Yesterday we ran out of hot water, and I figured out that the mechanical timer that controls the electric heating element had stopped turning (I presume the motor has burnt out) in one of the "off" positions. For now, I've switched the power to the element back on at the timer and it works (all the time).
So here are my questions.
1. Is it in fact inefficient to run the boiler for indirect hot water when it's not running anyway to heat the radiators?
2. Is it even worthwhile to switch the immersion heater off some of the time during the higher-rate period? (The cylinder is insulated with a "jacket".) In other words, should I bother replacing the timer, or just connect the element directly to the switch?
3. Is it unsanitary to let the hot water cool off by switching the heater off for several hours during the day?