2 way Light tripping MCB

[Shamus]

I have a client with a rental property who has a 2 way landing light that trips after about 5 mins of being switched on. Depending on which 2 way switch is used, depends how long it takes to trip. If the landing light is not used, it doesn't trip. The wiring is showing signs of the green goo, but not to the point that i think it presents a major issue.

I quickly checked for loose or broken wires, but nothing obvious.I don't think the MCB is at fault as the remaining lights work correctly even when they are all switched on, the MCB doesn't trip, only when the landing light is on.

The installation doesn't have an RCD, so i don't think an earth leakage is the problem.

My gut feeling is a loose, broken, damaged wire that is causing the current to increase slowly due to higher resistance, and then trip after a period of time. Unfortunately the switch wires are (as usual) not visible for inspection, other than at the switches and rose. I will go back to the property another time to do more extensive tests, IR etc.

Anyone had a similar problem, or got any suggestions. This is a bit of an unusual one for me. I've got the Tenant doing her nut at me all the time i was there. So when i go back i want to be able get the job done quickly and then get out. So if anyone has had a similar problem, i may be able to sort the problem a bit quicker.

Thanks

 

[NozSpark]

To me your assumptions just don't make sense, I would bet that there is an IR fault somewhere.

 

[steptoe]

I really dont get it,

you have been there, identified that there is a fault,

but not bothered to do a 2 minute test to prove/disprove your thoughts on what is causing the problem.

:shakehead

 

[Technician]

If the time it takes to trip is about 5 seconds,

suspect an insulation fault as Noz suggests.

Do not try to measure the current to trip it,

go for the jugular and do FULL tests INCLUDING

testing the strappers.

---------- Post Auto-Merged at 20:31 ---------- Previous post was made at 20:27 ----------

Apologies...5 MINUTES.

 

[Andy™]

The installation doesn't have an RCD, so i don't think an earth leakage is the problem.

Er... are you sure your competent to be doing this?

 

[OnOff]

Anyone put a new picture on the wall? New wall fitting? As in nail/screw - no RCD YOU NEED TO SORT IT ASAP! Rat chewed cable, water getting into a JB, has someone re-arranged the junk in the loft and squashed a cable or boarded it.....the list goes on. Proper testing the only way.

 

[samson337]

It's a short, not earth leakage. Have they been painting the ceiling and had the cover off the rose, seen a few of them were its been covered in paint inside. Just a thought

 

[Shamus]

I was trying not to put too much unneccessary detail in my post, as to why i didn't do any tests. The reasons for not testing at that moment in time were,

1) I nipped in on the way home from work, just in case it was a silly problem, most of the lights that are not working are generally down to loose wires.

2) I didn't have my meters with me as they were on another job

3) I had better things to do - like go home and eat after i had done a 12 hour shift.

I only wanted some pointers and straight answers so that i didn't waste any futher time on my next visit,

Thanks Technician your comments are appreciated.

---------- Post Auto-Merged at 21:00 ---------- Previous post was made at 20:50 ----------

[quote name='Andy

 

[steptoe]

you are getting >6amps (actually a lot more),[is it a 6amp MCB] , and you dont think that is serious,?

I dont want to be the one to find out where the fault is when its at 5.9amps! :|

 

[SLIPSHOD & SLAPDASH]

If there is green goo on the cables are there any Cpc's ?

You may find this (page 10) interesting

http://www.esc.org.uk/fileadmin/user_upload/documents/public/switched_on/SwitchedOn-Issue-19.pdf

Edit, I would say the fault is at oor behind the light.

 

[sellers]

Megger MFT1730 Onsite. Buy online or call

This thing in the right hands and you'll have found it in 30mins.

 

[steptoe]

or you could be about 3 months waiting for it coming back from the manufacturers after they've had to repair it yet again! :slap

 

[Shamus]

If there is green goo on the cables are there any Cpc's ? You may find this (page 10) interesting

http://www.esc.org.uk/fileadmin/user_upload/documents/public/switched_on/SwitchedOn-Issue-19.pdf

Edit, I would say the fault is at oor behind the light.

Yes i've seen that info, i will be passing it onto client. There are cpc's at the lights, albeit with no sleeving. The house dates around the 60's.

Can you elaborate on what you mean when you say "the fault is at oor behind the light". This is a ceiling rose, with 2 way switching.

 

[MSH1601]

or you could be about 3 months waiting for it coming back from the manufacturers after they've had to repair it yet again! :slap

Don't say that, mine's going back to them on Monday!

 

[SLIPSHOD & SLAPDASH]

Yes i've seen that info, i will be passing it onto client. There are cpc's at the lights, albeit with no sleeving. The house dates around the 60's.Can you elaborate on what you mean when you say "the fault is at oor behind the light". This is a ceiling rose, with 2 way switching.

oor should have been or. If the light has worked fine for years and now trips the breaker when energised the fault is more than likely on the switchline. My first check would be in the ceiling rose & cabling behind it. 2nd would be at the switches and then the test kit comes out.

 

[Shamus]

Thanks for that, planning to go back sat morning and sort the problem out.

 

[batty]

An insulation test is the only answer.