New mains tails for C/U from separate DB

[gazdkw82]

Had to install some new mains tails for a small C/U replacement. The new mains tails come off a 3phase enclosure bus bar system. It's pretty Jurassic by the look of it!

I understand the testing process for the new board and I understand how to test the tails, however, I'm not sure on how to test some of the other requirements.

The busbar enclosure is fed from another DB which has a main rcd switch. I cannot test this main rcd switch as I cannot loose power to the building. On the test schedule the method of fault protection would be ADS but putting no RCD trip times on the sheet would be wrong?

Also, do the tails need a separate test sheet with them being from a separate enclosure?

Thanks

 

[Dillb]

How are the tails from the Busbar protected?

 

[gazdkw82]

100A HRC fuses

 

[Dillb]

Whats the earthing arrangment?
What is the purpose of the upfront RCD protcting the whole install?

 

[gazdkw82]

TNS

I don't know why there is a upfront main switch RCD. Bad design

 

[Dillb]

Seems bizarre then. You will have to fill out a EIC. Are there no previous test sheets available to you so you can record the times and other origin details from? If not you will have to arrange with the customer a time when you can carry out the testing of the RCD and obtain your Ze.

You would also have to treat the switch fuse as a DB along with the new one you have installed.

 

[gazdkw82]

It's going to be impossible to turn the main board off as it's a 18 storey building with very sensitive equipment.

Would a Zdb not suffice?

 

[Dillb]

It's going to be impossible to turn the main board off as it's a 18 storey building with very sensitive equipment.

Would a Zdb not suffice?

One 30ma RCD protecting the whole building? How do they carry out the quarterly push button test?

If thats the case then it will have too, just make a note in the departures section of the test sheet.

 

[gazdkw82]

One 30ma RCD protecting the whole building? How do they carry out the quarterly push button test?

If thats the case then it will have too, just make a note in the departures section of the test sheet.

My guess is they don't and my other guess is my little board change will highlight this.

I will speak with the electrical engineer and highlight this