OP
Engineer54
I refuse to get involved!! lol!!! ....But please, when refering to TT systems it's ''Ra'' NOT Ze....
Discuss Very Hi ZS Reading on TT system? any advice in the Australia area at ElectriciansForums.net
ZE was 187
the system is protected by a 30ma RCD from the main house, and the new board is also protected by a 30 ma RCD.
would that be a 30mA RCD protecting the sub main and another 30mA RCD protecting the final circuits in the outbuilding i.e. 2 RCD's in series
too slow, specialist beat me
Hey: I've got to beat someone at posting at least once a year:lol:
I refuse to get involved!! lol!!! ....But please, when refering to TT systems it's ''Ra'' NOT Ze....
sorry if i read that wrong mechelec but why would 2 rcd`s in series slow the disconnection time
sorry if i read that wrong mechelec but why would 2 rcd`s in series slow the disconnection time
sorry if i read that wrong mechelec but why would 2 rcd`s in series slow the disconnection time
Ok then your maximum allowed Zs reading for each 30mA protected circuit is 1667 Ohms, problem solved in 31 posts.
Your RCD at the supply end should ideally be an 'S' type time delayed to achieve discrimination with the RCD at the remote end but I wouldn't loose sleep over that one.
So to confirm,
ZS readings of 2.6 ohms or there abouts is acceptable, providing the system and all circuits are protected by a 30ma RCD. (which they are)
??
To save me wading through all the posts, for clarity when you say 30ma RCD do you mean 1 RCD or multiple RCD's?
I refuse to get involved!! lol!!!
yeah well this one cropped up here a while back......2 RCDs..both 30mA...both in series...one feeds the house..the other the garage/outbuilding...theres a fault in the garage/outbuilding...which lets go first?...It wouldn't "slow the discrimination time? " but it would mean there was no discrimination between the RCD's and it would be pot luck which would trip first. inconvenient at best, dangerous at its worst. First one should be time delayed or S type
i got confused earlier, because a member said the my ZS reading could never be lower than my ZE...
My ZS of 2.6 etc is lower than 187 omhs.....?
It's often lower because of parallel paths from bonding conductors etc. I explained in post 4.
Your 187 Ohms is Ra NOT Ze on a TT system, this is all in the On-Site Guide that you already mentioned, PLEASE read it thoroughly, there are large gaps in your knowledge and someone could be hurt because of this!
You're scaring me Eng54. :aureola: This isn't some kinda new years resolution is it?
how about a lovely gas pipe..lol....Not really, just that there are more than enough posters on this thread already!! lol!!
Does seem strange though, that the OP is more than satisfied with his Ra of 185 ohms or whatever, ...and for his own house!! Seems he didn't even give a thought to adding a couple of rods at the workshop end, or adding on a rod, at the existing rod for the house.... Oh well, his house and his family!!! lol!!!
Not really, just that there are more than enough posters on this thread already!! lol!!
Does seem strange though, that the OP is more than satisfied with his Ra of 185 ohms or whatever, ...and for his own house!! Seems he didn't even give a thought to adding a couple of rods at the workshop end, or adding on a rod, at the existing rod for the house.... Oh well, his house and his family!!! lol!!!
how about a lovely gas pipe..lol....
Reply to Very Hi ZS Reading on TT system? any advice in the Australia area at ElectriciansForums.net
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