Make sure the immersion heater isn't swithced on (by accident)
oops
October 2012
Could be the unit faulty, or control cct fault or XX or XX. Start with temp unit, does it click when you adjust temperature. Probably not if water that hot, turn system off, to let it cool down, or take sensor of of tank, then check if clicks. clicking would indicate ok, and fault is in control. More details.
SD
October 2012
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