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jeremy · 10-06-2008

Tr25 you say he has done his 17th, 17TH what ??Joint before Breakfast!! (and I'm not talking crimped)Anything without an earth return becomes a special location that is not allowed under normal circumstances, ie domestic installations

ThrownRazor25 · 10-06-2008

Listen mate im on your side lol.Hes a wee know it all twat who has done a 17th course and is spouting out all this crap all the time.trouble is he is so sincere about it half the guys at work are starting to believe him.He is adamant the new regs say that if the board is protected by an rcd or if individual circuits all have rcbos then there is no need for an earth because the rcd/rcbo will operate on the imbalance of live and neutral.

Shakey · 10-06-2008

Quote:

Originally Posted by ThrownRazor25

Listen mate im on your side lol.Hes a wee know it all twat who has done a 17th course and is spouting out all this crap all the time.trouble is he is so sincere about it half the guys at work are starting to believe him.He is adamant the new regs say that if the board is protected by an rcd or if individual circuits all have rcbos then there is no need for an earth because the rcd/rcbo will operate on the imbalance of live and neutral.

ok, I have explained how an RCD COULD work without an incoming earth with an extraneous path of 7666 ohms or less (but probably not in the required time), but that is an accidental by-product of there being no earth in the first place

How the hell does this guy think ADS will be achieved

I teach 17th edition, and this guy is talking utter tosh

he has no doubt misenterpreted something he was told on the course

along the lines of RCD protected circuits only needing a Zs of 1667 ohms or less for their 60898 MCB's etc etc

If you want to 'douse his flames' a little, ask him for the relevant regs numbers to back up his 'theories'

Moog · 11-06-2008

Quote:

Originally Posted by LScotty

correct me if i am wrong here, but its not that they detect the earth leakage persay, but of an imbalance of the neutral and line, due to current flowing via earth... ?

Luke

I agree it will trip if the phase and neutral currents are not the same, however I would not sign off an installation without an adequate earth path unless it was SELV for instance You sure this guy isn't on about bonding? not done my 17th conversion yet but there was take about there not being a requirement for bonding in bathrooms anymore

Shakey · 11-06-2008

Quote:

Originally Posted by Moog

I agree it will trip if the phase and neutral currents are not the same, however I would not sign off an installation without an adequate earth path unless it was SELV for instance You sure this guy isn't on about bonding? not done my 17th conversion yet but there was take about there not being a requirement for bonding in bathrooms anymore

bit more complicated than that Moog, for bathrooms, but yeah, if all conditions are met, then no supplementary

WarrenG · 11-06-2008

O.K. it seems that there is some agreement on the workings of an RCD on this post.

An RCD protects by constantly monitoring the current flowing in the live and neutral wires supplying a circuit or an individual item of equipment.

The supply and the load are both connected to EARTH

Under normal circumstances, the current flowing in the two wires is equal. When an earth leakage occurs due to a fault in the circuit or an accident with the equipment, an imbalance occurs and this is detected by the RCD, which automatically cuts off the power before injury or damage can result.

If there is an imbalance in a circuit protected by the RCD, the leakage current has got to be going somewhere. If there is no earth path to take the current to earth, what is going to take it there? a person who recieves a shock from live metal work?

I think your friend should study the 16th Edition before trying the 17th Edition.

Shakey · 12-06-2008

Like I said Warren, there may be an 'accidental' earth path through any extraneous paths, which, if 7666 ohms or less, would still allow the RCD to trip, but it is most defintely NOT in the 17th that you dont need an inscoming earth because of it

Had8Lives · 14-06-2008

I think your mate is confusing a Main supply earth and equipotential bonding. The 17th does not require you to install equipotential bonding to pipes such as a bath room basin as long as the circuits in the bathroom are protected by an RCD. Every installation must have a main earth.

Sorry, meant supplimentary bonding not equipotential.

wattsup · 26-06-2008

Perhaps it's a double insulated house

alancp · 2 Weeks Ago

shakey, i understand about the 1667 ohms bit, but, shouldnt it be lower than that (exact figure not known at mo) to do away with an unreliable earth path??