Electrics provision for system boiler and megaflow with immersion heater

[Jupiter01]

Thanks for the response.
It's a boiler running on Gas.

@flameport thanks for the info. I spoke with Heatrae Sadia and Worcester this morning and they confirmed the ampage you have posted above. Before I could arrive at the conclusion that a 3 amp boiler and 13 amp Immersion will be adequately served by my ring based on 2.5mm cable, the technical department at Heatrae Sadia suggested that the Immersion Heater must be on a separate radial circuit.

Does that check out with you guys?

On the 35KW boiler and large house. My house isn't small but given the variance in sizing, I am inclined to over size rather than under. Worecester also advised me that the 35 CDI boiler is fully modulated which means it can be throttled back.

I would welcome your thoughts on the above.

 

[ban-all-sheds]

the technical department at Heatrae Sadia suggested that the Immersion Heater must be on a separate radial circuit.

Does that check out with you guys?

Who is going to be signing the EIC?

 

[Jupiter01]

the electrician

 

[EFLImpudence]

Then why is HE not advising you what HE wants doing?

 

[Jupiter01]

his advice as many had previously suggested here was to use the ring main there at the moment. I was hoping you guys could give me a view in light of the info from heatrae

 

[EFLImpudence]

Heatrae have said the immersion should be on a radial circuit; you have installed two.

If you want the electrician to sign the certificate then you must do what HE wants.

 

[Taylortwocities]

I was hoping you guys could give me a view in light of the info from heatrae

About a hundred years ago, on this thread, I posted the following.

It is what you have been advised to do, and I haven't changed my opinion.

as the immersion is the standby in the event of boiler failure, it is nuts to have the boiler and the immersion on the same circuit…
Think about it: you wake up and the RCD has tripped, you trace the problem to the circuit with the boiler on it, you try everything but the darn RCD keeps on tripping.
You cannot use the immersion because the RCD keeps tripping.
You have no hot water, nobody can have a shower and the electrician/plumber is 2 days away.

Immersion on its own radial, boiler on a separate circuit. you know it makes sense.

 

[Jupiter01]

You absolutely did! thanks @Taylortwocities
I think some of the others suggested that a ring main would suffice and I was trying to make sense of whether this was compulsory. I accept that there is a rational reason to do this as set out in your earlier post.

 

[EFLImpudence]

Of course it would suffice - so would 25mm² cable.

It is just pointless and of no benefit whatsoever.

 

[Jupiter01]

sorry @EFLImpudence. What's pointless and of no benefit?

 

[EFLImpudence]

Your so-called ring circuit - when all you have really is two radials joined together (two conductors in parallel).

Why don't you separate them then you can have the immersion on one and boiler and socket on the other?

 

[Jupiter01]

I thought you needed 4mm T&E for radial?

 

[EFLImpudence]

A 32A one would require 4mm².

Change the MCB (and extra one) to 20A.

 

[Taylortwocities]

I thought you needed 4mm T&E for radial?

That's why you need to get your electrician to stop taking holidays (or whatever) and to do the design of your installation.

 

[ban-all-sheds]

That's why you need to get your electrician to stop taking holidays (or whatever) and to do the design of your installation.

Jupiter - you really can't do this design yourself - there's too much that you don't know, and half of what you think you know is wrong.

Nor can anybody here do it by proxy, as they won't be able to sign the EIC.

Lastly, common decency says that if you want someone to sign a certificate to say he did something, you ought to have let him do it, not expect him to lie.