Immersion Heater Wiring

[poolballboy]

Evening all.

I have just had half of my house rewired due to refurbishing and moving the boiler and hot water tank. The old system had the boiler and immersion running off a separate 2.5mm cable from the consumer unit.

Now that the work has been finished the plumber has installed the boiler and hot water tank, however, has not wired up the immersion on the tank. When I asked him why, he said it needed its own supply from the consumer unit. Is this correct?

The boiler has its own 2,5mm supply. So is it possible for him to come off that with a 13Amp Fused spur to connect the immersion? Or is he correct and we do need a another seperate 2.5mm line running?

Thanks

Andy

 

[Deleted member 267285]

There should be an unfused connection unit by the cylinder, is there one there?

 

[Harry Bloomfield]

Now that the work has been finished the plumber has installed the boiler and hot water tank, however, has not wired up the immersion on the tank. When I asked him why, he said it needed its own supply from the consumer unit. Is this correct?

The boiler has its own 2,5mm supply. So is it possible for him to come off that with a 13Amp Fused spur to connect the immersion? Or is he correct and we do need a another seperate 2.5mm line running?

A boiler/ heating system doesn't normally need a 2.5mm, 1.5 or even 1.0mm is adequate and with an MCB of 6amps at the consumer unit - what rating is the MCB presently supplying the boiler?

Immersion heaters are usually fed with a 2.5mm, with a 16amp MCB.

 

[EFLImpudence]

Now that the work has been finished the plumber has installed the boiler and hot water tank, however, has not wired up the immersion on the tank. When I asked him why, he said it needed its own supply from the consumer unit. Is this correct?

It does not matter electrically, but a fault on the circuit will mean you have no means of heating water - the main reason for having the immersion.

The boiler has its own 2,5mm supply.

Why? The boiler does not need a 2.5mm² cable/circuit.

So is it possible for him to come off that with a 13Amp Fused spur to connect the immersion? Or is he correct and we do need a another seperate 2.5mm line running?

You can if you want - but you don't need a Fused Connector Unit (the cable is the spur) and should not use one for an immersion heater.

 

[Harry Bloomfield]

It does not matter electrically, but a fault on the circuit will mean you have no means of heating water - the main reason for having the immersion.


Why? The boiler does not need a 2.5mm² cable/circuit.


You can if you want - but you don't need a Fused Connector Unit (the cable is the spur) and should not use one for an immersion heater.

If the boiler circuit is fed via a 2.5mm and on a 16amp MCB, then the boiler circuit should be fed from a 5amp switched, fused spur. Your immersion heater could then be fed from the 2.5mm too, via a 20amp DB switch. That would enable its use in an emergency when you suffered an heating system failure.

It is not the best way, but it would work. The best way is entirely separate circuits for boiler (6amp) and immersion heater (16amp).