Plugs less safe then fused connection unit?

[JohnD]

there are some people who like the boiler on a plug and socket so they can run it off a generator or other supply in the event of a power cut.

 

[John D v2.0]

you're never going to elbow a plug and plug it back in by mistake, but an fcu can do easily!

I suspected there was a reg about this and there is:
"537.2.2.3 A device for isolation shall be designed and/or installed so as to prevent unintentional or inadvertent closure. "
So placing it near to a boiler that's being worked on would be not acceptable. Locking it off would be ok but not on a TT supply.

 

[bernardgreen]

Electrically, if you're isolating something on a standard domestic single phase TN supply, single pole isolator is fine.

Isolation requires both Live and Neutral to be dis-connected.

Dis-connection of only the Live is removal of supply from the circuit or simply "switching off " the circuit. A circuit that is switched off but not isolated can still cause RCDs to trip ( Earth-Neutral fault in the circuit )

 

[picasso]

This is from a vaillant ecotec manual.

 

[John D v2.0]

Isolation requires both Live and Neutral to be dis-connected

When i said electrically i meant from a safety and bs7671 point of view
"""537.2.1.1 Every circuit shall be capable of being isolated from each of the live supply conductors. In a TN-S or TN-C-S system, it is not necessary to isolate or switch the neutral conductor where it is regarded as being reliably connected to Earth by a suitably low impedance. """

A circuit that is switched off but not isolated can still cause RCDs to trip ( Earth-Neutral fault in the circuit

It can but that'sa nuisance not a danger, an RCD can be tripped by ELV as long as the supply can source 30mA.

 

[bernardgreen]

It can but that'sa nuisance not a danger,

Half way through a boiler service / repair and the lights go out ?

And if the boiler has a Neutral-Earth fault that is tripping the RCD then it needs to be isolated ( 2 pole )

 

[ianmcd]

Not all spurs are double pole either

Single pole fused spurs are for use on Lighting circuits only, I would have thought you would have known that

 

[John D v2.0]

Half way through a boiler service / repair and the lights go out ?

And if the boiler has a Neutral-Earth fault that is tripping the RCD then it needs to be isolated ( 2 pole )

That's an interesting point, so you're saying that it's a useful mitigation in case the boiler and lights etc share an RCD, so the existing electrical installation can more easily comply with reg 314.1 without the cost of an RCBO for the boiler.

"Every circuit should be divided, as necessary, to avoid hazards and minimize inconvenience in the event of a fault"

 

[Dan Robinson]

Single pole fused spurs are for use on Lighting circuits only, I would have thought you would have known that

Yep.. But when there's one already there and you don't realise ...... Bloody electricians.

 

[Hot&Cold]

This is from a vaillant ecotec manual.
View attachment 157594

Thats similar to the instruction in the manufacture installation instructions for the boiler in the video

diagrams are shown for a 3 pin plug & a fused spur. take your choice.

 

[ianmcd]

Thats similar to the instruction in the manufacture installation instructions for the boiler in the video

diagrams are shown for a 3 pin plug & a fused spur. take your choice.

exactly what myself and @gas112 have stated already , its not rocket science to understand it

 

[ericmark]

As @gas112 says if it was a plug into a switched socket most would just switch it off and not remove the plug, the socket that the plug is plugged into is only single pole disconnection a fused spur is dual pole disconnection, a plug can be used into an unswitched socket so that the plug has to be removed

It depends on the make and model, you can get FCU with single pole switches and sockets with double pole switches,

plugs can have double pole isolation, where with FCU putting a lock through fuse holder only disconnects the line.

 

[SimonH2]

It is one of "those" rules.

I reckon at some point most (all ?) installation manuals specified a fused switch (double pole with min 3mm contact separation) and so using a plug & socket doesn't technically comply with the installation instructions - even if it's better for several reasons. Thus it's become "the law" (to all those plumbers who know nowt about that new fangled electrical pipework stuff) that a boiler must be fed off an FCU and not a plug/socket.