Myths

[JohnW2]

This is definitely a myth

Why are you saying that your own statemeent is a myth?

 

[ebee]

^^ there are many people who say you can’t have a spur at the CU on a RFC

More nonsense

There are also people who suggest that 2,3,4 or 6 spurs on a ring final at the origin (i.e. t the "fuseway") would be dangerous.
And there are also some people who think that a spur at the origin of a ring final is OK but then if you decide to remove the ring itself from that circuit then the radial you are left with suddenly becomes dangerous.

 

[EFLImpudence]

Wasn't Murdochcat referring to a radial final circuit?

 

[SUNRAY]

Wasn't Murdochcat referring to a radial final circuit?

Does it make a difference?

 

[SUNRAY]

There are also people who suggest that 2,3,4 or 6 spurs on a ring final at the origin (i.e. t the "fuseway") would be dangerous.
And there are also some people who think that a spur at the origin of a ring final is OK but then if you decide to remove the ring itself from that circuit then the radial you are left with suddenly becomes dangerous.

It could contravene regulations

 

[JohnW2]

It could contravene regulations

If the cable is supplying, at most, one double socket, then the anomaly in the regs only exists if the CCC of the cable (as installed) is less than 26A (but not less than 20A).

In that situation, if there is not also a ring final supplied by the same OPD then upstream protection by a 32A OPD is not acceptable, because the (max) 26A downstream protection would not necessarily give adequate protection to a cable with a CCC <26A, BUT is acceptable if a ring final is also connected to the same OPD .... which is obviously a little on the daft side!

Kind Regards, John

 

[EFLImpudence]

In that situation, if there is not also a ring final supplied by the same OPD then upstream protection by a 32A OPD is not acceptable, because the (max) 26A downstream protection would not necessarily give adequate protection to a cable with a CCC <26A,

Well, no but that is a different reason. The 26A protection would not be allowed either (unless overload protection were not required).

BUT is acceptable if a ring final is also connected to the same OPD .... which is obviously a little on the daft side!

I disagree. Why is it acceptable?

You cannot have a spur supplying a double socket with a cable of less than 26A CCC (unless overload protection were not required).

 

[JohnW2]

Well, no but that is a different reason. The 26A protection would not be allowed either (unless overload protection were not required).

I don't understand what you are saying. There is no problem with a cable with CCC of 26A (or more) being protected by a 26A downstream OPD, is there?

I disagree. Why is it acceptable? You cannot have a spur supplying a double socket with a cable of less than 26A CCC (unless overload protection were not required).

We're back to a discussion we've often had. Many of us believe that 433.1.204 is saying that an unfused spur only has to have a CCC or 20A ...

Accessories to BS 1363 may be supplied through a ring final circuit, with or without unfused spurs, ....... The circuit shall be wired with ...... Such circuits are deemed to meet the requirements of Regulation 433.1.1 if the current-carrying capacity (Iz) of the cable is not less than 20 A ,,,

I take it that you are disagreeing with that belief?

Kind Regards, John

 

[EFLImpudence]

I don't understand what you are saying. There is no problem with a cable with CCC of 26A (or more) being protected by a 26A downstream OPD, is there?

I thought you said there was a problem. Apologies I must have misread it.

We're back to a discussion we've often had. Many of us believe that 433.1.204 is saying that an unfused spur only has to have a CCC or 20A ...

That's nonsense. The ring rules of 433.1.204 do not apply to the spurs.

I take it that you are disagreeing with that belief?

Yes, it is totally illogical. They are like any other radial.

 

[EFLImpudence]

Try again:

If the cable is supplying, at most, one double socket, then the anomaly in the regs only exists if the CCC of the cable (as installed) is less than 26A (but not less than 20A).

But it would not be <26A CCC to a double socket (except by mistake), would it?

In that situation, if there is not also a ring final supplied by the same OPD then upstream protection by a 32A OPD is not acceptable, because the (max) 26A downstream protection would not necessarily give adequate protection to a cable with a CCC <26A,

So that situation will never arise (except by mistake).

BUT is acceptable if a ring final is also connected to the same OPD .... which is obviously a little on the daft side!

No, it is not.

 

[Diver Fred]

Years ago I installed a shower in my first house. Had to have the 'electric board' people out to connect up the new consumer unit for the shower. When checking my work before leaving the 'technician' 'noticed' that the bathroom fan heater didn't have a separate pull cord switch by the door. He wanted to disconnect the house wiring leaving the house without power as he said; a) it's not safe with out explaining why, b) it's dangerous cause the switch is not separate to the heater (I'd connected it via an FCU outside the B/room).
Now at the time I was aware that there had been an incident due to a chain (3) of switches to a bathroom heater from the consumer unit without any obvious way of knowing when they where on or off.
After my dad had finished with him he went away rather humbled.

 

[JohnW2]

I thought you said there was a problem. Apologies I must have misread it.

Fair enough.

That's nonsense. The ring rules of 433.1.204 do not apply to the spurs. .... Yes, it is totally illogical. They are like any other radial.

I agree that it's nonsense and that the rules for spurs should be the same as for any other radsial. However, I'm not talking about 'sense' but, rather, about what the reg appears to say.

As per the pertinent bits I quoted in my previous post, it starts by saying that the reg applies to "a ring final circuit, with or without unfused spurs" and then goes on to say "... Such circuits are deemed to meet the requirements of Regulation 433.1.1 if the current-carrying capacity (Iz) of the cable is not less than 20 A ,,," ... and I so not see that, as written, those words do not mean that the 20A minimum apply to the spurs as well as the ring.

Kind Regards, John

 

[JohnW2]

Try again: .... But it would not be <26A CCC to a double socket (except by mistake), would it?

I was saying that IF the CCC of the cable were <26A (e.g. because of installation method), and if it were protected by a 32A OPD upstream and a 26A OPD downstream, that would not (in the absence of a ring) be acceptable. You appear to think that it would not be acceptable even if there were a ring.

So that situation will never arise (except by mistake).

See above.

No, it is not.

That is the discussion (about what the reg 'actually says') addressed in my previous post.

Kind Regards, John

 

[JohnW2]

.... before leaving the 'technician' 'noticed' that the bathroom fan heater didn't have a separate pull cord switch by the door. ...

I hope someone asked him "so what?"

Kind Regards, John

 

[SUNRAY]

If the cable is supplying, at most, one double socket, then the anomaly in the regs only exists if the CCC of the cable (as installed) is less than 26A (but not less than 20A).

In that situation, if there is not also a ring final supplied by the same OPD then upstream protection by a 32A OPD is not acceptable, because the (max) 26A downstream protection would not necessarily give adequate protection to a cable with a CCC <26A, BUT is acceptable if a ring final is also connected to the same OPD .... which is obviously a little on the daft side!

Kind Regards, John

Exactly