Shower Voltage Problem

dubmark74

Hi, I have Mira Elite electric shower, worked fine up to yesterday, light not on at pull cord or shower. Measured voltage at pull cord and got 230V Live-Earth and 230V neutral to earth (strange?). Opened shower and disconnected live and neutral on show side, measured 230V Live-Earth and about 170V neutral-earth, light lit at pull cord, but obvious only about 60V Live-Neutral. Pressed test button on RCD and nothing happened. Is it possible that the RCD is faulty and shorting between live and neutral, anyone seen this before. Any help apprectated, i'm beginning to smell already.

M cebee

do you know any electricians that could take a look

dubmark74

I'm an engineer myself, so i know a bit about electrical circuits, i'd have no problem changing the RCD, just wondering if anyone else had seen the problem before i buy a new one.

Bruthal

Sounds like neutral is open circuit, probably at the feed into the RCD or the RCD internal contacts, or at pullchord itself.

A way to test this is turn the re-connected shower back on again, and RCD on, and test between the main neutral bar and the neutral into rcd, and again between main neutral and outgoing neutral of rcd. If it reads 230v between main neutral and outgoing side of rcd then the rcd has open neutral, or there is a loose/bad connection on the neutral.

If above say 0v then test between the neutral in and neutral out of shower pullchord with the switch and shower on. If 230v then switch has open neutral, or bad connection into its terminals.

Easier for the above to be done by a sparks which is recommended. Should be easy to find the problem.

overhand_right

Never seen that before couldn't even think how the rcd would cause it did you check the voltage at the rcd terminals out going side ??

Bruthal

overhand_right wrote: »

Never seen that before couldn't even think how the rcd would cause it did you check the voltage at the rcd terminals out going side ??

It can cause it when the neutral is open circuit or bad/burnt contact or connection.

With shower load on, an open neutral will show 230v neutral to earth at appliance or switch for obvious reasons.

When OP disconnected the shower cable at the shower, the now open neutral which is connected to nothing at either end can show voltage to earth from inductance from the phase beside it in the cable, you can see an example of this with a phase tester lighting on a landing light which is off and bulb removed, because of inductance between strappers of 2 way switching.

It could be a faulty neutral contact in the RCD, or a bad/loose neutral connection into a terminal. I assume everything else is working in the house? Try the cooker if its electric.

dubmark74

I checked across the switch and it is switching fine, the one thing i didn't check before i put my tools away was the voltage at the RCD. My thinking is that there could be a short between the live and neutral internal to the RCD. Why is the RCD not tripping when i press the test button, surely this is an indication of some fault within it.

Bruthal

dubmark74 wrote: »

I checked across the switch and it is switching fine, the one thing i didn't check before i put my tools away was the voltage at the RCD. My thinking is that there could be a short between the live and neutral internal to the RCD. Why is the RCD not tripping when i press the test button, surely this is an indication of some fault within it.

There wont be a short live to neutral at the RCD. If the test button is not working then its likely the RCD is getting no supply, possibly because the neutral is missing.

Do this test i was talking about, switch the RCD on, shower pullchord on, shower on. Test voltage from neutral bar that supplies the RCD, to the neutral into RCD, and also between the neutral bar and RCD neutral out.

Normal reading should be 0v for these, if 230v then your open circuit is somewhere between the 2 test points.

Or you could just test the voltage out of the RCD live and neutral, but its best done with the load of the shower on, as bad connections sometimes appear ok with no load on.

dubmark74

robbie7730 wrote: »

With shower load on, an open neutral will show 230v neutral to earth at appliance or switch for obvious reasons.


It could be a faulty neutral contact in the RCD, or a bad/loose neutral connection into a terminal. I assume everything else is working in the house? Try the cooker if its electric.

Sorry, replied before i read this. This makes sense now, the shower push button switch was probably closed when i measured the voltage at the switch, i never pressed the button, 230V was feeding back through shower. Couldn't understand voltage with shower disconnected, but you have explained it. I'll check RCD connections tomorrow, but i think i'll change anyway. Are these usually changed live, i can't see anyway of isolating the mains unless with open the ESB switch?

Bruthal

dubmark74 wrote: »

Sorry, replied before i read this. This makes sense now, the shower push button switch was probably closed when i measured the voltage at the switch, i never pressed the button, 230V was feeding back through shower. Couldn't understand voltage with shower disconnected, but you have explained it. I'll check RCD connections tomorrow, but i think i'll change anyway. Are these usually changed live, i can't see anyway of isolating the mains unless with open the ESB switch?

No you should turn off the main switch at the MCB board and test voltage is gone to confirm. Make sure any PC`s etc are off first.

overdonenames

I have NO CLUE!

dubmark74

robbie7730 wrote: »

No you should turn off the main switch at the MCB board and test voltage is gone to confirm. Make sure any PC`s etc are off first.

Thanks for your help Robbie, much appreciated.

Bruthal

dubmark74 wrote: »

I'll check RCD connections tomorrow, but i think i'll change anyway.

You might change it and then it works, but this would not confirm it was actually the RCD at fault, (although open neutral contact in it is a likely possibility) as it could be a loose connection into the RCD, which would be fixed by swapping them anyway.

But the fact the test button is not working (assuming it was before this problem) would indicate the neutral feed from the neutral bar has a loose connection either at the neutral bar or into the RCD, or the RCD switching contact itself is open circuit when the RCD is switched on, this would also stop the test button working. Very simple tests to confirm as in previous posts.