reusing a disused shower circuit

[Goldberg]

No. Not in those terms.

So there are no regulations which say that 6.5 ≤ 30 ≤ 47 is not OK?

No. Not in those terms.

Why don't you ask the person who wrote those words?

You're agreeing with him - why can't I ask you?

Will you please stop trying to answer a question by asking another one.

Why do you believe the converse to be true for my proposed radial with a 5A loading?

Never mind what I believe or not about other circuits.

Oh but I do mind.

Will you please tell me why 6.5 ≤ 10 ≤ 47 is OK but 6.5 ≤ 30 ≤ 47 isn't, or please tell me why you refuse to answer that question?

I'm not refusing to answer, I'm trying to get you to use your loaf.

 

[ban-all-sheds]

Kai - will you please tell me why 6.5 ≤ 10 ≤ 47 is OK but 6.5 ≤ 30 ≤ 47 isn't?

Goldberg - will you please tell me why 6.5 ≤ 10 ≤ 47 is OK but 6.5 ≤ 30 ≤ 47 isn't?

 

[ColJack]

you're talking hypotheticals Goldberg..
if you were designing a circuit from scratch then you select the nearest size breaker for the load and then the cable to suit the installation conditions..

as this is specifically about re-using an existing circuit, and the protection of the smaller loads will be done by the fuses in the spurs, then I see no reason to pull out the cable and fit smaller and a smaller breaker..

 

[Goldberg]

you're talking hypotheticals Goldberg..
if you were designing a circuit from scratch then you select the nearest size breaker for the load and then the cable to suit the installation conditions..

as this is specifically about re-using an existing circuit, and the protection of the smaller loads will be done by the fuses in the spurs, then I see no reason to pull out the cable and fit smaller and a smaller breaker..

Hello and Greetings ColJack, you seem to be a pragmatic and personable fellow.

Please note that nobody meant to suggest pulling out the cable.

Can you think of any risk that arises when using a 30A breaker/cartridge on jpbunce's radial final, that either doesn't arise, or is to any extent mitigated, when using a 10A CPD?

 

[Goldberg]

I'm not refusing to answer, I'm trying to get you to use your loaf.

Kai - will you please tell me why 6.5 ≤ 10 ≤ 47 is OK but 6.5 ≤ 30 ≤ 47 isn't?

Goldberg - will you please tell me why 6.5 ≤ 10 ≤ 47 is OK but 6.5 ≤ 30 ≤ 47 isn't?

I'm trying, but clearly I'm failing.

 

[ban-all-sheds]

Maybe you'd have more success if you answered the question instead of asking other ones.

Will you please tell me why 6.5 ≤ 10 ≤ 47 is OK but 6.5 ≤ 30 ≤ 47 isn't?

 

[ban-all-sheds]

Yes, it should be safe, provided that the existing circuit is in good condition, and there is 30mA RCD protection, note the breaker MUST be swapped to a smaller Type B one rated at 10amps.

Assuming the original circuit was correctly designed for a 30A load, you can leave as is or reduce to any fuse size lower than 30A that will carry the new load - but it does'nt make any difference.

kai had it covered, right at the very beginning.

I know that you Doughnut.

 

[holmslaw]

..

 

[ban-all-sheds]

Kai, Goldberg - you have both told the OP that he must do something which will incur extra expense.

Nobody else agrees with you.

In other words, everybody else thinks you have given bad advice.

Do either of you intend to explain to the OP or the rest of us why you said what you did?

 

[Goldberg]

Kai, Goldberg - you have both told the OP that he must do something which will incur extra expense.

That's because we prioritise safety above cost.

Nobody else agrees with you.

You're wrong.

In other words, everybody else thinks you have given bad advice.

You're wrong.

Maybe you'd have more success if you answered the question instead of asking other ones.

I'd have more success if you simply answered the questions.

1. Imagine a radial circuit with a design load of 5A - let's make it easy and say the conditions make it acceptable to use a type B 6A MCB and 1.0mm² cable.

If I then chose to use 6mm² cable, for my own secret personal private secret private reason, would you then change the CPD to a 40A MCB?

If not, then why not?

2. Which BS 7671 regulations are you using?

3. Why do you believe that a 30A CPD is ok for my proposed radial with a 5A loading?

4. Can you think of any risk that arises when using a 30A breaker/cartridge on jpbunce's radial final, that either doesn't arise, or is to any extent mitigated, when using a 10A CPD?

 

[ColJack]

as I've already said..

a NEW circuit designed and installed from scratch, then you put in the closest breaker to the design load and cable size to suit..

as this is an existing circuit that complies with reg 433.1.1, then changing the OCPD is not needed.
further, the changing of the OCPD may cause problems such as loose connections if the installer doesn't tighten them correctly.
there's also the risk involved with a DIYer changing the OCPD in the first place, messing about in a CU with live wires in there..

 

[Goldberg]

as I've already said..

a NEW circuit designed and installed from scratch, then you put in the closest breaker to the design load and cable size to suit.

So, on a new circuit with a resistive design load of 5A, if I bought a new 6A MCB thinking that I had 1.0mm cable at home, then on a Sunday evening found that I had only 6mm cable and so decided to install that instead, would you advocate returning the 6A breaker the next morning and getting a 30A one instead?

as this is an existing circuit that complies with reg 433.1.1, then changing the OCPD is not needed.

433-01-01 isn't the only relevant regulation.

further, the changing of the OCPD may cause problems such as loose connections if the installer doesn't tighten them correctly.

Fair point. He does need to be competent.

there's also the risk involved with a DIYer changing the OCPD in the first place, messing about in a CU with live wires in there..

Why would anything in the CU be live except for the phase side of the main switch(es)?

 

[ColJack]

So, on a new circuit with a resistive design load of 5A, if I bought a new 6A MCB thinking that I had 1.0mm cable at home, then on a Sunday evening found that I had only 6mm cable and so decided to install that instead, would you advocate returning the 6A breaker the next morning and getting a 30A one instead?

that's not the point and you know it..
if you got home and found that the 6A was wrongly labled and was in fact a 10A, would you take it back and change it or just install it?
or if you found that there were no free ways in the CU, but a spare 20A and you had a roll of 2.5mm in the garage, would you still go out and but a roll of 1.0mm and a 6A breaker or install a 20A radial with a 5A fuse in the FCU

433-01-01 isn't the only relevant regulation.

for a start, we don't use -01-01 any more.. that refers to a completely different reg in the 16th edition...
secondly, it's the only one in there that I see relates to the cable capacity being larger than the breaker size and the braker size being larger than the design current.... what others do you think command you to reduce the breaker size ?

Why would anything in the CU be live except for the phase side of the main switch(es)?

it wouldn't if done by the correct proceedure, but some of the older boards still have dnagerous mains connections..

 

[holmslaw]

..

 

[Goldberg]

So, on a new circuit with a resistive design load of 5A, if I bought a new 6A MCB thinking that I had 1.0mm cable at home, then on a Sunday evening found that I had only 6mm cable and so decided to install that instead, would you advocate returning the 6A breaker the next morning and getting a 30A one instead?

that's not the point and you know it.

It is the point. It's been the point for many pages and days.

if you got home and found that the 6A was wrongly labled and was in fact a 10A, would you take it back and change it or just install it?

What?

or if you found that there were no free ways in the CU, but a spare 20A and you had a roll of 2.5mm in the garage, would you still go out and but a roll of 1.0mm and a 6A breaker or install a 20A radial with a 5A fuse in the FCU

That would be extremely bad planning, but in the unlikely event of it happening, then of course I'd use a 5A fuse for a 5A design load.

for a start, we don't use -01-01 any more.. that refers to a completely different reg in the 16th edition.

Fair play. Old habits die hard.

secondly, it's the only one in there that I see relates to the cable capacity being larger than the breaker size and the braker size being larger than the design current.... what others do you think command you to reduce the breaker size ?

Cable capacity, in this instance, has nothing to do with kai's proposed reduction in MCB nominal rating.

Can you think of any risk that arises when using a 30A breaker/cartridge on jpbunce's radial final, that either doesn't arise, or is to any extent mitigated, when using a 10A CPD?