New dist. board

[Hawk]

Have a job coming up to supply a new distribution board. I am planning on running a 25mm 4 core swa and 16mm earth of a distance of 30mtrs from incoming supply to new board. The supply is 3 phase 100a tncs. I was thinking of coming out of the Henley blocks into a 100A Glasgow switched fuse and then the swa out of the switched fuse to a 80A 30mA 4pole rccb supplying the new board. Thoughts?

 

[Flanders]

All the isolaters and sockets will be ip rated

Then what is the rson for rcds is it portable equipment that is being used outside ?

 

[Hawk]

The machinery is stainless steel, so was more thinking if water got into any of the connections.

 

[Flanders]

The companys method statement should say somthing in the Lines of Isolate the equipment before cleaning , do not use high presure water on equipment etc.

 

[davesparks]

Have a job coming up to supply a new distribution board. I am planning on running a 25mm 4 core swa and 16mm earth of a distance of 30mtrs from incoming supply to new board. The supply is 3 phase 100a tncs. I was thinking of coming out of the Henley blocks into a 100A Glasgow switched fuse and then the swa out of the switched fuse to a 80A 30mA 4pole rccb supplying the new board. Thoughts?

16mm separate earth is most likely oversized and a complete waste of time and money to boot, if main bonding is required at the sub-board then a 10mm bond will be required, but not if no main bonding is to be connected there.
Glasgows are fused switches not switched fuses, there is a difference.
An 80A RCD is no good on a 100A supply.
A 30mA RCD covering a whole board is just plain ridiculous.

 

[davesparks]

I mean when the cleaners are in they hose down everything

So make sure the install meets the appropriate IP rating, or is put into suitable enclosures. An RCD won't stop anything from getting wet, it will just switch it off and water will continue to enter the equipment.

 

[Hawk]

I think the best option is use individual rcds if required. So instead of the 16mm earth would you just use the swa?

 

[Darkwood]

I think the best option is use individual rcds if required. So instead of the 16mm earth would you just use the swa?

Using a seperate earth for the size you suggested wouldn't normally be required although it may be necessary in certain circumstances like reducing Zs due to high upstream initial values or bonding requirements may warrant running a seperate earth.

 

[davesparks]

I think the best option is use individual rcds if required. So instead of the 16mm earth would you just use the swa?

Yes, following on from carrying out the calculations I would use the armour. If the armour is not sufficient then I'd look at using a bigger cable or a fifth core within the cable.

 

[Hawk]

Had a look at the current set up. There is a main DB and 2 sub DB's. 1 of the sub boards is supplied from a fused switch and the other one is supplied from a 63A TP MCB. I would have thought both sub boards would have been supplied by fused switches.