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.

 

[Steve-S]

Perhaps the OP should pose these questions to the IET.

The key word is separate. It is common to see a sub CU off a say 40A beaker in the main CU. Similar arrangement is also done with garage CU units. So a 40A circuit has a number of sub circuits off it with one maybe being an immersion. So an immersion then does not have its own circuit back to the main CU. It is a circuit off a circuit, but regarded as separate and all above board. No different to taking an immersion off a final ring with its own mcb at the take off point.

 

[davesparks]

Looks like a sense of humour is banned on this forum now then!

The key word is separate. It is common to see a sub CU off a say 40A beaker in the main CU. Similar arrangement is also done with garage CU units. So a 40A circuit has a number of sub circuits off it with one maybe being an immersion. So an immersion then does not have its own circuit back to the main CU. It is a circuit off a circuit, but regarded as separate and all above board. No different to taking an immersion off a final ring with its own mcb at the take off point.

The key word is not separate it is final.

Sub circuit is not a currently recognised term, circuits are either final circuits or distribution circuits.

A distribution circuit is a circuit which feeds a distribution board or consumer unit which then in turn feeds other circuits.

A final circuit is a circuit which feeds final points of utilisation, either lighting points, sockets or fixed current using equipment.

A ring final circuit is, by definition, a final circuit and not a distribution circuit.

 

[Steve-S]

Looks like a sense of humour is banned on this forum now then!


The key word is not separate it is final.

Sub circuit is not a currently recognised term, circuits are either final circuits or distribution circuits.

A distribution circuit is a circuit which feeds a distribution board or consumer unit which then in turn feeds other circuits.

A final circuit is a circuit which feeds final points of utilisation, either lighting points, sockets or fixed current using equipment.

A ring final circuit is, by definition, a final circuit and not a distribution circuit.

Thanks. However it says:
"Should be supplied by their own separate circuit."

It does not say final.

 

[davesparks]

Thanks. However it says:
"Should be supplied by their own separate circuit."

It does not say final.

Yes a separate circuit, if it is not a seperate final circuit then it is not separate.

A distribution circuit is a type of circuit which, by definition, feeds multiple separate final circuits via a distribution board or consumer unit.

A final circuit does not feed any other circuit.

A ring final circuit cannot then feed another circuit.

 

[Steve-S]

Really needs the definitions in the regs to pin it down.

 

[mainline]

Really needs the definitions in the regs to pin it down.

Yes I agree with you.

You should go and spent some time revising.

 

[Steve-S]

I have not found anything yet to counter my initial assessment. I may do, you never know.

 

[nicebutdim]

Really needs the definitions in the regs to pin it down.

The Wiring Regulations contain clear definitions for both distribution and final circuits in the section appropriately titled 'Definitions'.

I have not found anything yet to counter my initial assessment. I may do, you never know.

It's not hard to find as 'Definitions' are afforded their own section in The Wiring Regulations - 'Section 2'.

Not so much a case of not having found anything yet, but one of deliberately ignoring regulatory instruction which does exactly what you 'haven't been able to find'.

You can read and understand The Wiring Regulations or you can continue to ignore them and form more of your own mad ideas - quite frankly it makes no odds to me. At this point I'm simply looking forward to the rapidly approaching moment when these threads stop appearing on this forum.

 

[Steve-S]

Mad is creating a new circuit to take an immersion off? my oh my! Such Entrenched views.

 

[nicebutdim]

Mad is creating a new circuit to take an immersion off? my oh my! Such Entrenched views.

The IET write The Wiring Regulations - as previously suggested it would be best to take this argument up with them. So far not a single member of this forum has expressed an opinion in favour of your idea, so it's unlikely that continuing to repeat the same action will yield a different result.