cpc way too high?

[Test Probes]

Hi all. I'm testing a new instaulation (care home) and have come across a problem in a lighting circuit and both my self and the tech can't make any sence of it. Unfortunately, the fittings are in place. The normal readings would be about .30 to .54 ohms on the cpc of the circuits I've tested. I've done almost all of the circuits and now this comes up. My cpc is 157ohms. How can this happen? I've checked earth conductors and have assumed there is some parallel paths. So I'm now thinking there may be a line conductor problem. :confused5:

 

[Guitarist]

Is this an R2 reading with a wander lead, or your R1R2 reading at each fitting and linked at the CU?

 

[loop3]

Loose?

 

[brman]

Is this an R2 reading with a wander lead, or your R1R2 reading at each fitting and linked at the CU?

I am hoping an R1+R2 test or he would not be thinking it might be a fault in the Line conduction

Was a R1+Rn test done?

 

[crow11]

did you do the new install or you just testing it for some one else,i would of thought by linking at the d/b and then continuity checks at each fitting would tell you which wire had the fault eg L + cpc N + cpc L + N obviously if your getting a good reading with L + N and a bad reading on both L + cpc and N + cpc the the fault is with the cpc as mentioned above prob a loose connection, or if you didnt do the install you don't know what they have done will prob get told this is wrong lol

 

[crow11]

brman beat me to it about doing the Rn lol

 

[Test Probes]

Appalogies for the confusion. I was doing R1 + R2, linked at the DB. I didn't do R1 + Rn as it's not required on the schedule of test results sheet. I should have also mentioned that I didn't do the instalation. I initialy thought of loose cpc and then thought the line conductor may be loose as well. Could be both!

 

[spark 68]

In this case I would have also done a R2+Rn, to narrow down which conductor was giving the problem, a process of elimination

 

[crow11]

do you know the person who did the install, only asking because iv'e seen it before people trying to guess the length of wire and ending up to short so they put a J/B on, if you know them ask them but they will probably say no even if they had,if all your connections are good then obviously whoever did the install as messed up somewhere

 

[Amp David]

Are all loads removed? Have you been able to confirm correct polarity at the point you are testing?

 

[Guitarist]

I am hoping an R1+R2 test or he would not be thinking it might be a fault in the Line conduction

Was a R1+Rn test done?

Agreed. However, I don't take anything for granted on this forum

 

[Test Probes]

I'm back at it on Monday. I'll do R1 + Rn. Loads are fitted but I've put the switches in the open position. There are 4 rooms to the circuit and each room is ensuit with fan, mirror light/shaver skt, PIR for 1 light in loo as well & a main light which is swiched. The bed lights & main lights are 2 way and one of the main lights is emergency. Alot of gear to dismantle.

 

[Amp David]

Loads fitted, you could be measuring the CPC then through said loads back down the neutral then to the point you are measuring, hence the high reading.

 

[Guitarist]

I'm back at it on Monday. I'll do R1 + Rn. Loads are fitted but I've put the switches in the open position. There are 4 rooms to the circuit and each room is ensuit with fan, mirror light/shaver skt, PIR for 1 light in loo as well & a main light which is swiched. The bed lights & main lights are 2 way and one of the main lights is emergency. Alot of gear to dismantle.

Just a quick tip for the installer... Don't put stuff together until circuits have been tested.

 

[brman]

I'm back at it on Monday. I'll do R1 + Rn. Loads are fitted but I've put the switches in the open position. There are 4 rooms to the circuit and each room is ensuit with fan, mirror light/shaver skt, PIR for 1 light in loo as well & a main light which is swiched. The bed lights & main lights are 2 way and one of the main lights is emergency. Alot of gear to dismantle.

This is pretty basic fault finding isn't it? Your R1+R2 should have showed you what part of the circuit the fault is on. R1+Rn or even long wire tests will narrow it down pretty quickly. You shouldn't have to dismantle much if you break it down logically.