Two Immersion Heater Elements on One Circuit?

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(Disclaimer, I am in no way a qualified electrician and will get someone to look at/do this for me. Just trying to work out what the best approach is).

I'm wondering if I can run two immersion heater elements (3kW each, so 12.5A each) on the same circuit? Getting another circuit upstairs will involve drilling through a 300mm high density concrete slab - which I'd like to try and avoid...


I don't think I can have these both powered up on the same circuit at the same time (MCB is rated to 16A, cable is 32A (I think), and the timeclock after the fused spur is only 16A). And that doesn't bother me - happy to only run one at once.

So it possible to have these wired up so that they can both run on the same circuit, but so that only one can run at a time? Any risks in doing so?


Any alternative suggestions welcome.


Thanks


Chris
 
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Yes there are timers for doing what you want.

Do you have Economy 7 or similar?
I have Octopus Agile (but was on Economy 7, and use it to heat water at night).

So there is no issue running both immersion elements off the same circuit, provided they're controlled not to come on at the same time?

Am I right in my assumption that I definitely could not run both at the same time? (Therefore I want to make sure I find some foolproof way of ensuring that this can't happen).


Re-measuring the cable, I think it might actually be 2.5mm T&E, so only 20A. Therefore imperative the two units do not operate at the same time - however, I'm not sure how to achieve this in a way that is somewhat foolproof (i.e if I forget to turn off the top element it will automatically turn off when the bottom element comes on on the timer).
 
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I have Octopus Agile (but was on Economy 7, and use it to heat water at night).
Not sure what agile is. Is it similar to E7 in that you want the lower element timed to come on at night?

So there is no issue running both immersion elements off the same circuit, provided they're controlled not to come on at the same time?

Am I right in my assumption that I definitely could not run both at the same time? (Therefore I want to make sure I find some foolproof way of ensuring that this can't happen).
Correct.

Re-measuring the cable, I think it might actually be 2.5mm T&E, so only 20A. Therefore imperative the two units do not operate at the same time - however, I'm not sure how to achieve this.
There are timers which do that if above is what you want.

E.g.

Not suggesting you buy form this site; just showing you.
 
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Not sure what agile is. Is it similar to E7 in that you want the lower element timed to come on at night?


Correct.


There are timers which do that if above is what you want.

E.g.

Not suggesting you buy form this site; just showing you.
Yeah, basically cheap rate at night.


Okay, that timer (or similar) looks like an option - thanks. It's not explicit in stating that the boost element would automatically turn off when the normal element turns on, though. Although the setting of the boost time should help in that respect.
 
Yeah, basically cheap rate at night.
Ok.

Okay, that timer (or similar) looks like an option - thanks. It's not explicit in stating that the boost element would automatically turn off when the normal element turns on, though.
I am not actually sure whether it does or not, but the boost is only a maximum of two hours so you are unlikely to switch it on at 10pm.

Although the setting of the boost time should help in that respect.
You can't set the boost time; you have to switch it on.
 
Just to add - when the boost switches off (after max. 2hrs.), the device does automatically switch back to the main timer.
 
Why do you think you need 2 immersion heaters?
Seems to be the norm for E7 cylinders. Bottom unit operates at night to heat whole tank, and if needed to top up during the day (e.g Mrs has a bath) I don't need to heat the whole tank, so just use the top element to heat the top part to get through the washing up.

Inefficient turning on a single element heater and heating the whole tank when I only need to do the dishes.


Ok.


I am not actually sure whether it does or not, but the boost is only a maximum of two hours so you are unlikely to switch it on at 10pm.


You can't set the boost time; you have to switch it on.

Sorry, by "boost time" I meant boost duration. e.g if I did go to turn it on at 10pm I should look at it and think "I don't need this to be on for 2 hours". Rather than just an on/off switch that could be forgotten to be switched off.
 
Seems to be the norm for E7 cylinders. Bottom unit operates at night to heat whole tank, and if needed to top up during the day (e.g Mrs has a bath) I don't need to heat the whole tank, so just use the top element to heat the top part to get through the washing up.
Inefficient turning on a single element heater and heating the whole tank when I only need to do the dishes.
(y)


Sorry, by "boost time" I meant boost duration. e.g if I did go to turn it on at 10pm I should look at it and think "I don't need this to be on for 2 hours". Rather than just an on/off switch that could be forgotten to be switched off.
Yes, exactly.
 
Back to basics.

Does your hot tank have 2 immersions? And if so how are they connected now ?
 
(y)



Yes, exactly.

The instructions for the following unit actually seem to suggest that it would not be possible to run the two elements at the same time, My fears of potentially overloading shouldn’t be a problem.

https://www.tlc-direct.co.uk/Products/SMTRTM7N.html


IMG_5673.jpeg


Thanks for your help
 
Back to basics.

Does your hot tank have 2 immersions? And if so how are they connected now ?
Current cylinder is a single top entry immersion element, and it’s wide on a simple manual time clock
 
The instructions for the following unit actually seem to suggest that it would not be possible to run the two elements at the same time, My fears of potentially overloading shouldn’t be a problem.
Well done.

Definitely knew it would not run both at the same time; just wasn't sure which would take priority.
 
Current cylinder is a single top entry immersion element, and it’s wide on a simple manual time clock

Are you keeping this tank or planning on replacing it ?


And if you only have 1 circuit to this area, then you don’t have a dedicated E7 or separate supply so the circuit is only a 24 x 7 circuit
 

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