Good evening, Just like to say hello and that I am not a gas engineer or an electrician, but I would just like to understand what I need to ask for. I have a question about an old y-plan central heating installation dating back to 2000. I have an old Gloworm micron 50ff boiler situated in the consumer unit cupboard. However, it is connected to the wiring centre situated in the hot water cupboard 6 meters away via 3 wires, switched live, neutral and earth. I also have an old Grundfoss pump connected into the wiring centre that has only 4 wires, Blue, orange, brown-white, and grey, (I notice new pumps have 5 wires). The pump also has 3 settings using 40,65 & 95 watts. I also have 3 port mid-position valve, room stat, hot water stat and 2 channel programmer, (all from Danfoss heatshare pack).

Due to limited access in consumer unit cupboard I am limited to fitting either a Worcester greenstar ri series boiler or a Baxi ecoblue advance. Looking at the wiring diagrams, with my limited understanding, does fitting the Bosch require separate mains supplies in each cupboard, one for the boiler and one for the wiring centre and will the pump kill the boiler using an extra 5 watts as the worcester boiler is rated at 90 watts, and could I still use it with only 4 wires or would I need a new 5 wire pump too.

Or would it be better to go for what seems to be the simpler option of the Baxi as it requires no pump overrun or permanent live and looks as though it is fed with just live, neutral and earth from the wiring centre as I have now.

Sorry about the long question, and many thanks in advance. Simon.