Have you looked at the water pressure? Sounds like it copes with a certain amount of heating then goes to an overheat lock-out, which re-sets once it cools down. If all the electrics are OK and it is occurring on multiple identical machines, then it may be that the water pressure is marginally too low? I presume it is fed directly from the mains, rather than from a header tank?EDIT: I see that it only happens on High, which is what you would expect if it was an overheat cut-out issue.
I’d be looking at the water pressure and / or flow rate too. Does the head need de-scaling, or had mains pressure dropped? It sounds as though there’s not enough water passing through so it’s tripping the fail-safe.Electric showers really can be a pain, is there any way that you can install one that runs from your hot water supply instead?
The evidence here points directly at an electrical supply fault as Risteard says. The fact that the indicator light in the pull switch goes off shows that the power has stopped before it reaches that light.
Lawdie!When the shower goes off, so does the neon light on the pull cord switch! Or, to put it the correct way around, when the light on the pull cord switch goes off, so does the shower.There is nothing to suggest the shower is at fault. Or the water supply. There is everything to indicate that it's due to a fault in the leccy supply betwixt the CU and the pull cord switch.First check the switch. Then check the MCB. Then check the cable in between.
Jeepers, I agree with most of what you say, but it is surely unusual for a wiring fault to be as predictable as the OP describes and it doesn't really answer for the fact that it only happens when the shower is at the high setting (although I guess this could be a thermal issue that varies with the power being drawn). I wonder if the switch is wired wrongly, so that the LED indicator is not on the live side of the switch, only showing as "on" when the shower unit is actually drawing power. When the overheat cut-out puts the shower into a safe-mode, that power draw ceases and the indicator light goes out. I know that my scenario postulates two faults, when a single fault is always the most logical conclusion, but this is a strange one!
@Ell_ma has the switch actually been tested yet?
Am I wrong, then, in thinking that if the pull-cord switch was wired so that the indicator LED was on the neutral side rather than the live, it would only be on when the shower was actually connected and not go off when the shower's fail-safe wiring disconnected it?
When you pay at supermarket fuel pumps
DON'T assume your landlord covers you
Incl £2ish sun cream & £1.50 disposable BBQs