6kA or 10kA?

[Piratepete]

On an existing 100 Amp 3ph supply I measured the single phase Ipf at the meter on each phase. Average 0.8kA.

My understanding is that for 3 phases, rule of thumb, you double this - so 1.6kA.


I specified to my supplier Wylex NSB 6kA MCBs in an NHTN4 125Amp 3ph board. Supplier has responded saying that 'NSB MCBs are not for 3ph DBs' and I have to fit the more expensive 10kA PSBs.

QQs
1. Am I correct in saying that 6ka MCBs are adequate for the job/
2. Is my supplier correct? If so, why does Wylex list the the 6kA NSBs as available in the catalogue?

Cheers

Pete :sick:
Ps. I'm a little out of my comfort zone on 3 phase work!

 

[plugsandsparks]

Does he mean the breakers wont fit the board because of their form factor ?
See plenty of 6K breakers in TP boards and may even have fitted some. 100A TP supply is only a baby anyway although your readings are a little lower than i normally see.

 

[Engineer54]

Not having any experience of Wylex boards to be honest, i would assume that it has something to do with the type of board you have chosen!! Probably in the form that the MCB's are mounted in the board!! Or the guy is talking out of his arse and looking for some extra cash!! lol!!

 

[sparkymalarky]

I would say its a ---- up between #1 the MCB's won't physically fit the distribution board/panel and #2 - he's a money hungry git. Depending on the fitment, I reckon you would be ok to install the 6kA rated MCB's.

 

[Engineer54]

What's the difference in price between the 6ka and 10KA MCB's then??

 

[Guest111]

As other people have said its either greed or BS if I were you I'd contact Wylex themselves ask the question then go and give the wholesaler what for.Wylex is made by electrium here's a contact number that may help.
Electrium Sales Limited A Siemens Company
Commercial
Centre, Lakeside Plaza, Walkmill Lane, Bridgtown, Cannock, WS11 0XE, United
Kingdom.
Tel: +44 (0) 1543 455000 Fax: +44 (0) 1543 455001

 

[Risteard]

I've had it before where I was conducting the initial verification and the boss claimed that 6kA rated protective devices could not be used in a three-phase installation. I pointed out that the maximum PFC was something like 2 or 3 kA (can't remember exactly), and that was with the maximum PSCC doubled already (giving pessimistically high values for a fault between phases)!

He still insisted that 10kA devices were required. I didn't really care as it wasn't my cost, nor had I installed the devices in the first place, but there was no convincing him that he was talking complete and utter nonsense.

 

[Piratepete]

My supplier has investigated and says that Wylex no longer supply the 6kA mcbs except for old boards and they are dearer than the 10kA mcbs.

 

[Marvo]

Maybe I'm not understanding, are the 10kA mcb's cheaper than the 6kA rated ones? Doesn't make sense and there's nothing wrong with using 6kA on 3-phase boards if your tests indicate it appropriate.