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pablo4321

Hi went to a job yesterday there was 3 ring mains so i thought, after testing them they were radials but were all terminated into 32 a mcbs 2 wire in them did R1 R2 TESTS and readings were high 3.2 ohms/ 1.9ohms these were the highest there are a further 4 radials which are around the 1.9 the house is a barn conversion
so the runs are quite long the system is TT and the zs is around 70 ohms on most sockets will this be acceptable not quite sure what to do here, just need some advice please.
 
Hi went to a job yesterday there was 3 ring mains so i thought, after testing them they were radials but were all terminated into 32 a mcbs 2 wire in them Presumably 6 radials then..?did R1 R2 TESTS and readings were high 3.2 ohms/ 1.9ohms these were the highest there are a further 4 radials which are around the 1.9 the house is a barn conversion....if they are wired in 2.5 then thet would need to be on 20 OCPD's
so the runs are quite long the system is TT and the zs is around 70 ohms on most sockets will this be acceptable not quite sure what to do here, just need some advice please.70 ohms on a TT is acceptable as long as there is RCD protection in place to provide earth fault protection

I have to ask the reasons for testing...is it an EICR or is work being carried out?.....If these really are long 2.5mm radials on 32a mcb's it would suggest 'builder wired' and there are lkely to be a shedload of other issues as well.
 
It is work carried out, im pretty sure the builder has done it ITS ONLY 7 YEARS OLD AND SHE SAID THERE IS OTHER THINGS NOT WORKING TOO. i have put them on 16 amp mcbs but the cables are pretty long by the R1 R2 readings DONE ZS READINGS WHICH ARE 70 OHMS NOT SURE WHERE TO GO FROM HERE
 
It is work carried out, im pretty sure the builder has done it ITS ONLY 7 YEARS OLD AND SHE SAID THERE IS OTHER THINGS NOT WORKING TOO. i have put them on 16 amp mcbs but the cables are pretty long by the R1 R2 readings DONE ZS READINGS WHICH ARE 70 OHMS NOT SURE WHERE TO GO FROM HERE

A full EICR is where to go by the sound of it.
 
The sizing of the MCB's are clearly incorrect, however, the Zs values are ok as long as you have 30mA RCD protection as required. Firstly because you have exceeded the 1.4 ohm tolerance of the device and secondly because they are more than likely useable for external applications by unskilled persons. With a 20a radial you have an allowance of 50m2 floor area. Table 7.1 in the O.S.G fails to include max lengths for a T.T set up.
 
Hi went to a job yesterday there was 3 ring mains so i thought, after testing them they were radials but were all terminated into 32 a mcbs 2 wire in them did R1 R2 TESTS and readings were high 3.2 ohms/ 1.9ohms these were the highest there are a further 4 radials which are around the 1.9 the house is a barn conversion
so the runs are quite long the system is TT and the zs is around 70 ohms on most sockets will this be acceptable not quite sure what to do here, just need some advice please.

When you say 'terminated into 32 a mcbs 2 wire in them' are you saying that 2 of the 3 circuits have been terminated into 1 MCB? It also sounds like you're saying that you have 2 X 32A MCBs that each have 2 wires terminated into them. As 3 circuits would only obviously have 3 line conductors, what is also going into the 2nd MCB?
 
sounds to me as if they originally made a ring and somebody has been a tampering!! Have you dropped any points to see if you have cables cut or sealed off behind or possibly even open line conductors. This would send your Zs values soaring.
 
When you say 'terminated into 32 a mcbs 2 wire in them' are you saying that 2 of the 3 circuits have been terminated into 1 MCB? It also sounds like you're saying that you have 2 X 32A MCBs that each have 2 wires terminated into them. As 3 circuits would only obviously have 3 line conductors, what is also going into the 2nd MCB?
sorry meant to say all 3 circuits were wired up as ring mains but when tested end to end there was no continuity on any of them so i have seperated them and put them in 16 amp mcbs

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surely this canot happen on all 3 circuits
 
Did you do any investigation work on the sockets or was it a case of check end to end no ring so whack 16's job done?
 
Definitely sounds like some playing about has happened here. Make sure you don't end up with 2 devices switching on the same wiring. Did you check if you had end to end across 2 devices with them both off. Could be you have the wiring mixed up and do actually have rings.
 
My regs book is in my van, so can't check the details, but with R1R2 readings that high I would assume bad connections all round, seeing as it is pretty certain that its builder wired. Someone on here will be able to tell you the expected resistance per meter of 2.5 t&e.
the Zs readings are acceptable as long as you have 30mA protection on the circuits, provided that your earth electrode is within tolerances, and not relying on main bonding to bring the Zs down.
I would suggest to the customer a full EICR with 100% of the accessories checked, and explain everything to them, verbally and in writing.would be good to hear what you find
 
no i checked all six lives for continuity and same for others neut and earth

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cant get to wires above as barn conversion no loft
 
Forget the length theory. This is clouding your judgement mate. Go and do some socket investigation. If they are genuine radials then split them onto separate 20a and make sure you dont exceed the floor area limits. Also assess what sort of loads these radials will serve. You may need to run some legs and convert into rings if the demand is questionable or if you do not have the C.U space to accommodate so many radials.
 
Could there be a section where the rings have not been connected and plastered over? Do they still have a copy of any drawings if its 7 months old
 

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