Double Pole Isolation Help!

[horaceg]

Hi Guys,
Although it is generally accepted that a Fixed Appliance must be capable of being isolated via a DP Switch, the regs seem a bit contradictory on this.
Can anyone actually point me to the regulation(s) that states that this must be the case,
Cheers
HoraceG

 

[dingbat]

Nothing contrary at all. Read BS 7671, Chapter 46, which tells you all you need to know about isolation and switching.

Without knowing whether you mean simple isolation, isolation for maintenance, emergency isolation or functional switching nobody can quote you the requirement and, in any case, the means of isolation is up to you.

 

[horaceg]

Nothing contrary at all. Read BS 7671, Chapter 46, which tells you all you need to know about isolation and switching.

Without knowing whether you mean simple isolation, isolation for maintenance, emergency isolation or functional switching nobody can quote you the requirement and, in any case, the means of isolation is up to you.

Thanks, Dingbat, for the Reply.
I have studied Chapter 46 at some length and there ARE some possible conflictions.
To spell it out.
The situation is regarding a wall panel heater and it's connection via a 3core flex to an 'Isolator' on the wall connecting to the fixed wiring.
I doubt if the switch would be regarded as for Emergency Switching but could be classed within the others.
I'm not a novice at this so please refrain from 'talking down' to me, however I apologise if my question was in anyway vague.
HoraceG

 

[JohnD]

Tell us about the contradictions you see.

 

[horaceg]

Tell us about the contradictions you see.

OK,
Here goes!

460-01-04 states:
"....Except as required by 476-01-03, in TN-S or TN-C-s systems the neutral conductor need NOT be isolated or switched......"

(476-01-03 states A MAIN SWITCH should interupt both live conductors)

HOWEVER

461-01-01 states " Every circuit shall be capable of being isolated from each of the live supply conductors, except as detailed in Reg 460-01-04 (See above)

If you were to ask 100 electricians "Should a Heater (Storage, Immersion or Panel) be switched by a DP switch, probably 98 would say yes however the above regulations seem to indicate otherwise"

Horaceg

 

[dingbat]

Do you think your PEN conductor continues to the isolator on the wall? (It's 'no' by the way)

Those regs are to do with isolation of circuits and/or the whole installation. Your question is about isolation of a connected appliance.

so, now I don't understand your problem.

 

[horaceg]

Do you think your PEN conductor continues to the isolator on the wall? (It's 'no' by the way)

Those regs are to do with isolation of circuits and/or the whole installation. Your question is about isolation of a connected appliance.

so, now I don't understand your problem.

Please see my previous post.
Are we to believe that 98 out of 100 electricians would be wrong!
I accept this is entirely possible which is why I posted the query originally.
Horaceg

 

[dingbat]

Horace, Reg 460-01-04 says that "Combined protective and neutral conductors shall not be isolated or switched."

The PEN is external to your installation and is split at the service head into separate neutral and protective conductors.

So this regulation does not apply to your panel heater.

461-01-01 refers to circuits.

This regulation also, does not apply to your panel heater.

There is no set requirement for double-pole switching for a connected appliance, but you should consider the requirements of 460-01-01, 461-01-02/03/04/05, 462-01-01/02/03 and 463-01-01/02/03/04 when making your decision as to what to use.

As stated before, there is no contradiction.

 

[horaceg]

Horace, Reg 460-01-04 says that "Combined protective and neutral conductors shall not be isolated or switched."

The PEN is external to your installation and is split at the service head into separate neutral and protective conductors.

So this regulation does not apply to your panel heater.

461-01-01 refers to circuits.

This regulation also, does not apply to your panel heater.

There is no set requirement for double-pole switching for a connected appliance, but you should consider the requirements of 460-01-01, 461-01-02/03/04/05, 462-01-01/02/03 and 463-01-01/02/03/04 when making your decision as to what to use.

As stated before, there is no contradiction.

Dingbat,

It would seem that your reply DOES indicate that there is NO specific requirement in BS7671 for DP Switching in the situations I described.
I find it quite surprising as I, along with many other electricians, believed the opposite!
Still one lives and learns! This will be a good one to throw at the Inspector on my next NICEIC visit!
Thanks for the replies.
HoraceG

 

[dingbat]

I find it quite surprising as I, along with many other electricians, believed the opposite!

And, sadly, the majority of practising electricians have only a tenuous relationship with the regulations that govern their working lives. Most subscribe to the, "I've always done it this way so it must be right" school of thought.

Still one lives and learns!

Quite right. If only the others would open the book from time to time.

Next thorny subject... earthing and bonding! (only kidding!)

 

[Pensdown]

As far as I'm aware, the only requirement (in the context of this post) for DP switching is 554-05-03

 

[horaceg]

I find it quite surprising as I, along with many other electricians, believed the opposite!

And, sadly, the majority of practising electricians have only a tenuous relationship with the regulations that govern their working lives. Most subscribe to the, "I've always done it this way so it must be right" school of thought.

Still one lives and learns!

Quite right. If only the others would open the book from time to time.

Next thorny subject... earthing and bonding! (only kidding!)

Dingbat,
WO! Strong stuff! Be careful
and let's not get onto Earthing & Bonding!

The reason I brought this up may help others so I'll explain.

Dimplex have brought out a range of heaters that require a seperate 'control wire' @ 240v fed from a seperate timer in addition to the normal circuit.
Assuming (incorrectly it turns out!) that DP isolation is required, then a three pole isolating switch would be required. Fan Isolator switches @ 10a would be oK for this but they do not have a flex outlet. Dimplex recommend a 3 gang grid switch arrangement (1xDP switch, 1xSP switch & a flex outlet). They correctly add that a label must be fixed on the switch stating that both switches must be switched to isolate the heater. Not very asthetically pleasing especially on Chrome Plates!
However now it has been confirmed that DP Isolation is not required, a standard 20a DP switch would do the job. May have to e-mail Dimplex on this and probably win an award!
Horaceg

 

[horaceg]

As far as I'm aware, the only requirement (in the context of this post) for DP switching is 554-05-03

Good Point, Pensdown!
That's ruled Immersion Heaters back into the DP camp!

Thanks

HoraceG

 

[securespark]

Dimplex recommend a 3 gang grid switch arrangement (1xDP switch, 1xSP switch & a flex outlet). They correctly add that a label must be fixed on the switch stating that both switches must be switched to isolate the heater.

That doesn't sound right! Having two separate switches does not make for positive isolation....

Re DP switches...Yes, the regs do not require them, but there's nothing wrong in exceeding the requirements of the regs. A local DP isolator would be handy for maintenance...

 

[Andy-W]

May have to e-mail Dimplex on this and probably win an award!

Did you ever email Dimplex with these findings, horaceg? The reason I ask is that I just got a response from them on a similar question (before I found this thread), and they wrote that it is a requirement of the IEE regulations and the BS/EN safety certifications that products are fitted with double pole isolation. If you've pressed them further on this, I'd be interested to know their response.

I'm installing EPX panel heaters with the RXPW4 controller. They suggested a grid switch assembly to me too, but didn't mention how many gangs. I don't like that idea too much, because in my case, I think I'd need 4 gangs at each heater (1 DP switch, 1 SP switch, 1 fuse, 1 flex outlet), plus the the label as you mention. It will look a bit obtrusive.

But my only concern is that if I use a DP FCU to switch the phase and pilot, someone in future may mistakenly believe that flicking that switch has isolated the heater completely.

P.S. Please be kind - it's my first post.

Edit: Oops - just noticed that the original post was 2006, and I currently find myself in the year 2007. Sorry!