MCB Submain and RCBO Protected circuits

[Squid_uk]

Hey guys!

I have recently been ask to install a submain to a customers workshop.

The installation I was going to use was a 100mA DP Timedelay RCD with a 32A MCB at the supply origin for the SWA submain. In the workshop I was wondering if I can install and DP Isolator with RCBOs to protect the circuits?

Obviously the RCBO's I would use will be 20A and under to allow for discrimination.

Thanks for taking time to read my post!

 

[Risteard]

Why do you think the 20A will discriminate with the 32A?

 

[shocking_eg]

why the 100ma up front ?

or is the workshop going to be TT'ed ?

 

[Squid_uk]

Risteard: Another Sparky mentioned it to me and said that the breakers in the new DB should be lower that the supply feed to avoid nuisance tripping.

Shocking_eg: Sorry I should have mention that the current supply is TT so yes the supply in the workshop will also be TT.

 

[GLENNSPARK]

use an 100mA s type top end....
what CSA is the swa you intend to use...and whats the length of run?

 

[Engineer54]

Hey guys!

I have recently been ask to install a submain to a customers workshop.

The installation I was going to use was a 100mA DP Timedelay RCD with a 32A MCB at the supply origin for the SWA submain. In the workshop I was wondering if I can install and DP Isolator with RCBOs to protect the circuits?

Obviously the RCBO's I would use will be 20A and under to allow for discrimination.

Thanks for taking time to read my post!

Nothing wrong with using a DP isolator and RCBO's in the workshop CU. Size the RCBO's for the the circuit it's protecting....

 

[Squid_uk]

use an 100mA s type top end....
what CSA is the swa you intend to use...and whats the length of run?

It will be a 16mm 2-Core protected by a 32amp, the length is 110m

 

[Knobhead]

You're pushing you're luck with volt drop.

 

[Welchyboy1]

What's your maximum expected demand?

 

[Outspoken]

Hey guys!

I have recently been ask to install a submain to a customers workshop.

The installation I was going to use was a 100mA DP Timedelay RCD with a 32A MCB at the supply origin for the SWA submain. In the workshop I was wondering if I can install and DP Isolator with RCBOs to protect the circuits?

Obviously the RCBO's I would use will be 20A and under to allow for discrimination.

Thanks for taking time to read my post!

The experience of the Electrical Trainee brigade never ceases to amaze..that is such a simple solution it is painful to see a "spark" ask it.

 

[Engineer54]

You're pushing you're luck with volt drop.

He'll be pushing his luck as far as his Zs values are concerned too, if he's only using the SWA armour for his earthing requirements at the workshop. Especially if any of the machines, equipment require type C/D MCB's!! If the workshop has any services within (eg Water) let's hope the DNO supply isn't PME/TNC-S!! lol!!

 

[Squid_uk]

Tony: Yes your right, I did the calculations and it does comply as its only 9.8v drop and im allowed 12v.

Welchyboy1: The workshop had 6 machines in it but the chance of them all running all at the same time is minimal so I went with 4KW.

Outspoken: Isnt this site for people asking other opinions?! And maybe we dont all know everything off by heart!?

Engineer54: I stated that the system is TT so the DB in the workshop will have its own earth electrode and the steel of the SWA will only be earth to the house DB and not the workshop.

 

[shocking_eg]

here we go .... lol

 

[GLENNSPARK]

Tony: Yes your right, I did the calculations and it does comply as its only 9.8v drop and im allowed 12v.

Welchyboy1: The workshop had 6 machines in it but the chance of them all running all at the same time is minimal so I went with 4KW.

Outspoken: Isnt this site for people asking other opinions?! And maybe we dont all know everything off by heart!?

Engineer54: I stated that the system is TT so the DB in the workshop will have its own earth electrode and the steel of the SWA will only be earth to the house DB and not the workshop.

grow up

any lighting in here?

 

[Squid_uk]

Now that you mentioned it, I didnt include any lighting!

Not sure I understand the 'grow up' remark?!