callout to shop

[Hawk]

Had a callout there to a shop. Outside lights tripping the main rcd. One of the son lamps was causing it. Replaced it and seems fine now. Done an ir test between live and neutral to earth and got a reading of >999. Bad set up cause if one circuit has a fault it takes out the whole shop not good when customers are in.
I have recommended putting rcbo's in. What are your thoughts? I have a system in place that notifies the customer of power cuts. He got a message at 4am this morning to notify him of a power cut. The system is good as there is freezers and fridges in the shop. However this doesn't solve the problem of the whole shop tripping!

 

[Welchyboy1]

How can a son lamp be causing an earth fault?

its more likely the control gear i would think

i had a similiar job where a whole farm all the out buildings and the farmers house was protected at scource by one 100ma rcd, no down stream devices at all

getting calls every month

only thing you can do is split up the circuits over more rcd devices or rcbos, or could you not put freezers etc on dedicated circuits with own rcd(if required) for a start

im only guessing here as you dont say much about the existing set up

 

[Barry White]

Most RCBOs are single pole so if you get a N-E fault it will trip but wont disconnect the N causing your main rcd to trip and you are back to square 1.
A dedicated supply to the freezers etc or split circuits over another RCD as mentioned above is a good option

 

[Deleted member 9648]

Most RCBOs are single pole so if you get a N-E fault it will trip but wont disconnect the N causing your main rcd to trip and you are back to square 1.
A dedicated supply to the freezers etc or split circuits over another RCD as mentioned above is a good option

He'd only need a main RCD if the RCBO's were for earth fault protection.

 

[Hawk]

TT system done about 8 years ago in line with the 16th edition. 100mA rcd supplying a dis board and a sub main to another dis board which is protected by a 30mA rcd.

 

[Deleted member 9648]

RCBO's with an S type 100ma Main switch would be perfick then.

 

[Hawk]

But what about what mykey is saying then about the neutral to earth fault then? Would it not take out the main rcd if the rcbos are single pole?

 

[davesparks]

Yes a N-E fault will take the main RCD out if the RCBOs are single pole

 

[Hawk]

So a better option is to use double pole rcbos? Also is it possible for a son lamp to take out an rcd? I ask because I replaced the lamp and all seems fine now.

 

[davesparks]

double pole or SPSN RCBOs yes.

A son lamp won't trip it on its own, but a son fitting might develop a fault.

 

[Hawk]

So how come when I replaced the old lamp with a new one, it cured the tripping of the rcd? Would there not be an imbalance between live and neutral if the control gear is trying to ignite the faulty lamp hence causing the rcd to trip?

 

[Lucien Nunes]

It's possible that the high voltage developed when trying to strike the dead lamp is causing breakdown of some faulty insulation in the luminaire, e.g. in the ballast windings. With the new lamp that strikes easily, the peak voltage is lower and it doesn't flash over, and it also survived your IR test. Some types of control gear can cause high leakage currents while striking even withouta fault, not so much with sodium but if the RCD is already carrying some leakage the increased capacitive current from the ignition impulses might have just pushed it over the limit.

 

[Hawk]

Thanks for the info.