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Aquastat Relay: Boiler does not turn on/off as required
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- Check aquastat settings match expected boiler temperatures for call for heat and shutdown. Adjust settings as needed.
- Inspect aquastat sensing bulb and capillary tube for damage. Replace aquastat if bulb or tube is broken or separated.
- Verify aquastat differential/deadband is properly set, not too wide to prevent burner shutdown. Adjust differential tighter if needed.
- Remove aquastat bulb and check it responds to hot and cold temperatures. Replace if unresponsive.
- Check for loose wire connections or faulty wiring between aquastat and boiler controls. Repair wiring if found.
- Bypass aquastat with jumper wire and test burner ignition. If ignition works, replace defective aquastat.
- Clean aquastat contacts if pitted or corroded. Chatter can disrupt control signal.
- Install new aquastat if cleaning contacts does not resolve. Select model with proper temperature range.
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