Immersion heater - timer control

[Twinkle]

I am having my direct unvented cylinder replaced shortly with a Heatrae Sadia Megaflo Eco 145dd. As part of this I want to have more control over the immersion heaters. I'm on an Economy 10 tariff and the current set up is a 1) dedicated Economy 10 circuit from a 16A breaker to a 20A DP switch then to the bottom immersion and 2) a 'normal' circuit again running from a 16A breaker to a 20A DP switch then to the top immersion. I'm thinking of using a NTT08 Timeguard 7day immersion time switch (it's rated at 16A) for the new bottom immersion and have this placed between the 20A switch and the immersion. Timeguard have advised that the rechargeable battery back-up feature will ensure the clock stays on all the time. I'd leave the new top immersion as it is i.e. straight to its 20A DP switch. As part of this I'll also replace both DP switches with decent ones (MK, Crabtree) as the current ones get warm!

I wonder if people think the above sounds fine - I've attached a couple of pictures - the wiring from the DP switches is actually inside the wall rather than surface mounted) - I guess this shouldn't be an issue? Also, should the new wiring from the wall to the new cylinder be in trunking as it is now? Any other comments gratefully received!

 

[Murdochcat]

What are you trying to achieve?

Heating by E10 is the cheapest solution and having the ability to heat the top section should you need is helpful BUT once up to temperature, the immersion doesn’t take any more energy

 

[MeldrewsMate]

The way I read it the OP wants to sub-control the bottom immersion heater within the economy 10 period.

 

[Murdochcat]

The way I read it the OP wants to sub-control the bottom immersion heater within the economy 10 period.

Which makes no sense really

 

[ericmark]

A few points, if bottom immersion thermostat set higher than top on, then top one will only activate when there has been a heavy draw on hot water, so only really need timer on bottom immersion.

Point two is running two immersion heaters together one needs to consider if anything will be overloaded.

 

[MeldrewsMate]

Which makes no sense really

Perhaps it does to him?

 

[Twinkle]

Hi all - thanks for your replies - I want to add some form of control to the bottom immersion as I think the amount of water heated during the nightime Economy 10 period (5 hours) will be sufficient for our hot water needs i.e. I don't think there is any need for the immersion to come on during the other two Economy 10 periods - one in the mid-afternoon and the other in the late evening. Of course, I realise that the immersion has a thermostat and will cut out when the set temperature is reached.

I'd be grateful if you could comment on the other points in my original post.

 

[Murdochcat]

How many units do you use per week on the E10 ?

 

[MeldrewsMate]

I'd be grateful if you could comment on the other points in my original post.

The power to the timer will go off for 14 hours each day, but if you're confident that the rechargeable battery will manage the clock during those periods then the timer you proposed will suffice. I suggest you set the ON period to start 1.5 hour after the nominal start of Eco10 start period, to ensure there is power to the output relay when your time period comes on, and to allow for the clocks going fwd/back.

 

[Twinkle]

Thanks for the further comments - I use around 3 times as much E10 units as normal units per week.