Hello,


I have a honeywell st6400c controller and an immersion heater. 

My heater has 2 switches, off and on peak. My concern is that the heating works only with both switches on. Even if its set to trigger at off peak time only, which it does, both switches light up and if I switch off the onpeak one, the heating stops even tho the offpeak is still lit (testing this at off peak hours ofc). Is this correct ? does this not use much more electricity? I was monitoring this and Im sure it goes against the "night" hours, but my worry is that it uses much more power than it should.

Thank you for your advice

Tom