Intermitant RCD tripping

[thomasn]

My apologies I think my last reply should be better dealt with in another forum, sorry for the lapse got carried away

 

[Engineer54]

It's going to be a while before this project is ready for the fire alarm systems to be installed, or any of the other specified MICC installations, i'm afraid ...lol!!

Never been a problem with moisture absorption, that can't be corrected on MICC cable. Only for those that have never used it or are new to the cabling system. Personally, i wouldn't even think of doing any IR tests before terminating.

When any installed MICC cables are going to be left for any length of time before terminating, then a dob of potting compound is used to seal the ends...
It's always best have a heat gun handy, to chase any suspected moisture from any stored MICC coil ends before using it.

 

[alarm man]

Hi nothing to do with your query just the comments on pyro. Pyro is self sealing and will only allow moisture for approx 100 mill, cut this off and you are in good cable. Also there is no point in testing pyro until both ends are terminated, after terminating, do ir test,if slightly low wait 24 hrs and retest you will find cable is up to scratch with no need to apply 1000 volts which doesnt produce any heat anyway. I've seen loads of guys over the years trying to condemn pyro or micc when ther is nothing wrong with it.

while pyro is the best cable around a bad pot is not uncommon,and it could be any length that you need to re pot depending on the conditions,100mm would be ideal,but not always the case

 

[thomasn]

while pyro is the best cable around a bad pot is not uncommon,and it could be any length that you need to re pot depending on the conditions,100mm would be ideal,but not always the case

Point taken, must have been lucky all these years

 

[Engineer54]

while pyro is the best cable around a bad pot is not uncommon,and it could be any length that you need to re pot depending on the conditions,100mm would be ideal,but not always the case

Even re-potting a bad pot isn't going to be that much of a problem, just a real pain in the arse for the guy who gets the job...lol!! Always a good idea to do a quickie confirmation test on a freshly made pot before connecting glands to enclosures....

 

[thomasn]

Even re-potting a bad pot isn't going to be that much of a problem, just a real pain in the arse for the guy who gets the job...lol!! Always a good idea to do a quickie confirmation test on a freshly made pot before connecting glands to enclosures....

Especially after you have destroyed the pvc insulation using your heat gun to chase the supposed moisture in a flammable area lol

 

[Engineer54]

Especially after you have destroyed the pvc insulation using your heat gun to chase the supposed moisture in a flammable area lol

If you are silly enough to destroy the PVC outer covering (if there is a covering) just to chase a bit of moisture from a MICC cable, then more fool you!! Minimal heat from a decent distance is more than adequate to achieve that....

 

[trebor]

is it possible to contact the prevoius occupants to see if they had the problem. a negative answer would point to an appliance, you mention a high integrity ccu is this a circuit with it equipment attached

I had a customer call me out yesterday and here is the script.

Thety move into the house 3 weeks ago,

since they moved in the RCD on the high integrity CU (main switch with 5 MCB's and RCD with 5 MCB's)
has been tripping regularly. (upto 3 times in one day)
The most comon time the RCD has been tripping has been around 3am but it has been tripping during the day and evening.

I look around the premises for an outside light that mayb egetting damp and causing the tripping, however the outside light was on the lighting circuit (on the mainswitch side of the CU)

On the RCD side of the CU I found the following circuits
cooker 6mm cable 32amp MCB
on 500v range on insulation resistance test >500M ohms between Nuetral and earth

power radial
2.5mm cable 16amp
on 500v range on insulation resistance test >110M ohms between Nuetral and earth

power radial (2 radial circuits bunched on one MCB)
2.5mm cable 32amp
on 500v range on insulation resistance test >115M ohms between Nuetral and earth

Trip load on RCD was 27mA @ 7.6ms
this was a 30mA RCD

The customer had a new fridge delivered a bout the time they moved into the house, so I suspect that it maybe the fridges compressor tripping the RCD.
For test purposes I moved the Fridge onto a spare 6amp MCB on the non RCD side of the CU so that we eirther confirm a problem with the fridge or not.


Basically I think the Fridge compressor maybe tripping the RCD

I didn't have my PAT test equipment with me so when I return I will PAT test the fridge

any thorghts anyone?