Single pole rotary isolator

Tommydeek · Apr 4, 2023

Hi everyone,

I have moved into a property with a 63a single pole rotary isolator controling a inline water heater. Is this safe? Surely it should be a 63a two pole isolator switching both the live and neutral?

Any advice would be much appreciated.

Thanks.

LukeD · Apr 4, 2023

Most certainly NOT a single ! Is this a rental or you have purchased ?

Tommydeek · Apr 4, 2023

LukeD said:
Most certainly NOT a single ! Is this a rental or you have purchased ?

Purchased.
It has the earth and neutral terminated within the isolator just the rotary switch is disconnecting the live only when isolated.

Just thought a high current appliance should isolate both live and neutral when in the off position.

Lucien Nunes · Apr 4, 2023

a high current appliance should isolate both live and neutral

The current is unimportant, as you can get just as bad a shock from a 6A circuit as a 60A. On a domestic single-phase circuit, an isolator (which you would turn off to enable maintenance, for example) is expected to break all conductors with a 3mm contact separation. A control switch need only break the line, so is it possible that this was the intended purpose of your rotary switch, and the means of isolation (if required) is something else?

Tommydeek · Apr 4, 2023

Lucien Nunes said:
The current is unimportant, as you can get just as bad a shock from a 6A circuit as a 60A. On a domestic single-phase circuit, an isolator (which you would turn off to enable maintenance, for example) is expected to break all conductors with a 3mm contact separation. A control switch need only break the line, so is it possible that this was the intended purpose of your rotary switch, and the means of isolation (if required) is something else?

Thanks for your reply, I would imagine the rotary switch would be used for maintenance as the only other way to isolate the water heater would be from the 50a MCB at the board. Perhaps I am wrong and it is just used as a control switch.

So for use as an isolator for maintenance it would need to break live, neutral and earth?

Risteard · Apr 4, 2023

Tommydeek said:
Thanks for your reply, I would imagine the rotary switch would be used for maintenance as the only other way to isolate the water heater would be from the 50a MCB at the board. Perhaps I am wrong and it is just used as a control switch.

So for use as an isolator for maintenance it would need to break live, neutral and earth?

Never break the cpc!!!!!

LukeD · Apr 4, 2023

Risteard said:
Never break the cpc!!!!!

D/P is fine

snowhead · Apr 4, 2023

I'd be surprised if it is a Single pole rotary isolator, more likely a Double pole but only one pole used so shouldn't be too hard to rectify.
Any pictures of the internals?

Lucien Nunes · Apr 4, 2023

Sorry I meant break all live conductors, not protective ones. Earthing must never be switched

LukeD · Apr 4, 2023

snowhead said:
I'd be surprised if it is a Single pole rotary isolator, more likely a Double pole but only one pole used so shouldn't be too hard to rectify.
Any pictures of the internals?

Ive never seen a single pole before been used domestically ?

davesparks · Apr 4, 2023

Lucien Nunes said:
On a domestic single-phase circuit, an isolator (which you would turn off to enable maintenance, for example) is expected to break all conductors with a 3mm contact separation.

The way I read 464.1 and 461.2 I'd say, if a TNCS or TNS supply, the requirement is only for single pole isolation.

Tommydeek · Apr 4, 2023

snowhead said:
I'd be surprised if it is a Single pole rotary isolator, more likely a Double pole but only one pole used so shouldn't be too hard to rectify.
Any pictures of the internals?

[ElectriciansForums.net] Single pole rotary isolator

DPG · Apr 4, 2023

I don't think it's that the switch isn't DP, more that the neutral is just bypassing the switch.

Risteard · Apr 4, 2023

DPG said:
I don't think it's that the switch isn't DP, more that the neutral is just bypassing the switch.

If you look up the part code it actually does appear to be a single pole switch disconnector.

https://uk.farnell.com/eaton-moeller/t5b-1-8200-a-svb/isolator-flush-63a-1pole/dp/3203270

DPG · Apr 4, 2023

Risteard said:
If you look up the part code it actually does appear to be a single pole switch disconnector.

https://uk.farnell.com/eaton-moeller/t5b-1-8200-a-svb/isolator-flush-63a-1pole/dp/3203270

My mistake - I ought to have looked it up really.

LukeD · Apr 4, 2023

Risteard said:
If you look up the part code it actually does appear to be a single pole switch disconnector.

https://uk.farnell.com/eaton-moeller/t5b-1-8200-a-svb/isolator-flush-63a-1pole/dp/3203270

It looks like they just "add" in another screw terminal for the double pole version !

Lucien Nunes · Apr 4, 2023

The way I read 464.1 and 461.2 I'd say, if a TNCS or TNS supply, the requirement is only for single pole isolation.

It's an interesting point; from the point of view of final circuits controlled by a DP main switch or RCD in the CU, does the presence of a switching pole in the neutral negate the 'reliably connected to earth' that would otherwise be implied by the ESQCR? (Such DP switch being required by 462.1.201).

Tommydeek · Apr 4, 2023

So from what I gather the single pole isolator is adequate however, a double pole isolator would be the preferred option but not necessary.

Single pole rotary isolator

Tommydeek

LukeD

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Tommydeek

Lucien Nunes

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Tommydeek

Risteard

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LukeD

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snowhead

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Lucien Nunes

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LukeD

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davesparks

Tommydeek

DPG

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Risteard

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DPG

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LukeD

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Lucien Nunes

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Tommydeek

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