The intention is that you can isolate the whole installation with one switch, rather than having to flip a whole bank of breakers.  If there is a main switch in the distribution board, then that is the isolator.  Otherwise, there should be an isolator before the DB.


If it's a DB, then that implies that it's just one part of a larger installation.  In which case, is there an isolator at the origin of the supply?

Thank you for your reply, but probably I have not been so clear as I thought.

I'm going to provide you with all the information. 

We are a company that installs ground source heat pump.

Usually, we install all our equipment in the same plant room and we provide our distribution board.

On the Distribution board there is the main isolator and after that, there are all the switches for every single equipment.  

What we normally do is to install an addiction rotary isolator between the MCB and the heat pump.

Is it really necessary?

Or we can isolate the heat pump directly on MCB?

I don't think that there's a specific requirement to have a separate isolator from the MCB.


But the manufacturer's instructions may require such an isolator.  There may also be a good safety reason to have a lockable isolator so that the equipment can be shut off for maintenance while everything else is left powered on.  That's really a judgement call based on where the equipment is, and the possibility of someone turning the equipment back on when they shouldn't do.

If you are looking at a UK installation then the minimum requirement under BS 7671 is covered in regulations group 464, "Switching off for mechanical maintenance".

461.1 Says that means "shall" be provided, & that it "shall" disconnect all live conductors.

So, if you are going to remove the local isolator from between the MCB and the heat pump, then for compliance with BS 7671 you will need to isolate at the DB, which must have a 2 (if single phase) or 4 (if 3 phase) pole main switch, as Neutral is a live and current carrying conductor, thus it must also be isolated.


As a heat pump is also machinery under the Machinery Directive, then a similar requirement is within EN 60204-1, so whichever way you argue the isolator, installation or machinery it is realistically required.

If the heat pump has a built in isolator then there is the possibility that this can meet the requirements.


Also the requirement under EN 60204-1 for means of isolation for maintenance is that means of emergency isolation are coloured red/yellow, isolation for maintenance would be coloured black/grey.

Thank you, everybody, for your help and for your support. Now I have the ideas more clear.

Don't forget, in accordance with BS 7671, isolators for LV systems must disconnect ALL poles (including Neutral), unless the supply is a TN system (TN-S or TN-C-S) in which isolation of the Neutral is not always required.

Hi Andrea,


having previously worked in a similar industry as yourself I can confirm we always installed a rotary Isolator so it disconnected all live terminals and was lockable for routine maintenance. It also provides a valuable testing point.


Regards Peter