Zs a little out, what can I do to fix it?

[Inteificio]

Hi.

Am working in a factory, most of the machinery on the main floor is fed from are fed from spurs (2/3 machines per spur).

As they have all been fitted with D type breakers, we need a tight Zs.
We have not got it.

I am trying to think of the easiest way of fixing it.
Turns out I'm not 100% sure what you can do with CPCs.

If each circuit has it's own dedicated CPC, can I also link a supplementary CPC (or even make a link between each CPC to have a star supplementary earth in addition to the original?)
I've flicked through the regs and can't find any info on supplementary earths!

The way I read it, is as long as all the CPCs are in the same enclosure you can do what you want!

Anyone with a bit more experience got a few tips?

Thanks,

 

[robsparky1975]

What Zs readings have you got? is this a new install

 

[telectrix]

what size breakers and what load?

 

[Inteificio]

Sorry for not giving more details.
Existing circuit that seems to be thrown together from spare parts.
Break size from 20 up to 32.
Zdb a rather nice 0.09

I have done most investigation on 1 circuit as I got a shock off it (from touching the chassis!!!)

D20 Zs 1.18

All circuits are feeding a selection of 3phase 16/32, single phase 16/13. Equipment is moved around room a lot so load varies.

Basically it is a mess, hence why I need help!

 

[Inteificio]

Reason for shock is there was a disconnected earth. Only 24v on the chassis, not enough to cause harm, but enough to think WTF!

 

[GLENNSPARK]

parrallel up them CPCs....
that should get it down...

 

[Inteificio]

Thanks.

So to confirm.

I am going to link all the CPCs in the trunking together to get a ton of parallel paths going.

 

[plugsandsparks]

Warehouse girders can be good for getting the ZS down and usually a much shorter run, especially if they are earthed at the board

 

[amethyst]

Anyone with a bit more experience got a few tips?

To solve your problem in the most efficient and best way, you should contact an expert to do it. They will check it up and could fix the damage as well. If you will do it by yourself, then there is a big possibility that you get to risk.

 

[telectrix]

if the trunking is steel, then use that as well as a parallel path.

 

[bartkusal]

To solve your problem in the most efficient and best way, you should contact an expert to do it. They will check it up and could fix the damage as well. If you will do it by yourself, then there is a big possibility that you get to risk.

I bet you know best and you are an expert of all experts.

 

[Silly Sausage]

Ignore him, he's a Yank. They use wire nuts! :smilielol5:

 

[johnboy6083]

I would run supplementary bonding to any nearby steelwork, and also common the CPCs to the machinery, by Bonding them all to Common steelwork. It's in our contract specifications to do this, but I think it's good practice, and doesn't take long. Even linking nearby containment together can reduce Zs.
on our jobs we have to link any glands to the containment that feeds it, and also the chassis of any equipment, to maintain an equipotential zone.

 

[D Skelton]

If all the above doesn't work, you can always sling a TP+N RCD inline

 

[Stuuk1]

Reason for shock is there was a disconnected earth. Only 24v on the chassis, not enough to cause harm, but enough to think WTF!

You must have soft hands...! I'd love to be able to feel a 24v shock!

I used to disconnect 8inch x 8 stack 50v live bus bars bare handed. I'm such a man