EICR Limitation - no L to N IR Test

[smity]

Alrite lads,

i am am currently buying a house and as part of the valuation report they wanted a EICR doing as the electrics are clearly old.

So the owner employed a company to do the report and I have been passed on a copy. Now i I don't do EICR's but one of the limitations sounded strange to me and they haven't given a reason.

The limitation is - no L to N IR test

Why are your thoughts on this? Seems abit of a cop out to me, is this an acceptable limitation especially with no reason on the document? Iam not too bothered as I will be rewiring at some stage and putting a split board in straight away so will end up having it tested but seemed strange.

cheers

 

[Engineer54]

Could you please explain how to do a live Zs test 'correctly' when there is an RCD present?
I have to explain????

The only accurate test is an high current test, which would have to bypass the RCD. With terminals and CUs so small in domestic environments, it is not practical, or advisable, to bypass the RCD during a Periodic I&T.
That's a typical modern day response. And why is it not advisable??
Again, I come back to the UK Regs. They clearly state that a live Zs is not mandatory, so long as other tests have been done beforehand.
How accurate are your calculated values going to be then??
Look if it's unavoidable, fine calculate, if it just means a little disconnecting, then get on and conduct correct Zs/ELI testing

Exactly, .... i rest my case!! You stick to the convenient let out clauses in the Reg's/GN's/OSG, you'll probably go far!!

 

[Silly Sausage]

Could you please explain how to do a live Zs test 'correctly' when there is an RCD present?

The only accurate test is an high current test, which would have to bypass the RCD. With terminals and CUs so small in domestic environments, it is not practical, or advisable, to bypass the RCD during a Periodic I&T.

Again, I come back to the UK Regs. They clearly state that a live Zs is not mandatory, so long as other tests have been done beforehand.

I'll just throw this in...
By calculating Zs from your Ze and R1+R2 measurements, you are also summing the errors, which could start to be significant at sub 1 Ohm readings.

 

[ImpededLoop]

Although GN3 says that Ze+(R1+R2) is acceptable, I also like to measure the Zs as it proves that the circuit cpc is properly connected again following the "dead tests" where the circuit has been disconnected.

 

[Lucien Nunes]

Exactly. It's the first test of the completed circuit under normal working conditions and (instrument accuracy permitting) reads directly one of the most important safety parameters.
If I'm unimpressed with the readings from a no-trip test or anything is near a maximum or minimum permitted figure, I'll take the time to bypass the RCD.

E2A see method below - which also works well when circuit is optionally supplied from control devices through which the tester can't test.

 

[davesparks]

Could you please explain how to do a live Zs test 'correctly' when there is an RCD present?

.

Seriously? You don't even know the alternative Zs test method?

With the circuit isolated at the mcb:
Link L to E at the far end of the circuit
Connect the tester live probe to the incoming L of the RCD
Connect the tester E probe to the outgoing side of the appropriate MCB
Carry out the test.

This way you are testing exactly the same circuit but from a different point within the circuit.

 

[Carlosfandango]

Seriously? You don't even know the alternative Zs test method?

With the circuit isolated at the mcb:
Link L to E at the far end of the circuit
Connect the tester live probe to the incoming L of the RCD
Connect the tester E probe to the outgoing side of the appropriate MCB
Carry out the test.

This way you are testing exactly the same circuit but from a different point within the circuit.

I didn't know that either. Another nugget of knowledge I've learned today!

 

[trev]

There is no reason why this test should be omitted ,especially in a house,where I would of thought it would be no problem isolating all equipment plugged in etc,cheers

A little more difficult in a warehouse though, the roof is 5 or 6 metres from floor level and they don't want to shift things around so you can get access to delamp. For example.

 

[smity]

Thanks for all your replys, In my opinion I think it's a bit lazy not to check in this circunstance but I presume he said to the client it will be an extra £££ to do this and they said well don't bother but I can fully understand in some circumstances and definitely in commercial jobs.

 

[Deleted member 26818]

Was the IR tested by linking the L+N and testing to earth?
I don't have the latest copy of GN3, but I would be very concerned that it would suggest the results of a test can be calculated.
I would also wonder what point would be served by recording such a value?

 

[N6rul]

Thanks

Brilliant tip buddy...

 

[N6rul]

Could you please explain how to do a live Zs test 'correctly' when there is an RCD present?

.

Seriously? You don't even know the alternative Zs test method?

With the circuit isolated at the mcb:
Link L to E at the far end of the circuit
Connect the tester live probe to the incoming L of the RCD
Connect the tester E probe to the outgoing side of the appropriate MCB
Carry out the test.

This way you are testing exactly the same circuit but from a different point within the circuit.

Brilliant tip!!! Thanks