Acceptable Immersion heater/Shower pump cicuit?

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My Central heating is down at the minute so I dont have any hot water. I have replaced an old and failed Immersion element in my hot water cylinder with a new one.

Having read through the forums as to how to connect the element to a supply, I have put this drawing together to show what the setup will be like.

Basically a 20A MCB from the consumer unit will supply the Immersion heater through a 20A double connection unit in the airing cupboard upstairs.
A 1.5mm2 T&E cable will spur of the 20A double pole connection unit into a 5A FCU which supplies my shower pump, also in the airing cupboard.

The immersion/shower pump circuit utilises the old 10mm2 electric shower circuit from the consumer unit.

Here's a sketchup drawing to show what I mean:


Does this look acceptable and comply with regulations-wise?

Thanks in advance for any help.

Steve
 
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The immersion should be on a dedicated radial circuit.

Ie. with no spurs off it (your pump).
 
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Simple solution - disconnect the immersion. You probably use the boiler to heat it anyway.
 
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The proposed layout is fine.
While the OSG suggests that water heaters have their own circuit, there is no regulation in BS7671 which requires this.
 
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Immersion heater 13A
Pump 5A
Total 18A.

Pump likely to be quite a bit less than 5A and occasional use only.
 
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Thanks very much for the input all!

The proposed setup with the immersion heater will only be a temporary affair for the coming week as my back boiler has a blocked cold feed which needs sorting out.

I appreciate, as someone mentioned, the immersion heater having a dedicated circuit which could be overloaded should another appliance be drawing from that same circuit simultaneously.

That won't be the case here, as the Immersion heater will be switched on manually for 40 minutes and then manually switched of before the shower pump is then used.

Once central heating is back up and running, I'll disconnect the immersion heater from the circuit and coil up the flex and leave it off until the next time my central heating decides to breakdown.
 
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13A FCU for the immersion ( you've got unprotected 2.5 on a 30A supply otherwise.. not allowed.. )

2.5mm for the "spur" to the shower pump ( allowed in 2.5 because you have an FCU before the load.. )
 
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If the CPD is 20amp. Then the cable to the FCU should be 2.5mm², not 1.5mm

Strictly speaking, water heaters fitted to storage vessels in excess of 15litres should be supplied with their own circuit.

This is mentioned in the on-site guide and the Electrician's guide to the Building Regs but I cannot find an actual BS7671 reference to it.
Anybody spot one???

If you were to take a design for this 20A radial circuit, you have a load of 13A for the immersion (no diversity allowed) and the shower pump - probably 3A max.

CPD = 20A
Demand 16A
Cable adequate for the load


I would say that you are good to go.

Is this a new circuit though?




:evil:
 
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Thanks for that Taylortwocities.

Yes it is a new circuit in as far as the shower pump spur bit. The 'old' exisitng 10mm2 cable was for an electric shower I scrapped a couple of years ago.


Steve
 

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