Mcb tripping ???? | Page 2 | on ElectriciansForums

Discuss Mcb tripping ???? in the Australia area at ElectriciansForums.net

W

waitees

Hi guys

has anyone had this problem before ?

I changed a old board to a 10 way wylex with 2 rcds

the testing was all ok apart from the kitchen, so this was rewired.

Everything is back on all the testing is ok, however as the house
is empty at the moment went back and noticed the downstairs
ring off, thought was odd as I remember turning everything on. Switched it back on and 15 mins later the mcb trips.
Changed the mcb for another, stayed there for a couple of hours all ok switch everything on, all ok, then unplugged everthing again and left.

Went this morning and it had tripped again ! Hardly any load !Took off every socket and checked all ok apart from a fcu had a chunk missing out of the neutral, so fixed that and switched back in all ok at the moment will go back to house tonight to see if has tripped again, not had this problem before if trips again anyone god any ideas what it could.
be ??
 
Last edited by a moderator:
if all else fails, try splitting the ring, then try both halves in the mcb and see which side trips?
might help narrow the fault down and then work back...............might be a long process, but the house is empty.

:D
 
Hi mate,

Any sockets outside? UT room? It could be a moisture problem. What loads are permanently on?



Moisture problem??

There are two rcd's in the board? The mcb can only trip on overload or short circuit. There is no way the rcd would stay in with a moisture problem large enough to trip an mcb.

What is your measured ZS on this circuit?

What is your measured ZE?

Regards

Dichroic
 
Measured zs was 0.73 and ze reading is 0.13.

I am starting to think it's a moisture problem as well. I'm here now yes on a sunday ! I really need to get this sorted and move on !

I tested this circuit again and this time got low readings on IR test On all three L-N L-E N-E although it would pass, however put 500v through a few times and now it's hitting the best readings, which on
my kt64 is 1999. This surely must be a moisture problem have been here for 45 mins and still has not tripped.
 
Check back in some earlier posts, there was a recall of some Wylex switchgear recently but i dont know what exacty it was for and what was affected, but it was well covered in this forum and there was also a notice up at the Electrifix counter at Screwfix.

If your IR tests are Ok and there is no load then i cant see why it would trip 2 different breakers. The only time i came across this problem was a 6a MCB with a hairline crack in it which would trip when it feels like it, but to have 2 do it, not impossible but highly unlikely, probably more chance of winning the lottery.

Cheers............Howard.
 
Last edited by a moderator:
No the rcd has not tripped, when I tested the rcd I plugged the meter into that ring with good results and in the required times.


Ok. We keep coming back to the L-N short circuit then. It sounds like a very small short between the two, possibly caused by moisture ingress.

To confirm then.......there are no loads connected to the ring, no fused units supplying other equipment at all etc etc.

I feel you need to start splitting up the circuit and testing legs individually to see if a certain part gives a lower reading than another and continue this practice until you've measured each leg.

Also it has been known for socket outlets themselves to be faulty inside, you could try removing a faceplate at a time and re-testing to see if there is a problem with one of them.
 
Some of the sockets are pretty old so will change them, also there is 3 fcu one is supplying a light in the conservatory and a wall light the other a rad in the toilet however these are all switched off when it's tripping. It's just tripped now and that was after an hour !
 
If yo are absolutely sure there are no sensitive loads on the circuit try putting 1000v up it L-N....I have had instances before where nothing showed on 500v but 1000v broke it down and a fault showed up.
Also put a clamp meter on at the mcb...this will show if you have a continuous fault current running.
 
Last edited by a moderator:
Just retested again and now getting no continuntiy with cpc 2 cpc also when the breaker does trip now it comes with a popping sound. The owners have told me that they have had problems with mice may be have bitten threw cable ?

What is the best way to narrow this faulty part of the cable ? As all the sockets have Now been replaced I can only assume one of these buggers have bitten threw one of my cables !!:(

the owners are on hols Till end of week and start to think it will be quicker to rewire !
 
Disconnect one leg of the ring somewhere near the centre. Take out 32A mcb and connect as two radials on seperate 16A mcb's. See which one ( if any ) trips out. That will eliminate possibility of faulty 32A mcb and narrow things down for you.

Regards

Dichroic:rolleyes:
 
What is the best way to narrow this faulty part of the cable ? As all the sockets have Now been replaced I can only assume one of these buggers have bitten threw one of my cables !!:(


Disconnect one of the sockets near the centre of the ring, test LN,LE,NE at board for both legs of the ring. This will show you which leg its on. Repeat this by then disconnecting at the middle of the dodgy leg and keep going like that until you fing yr dodgy bit of cable
 

Reply to Mcb tripping ???? in the Australia area at ElectriciansForums.net

News and Offers from Sponsors

  • Article
Hi everyone, If you are looking for reliable EV chargers, check out our top-rated selection at E2GO! ⚡ Please note that all EV Chargers and...
Replies
0
Views
164
  • Article
As the holiday season approaches, PCBWay is thrilled to announce their Christmas & New Year Promotions! Whether you’re an engineer or an...
Replies
0
Views
1K
  • Article
Bloody Hell! Wishing you a speedy recovery and hope (if) anyone else involved is ok. Ivan
    • Friendly
    • Like
Replies
13
Views
1K

Similar threads

Exactly. I was going to ask on the earthing once he clears this boiler fault (suspect on internal component). OP mentions oil boiler but makes no...
2
Replies
19
Views
983
And fully tested it with an MFT obviously
Replies
9
Views
722

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

YOUR Unread Posts

This website was designed, optimised and is hosted by untold.media Operating under the name Untold Media since 2001.
Back
Top