Electrics provision for system boiler and megaflow with immersion heater

[Jupiter01]

Hi,

I am preparing a boiler room to accommodate the above and was wondering if someone can advise me on what provision I need to make by way of electrics. Currently I have a separate ring main which comprises of a double power socket and a FCU.

Thanks

 

[Newboy]

You've got a separate ring final with just a 2-gang socket and a fused spur?

The supply for the boiler would usually be a switched fused spur (with fuse size as specified in MIs) and an additional switched fused spur can cope with a standard (3kW) immersion heater although better to fit a 20 amp DP switch and have an appropriately fused dedicated circuit back to the consumer unit - notification required as this is a new circuit.

 

[Jupiter01]

Thanks for the response. I have created a new ring/circuit for the purposes of the boiler room. To make sure that my terminology isn't skewed. I have a 2.5mm twin and earth coming from the consumer unit, off a dedicated trip switch. This serves a double socket and a FCU in teh form of a ring and then returns back to the consumer unit. It's in first fix stage so I can easily add more sockets, FCU's, etc.

Thanks for your help

 

[Agile]

I don't see any need for a ring main when a spur would do.

Tony

 

[flameport]

Single 20A radial circuit, 2.5mm cable would typically be suitable, at the end a 20A switch with neon indicator for the immersion and a 3A fused spur for the boiler & controls.

 

[Jupiter01]

sorry for the incessant questions but I've already laid a ring main. I appreciate that a spur would have sufficed but since I've alreday gone to this effort, I assume you aren't suggesting that i scrap it? Do I have to have a radial?
also aren't the fused spur and neon switch just additional points on my current ring? I.e. I leave another 1 gang on the ring as I already have one on there along with the double socket.

 

[Agile]

But traditionally you will have a 32 A MCB feeding a single 20 A DP switch and a 3 A spur.

 

[Jupiter01]

Guys,

I thought it would be helpful to send you a picture of my first fix. I appreciate that the double socket may not be required. Presumably, the other two can connect into the FCU shown in the picture?

 

[flameport]

You can use what you have, it's just totally over the top for a 3A boiler and an immersion heater which will seldom be used.

 

[Jupiter01]

thanks @flameport.
I've got a 21 way consumer unit and thought it would make sense to devote a circuit to this rather than share with something else.

 

[Newboy]

Presumably, the other two can connect into the FCU shown in the picture?

You will need to provide a separate switched fused spur for each appliance

 

[Jupiter01]

is a switched fuse spur the same as a fused connection unit? If yes, as per picture, I have two of them along with a double socket.

 

[Jupiter01]

I had an plumber around today to quote me for the installation of the megaflow and system boiler. He suggested that I may need to go thicker than the current 2.5mm twin and earth given that the circuit would be powering the immersion heater. Any substance to that?

 

[Sim777]

No

 

[Jupiter01]

Thanks for the response. To be clear, are you suggesting that irrespective of the megaflow size e.g. 300 litres or boiler size 35 KW, 2.5mm cable will be sufficient?