power to valves but no closure of the end switches to activate boiler. Replaced valve actuators.

Additional Information:  L8148 Aquastat Relay, Vent Damper

• "TV" terminal from Aquastat Relay wires in parallel through actuator end switches back to "T" terminal to start pump and enable boiler through water temperature controller.
  • Check for 24Vac across actuator motor terminals to make sure zone thermostats are calling for heat.
  • Opening of any zone valve should close end switch and activate boiler.
  • If necessary, place a jumper between "TV" and "T" to test Aquastat Relay and see if circulating pump starts.
• Vent damper must prove open before energizing ignition.