It could be if none of them are working. Is it a radio teleswitch? Not sure how common a fault it is though
Have you got a multimeter? If so then you could check to see if 230v is present at each heater/FCU. Have any fuses blown/MCBs tripped? If there is not 230v present anywhere on the E7 installation then it does suggest a problem with the supply switch.
It would be rare for all the fuses to blow anyway.
When E7 becomes live (or is due to), watch the meter / teleswitch - they may have an indicator on them which shows they have changed over. They may also click or thump on the boards they are mounted on - the teleswitch has a pretty big contactor (magnetic switch) in it.
If nothing happens at the meter, or you cant tell, see if the E7 board is live - test the voltage at one of the live outputs. Should be 230 ish. If all are zero volts, you have a problem with the teleswitch.
A picture will help us familiarise ourselves with your setup. A lot of E7 installations are done differently.
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