Another High Protective Conductor Current issue

[ian932]

Been to a job where they have the following:

2.5mm 4 core SWA at the DB. The four cores are connected as two radial circuits, cores 1 & 2 are fed from MCB 'X' 20A and cores 3 & 4 are fed from MCB 'Y' 15A, the steel wire armour is being used as the cpc for both circuits, the SWA has been earthed at the DB by a brass gland and lock nut to the top gland plate with no flying earth/banjo.

The other end of the SWA 39m away has been made off into a rotary isolator (radial 1), a 2nd rotary isolator is coupled to the 1st isolator (radial 2 not used).

The 1st Isolator then feeds a 12m dado trunking below some metal benches all wired in 2.5mm T&E. This is connected to 14 switched FCU equally spaced along the trunking.

Each FCU has a four gang 13amp plug adapter connected to the load side via a flexible cable, into each of these is a PC + monitor, label printer and scales.

I was there to quote to do a mirror image of the setup on the opposite side of the 12m belt conveyor belt so they can have 28 stations chucking mail onto the conveyor.

The issues are:

1. High Protective Conductor Current (HPCC) and the failure to have earths in separate terminals at all points in the circuit.

2. No second cpc or suitably sized single cpc.

3. 4 Gang adapters don

 

[Zeespark]

Install a second SWA and sort it out that way, with new circuits installed.

AndyGuinness

 

[spinlondon]

As far as I can see, the CSA of the armour of SWA is at least 20mm

 

[ian932]

As far as I can see, the CSA of the armour of SWA is at least 20mm

 

[steptoe]

Ive always been of the understanding that upto 16mm SWA there is no requirement to calc the armour size as it is adequate.

 

[ian932]

Ive always been of the understanding that upto 16mm SWA there is no requirement to calc the armour size as it is adequate.

As a standard cpc yes on the old PVC bs6346, but I dont think that works for XPLE bs5467 & 6724.

In this case it would be acting as a single cpc without mechanical protection on a circuit with high protective conductor current so it would need to be calculated to ensure it is equal or greater than the 10mm copper its acting as.

 

[ianmacd]

http://www.prysmian.co.uk/export/sites/prysmian-enGB/attach/pdf/BS5467.pdf

That suggests for 4 core its 20mm (as spin said) but guess you still need to convert that to copper equiv.

 

[spinlondon]

It's up to you, but if you read 543.7.1.3(i) and (ii).

(i) states 10mm

 

[ianmacd]

It's up to you, but if you read 543.7.1.3(i) and (ii).(i) states 10mm

 

[ian932]

It's up to you, but if you read 543.7.1.3(i) and (ii).(i) states 10mm

 

[spinlondon]

543.2.2 allows the SWA to be used.

543.2.3 requires the items of the list before the SWA to be in copper, if ≤ 10mm

 

[steptoe]

As a standard cpc yes on the old PVC bs6346, but I dont think that works for XPLE bs5467 & 6724. In this case it would be acting as a single cpc without mechanical protection on a circuit with high protective conductor current so it would need to be calculated to ensure it is equal or greater than the 10mm copper its acting as.

yes, sorry, my assumption as to the olden days of gas radios,

am I not glad now deke has finally got himself a battery wireless.