Double pole isolation??????????

[mickytuff]

Got a puzzler here all..........double pole isolation is used in certain circumstances ie immersion switch, shower pullcord etc, but is it a requirement for it to be double pole and where location wise, special location only or other area's, got me thinking......cant find it in the regs book either, please anybody )) reg number would be the icing on the cake.

 

[Moses]

i do have another puzzler for you, and it is simliar in nature......a single phase board 48 way,(made by ABB) which has been converted by ABB (was a 3 phase board converted to single phase,why i dont know) but the supply to the board is isolated by only breaking the live, and not the neutral-this is connected directly to the main neutral bar, this cant be good practice as the neutral should be isolated like the live via a double pole main isolator, the rating of the isolator is 125Amps, any opinions on this................

Yeah, well nobody is perfect!

 

[Guest111]

i do have another puzzler for you, and it is simliar in nature......a single phase board 48 way,(made by ABB) which has been converted by ABB (was a 3 phase board converted to single phase,why i dont know) but the supply to the board is isolated by only breaking the live, and not the neutral-this is connected directly to the main neutral bar, this cant be good practice as the neutral should be isolated like the live via a double pole main isolator, the rating of the isolator is 125Amps, any opinions on this................

thats pretty common on 3 phase boards,3 phases through mainswitch and neutral direct to neutral rail.when converted to single phase its usually a metal rail that straps all 3 phases on incomer so no mod to neutral.

 

[mickytuff]

Thankyou Geoffsd, i shall look that reg up, top man )))

 

[johnboy6083]

Only on TT systems is isolation required on neutrals. On TN systems the neutral is solidly earthed at the supply transformer, or at the supply position and so when the live is isolated, the neutral is at earth potential. Don't know regs off top of my head though.

 

[JUD]

Only on TT systems is isolation required on neutrals. On TN systems the neutral is solidly earthed at the supply transformer, or at the supply position and so when the live is isolated, the neutral is at earth potential. Don't know regs off top of my head though.

That would be 537.1.2 and/or 537.2.1.1

 

[oba]

Dp isolation required on tt systems due to possibe difference in neutral/earth potential
Unswitched fcu is single pole most 1 module rcbos are also single pole

 

[Tonkatoy27]

I chased myself up my own backside at a microbrewery yesterday trying to find a N-E fault. Turns out the prat who installed the boiler circuit fitted a rotary isolator and only switched the live! That'll teach me to presume equipment is isolated and wired correctly. They did tip me a case of ale though.......

A lot of manufacturers equipment specifies dp switch with 3mm contact seperation etc. BGB is in the van so can't give you a number but we've got a reg about following manufacturers instructions in ammendment 1.

 

[Engineer54]

By switched and unswitched spurs I assume you mean fused connection units. These are double pole.......always....in my experience at least......

Only ''Unswitched FCU's are single pole, (for obvious reasons) switched FCU's are almost universally Double Pole!!

 

[Guitarist]

Only ''Unswitched FCU's are single pole, (for obvious reasons) switched FCU's are almost universally Double Pole!!

Totally agree here. I remember single-pole SFCU's being phased out many many years ago (I'm sure someone can give me the date).
Maybe there are a few from foreign parts still doing the rounds tho....

 

[kingeri]

I agree, that's kinda what I was saying at the beginning!