Importance of space heater in control and starter panels

What happened

Upon preparation of the bow thruster for departure, an alarm panel indicated PHASE FAILURE and MAIN MOTOR ABNORMAL TRIP alarm. During troubleshooting suspected the problem with the soft starter circuit. The vessel has spare PCB cards but the problem was not sorted after replacing a PCB card.
A service engineer attended. The PCB card was exchanged with a new one supplied by service engineer and the problem was sorted out. It was observed that the rust has been accumulated at the SCR (Silicon Controlled Rectifier) connection points due to condensation caused by repeated heating and cooling down.

Root cause

Corrosion caused by moisture condensation due to repeated heating and cooling down.

Corrective actions

1. Keep a Space Heater on to prevent moisture accumulation during equipment stand still periods
2. Keep moisture absorbent material inside the starter and control panels where Space Heater is not installed or it's capacity is not sufficient.