Sanity Check Required - Do I really need 3 Phase Upgrade?

[JohnW2]

In the case of a socket circuit, it is difficult to allow for all scenarios when designing a circuit. Therefore I feel there is always a possibility of end users overloading a socket circuit.

Indeed. As I'm always saying, 'proper design' of a sockets circuit is simply not possible, since it requires a crystal ball.

But, and I think this is where we differ, I feel that if you think like that, you would never install a 20A socket circuit.

I must say that I often tend to think like that - unless the location is such that only very light loading is likely. I have no problem with 32A radials, but 20A is less than "two plugs full", and if there are multiple sockets on the circuit, I would often find it impossible to feel confident that a load >20A was 'unlikely'. I do have some 20A sockets circuits, but they are 'intended for' (and only 'likely' to be used for small loads (e.g. multiple electronic devices).

If I can attempt to 'referee' a bit, I think that's what, in practice, it's about - what a designer 'considers likely'. Agreeing, as above, that a designer can never know for certain how a sockets circuit is to be used, if, for whatever reason, a designer feels it 'likely' that the circuit will sometimes be asked to supply a current >20A (26A or whatever) then (s)he should not really design it as a "20A circuit", with a 20A OPD.

Kind Regards, John

 

[securespark]

Is that blue phase repurposed as a neutral?

Is it fused?

 

[RF Lighting]

The central part of the cutout is the neutral with a solid copper link, and the red and blue fuses are both phase conductors.

 

[PBC_1966]

And originally they weren't phases, but d.c. poles - Positive outer on red, negative outer on blue, neutral in the middle

 

[securespark]

RF, sorry matey....I wasn't looking properly at the white holder: I thought it just had a fuseholder removed...

 

[Iggifer]

If I can attempt to 'referee' a bit, I think that's what, in practice, it's about - what a designer 'considers likely'. Agreeing, as above, that a designer can never know for certain how a sockets circuit is to be used, if, for whatever reason, a designer feels it 'likely' that the circuit will sometimes be asked to supply a current >20A (26A or whatever) then (s)he should not really design it as a "20A circuit", with a 20A OPD.

Job we're on at the moment, victorian HMO, 4 beds. Looks like it's going to be 2 x 20a radials, covering 2 bedrooms each and then a 32a ring covering the kitchen.

I have no doubt that they'll never approach 20a on those two radials, they have the gas CH on 24/7 as it's bills in.

Plus the house currently has one 32a ring and one 6a lighting circuit. On what appears to be 10mm tails (into a new board! - dog rough).

Wouldn't put a 20a radial in a kitchen though.

 

[JohnW2]

I have no doubt that they'll never approach 20a on those two radials ...

Fair enough, then - as I said, if a designer believes that, then fine. It's the best onbe can do without a crystal ball.

Wouldn't put a 20a radial in a kitchen though.

Same here, and probably not in a living area or any other 'work' area.

Kind Regards, John

 

[PBC_1966]

As I'm always saying, 'proper design' of a sockets circuit is simply not possible, since it requires a crystal ball.

The only way to be absolutely certain would be to put no more than one single 13A socket on a 15 or 16A circuit and no more than two singles or one double on a 30 or 32A circuit! (Notwithstanding the arguments about whether a double can take 26A etc.).

Similar crystal-ball gazing would be needed here in the U.S. to be certain as well, of course. General-purpose oultets around the house are rated for 15A and connected on 15 or 20A branch circuits, but code minimum requirement is only to provide for a loading of 3 watts per square foot, no matter how many receptacles are on the circuit. So a 15A circuit can supply up to 600 sq. ft. in living and bedroom areas, although there's long been a recommendation to limit it to less. But in theory, you could wire, say, three bedrooms all on a single 15A circuit. In a house with central heating/cooling that may well be adequate most of the time, but obviously could start to cause problems if, for example, the heating fails and people want to start using multiple portable heaters in the bedrooms at night. (I'm also told by those with two or more teenage daughters that even having two bedrooms on the same 15A circuit can cause problems when both decide to use simultaneously the ridiculously high-powered hair dryers which are around these days.) For my money, restricting a 15A circuit to one room (plus oddments like hallway lights & receptacles) is far more sensible.

 

[JohnW2]

As I'm always saying, 'proper design' of a sockets circuit is simply not possible, since it requires a crystal ball.

The only way to be absolutely certain would be to put no more than one single 13A socket on a 15 or 16A circuit and no more than two singles or one double on a 30 or 32A circuit!

Exactly.

(Notwithstanding the arguments about whether a double can take 26A etc.).

Well, talking about three singles, or one double and one single (which is far less than most circuits have) - since no-one could then argue that it didn't represent a potential load of more than 30/32A!

Kind Regards, John

 

[ban-all-sheds]

I feel that if you think like that

Do I?

Are you still not able to find the post where I didn't say what you are insisting I did?

 

[ban-all-sheds]

if, for whatever reason, a designer feels it 'likely' that the circuit will sometimes be asked to supply a current >20A (26A or whatever) then (s)he should not really design it as a "20A circuit", with a 20A OPD.

That's what I said.

But it seems to have upset secure so much that he thinks pursuing me over it from one topic to another is the right thing to do,as was "having a dig" at me by saying "don't tell Ban that we're advising putting a 100A+ load onto a 100A fuse" even though he agreed 100% that that was not the advice being given.

 

[ban-all-sheds]

Wouldn't put a 20a radial in a kitchen though.

Same here, and probably not in a living area or any other 'work' area.

What about multiple ones?

 

[JohnW2]

Time to put it to bed, IMO.

Kind Regards, John

 

[JohnW2]

Wouldn't put a 20a radial in a kitchen though.

Same here, and probably not in a living area or any other 'work' area.

What about multiple ones?

Only if it were possible for me to arrange the multiple circuits in such a manner that I was confident that it was unlikley that none of them would be loaded to >20A and/or the sockets were for the use of people who understood the arrangement of circuits and the need to avoid loading any of them to >20A. In practice, I would probably rarely be comfortable unless I was the person using the sockets!

Kind Regards, John

 

[ban-all-sheds]

So, you would be unhappy with a number of 20A radials serving only sockets at the backs of worktops, knowing that it was vanishingly improbable that they'd be used for anything other than mixers/blenders/kettles/toasters/chargers/etc?