Feed to outside oil boiler.

[omits]

I now have the boiler instructions for the supply. I guess a double pole isolating switch inside the house maintaining earth. As follows:
Many thanks for informative replies.
"
The supply must be fused at 5 Amp and there must only be one common isolator for the boiler and control system, providing complete electrical isolation.
A fused double pole switch or a fused three pin plug and shuttered outlet socket should be used for the connection.
The power supply cable should be at least 0.75 mm² PVC as specified in BS 6500, Table 16.
All the wiring and supplementary earth bonding external to the boiler must be in accordance with the current IET Wiring Regulations."

 

[SUNRAY]

I now have the boiler instructions for the supply. I guess a double pole isolating switch inside the house maintaining earth. As follows:
Many thanks for informative replies.
"
The supply must be fused at 5 Amp and there must only be one common isolator for the boiler and control system, providing complete electrical isolation.
A fused double pole switch or a fused three pin plug and shuttered outlet socket should be used for the connection.
The power supply cable should be at least 0.75 mm² PVC as specified in BS 6500, Table 16.
All the wiring and supplementary earth bonding external to the boiler must be in accordance with the current IET Wiring Regulations."

I would expect to see an isolator adjacent to the boiler. If I was the boiler engineer I wouln't be wanting to be looking for a way to make it safe and also be able to isolate it in a hurry if there was a problem while I was working on it.
Something of this ilke as it's outside and isolate all live wires (L, N, switch wires etc) in fact everything except earth wiring :

 

[SUNRAY]

In my experience of domestic heating systems (bearing in mind I've far more experience of commercial system) involving a hot water cylinder I reckon the mains supply is most likely to be in the order shown. Combi's are more likely to have the wiring centre within the boiler, along with the time clock and/or radio kit.

 

[omits]

Yep, that's about it with your diag. The electrician put this huge switch on the wall with the cable pinned to the wall along to the boiler. I will have to redo it and get the wiring hidden. It's just too ugly!