GasCH plus Immersion question

[Lorena]

Hello,
If a house has full gas fired central heating with Ideal Mexico 2 boiler, plus an airing cupboard housing foam lagged copper cylinder with immersion heater with computerised control switching, can anyone advise me what is the point of having this immersion heater when GasGH is installed?
...and what is this computerised control switching for please? is that just like a timer for economy 7 use? presumably this immersion heater would hardly ever be needed if there's already GasGH in place, is that right?

thanks for any advice

 

[spudkey]

The imersion is for back if boiler is not working it should be left off

 

[Lorena]

thanks for your help