Live testing at sub main boards

[markysparky]

Hi

Just starting a job testing a hotel with 1200 circuits and a lot of ccu's and dbb's across 6 floors of a hotel.

I am just the apprentice so will get some great experience on practical testing and inspecting from my work colleagues. My question is that a lot of the installation is earthed via conduit with no seperate earthing conductors from the sub mains. What is the best way to live test at these boards with regarding to ze and pfc. The hotel is continually being used so how can we safely test with a view to not zapping any of the public!! Mark

 

[green-hornet]

When you start the job your employer would have done a method statement and a risk assesment.

Parts of the installation would have to be disconnected from supply to do some of the tests.

Zs would be carried out in the same way as if you had a green and yellow earthing lead,

Ze or ZDB would be carried out at the distribution boards direct to the earth connected to that board.

On any 3 phase section board I would install a seperate 16mm earth to each 3phase db, however this was not always done.

The first part of any inspection is visual so if there are many things wrong with the installation you may not even get to put a tester on it.

 

[markysparky]

thank green hornet, spoke to niceic today before we started the zs and pfc at the ccu's on the top floor this afternoon.

There are 50 boards in total so got through 5 ccus this week and 40 circuits. the readings were ok for the ze and pfc.

The building is very old and it is quite interesting finding the things added over the years.And the bodge jobs added by the maintenance man.

 

[Andy™]

if there are any really bad bodges anywhere, get a few pics for our black museum

 

[green-hornet]

thank green hornet, spoke to niceic today before we started the zs and pfc at the ccu's on the top floor this afternoon. There are 50 boards in total so got through 5 ccus this week and 40 circuits. the readings were ok for the ze and pfc.

The building is very old and it is quite interesting finding the things added over the years.And the bodge jobs added by the maintenance man.

Just remember when testing for PFC and PSC on three phase supplies the PSC will always be larger than the PFC.

Use the rule of thumb calculation for three phase only for the short circuit current of double the single phase value.