Hello
Sounds like the thermal switch is cutting in. This happens because there is a blockage on the outlet of the shower, and the water stays in the heater tank too long and therefore gets to an unsafe level. Check that the hose isn't kinked and clean and descale the handset. If this doesn't work, please contact us on 0845 126 4141 and we can try and help.
NATIONAL SHOWER SPARES, July 2008
