Definition of own circuit

[Steve-S]

H5 relating to an immersion heating over 15 litres of water says:

Should be supplied by their own separate circuit.

No mention of sub circuits, nothing. A final ring with 13A mcb off the ring, then a 20A switched-cord outlet connection unit complies. It then has its own separate circuit. A circuit not shared with any other outlet or appliance.

photo by Westward10

20A switched cord outlet below:

 

[timhoward]

Ok, 1 post from me and then I’m done here.

My only comment is that bs7671 appendix 15 gives advice about ring final circuits and suggests that various large loads over 2kw should be on a dedicated circuit. While not mentioned by name, immersion heaters draw more than the items that are mentioned.

I believe it’s been established that the regs don’t allow you to put an MCB on the ring.

Strictly and pedantically speaking it may not be against normative regs in BS7671 itself to connect an IH directly to the ring using a 20amp isolator, omitting over currrent protection for a fixed load. However the overall compliance of the ring relies on less than a 20amp load on any section of cable, and having a high current drawing device on the circuit for large chunks of time reduces the capacity of the rest of the circuit by a good margin.
Plenty of guidance documents and the informative appendix advise against doing this.

So please enlighten us - why would you want to do this?
Consumer unit, 16amp MCB, cable, 20amp DP isolator, job done. I don’t understand any motivation to do otherwise?!

 

[Julie.]

H5 relating to an immersion heating over 15 litres of water says:

Should be supplied by their own separate circuit.

No mention of sub circuits, nothing. A final ring with 13A mcb off the ring, then a 20A switched-cord outlet connection unit complies. It then has its own separate circuit. A circuit not shared with any other outlet or appliance.

photo by Westward10

View attachment 117633

20A switched cord outlet below:

View attachment 117634

May I suggest you familiarise yourself with part 2 (definitions) of the regs.

A circuit is defined quite clearly in there, a seperate circuit is therefore a separate one of those.

The definitions as used/defined by the regs are what we all must follow, so learning those would be far better than random understandings by others merely trying to remember them.

 

[DPG]

Not even getting involved. It's the same pointless thread as the last one.

 

[nicebutdim]

Circuit: An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s).

This is really basic stuff and the OP is clearly a liability to themselves and others. These threads remind me of that old adage "a little knowledge is a dangerous thing".

 

[mainline]

H5 relating to an immersion heating over 15 litres of water says:

Should be supplied by their own separate circuit.

No mention of sub circuits, nothing. A final ring with 13A mcb off the ring, then a 20A switched-cord outlet connection unit complies. It then has its own separate circuit. A circuit not shared with any other outlet or appliance.

photo by Westward10

View attachment 117633

20A switched cord outlet below:

View attachment 117634

On to something more interesting, how do you feel about beards, are you for or against ?

 

[Steve-S]

Mr Howard,
"I believe it’s been established that the regs don’t allow you to put an MCB on the ring."
It has not been established.

If there was a 30A breaker at CU, a 4mm radial circuit then a 13A single socket off it and a 13A FCU at a 3kW immersion, there is lots of amps available, but that is not a separate circuit as it is shared.

But a 13A MCB off a final ring, a cable, then a 20A switch and cord outlet, then separate circuit has been created. It may be a sub circuit but clearly separate. Does it meet regs tough?

One scenario is an upstairs final ring. It will take most of the time a TV and a few computers - nothing at all. The biggest load will the a vacuum cleaner every now and then. I see no reason why a 3kW immersion cannot be taken off the ring. The ring will never come anywhere close to 32A.

Nephew has had a substantial solar array installed. There was no immersion cable run to the upstairs cylinder by the builder 20 years ago as it was heated an still heated by gas. So he naturally wants to heat it via electricity for free a lot of the time. On a cloudy day he can pull in around 3kW. To get a cable to it will be a nightmare when a little used final ring is adjacent. Electrically and safety-wise there is no problem, only the regs may get in the way.

Splitting the ring may be an option.

 

[Steve-S]

May I suggest you familiarise yourself with part 2 (definitions) of the regs.

A circuit is defined quite clearly in there, a seperate circuit is therefore a separate one of those.

The definitions as used/defined by the regs are what we all must follow, so learning those would be far better than random understandings by others merely trying to remember them.

Will do.

 

[Steve-S]

Circuit: An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s).

Exactly what I outlined. At the ring an over-current device at the origin then a separate radial circuit created supplying only one appliance. All circuit protected by the over-current device.

 

[mainline]

Exactly what I outlined. At the ring an over-current device at the origin then a separate radial circuit created supplying only one appliance. All circuit protected by the over-current device.

There is nothing to stop a competent designer from doing whatever they want, as long they note it as a deviation on the certification, and declare that it is no less safe than it would be if the design was done strictly to BS7671.

 

[Steve-S]

I added to my post above.

 

[mainline]

Splitting the ring may be an option.

Calling a competent electrician may also be an option.

 

[Steve-S]

I picked up this.. Looks to conform to BS 7671.

Every circuit must be separate from others and must be connected to its own overcurrent protective fuse or circuit breaker in a switch fuse, distribution board, consumer's unit, etc.

 

[Steve-S]

Calling a competent electrician may also be an option.

You are funny. Missed your calling in life.

 

[nicebutdim]

Perhaps the OP should pose these questions to the IET.