TT System??
- Thread starter leckydee
- Start date
this is the set up, also an old consumer protected by a standalone rcd, very confusing here the street supply showed 2 cables coming in then it went to 3? the 3 Browns as seen, no earth rod present as is required for a TT,well maybe back then the RCD was suffice
TT refers to the earthing type, I can't see any earthing in your pic. A TT system needs a connection with Mother Earth be it a rod or similar. I don't think it was ever acceptable to have just an RCD and no earthing.
At a guess I'd say 1990s for those MCBs
At a guess I'd say 1990s for those MCBs
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Back when that consumer unit does not look very old and looking at 1960's when we could use water pipes as earth.
It does look like TT so yes there should be an earth rod. But today the rules on RCD's have changed 2008 the date and from that point it required 30mA RCD not 100mA so likely if the CU will take RCBO's then it will need those fitting if not a new consumer unit as well as the earth rod.
It does look like TT so yes there should be an earth rod. But today the rules on RCD's have changed 2008 the date and from that point it required 30mA RCD not 100mA so likely if the CU will take RCBO's then it will need those fitting if not a new consumer unit as well as the earth rod.
so this is a TT system but no earth rod installed so a total cowboy or girl job back in the 90s, it has no earthing whatsoever even to bonding! also why the 2 connected incoming cables to N and Live but the thirds not connected just terminated at the service fuse? whats that 3rd cable a second live ?
there were 2 cables running from the street pylon to the house (i presume phase and neutral), then that ran into some partitioned external stud work and 3 cables on th either side, i could not get access to the external stud work so i guess the phase has just been split and the neutral ran solo, I'm assuming
Not really. If it had an earth rod connected, it could be a TT system. However, as has been said, TT (just like TN-S and TN-C-S) refers the the nature of the earthing system - so, if there is neither a DNO-supplied earth (TN-S or TN-CS) nor an earth rod, then it is not any of those things (TT, TN-S or TN-C-S) - it is merely "an installation with no earth at all"!
Do I see a small green wire above the CU? If so, do you have any idea where that goes?
Kind Regards, John
thanks for all your replys, the house is a friend of ours and i will have a closer inspection on that earth John. anyway a bit about myself i studied electrical installation C&G 236 pt1 quite a while ago, and worked on domestics, I've been out of the game but have decided to invest in myself and am starting a months intensive domestic installer package, that gives me part P 2393, inspection & testing 2392 and 2382 17th edition regs, a lot has changed and I've got some catching up to do but I'm enjoying the challenges. any views on a reliable multifunction tester would be appreciated, i was looking at the Kewtech KT65 or the Megger MFT1720 cheers peeps
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I had assumed with single RCD it would be 100mA specially since talking about TT with 30mA there is a problem should there be any faulty equipment working out what is faulty but that does not really cause a danger.
As to two line supplies likely had economy 7 or similar at one point.
Earth rod is likely required but would need to test I know on one job the earth rod was under the floor boards. Where earth is missing my loop impedance meter refuses to test. Oddly the RCD tester still worked. My tester will not raise an earth over 50 volts from neutral while testing so simple thing is plug in and press test button.
Clearly if fitting an earth rod you will need a tester either earth rod or loop impedance. Lack of earth is quite common considering the danger involved. With my parents the electrician connected up the telephone earth from the old days of a party line in spite of it using around 1.5mm bare copper. I have also seen where the electrician was told by DNO it would be a TN supply but on arrival the DNO gave the house a TT supply. Only when electrician returned to complete the inspection and testing did he find the error.
Mistakes do happen.
As to two line supplies likely had economy 7 or similar at one point.
Earth rod is likely required but would need to test I know on one job the earth rod was under the floor boards. Where earth is missing my loop impedance meter refuses to test. Oddly the RCD tester still worked. My tester will not raise an earth over 50 volts from neutral while testing so simple thing is plug in and press test button.
Clearly if fitting an earth rod you will need a tester either earth rod or loop impedance. Lack of earth is quite common considering the danger involved. With my parents the electrician connected up the telephone earth from the old days of a party line in spite of it using around 1.5mm bare copper. I have also seen where the electrician was told by DNO it would be a TN supply but on arrival the DNO gave the house a TT supply. Only when electrician returned to complete the inspection and testing did he find the error.
Mistakes do happen.
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