Switchfuse - SP or DP?

[Piratepete]

Evening All!
I notice that some folks recommend the MEM KMF 800 or 600 for an 80 amp or 60 amp switch fuse between the meter and a distant consumer unit.

I think it only has a single pole switch. Is there any requirement for it to be double pole? Where is it specified?

Cheers

 

[Deleted member 26818]

Depends what the earthing arrangements are. TT would require DP, whereas TN-C-S wouldn't matter as the earth would still be connected. Have a look at Regulation 537.1.2.

 

[Piratepete]

Taking this further, should I be using dp switched sockets on TT installations? 537.2.2.1 seems to suggest it. It would seem that the cb in your normal consumer unit would not be sufficient nor a sp light switch.

 

[Spudnik]

i think KMF's are DP?

Also, TT systems require DP isolation, which is in the form of the CU main switch.

 

[IQ Electrical]

i think KMF's are DP?

Also, TT systems require DP isolation, which is in the form of the CU main switch.

Yes, as Jason said, a 'linked' double pole main switch will satisfy 537.2.2.1 the requirement does not need to extend to accessories etc.

 

[Deleted member 26818]

My understanding, is that DP is required for isolation only.
With socket-outlets, functional switching is provided by the switch, isolation by removing the plug.
With SFCU and lighy switches, the switch is functional and thw Main switch at the CU provides isolation, unless DP MCBs or RCBOs are used.

 

[Piratepete]

Interesting! Some sockets have dp switching such as MK Logic Plus, but loads don't and you wouldn't know without testing them! I've never seen dp MCBs in a domestic installation. So we have these nice kits for locking circuit breakers (for isolation?). But, I think you're right - there is an addendum to the Regs for the Isolation column of Table 53.2 which states that for TT isolation requires disconnection of all the live conductors.

So on TT installations - be aware!

 

[IQ Electrical]

I'm not sure from your 'be aware' advice whether you still believe sockets have to be double pole on TT supplies?

A double pole main switch satisfies the requirements of 537.2.2.1