is there really any point in rcds

[calum63]

Hi, My biggest concern about rcds is if you were to receive an electric shock between live to neutral which is quite easy to achieve when you are removing a socket or a ceiling rose you would very likely be electrocuted as there will be no imbalance and it will just think you are a normal load. If you were to grab live and earth I still think you be electrocuted as the shock would be massive, the only situation I think an rcd could possibly save you is if you only had hold of the live wire only and not working at height but even then I still think it is a hit or miss whether the rcd would operate and it has been know for people to die of currents a lot less than 30ma. Lets say you were working at height and you grabbed hold of a live wire on an rcd protected circuit, how would the rcd save you in that scenario? As I am sure you know the rcd does not stop you feeling the shock and it does not limit the current that flows through your body that is determined by your body resistance, in either case whether the circuit is rcd protected or not you are likely going to fall off the ladder and break your neck, so how has the rcd saved you? Its not a safety blanket that will catch you when you fall.

Now obviously you are thinking turn the power off and check, but circuits can also be incorrectly labelled and I am sure there are a lot of people who don't follow the safe isolation procedure.

 

[bernardgreen]

and it does not limit the current that flows through your body

But it can limit the time the current flows through the body. The longer the current flows the more irreversible damage is caused to the body. After a short shock that stops the heart the heart will invariable recover and start beating. That is how a de-fribrillator works. The shock from the de-frib stuns the heart to stop the fribillation and then the heart auto restarts in a normal rythym.

Cutting the power reduces the risks of harm to those going to the aid of the person who has had an electric shock.

A Live to Ground fault current can be large enough to create enough heat to ignite materials but not large enough current to trip the MCB ( or fuse wire ). An RCD will trop before the material can ignite.

 

[AndyPRK]

RCD's aren't designed to mitigate against people working on wiring and forgetting to isolate things correctly! (or test for dead).

They are to protect the installation and home owner going about their normal routine

 

[boringoldcodger]

I had assumed that, whatever the original intention was, in practice RCDs force us to correct minor (if there is such a thing) or intermittent faults before they have a chance to cause real danger.

 

[333rocky333]

I had assumed that, whatever the original intention was, in practice RCDs force us to correct minor (if there is such a thing) or intermittent faults before they have a chance to cause real danger.

Throughout the regs books, Rcd's are often required for what they call ADDITIONAL PROTECTION, this includes reducing a fire risk , as you say it will turn the circuit off before possibly a fire starts, leaving you no option to trace and resolve the problem.

 

[ban-all-sheds]

I am sure there are a lot of people who don't follow the safe isolation procedure.

There are a lot of people who don't follow the safe road crossing procedure.

Should we be questioning the point in zebra and pelican crossings?

 

[aptsys]

Hi, My biggest concern about rcds is if you were to receive an electric shock between live to neutral which is quite easy to achieve when you are removing a socket or a ceiling rose you would very likely be electrocuted as there will be no imbalance and it will just think you are a normal load.

If you only touched the line conductor, would you not receive a shock?

 

[DetlefSchmitz]

If you only touched the line conductor, would you not receive a shock?

Huh? How?

 

[aptsys]

Huh? How?

Assuming you're not standing on fibreglass ladders, there is a measurable impedance to mains earth through most structures.

 

[bernardgreen]

Huh? How?

In the same way that birds can perch on 11kV over head cables.

 

[ban-all-sheds]

Assuming you're not standing on fibreglass ladders, there is a measurable impedance to mains earth through most structures.

Even if there is, you're not touching any other structures:

If you only touched the line conductor, would you not receive a shock?