M

michufc

Hi to all I need a bit of help please I hate wiring for heating but it's for my mate as the plumber hasn't sorted it
Right he has got a new Bosch combi boiler and with that a linked in unvented cylinder
I have no idea really how to wire it up and my mat has got both hives one for just combi boilers and the one for system boilers and I am not sure which one to use and what wires go where
I would really appreciate the help thanks Mike
 
What model Worcester is it? Are you sure its a combi boiler and not a system boiler? How many valves are there?
 
So its a system boiler not a combi. What combination of valves do you have? for example two x two port valves or 1x 3port and 1x 2port.
 
Sorry it has two two port valves

So you supply the boiler and the boiler has an internal connection labelled 230V out and all the control wiring needs feeding from these terminals as they are protected by the boilers internal fuse. This is a requirement of the manufacturers instructions and may void the warranty if not wired as such.

You need a to feed the boiler from a switch fused spur with a 3A fuse connected to the 230V in terminals.

4 core flex from boiler to wiring centre which gives you LNE out as explained above and switched live which connects to LR with the radiator symbol.

5 core flex to dual channel receiver from wiring centre.

3core flex to cylinder thermostat from wiring centre

obviously both valves back to wiring centre

First of all connect all cpc's together to get them out the way

Same again with neutrals from boiler, receiver and both valves

Connect all permanent lives together L out from boiler, L from receiver and both greys of the valves

Brown from central heating valve connects to terminal 4 on receiver

Common from cylinder thermostat connects to terminal 3 on receiver

Normally closed on cylinder thermostat connects to brown of the hot water valve

The oranges from both valves connect to LR with radiator symbol

As its an unvented cylinder the cylinder thermostat will have a high limit thermostat and temperature control thermostat contained within the same enclosure so HW ON from receiver connects to common of the high limit thermostat, normally closed from high limit thermostat connects to common of the temperature control thermostat and normally closed from temperature control thermostat connects to the brown of the hot water valve (connected in series).
 

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Title
Wiring A Bosch Combi Boiler
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Central Heating Systems
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