Immersion Heater
Thanks again for taking the time to reply,the only reason I am changing the switch is that, I only need the hot water from the immersion in the morning,it only takes about an hour to heat the water and I do not want to have the immersion on the whole night just to get hot water in the morning,the problem with this switch is that it does not have a timer on it,it has a boost timer but that has to be switched on manually which means I have to get up early to switch it on,go back to bed then get up an hour later,is their another solution to this, other than changing the switch?
Thanks again
OK, there are ways of doing what you want - though not with the existing timer. It would be possible with the new one, with some adjustment.
Firstly though, if your tank is well insulated, once it has heated up to the set temperature, it uses far less power to maintain the temperature (when it's not being used) - so you may not save as much as you expect having it only on for 1 hour rather than the 7 - How much will depend on your setup, but it will be a lot less than 6/7th of the total. If you have a smart meter then it might be worth checking.
Factoring in the price of a timer and installation etc, the savings may not pay for the work for a while and good insulation on the tank may be a better investment in terms of saving money.
However, setting that aside, there are a couple of ways of achieving what you want. This assumes you currently have two feeds to the existing timer in at your cupboard, a permanent feed from the normal CU that is always live, and an off peak feed from the off peak CU, that only becomes live at 12-7(ish)
1. Use the new timer you have, using the permanent live feed, to run the lower immersion only for an hour, just before you usually wake up. In this case, the off peak feed in the existing timer will need to be terminated safely but not connected to the new timer as it will not be used.
2. Separate the feeds in the cupboard - and set up a suitable timer on the off peak feed so that it runs for an hour at the time you want, with a simple switch for the "boost" top immersion. The only issue with this is that you'll need a timer that can function with battery backup, as the live feed to it will be off for 17 hours. The benefit is that it can only ever come on at 'cheap rate' times, even if the timer gets out of sync.
There may be other ways, with smart tech, etc. but they are probably more complicated and expensive than the situation demands.
So short answer: The only way of doing what you want is to put in a timer that you can change to come on only for an hour, during the off peak time. It can be done with the new timer you have bought, but if you are at all unsure about the connections and identifying which is which or isolating, then find a local electrician who shouldn't take more than an hour to swap things out properly.