B6 circuit breaker

[endecotp]

Surely you would agree a commando socket is safer.

No.

 

[Harry Bloomfield]

The RCDs fitted on hot tubs are often 10mA trip, i.e. 3 times as sensitive as ones in your CU. There is a reason for this - your safety. It should not have been removed.

I cannot see any regulation which requires an RCD as sensitive as 10mA for a hot tub, but if the one removed was more sensitive than the 30mA at the mains - then its removal was wrong. 30mA provides very little if any protection for a sopping wet body, in a sopping wet environment - 12mA is enough to kill. Having been in such a situation due to faulty equipment and another's stupidity, I can assure you it is not fun being in contact with live parts whilst sopping wet.

A further risk, is that someone might possibly decide to use that portable hot tub at a location where there is a socket not protected by any RCD. Yes I know the OP said it is now fitted with a commando plug, but plugs can be changed.

I must agree with the OP though, that a 16amp commando plug and socket is much more suitable for an outdoor environment - especially so if the load is close to the 13amp limit of a 13amp plug.

 

[JohnW2]

I cannot see any regulation which requires an RCD as sensitive as 10mA for a hot tub, but if the one removed was more sensitive than the 30mA at the mains - then its removal was wrong. 30mA provides very little if any protection for a sopping wet body, in a sopping wet environment - 12mA is enough to kill.

You appear to be making the common mistake oof assuming (incorrectly) that an RCD can limit the current that flows through a human body receiving an electric shock.

Yes, 12mA (and less, in certain circumstances) can kill, but the current which flows through a person receiving a shock is determined solely by the voltage and their 'body resistance'- and will almost inevitably be considerably more than 30mA in the case of "a sopping wet body, in a sopping wet environment". If a person in such an environment receives a full blown L-E shock, then a 30mA RCD will almost certainly trip, and there is little/no reason to believe that a 10mA one would trip when a 30mA one didn't.

A 10mA one would trip when a 30mA one didn't only if there were not only contact with something 'live' (and earth) but also a 'relatively high' impedance in the fault path external to the person's body (reducing the current to something between 10 and 30 mA) - but that is an extremely improbable situation.

All an RCD can do is reduce the duration (not magnitude) of the current flowing through a person and (although I may be wrong), I am not aware of 10mA ones being able to operate any more quickly (with the same 'residual current') than a 30mA one.

Kind Regards, John

 

[Harry Bloomfield]

All an RCD can do is reduce the duration (not magnitude) of the current flowing through a person and (although I may be wrong), I am not aware of 10mA ones being able to operate any more quickly (with the same 'residual current') than a 30mA one.

So, would a 10mA one offer better protection in the circumstances, than a 30mA RCD?

 

[JohnW2]

So, would a 10mA one offer better protection in the circumstances, than a 30mA RCD?

As I said (and you quoted), in the the scenario you described, I very much doubt it, since I doubt that, in the face of a current through the victim which was considerably greater than 30mA, a 30mA one would trip appreciably less rapidly than a 10mA one - but, as I said, I'm not certain about the characteristics of these devices.

To be frank, in the case of "a sopping wet body, in a sopping wet environment", it would not surprise me at all if even a 100mA one would trip almost as fast (hence providing 'as much protection') as a 10mA one - but, again, I am not certain of the operating characteristics.

In fact, if a 10mA one ever did offer 'more protection', it would be likely to be in the opposite situation to that which you describe. If someone had extremely dry skin, and particularly if they had 'very thick skin', it's just possible (but, I suspect, very unlikley) that the current through them would be less than 30mA, but more than 10mA - in which case the 10mA one would trip, but the 30ma one would not.

However, returning to the main point, whether the IΔn of the device is 10mA, 30mA or 100mA, it can only (if tripped) limit the duration of the shock, not the current through the person for the duration of the shock (which will be the same in all cases).

Kind Regards, John

 

[chivers67]

The DB2 inside the Garage will need relabeling as instead of all circuits being NON RCD protected they are actually ALL RCD protected albeit from the one RCD inside the house. Be a right pain if you were using the Garage equipment and it tripped the RCD or you were inside the HOT Tab and it tripped and got reset in the house by someone!

I'd much rather that was on it's own RCBO or all the circuits in the garage were on a separate RCD.

 

[JohnW2]

I'd much rather that was on it's own RCBO or all the circuits in the garage were on a separate RCD.

Yes, that would certainly be preferable. It would require either a new busbar or a wire link, but the house CU could presumably be adapted by moving the garage circuit from the B16 MCB on the RCD side to a 16A RCBO on the non-RCD side.

Kind Regards, John