Good evening all,
I need a sanity check and hoping you guys can help.
I'm currently working in Bournemouth upgrading a load of displays in bus shelters and the company who owns them have asked me to provide certs for our connections.
The problem I am having is that the last 10 shelters I have been to have no earth connection whatsoever.
I'll explain how they are wired.
The DNO has put their cut out underneath the poster panel in the bus shelter. These are TN-C-S supplies fed directly from the road. The incoming cable is a hybrid 2 core DNO cable, with an aluminium core and copper outer sheath that is for combined neutral and earth. I've watched the guys put them in before so it's definitely direct from the road.
The cpcs of the lights, poster panel and our bus departure sign are all connected to an earth stud and bonding is taken from there to other parts of the shelter.
Now the part I am concerned about. The earth stud on the shelter is not then connected back to the combined N + E terminal in the cut out, meaning the whole bloody shelter isn't earthed. When taking a ZS from my sign I have been getting readings from 45 ohms up to 180 ohms! These are protected by RCBO's so hopefully they'll kick in if there are faults in the lights and signs. (Although a lot of them don't trip in time / at all)
Surely I'm right in thinking that if there was a fault in one of the "tails" from the cutout to the RCBOs feeding the other circuits, for example the cables becoming trapped in the door or rubbing against the enclosure, then the whole shelter will become live. By my calculations at 180 ohms (230/180) means that you would only get a current of 1.2 amps, obviously no where near enough to blow the main 6 - 16 a fuse in the cut out.
Like I say, I'm 99% sure there person installing these has got confused as there isn't a terminal that says "earth" and not connected it. In some instances there are cables from the main earthing stud flapping around in the enclosure as if they should be connected. I just want to be sure as I've found 10 of these in a row with the same fault. I work all over the UK and all the other shelter manufacturers, and the way I wire street lamps all have earth cables back to the cut out.
The live conductors are then connected to double pole RCBO's, most of which are covered in crap and don't trip when pressed or tested, and even if they do well over stated tripping times.
Thanks for your input in advance,
Rich
Here's a picture of one, with the earth lead loose.
https://www.dropbox.com/s/0j2r84n873x75dv/shelter.JPG
I need a sanity check and hoping you guys can help.
I'm currently working in Bournemouth upgrading a load of displays in bus shelters and the company who owns them have asked me to provide certs for our connections.
The problem I am having is that the last 10 shelters I have been to have no earth connection whatsoever.
I'll explain how they are wired.
The DNO has put their cut out underneath the poster panel in the bus shelter. These are TN-C-S supplies fed directly from the road. The incoming cable is a hybrid 2 core DNO cable, with an aluminium core and copper outer sheath that is for combined neutral and earth. I've watched the guys put them in before so it's definitely direct from the road.
The cpcs of the lights, poster panel and our bus departure sign are all connected to an earth stud and bonding is taken from there to other parts of the shelter.
Now the part I am concerned about. The earth stud on the shelter is not then connected back to the combined N + E terminal in the cut out, meaning the whole bloody shelter isn't earthed. When taking a ZS from my sign I have been getting readings from 45 ohms up to 180 ohms! These are protected by RCBO's so hopefully they'll kick in if there are faults in the lights and signs. (Although a lot of them don't trip in time / at all)
Surely I'm right in thinking that if there was a fault in one of the "tails" from the cutout to the RCBOs feeding the other circuits, for example the cables becoming trapped in the door or rubbing against the enclosure, then the whole shelter will become live. By my calculations at 180 ohms (230/180) means that you would only get a current of 1.2 amps, obviously no where near enough to blow the main 6 - 16 a fuse in the cut out.
Like I say, I'm 99% sure there person installing these has got confused as there isn't a terminal that says "earth" and not connected it. In some instances there are cables from the main earthing stud flapping around in the enclosure as if they should be connected. I just want to be sure as I've found 10 of these in a row with the same fault. I work all over the UK and all the other shelter manufacturers, and the way I wire street lamps all have earth cables back to the cut out.
The live conductors are then connected to double pole RCBO's, most of which are covered in crap and don't trip when pressed or tested, and even if they do well over stated tripping times.
Thanks for your input in advance,
Rich
Here's a picture of one, with the earth lead loose.
https://www.dropbox.com/s/0j2r84n873x75dv/shelter.JPG
