RCCB TRIPPING


Postby micky b » Mon Nov 15, 2010 12:44 pm

Hi I have just installed a 10.5 kw shower and it keeps tripping out
I have installed a crabtree RCCB 63a/30ma and a crabtree B50 61/B50 MCB just for the shower. the wiring i have used is 10mm to the 50 amp pull switch and 10mm wire from the switch to the shower.I have power to the switch but when i turn the shower on the rccb trips out please help! as i haven`t much hair let to pull out
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Postby ericmark » Tue Nov 16, 2010 6:49 am

Is the neutral in the correct neutral bar. That is easy mistake to make.
It all comes down to inspection and testing. After fitting any new circuit you need to test and this will involve insulation with a 500v high ohm meter, continuity of earth with a low ohm meter drawing at least 200ma on the test. Measuring or calculating the prospective short circuit current and earth loop impedance and testing the RCD with a proper tester not test button to ensure it trips at 30ma within 40ms and does not trip at 15ma. All these need writing down and with bathrooms, kitchens and outside need submitting to the local authority building control to get the completion certificate under Part P.
If you list the readings maybe we can spot the fault.
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Postby micky b » Tue Nov 16, 2010 4:11 pm

ericmark wrote:Is the neutral in the correct neutral bar. That is easy mistake to make.
It all comes down to inspection and testing. After fitting any new circuit you need to test and this will involve insulation with a 500v high ohm meter, continuity of earth with a low ohm meter drawing at least 200ma on the test. Measuring or calculating the prospective short circuit current and earth loop impedance and testing the RCD with a proper tester not test button to ensure it trips at 30ma within 40ms and does not trip at 15ma. All these need writing down and with bathrooms, kitchens and outside need submitting to the local authority building control to get the completion certificate under Part P.
If you list the readings maybe we can spot the fault.

thanx ericmark for the info my neutral is in the correct bar could it just be that the RCCB is too sensitive?
micky b
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Postby ericmark » Tue Nov 16, 2010 5:35 pm

30ma is the correct size of RCD. However you have not given the results of the tests done when it was installed. The RCD meter has a 1/2x, 1x and 5x setting with a positive and negative half cycle so the RCD should be tested 6 times. For the 1/2x test it should not trip and for 1x test it should trip and for 5x test it should trip within the 40ms allowed. What was the results of the test?

Often we do get faulty RCD's but since they have to be tested on fitting this is not a problem.

If you don't have access to test equipment you should not do the job. My set cost around £750 and it is essential equipment for any electrician so if you don't have your own likely just as cheap to get some one in to test as it is to hire a set. Around £75 a week to hire and week was shortest hire time when mine was sent for calibration.

Often it is the cables which have slightly twisted the RCD which cause the problem but with meter you will soon see what the problem is. As with all things you need tools for the job.

Also you will need to supply the readings to the LABC to get the completion certificate under Part P.
ericmark
Rank: Project Manager
Posts: 1661
Joined: Fri Oct 02, 2009 8:49 pm
Location: Mold, North Wales.

Postby micky b » Wed Nov 17, 2010 6:33 pm

ericmark wrote:30ma is the correct size of RCD. However you have not given the results of the tests done when it was installed. The RCD meter has a 1/2x, 1x and 5x setting with a positive and negative half cycle so the RCD should be tested 6 times. For the 1/2x test it should not trip and for 1x test it should trip and for 5x test it should trip within the 40ms allowed. What was the results of the test?

Often we do get faulty RCD's but since they have to be tested on fitting this is not a problem.

If you don't have access to test equipment you should not do the job. My set cost around £750 and it is essential equipment for any electrician so if you don't have your own likely just as cheap to get some one in to test as it is to hire a set. Around £75 a week to hire and week was shortest hire time when mine was sent for calibration.

Often it is the cables which have slightly twisted the RCD which cause the problem but with meter you will soon see what the problem is. As with all things you need tools for the job.

Also you will need to supply the readings to the LABC to get the completion certificate under Part P.
ok ericmark I will get a sparky in to check thanx for your help
micky b
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Joined: Mon Nov 15, 2010 12:20 pm

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