Are these reading within Regs?

[jamesjay]

Good afternoon All,

I was hoping to get some advice regarding a 2 up 2 down property was partly rewired about 8 years ago by the previous owner, the downstairs wiring and all sockets were done, although the CU was not changed there is an old Wylex with MCB's in.

The is an earth bond on the incoming gas supply which is also bonded to the water mains and then to the CU and lastly to the suppliers fuse. Using a calibrated Robin 4120DL set on the loop impedance function I have taken reading at all sockets and they are between 0.22 ohms and 0.38 on the 20ohm range.

Are these acceptable readings and within regulations or do I need to do other tests?

kind regards
James.

 

[PrenticeBoyofDerry]

Firstly I would confirm continuity of bonding to water and gas pipes back to the MET. Take this from the copper pipework (not the earth clamp or cable end) at the last connection of the bonding back to MET your are looking for less than 0.05ohms.
You also want Ze readings and r1+r2 readings.
The Zs conformity would depend on your breaker type and rating.
If a standard ring on 32A Type B (BSEN60898), then your looking at less than 1.44ohms with a 0.80 correction factor, so no greater than 1.15 ohms.
Lower rated type B breakers will allow for a greater Zs.

 

[Spark123]

What is the reason for your testing?

 

[jamesjay]

Thanks for the quick replies.

@PrenticeBoyofDerry

The sockets are on a 16Amp type B and yes on them there is BSEN60898.
You got me on the "You also want Ze readings and r1+r2 readings. The Zs conformity would depend on your breaker type and rating" I just had the meter at home and decided to connect it to my sockets and wondered whether the readings were significant in indicating the general condition of the wiring or not.

@Spark123

There is no reason for testing I have had no tripping or other faults, I bought a couple of second hand meters for a relation that is soon starting to train as a spark, and I got him these thinking they would help him to get used to testing stuff, after I had them calibrated I just thought I would test them on my house sockets to see what reading I got.

Thanks again lads,
James.

 

[PrenticeBoyofDerry]

The sockets are on a 16Amp type B and yes on them there is BSEN60898.
You got me on the "You also want Ze readings and r1+r2 readings. The Zs conformity would depend on your breaker type and rating" I just had the meter at home and decided to connect it to my sockets and wondered whether the readings were significant in indicating the general condition of the wiring or not.

The Zs of 16A Type B is 2.87x0.8= 2.39Ω the Zs measured should be less than this total.
The Ze is the earth-fault loop impedance external to the installation
r1+r2 is the connected measurement of the live/phase and CPC(earth) of a circuit at it's extreme point.
These two together will give you the calculated Zs of the circuit. Ze+(r1+r2)=Zs
With regards to the condition of the installation, there is quite a lot more to it than that, the Zs confirms that you protective device will operate in it's required disconnection time.
Zs tables (don't forget 0.8 correction factor)

@Spark123
There is no reason for testing I have had no tripping or other faults, I bought a couple of second hand meters for a relation that is soon starting to train as a spark, and I got him these thinking they would help him to get used to testing stuff, after I had them calibrated I just thought I would test them on my house sockets to see what reading I got.

Link below regarding testing procedures, if you browse through them, you will find a lot of valuable information regarding inspection and testing.
http://www.tlc-direct.co.uk/Book/8.6.2.htm

 

[Spark123]

Thanks for the quick replies.

@PrenticeBoyofDerry

The sockets are on a 16Amp type B and yes on them there is BSEN60898.
You got me on the "You also want Ze readings and r1+r2 readings. The Zs conformity would depend on your breaker type and rating" I just had the meter at home and decided to connect it to my sockets and wondered whether the readings were significant in indicating the general condition of the wiring or not.

@Spark123

There is no reason for testing I have had no tripping or other faults, I bought a couple of second hand meters for a relation that is soon starting to train as a spark, and I got him these thinking they would help him to get used to testing stuff, after I had them calibrated I just thought I would test them on my house sockets to see what reading I got.

Thanks again lads,
James.

Those readings are more to do with wether or not your MCB will trip within the specified time, there are more tests which are usually carried out first using different testers such as a low resistance ohm meter, Insulation resistance tester, voltage tester, then EFLI, followed by PFC and RCD testing where applicable.