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Discuss Suitability of circuit accessories. in the Commercial Electrical Advice area at ElectriciansForums.net

Julie.

Arms
Advent Win
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That's about protective devices, it certainly doesn't refer to selection of under rated accessories?

I think you need to take a break and cool off.

Just relax and re-read what you have said and the responses, then think about it, it appears like you are reacting rather than analysing.
 
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  • Thread Starter Thread Starter
  • #17
Since the advent of plastic, self extinguishing, isolators / accessories, Yes, many times.
Moreso on circuits with a protective device that matches the Isolator rating, or even less, than those where it didn't.

You've reported your concerns, they've been dismissed, that's it as far as you're concerned.
Having re-read your post I understand what you're saying about reporting my concerns & I apologize unequivocally for my somewhat surly reaction. :)
 
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Julie.

Arms
Advent Win
That's funny, I just haven't seen anyone post anything that makes sense, you were doing ok though Julie until you quoted a completely irrelevant regulation.

Ok, let's try this

You have a cable capable of 20A on a 10A load

If I fit a 40A MCB, is the cable undersized, or is the MCB over sized?

If you say it's the MCB that's too large then 432.3 would be appropiate

The standards always work from one direction only.

They don't put the point in both directions

There isn't "1.2.3.4 :equipment must be suitable for the Voltage of the system" followed by the opposite viewpoint "1.2.3.5 : A Voltage unsuitable for the equipment must not be used"

It is necessary only to confirm one point of view.
 
  • Thread Starter Thread Starter
  • #19
Ok, let's try this

You have a cable capable of 20A on a 10A load

If I fit a 40A MCB, is the cable undersized, or is the MCB over sized?

If you say it's the MCB that's too large then 432.3 would be appropiate

The standards always work from one direction only.

They don't put the point in both directions

There isn't "1.2.3.4 :equipment must be suitable for the Voltage of the system" followed by the opposite viewpoint "1.2.3.5 : A Voltage unsuitable for the equipment must not be used"

It is necessary only to confirm one point of view.
You've lost me...
 

Julie.

Arms
Advent Win
You've lost me...
Your thought, that the isolator is undersized @ 20A, is based on the fact that the protection is 32A

This is EXACTLY the same as saying the protection @32A is oversized as the isolator is only 20A

The regs only need to cover one point of view as the other is automatically covered!
 

David Prosser

-
Arms
Esteemed
IEC standard 60947-3 (same BSEN number) which covers switch disconnectors or isolators will tell you that they must be designed to withstand fault currents flowing through them until the protective device operates.

From what you have discribed there is no problem with the way the circuit has been installed.
 
  • Thread Starter Thread Starter
  • #22
Your thought, that the isolator is undersized @ 20A, is based on the fact that the protection is 32A

This is EXACTLY the same as saying the protection @32A is oversized as the isolator is only 20A

The regs only need to cover one point of view as the other is automatically covered!
Not really, the circuit supplies 2 split units each drawing around 12A so it has been designed as a 32A cct for that reason. I see what you're getting at but this has been designed as a 32A cct & is wired in 4mm singles. The isolators that have been fitted are there because of the availability of the correct parts in the location I'm in.
 

Julie.

Arms
Advent Win
Not really, the circuit supplies 2 split units each drawing around 12A so it has been designed as a 32A cct for that reason. I see what you're getting at but this has been designed as a 32A cct & is wired in 4mm singles. The isolators that have been fitted are there because of the availability of the correct parts in the location I'm in.
OK, but your view is that the isolators are undersized @20A, based on the protection device of 32A. This is exactly the same as the protection device is oversized @ 32A compared to the 20A isolators as far as the regs are concerned; 432.3 details why this situation is permissible.

As long as it's a fixed load and it has fault protection, it is compliant

If these same isolators supplied multiple outlets, then it's not a fixed load and your point would be valid as someone could just plug in more loads resulting in overloaded isolators.
 

Strima

-
Arms
Esteemed
The what about 20AX switches on a ring final circuit with a 32 amp protective device? Millions of homes in the UK have this set up with no adverse effects.
 
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