Swa main incomer size

[E.E.I]

I wouldn't terminate the cpc through the isolator switch, make sure the isolator has a separate earth terminal/earth bar. Having a separate MET would look messy IMO.

 

[Engineer54]

Yes the people ordering the work said 25mm 3 core. How ever I think that's a general spec rather than specific which we are struggling to get hold off.
Also if it's a 3 core and terminate the cpc in the isolator once this is isolated there would be no earth at the cu. would you install spectate met at isolator end too?

Are you actually being serious here??

You follow the Spec that was issued as part of the contract details the job was priced against, any retrospect amendments to that spec (eg, any so-called specific spec) then both contractual parties would need to agree on any changes made, along with any increase/decrease in the contract price...

 

[Knobhead]

Personally I’d let him go ahead and change the spec. I used to get a perverse pleasure out of telling a contractor to rip it out and do it again at their expense.

 

[shanky887614]

Yes the people ordering the work said 25mm 3 core. How ever I think that's a general spec rather than specific which we are struggling to get hold off.
Also if it's a 3 core and terminate the cpc in the isolator once this is isolated there would be no earth at the cu. would you install spectate met at isolator end too?

isolators have an earth+neutrel terminal mate that isnt isolated by isolator

 

[davesparks]

Not always, a Double pole or a TPSN/four pole isolator isolates the neutral.
And most plug and socket arrangements used for isolation will isolate the earth.

 

[shanky887614]

Not always, a Double pole or a TPSN/four pole isolator isolates the neutral.
And most plug and socket arrangements used for isolation will isolate the earth.

our 4pole isolators early make, late break

have a seperate earth and n connection as well mate.

buy a different brand then mate

 

[davesparks]

our 4pole isolators early make, late break

have a seperate earth and n connection as well mate.

buy a different brand then mate

Why would you need a seperate N in a four pole isolator? That's what the fourth pole is there for!

And I am quite happy with the brand if isolator I use, MEM are tried and tested.

 

[shanky887614]

Why would you need a seperate N in a four pole isolator? That's what the fourth pole is there for!

And I am quite happy with the brand if isolator I use, MEM are tried and tested.

really? we have controls going through our isolators as well sometimes depending on spec

 

[davesparks]

Having controls through a pole of an isolator sounds quite unusual.
Id expect to see control circuits use auxiliary contacts, but then I guess it depends on the equipment and budget.

 

[Knobhead]

For Christ’s sake!

You use 3P+N or SP+N never 4P for distribution!

 

[Knobhead]

It would be great if people learnt the difference between 3P+N and 4P. As Shanky rightly said in a 3P+N the neutral is early make late break. The reason, because you will get voltage imbalance akin to a floating neutral.




I’ve only ever specified four pole ACB/MCCB’s twice in 40 years.

Both breakers were for a 2.6MW 660V two wire earth free system. Four pole because I put two poles in series to handle the fault current. If you look at the manufacturer’s maximum fault current tables for 400V against 690V it drops dramatically!

 

[Engineer54]

It would be great if people learnt the difference between 3P+N and 4P. As Shanky rightly said in a 3P+N the neutral is early make late break. The reason, because you will get voltage imbalance akin to a floating neutral.
I’ve only ever specified four pole ACB/MCCB’s twice in 40 years.

Both breakers were for a 2.6MW 660V two wire earth free system. Four pole because I put two poles in series to handle the fault current. If you look at the manufacturer’s maximum fault current tables for 400V against 690V it drops dramatically!

Yep, all our 2.5-3.2 KA main switchboard TX ACB incomers and the bus couplings are 3 Pole + N with the early make late break function.

 

[davesparks]

For Christ’s sake!

You use 3P+N or SP+N never 4P for distribution!

Sorry Tony, I'm mixing manufacturers terminology with the correct terminology.