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Twin immersion heaters

Former Community Member
Former Community Member
I am in the process of going unvented.  I have to use immersion heaters, and the new cylinder has two.  I have one feed to the existing immersion.  It is on 2.5mm2 T&E and connects to a 32A MCB on the CU.  I'm adding a DP isolating switch in the cylinder cupboard.  Will that be complaint for one of the immersion heaters?

To fully install the cylinder (ie the second immersion), I plan ask an electrician to either
(1) run an additional 2.5mm2 T&E cable back to the CU, connect it to the existing 32A immersion heater MCB at the CU. So the MCB protects two separate cables and the 2.5 T&E is within its capacities. 

Or
(2) run a new 6mm2 T&E cable back to the CU, connect to the existing MCB and in the cylinder cupboard, split the feed to two DP isolators, one for each immersion and its timer.


I'd be grateful for advice - are both approaches compliant?  Is one better than the other?  The amount of work will be similar.
Parents
  • 0
    1. Keep the existing circuit with a B16 MCB and install a bath/basin switch to control both immersion heaters.  https://www.electrical2go.co.uk/mode-20a-dp-bath-sink-switch.html


    2. Keep the existing circuit with a B16 MCB and install a timer to control the bottom heater with a manual boost for the top Economy 7 Digital Timeswitch + Boost Control (tlc-direct.co.uk)


    3. Keep the existing circuit with a B16 MCB and install a new circuit with another B16 MCB to supply each immersion heater through separate timers, however both heaters should not be run at the same time, so this is not a good plan.


    Because it is an unvented cylinder both immersion heaters must be controlled through separate dual thermostats to avoid overheating of the cylinder. As the cylinder is pressurised the boiling point of the water within it is raised and you really don't want installation to be incorrect.
Reply
  • 0
    1. Keep the existing circuit with a B16 MCB and install a bath/basin switch to control both immersion heaters.  https://www.electrical2go.co.uk/mode-20a-dp-bath-sink-switch.html


    2. Keep the existing circuit with a B16 MCB and install a timer to control the bottom heater with a manual boost for the top Economy 7 Digital Timeswitch + Boost Control (tlc-direct.co.uk)


    3. Keep the existing circuit with a B16 MCB and install a new circuit with another B16 MCB to supply each immersion heater through separate timers, however both heaters should not be run at the same time, so this is not a good plan.


    Because it is an unvented cylinder both immersion heaters must be controlled through separate dual thermostats to avoid overheating of the cylinder. As the cylinder is pressurised the boiling point of the water within it is raised and you really don't want installation to be incorrect.
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