Shock off shower

Justinsane · Mar 1, 2010

Hi, a customer of mine phoned me the other night to say she had just touched the water inlet pipe to the shower and had a shock off it (she was in the shower at the time!)

I've been and looked at the job today and can't work out what is going on. I get a reading of 1 - 2 volts off the pipe whilest the shower is on. I also get this reading at different points on the pipework around the house.

Nothing when the shower is off. Surely this shouldn't happen but I wouldn't have thought she could get a shock off it....

I've check the bonding, its a TT system where a new c/unit has been run from the existing supply and the earth rod has been connected to the new box and then ran back to the old one. The installation is on a 100amp voltage controlled breaker and the shower circuit is on a 40amp mcb from the new box which has an RCD main switch. All pipework is bonded.

The loop reading from the shower is 181ohms.

Anyone got any ideas whats happening and why nothing is tripping....

cheers,
Justin

Justinsane · Mar 19, 2010

Well I've think I've found the problem.....The electric bar heater in the bathroom (in the old part of the house ) had a live to earth fault when switched on. As this was on the old system it was making the earth bar live and therefore the metalwork bonded to it. The ELCB which was protecting the system wasn't tripping as the earth loop reading to the electrode was to high at 240ohms.

The shower wasn't tripping as the metalwork to it was bonded on the old c/unit not the new one.

I've disconnected the bar heater and ripped out the old fuse box and replaced it with a dual rcd board.
I've also installed a new earth rod and got the earth loop down to 135ohms. (although it was raining)

I'm going to bond the water pipe in the new bathroom (where the shower is) to the same c/unit which has the shower on and leave the rest bonded to the new unit i have just put in.

Should i try to get the earth loop reading lower? if so does anyone have any tips as to how?

cheers

marksparky · Mar 20, 2010

well technically ur reading is acceptable as the max ze for a tt system is 200 ohms although i know niceic's limit is 100 ohms im not sure about other scheme's, to get reading lower u put another rod in at least the length of a rod apart and connect 2 together or u could bury a earth tape if possible? hope this helps.