Lighting Circuit r1+r2 values.

CDB · Jul 17, 2017

Hi,

I was doing my r1+r2 tests on a lighting circuit yesterday in a 6 bed house over 3 floors. Approximately 20 points not including switches. Mainly pendants but some light bars etc and almost all LED or low energy halogen type bulbs. Closed circuit r1+r2 values range from 0.88 on ground floor to 3.06 on top floor.

The lights all work ok. I believe I have found one pendant with a discontinuous earth not picked up on a recent EICR done by a 3rd party, which I will return to this week and fix.

However, a couple of pendants were giving me values of over 130 ohms when the switch was open (light off), which I check as part of the polarity test.

Can someone help me understand why these high r1+r2 values might be occurring?

Thanks

Chris

[ElectriciansForums.net] Lighting Circuit r1+r2 values.

westward10 · Jul 17, 2017

Are you doing an EICR or fault finding.

CDB · Jul 17, 2017

Thanks for all the help guys.

An EICR was done but NOT by me. This issue was not raised and neither was the discontinuous earth. The remedials listed were fixed and I have since changed the CU and am testing all the circuits I've moved for my EIC.

There is two way on the hallway lights but not the ones affected. Screenshot below shows my readings.

Thanks again.

westward10 · Jul 17, 2017

Are you registering voltage between line/earth at the light fitting and is the insulation resistance clear.

westward10 · Jul 17, 2017

Is this 130 and 150 ohms or meg ohms.

CDB · Jul 17, 2017

westward10 said:
Is this 130 and 150 ohms or meg ohms.

ohms for the switch on / closed for those particular circuits. 130Meg Ohm for the r1rn to r2 insulation resistance.

CDB · Jul 17, 2017

westward10 said:
Are you registering voltage between line/earth at the light fitting and is the insulation resistance clear.

Obviously this is a dead test so if you are asking about 230v I have not looked.

But could I be picking up on Smoke/Heat alarms or Emergency Lighting?

But if that is the case then why are the other lights not seeing the same issue. Argh - my computer scientist brain likes consistency!

Thanks for the continued help by the way!

westward10 · Jul 17, 2017

It isn't a problem I thought you meant ohms for when the switch was open. I assume you get 130 meg ohm when you IR test the whole circuit with all switches closed.

CDB · Jul 17, 2017

westward10 said:
It isn't a problem I thought you meant ohms for when the switch was open. I assume you get 130 meg ohm when you IR test the whole circuit with all switches closed.

Yes 130 meg ohm for IR.

But either 130 or 150 ohm for the two problem pendants when switch is closed.

westward10 · Jul 17, 2017

It is not a problem 130 meg ohm is well above what you require. Your picture indicates the wiring to be 50 odd years old and you would not necessarily expect an infinite IR reading especially on a lighting circuit, I would think no more of it.

CDB · Jul 17, 2017

It's not the IR that concerns me because as you put it the wiring is old and it's well above the minimum.

My question relates to the 130 OHM and 150 OHM I'm getting for the R1+R2 test on two different pendants when the switch is open. If the switch is open I should be getting open circuit or in my case >2000 ohm as I do with all the other lights on that circuit.

Ian1981 · Jul 17, 2017

Are the switches relatively old as you could be getting dirt on the contacts at the switch tracking across or you may have leakage through lower insulation resistance

westward10 · Jul 17, 2017

It is possible old, worn switches are the cause but I wouldn't have thought low ohms would pick this up but yes ditch the wiring from the switch.

Ian1981 · Jul 17, 2017

Disconnect at switches and see what you get

CDB · Jul 17, 2017

Ian1981 said:
Are the switches relatively old as you could be getting dirt on the contacts at the switch tracking across or you may have leakage through lower insulation resistance

Hi Ian,

Dodgy switches was my first thought. They are old.

To determine your second suggestion I guess I would need to do a full IR which is pretty difficult given the installation.

Switches first!

Thanks for the ideas.

Deleted member 26818 · Jul 18, 2017

Are the CPCs for these pendants connected in terminals, or twisted together either at the roses or perhaps in JBs in the loft?

Lighting Circuit r1+r2 values.

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Deleted member 26818

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