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Baxi 105e Instant repair – hot water problems

posted on 22 Aug 2015

This time we are looking at Baxi 105e Instant combination boiler repair. This particular boiler has a preheat function which stores preheated hot water in a store build into expansion vessel. This boiler has a DHW pressure differential valve and 3 way diverter operated by electric actuator. Client described problem as follows:

‘It seems that we have to wait for a long time before the boiler starts to heat the water’

Baxi 105e Instant in question picture below:


Things that I noticed on initial inspection:

– boiler fires up on preheat function and flow pipe gets hot. This pointed to stuck 3 way diverter valve or faulty actuator

– boiler does not fire up on hot water, although it provides some hot water when set to preheat function. This pointed to stuck DHW differential valve or perished membrane.

After removing the cover and micro switch from DHW differential valve I noticed that spindle on the valve does not move out. I also noticed leaks from sensing tubes to DHW differential valve and scaled up automatic air vent (pictures below)

Repair consisted of:

– replacement of DHW pressure differential valve

– replacement of 3 way valve actuator

– replacement of auto air vent

Boiler being drained down, side and front panel removed for parts replacement.

New pressure differential and new washers on sensing tubes. New auto air vent below.

Hot water performance has been restored and flow switch operates now on hot water demand. During the repair I also noticed damaged combustion chamber insulating pads and order new ones for replacement.