Weird earth fault

[extension15]

Well, I think I'm certain what's going on here..

Installation with newly installed 17th CU, with many repairs etc..

And yes I should of picked this up on the inspection, any way, 3 way lighting on Landing/hallway (switching OK)....

ONLY with bulb in place at Landing light, switch on and RCD trips..

Have isolated feed from CU and when switch is on, there is 100 ohms from live to earth...

My view is that (old Wylex fuseboard prior), this fault has been there a long time.

I would of expected to see a near short.

I'm going back in the morning, hopefully to resolve very quickly

So why 100 ohms? Just coincidence? Or would you agree a trapped/damaged cable, with poor contact?

; \

 

[SPECIAL LOCATION]

Well, I think I'm certain what's going on here..Installation with newly installed 17th CU, with many repairs etc..

And yes I should of picked this up on the inspection, any way, 3 way lighting on Landing/hallway (switching OK)....

ONLY with bulb in place at Landing light, switch on and RCD trips..

This just sounds so much like a borrowed neutral, (landing & halls always prime suspects!!)

Have isolated feed from CU and when switch is on' date=' there is 100 ohms from live to earth...

[/quote']

Presume you mean the L & N on the circuit you think is a the faulty one.

what about the rest of the CU.. are other neutrals connected & main switch "ON"???

My view is that (old Wylex fuseboard prior)' date=' this fault has been there a long time.

I would of expected to see a near short.

I'm going back in the morning, [b']hopefully to resolve very quickly

So why 100 ohms? Just coincidence? Or would you agree a trapped/damaged cable, with poor contact?

; \

If the "faulty circuit" has a joint back to neutral via another circuit / light fitting...

then if main switch still on could have a path back to earth via CU.

Do you still get your reading with main switch OFF???

100ohm just sounds like classic reading across a bulb somewhere?

cold readings across bog-standard bulbs typically...

100watt approx 40 - 45ohm

60watt approx 60 - 65ohm

40watt approx 100 - 105ohms.

I'd double check readings with other light circuit isolated at CU as well! :|

hopefully to resolve very quickly

hope so m8

these things can sometimes turn into nightmare jobs!!

 

[extension15]

Thanks SL...

Borrowed neutral did come to mind, but I think not...

(Switching off other RCD, isolating remaining light circuits from RCD2, still causes a fault)

The 100 ohms is only in place when the LIGHT switch is on, (switch) LIVE to CPC..............not L to N..

AND I can have all other lights on up/down without any issues..

ALL other loads were removed during fault finding exercise..

Applaud Smiley

 

[extension15]

I might also add, only the lives/cpc's are at the switches, all neutrals are at the roses..



(Back later)

 

[steptoe]

smoke detector and someone mixed up their linked sw and the cpc?

only a thought!

100 ohm LE really does sound like a mixed up cable (NE reverse) somewhere tho, whether by a fan or something else and then a faulty fault by default! LOL.

 

[extension15]

smoke detector and someone mixed up their linked sw and the cpc? only a thought!

100 ohm LE really does sound like a mixed up cable (NE reverse) somewhere tho, whether by a fan or something else and then a faulty fault by default! LOL.

No fans or smokes, steptoe..

; \

 

[steptoe]

well, if it only happens when the bulb is in place, and therefore sw is on, it is actually a N E fault, rather than a L E fault, otherwise it would show up all the time, am I thinking right?

 

[steptoe]

isolated supply? what supply is it? and have you also isolated N and E?

 

[extension15]

well, if it only happens when the bulb is in place, and therefore sw is on, it is actually a N E fault, rather than a L E fault, otherwise it would show up all the time, am I thinking right?

Well, by mid afternoon, my head was spinning... :z

So tomorrow I'll take on board what's been suggested.... :x

But.........................................................

With a bulb in place AND the switch ON...............

100 ohms was measured Live to cpc, Neutral to cpc was considerably higher, but I will confirm this tomorrow..

 

[extension15]

isolated supply? what supply is it? and have you also isolated N and E?

TN-S, circuit was TOTALLY isolated from board...

 

[steptoe]

perhaps N finding a path via some other circuit to Earth? or vice versa, N shorting to eart straight after lamp and then finding a path to earth via another circuit? really does sound like a borrowed cable of sorts! maybe an RCBO could discriminate and not drop out so quickly, RCD could be tripping on multiple leakage. have you tried a ramp test to see the leakage before trip?

 

[extension15]

With circuit isolated, steptoe, I did look for a neutral link to other lighting circuits but couldn't find one..

:|

Like I say, I will take a very methodical approach tomorrow...

 

[extension15]

I might also add, this is a job from hell, I'm just making (have/will) the place safe®.......



I did tell the landlord, this really needs a rewire...

(JB/bodge central)

 

[steptoe]

can I pm you to suggest something?

 

[extension15]

can I pm you to suggest something?

Be my guest....

:x

 

[steptoe]

Now, this will be the big tell if my neon thing is good or not?!?!?!?!?

 

[extension15]

 

[extension15]

Now, this will be the big tell if my neon thing is good or not?!?!?!?!?

Property is empty, by the way...

 

[steptoe]

that was prob one of those things for the passwordy place that no one has the password for!!!!

 

[a2]

that was prob one of those things for the passwordy place that no one has the password for!!!!

Who doesnt have a password??