Automatic disconnection of supply

[Risteard]

How about electrical separation can this afford basic protection

Electrical separation is in no way comparable to an RCD. This gives us two phase conductors with no neutral or Earth reference.

 

[Risteard]

Don't get me wrong I totally understand the principle I'm simply pointing out the ambiguity of the regs

But I don't accept that it is in any way ambiguous. That's why I am asking where precisely you believe that the Regulation in question supports your claim.

 

[Deleted member 26818]

Since when did an RCD limit the current to a non hazardous level?

 

[rich3009]

By time limited fault duration

 

[Risteard]

By time limited fault duration

Limiting the time isn't the same as limiting the current, though, which is what the Regulation stipulates.

 

[Deleted member 26818]

It also won’t limit anything in a short circuit situation.

 

[Wilko]

The title of reg 131.2.1 is : Basic protection (protection against direct contact)
I know I'm simple, but I don't need to think much beyond that do I?

 

[rich3009]

But it states you can achieve it by reducing the current to a non hazardous level I would like to know how, and if an RCD can't do it what can

 

[rich3009]

Why is an RCD designed to detect 30mA there is a reason, because fault currents start at zero and climb in a time curve. And at 30mA we want it off and quick

 

[Risteard]

fault currents start at zero and climb in a time curve

No they don't. Ohm's Law is what you need.

The thermal effects of the fault increase - the fault current is simply a product of the voltage and impedance.

 

[rich3009]

Why do we have a 30ma RCD if the result is a pass through of a massive current, it would make a mockery of it

 

[Amp David]

I know it's not true but based on that reg alone it states :

Basic Protection
Persons and livestock shall be protected against dangers that may arise from contact with live parts of the installation.

This protection can be achieved by one of the following methods:

1. Preventing a current passing through the body of any person or any livestock
2. Limiting the current which can pass through a body to a non-hazardous valve

Now taking that to the letter without referring to any other regulation an RCD does exactly that, this is a very poorly written regulation and would afford you great defence in court.

What would your rcd do if you decided to prod at line and neutral?

 

[Amp David]

I know it's not true but based on that reg alone it states :

Basic Protection
Persons and livestock shall be protected against dangers that may arise from contact with live parts of the installation.

This protection can be achieved by one of the following methods:

1. Preventing a current passing through the body of any person or any livestock
2. Limiting the current which can pass through a body to a non-hazardous valve

Now taking that to the letter without referring to any other regulation an RCD does exactly that, this is a very poorly written regulation and would afford you great defence in court.

What would your rcd do if you decided to prod at line and neutral?

 

[Amp David]

I know it's not true but based on that reg alone it states :

Basic Protection
Persons and livestock shall be protected against dangers that may arise from contact with live parts of the installation.

This protection can be achieved by one of the following methods:

1. Preventing a current passing through the body of any person or any livestock
2. Limiting the current which can pass through a body to a non-hazardous valve

Now taking that to the letter without referring to any other regulation an RCD does exactly that, this is a very poorly written regulation and would afford you great defence in court.

What would your rcd do if you decided to prod at line and neutral?

 

[rich3009]

Depends if you got any leakage to earth, failing that it would do nothing

 

[Risteard]

Why do we have a 30ma RCD if the result is a pass through of a massive current, it would make a mockery of it

It means that it will operate if there is a nominal 30mA earth fault current through it (between 0.5 and 1 times this in reality). So if you were in contact with a phase conductor and 30mA passed through your body it should operate. The 30mA rating has nothing to do with limiting the fault current to 30mA as this would defy Ohm's Law.

 

[Amp David]

Depends if you got any leakage to earth, failing that it would do nothing

Ok lets for the sake of this stupid thread lets presume theres no leakage, except in his y fronts

 

[rich3009]

I see so what's the point of that level, 30mA

 

[rich3009]

Ok lets for the sake of this stupid thread lets presume theres no leakage, except in his y fronts

Fair point no protection

 

[Risteard]

I see so what's the point of that level, 30mA

To protect human life.

It's not about limiting the current to 30mA but ensuring that it operates if 30mA is passing through - well actually 150mA for additional protection to operate within 40mS.