High Zs on lighting circuit

[Maxstone89]

Hi all

I have a house where all the circuits meet the Max Zs for that circuit yet the lighting circuit is testing as 747 ohms Zs

It looks like it used to be a TT system and been converted to a TN-C-S system. As its also got an main tcd before the board. Could this somehow be causing this high reading, even though the lighting circuit is connected to the main pme where all other circuits are or is their other possibilities.

Thanks max

 

[Maxstone89]

Thanks Richard, would you mark the report as unsatisfactory then?

 

[Maxstone89]

If you have 747Ω as the resistance of a domestic circuit then there is something very wrong, this is equivalent to a 60W light bulb connected through the cpc.
Even though it does meet the 1667Ω requirement for a 30mA RCD it is very likely that you have a very poor / corroded connection somewhere (or a major wiring error) and that this will get worse over time.
There is no sensible way this can be a result from a satisfactory circuit.
The fault needs to be identified and resolved.
However if the customer does not want to do it then you do have to leave it, but I would recommend putting an advisory of a faulty circuit in writing.

Thanks

 

[Maxstone89]

I would guess.the problem is, did you measure some thing wrong and it looking daft on you

Maybe do.it for free to make sure you didn't cook up
If you did cook up some way it would look like your trying to con the person

Whats with the sarcastic remarks.
Please do not comment if its gonna be sarcasm.

 

[DuaneMHunt1976]

Well I can tell you this.... You dam miss read what I said
When I'm being sarcasm it's very strange

 

[NDG Elecs]

Whats with the sarcastic remarks.
Please do not comment if its gonna be sarcasm.

I think Duane was just thinking out aloud there and was not trying to be sarcy... He was just saying are you 100% that the test result is the correct one given all others are OK. We all makes mistakes from time to time after all. I can see Duane's point that if it was a mistake then it could look like you were creating work.

 

[Maxstone89]

Fair enough, just the amount of people being sarcy on here is just daft, so if you weren't then no worries.

Yes all the readings on both light citcuits where all coming out at the same which is odd.

 

[DuaneMHunt1976]

So, there is TWO Circuits, two MCBs 6A about, and all the Light Points the Zs is 747Ohms when you need Zs Max of 7Ohms (5A) and 5.87Ohms (6A) I think [NB i put i think, as someone may correct me]
So 747Ohms is not great even if it was 7.47Ohms still above the Max Zs

As Zs = Ze + R1 + R2 , if R1+R2 is Dam high you know the fault is on it, which would be the logical thing
But any thing could happen i guess, could be lose wires hangin in a pool of water, or just hold on by one strand.

Sounds a bit like someone has wiring a Light bulb in series, Live to Bulb to Light Sockets, then as long as one light comes on you wil get the light on, but would give you a high ohms reading.



I know your with NICEIC (looked up on your other account
NICEIC Consulting
Tel: 0500 600 545
Email: [email protected] - See more at:

Im not one who can be sarcasm because of my problems, it will just blow back at me.
I can be dam Strange like the Uniform YCMA Post, and As you Noticed the Zs Test without a CPC, what you know is impossible but people still get figures for, so i googled it and someone JOKED about a Meter that could measure it.
But as your results, I understand wanting to get every thing perfect and when things aint spot on, one can tend to get worried. I do JOKE to Try and Lighting the mood, im like that in Group Orgies too, ----ing a Coin heads of tails for what end one gets.

 

[davesparks]

What job are you doing here?
Are you working on the lighting circuit or are you carrying out periodic testing?

 

[Maxstone89]

So if customer doesnt want a return visit, do i code it c2 on eicr or as it has an rcd or c3?

U would say c3 as if it was a tt system it would pass??

And As its already there, if a new circuit then it would be a no no.??

What would you guys code it?

Thanks

 

[davesparks]

So if customer doesnt want a return visit, do i code it c3 as it has an rcd or c2?

U would say c3 as if it was a tt system it would pass??

And As its already there, if a new circuit then it would be a no no.??

What would you guys code it?

Thanks

What do you mean by a return visit? What exactly is the job you are doing here?

 

[Maxstone89]

Carrying out an Eicr.

I have possible ideas why which some have been stated, just thought why not ask in case a simpler answer/possible cause is out there

 

[andyb]

So if customer doesnt want a return visit, do i code it c3 as it has an rcd or c2?

U would say c3 as if it was a tt system it would pass??

And As its already there, if a new circuit then it would be a no no.??

What would you guys code it?

Thanks

I'm assuming that you are undertaking a PIR here,

Whether the customer wants a return visit or not is not the point, you've carried out an inspection so you must code as you see fit.
Also you can't code as you would a different system, the earthing system you have is what you must assess the installation on.

For what it's worth, providing I've understood correctly I would give this a code 2.

 

[davesparks]

Carrying out an Eicr.

I have possible ideas why which some have been stated, just thought why not ask in case a simpler answer/possible cause is out there

Right, it's an EICR so you are there to carry out the tests, record the results and make your decisions about coding, you would not normally be there to do any investigation of the faults.

You have a Zs result which is abnormally high considering the supply type (TNCS) so there is a very strong possibilty that there is a fault there and it's not just a circuit with a high Zs. So I would be inclined towards a C2

 

[Maxstone89]

Would anyone else code it C1/C3??

I think C2 seems correct, just always worth asking other people's opinions and thoughts how they have come to it.

 

[telectrix]

it's a C2 in my book. ( an exposed part could become live under fault conditions. with no cpc, then this could be lethal.) with a comment that further investigation is required.