Errors

Boiler type Greenstar ZWB42-3A

Error code d3

Cause:

Temperature high limit defective.
External guard has tripped.
Temperature limiter locked out.

Solution:

Check temperature sensor and leads for interruptions or shorts, and replace if defective.
Temperature guard TB1 has tripped. Check if jumper across8-9 or PR-P0 is missing.
Reset external temperature limiter (if installed).
Reset LWCO (if installed).