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RCD trip times



 
 
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  #1  
Old November 26th 04, 10:01 PM
[email protected]
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Default RCD trip times

Testing an RCD (part of a split-load CU) I found that at the rated
current (30mA) it would trip anywhere between 16-17ms to not at all
(even with the meter set to the 2s range). Suspecting the RCD I swapped
in another from a spare box (same make - Clipsal - but almost certainly
different batch as I bought them at different times from different
suppliers). However the other RCD showed much the same behaviour. Both
tripped reliably at 50mA.
Is this typical, or are both faulty? (Is Clipsal crap? :-)

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  #3  
Old November 26th 04, 10:48 PM
BigWallop
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wrote in message
oups.com...
Testing an RCD (part of a split-load CU) I found that at the rated
current (30mA) it would trip anywhere between 16-17ms to not at all
(even with the meter set to the 2s range). Suspecting the RCD I swapped
in another from a spare box (same make - Clipsal - but almost certainly
different batch as I bought them at different times from different
suppliers). However the other RCD showed much the same behaviour. Both
tripped reliably at 50mA.
Is this typical, or are both faulty? (Is Clipsal crap? :-)


When was the test meter last calibrated? Is the battery still good, or is
it a mains operated test meter? It could be your meter and not the RCD's
you know. The most reliable test gear is connected across the supply and
doesn't rely on a battery.

The mains operated test meters have crimp ends which connect with main
supply leads to the RCD switching. Then the test leads are connected across
the consumer side of the same switch. It then slowly increases the current
to a point where it causes the RCD to trip out. They then store the info'
on the display for easy reading after they're disconnected. They do have a
battery to make the display work and keep the NVM chip working after
disconnection, but they don't rely solely on a battery for the full test.

They're also very expensive, especially if you have to buy three like we
did.


  #4  
Old November 27th 04, 03:40 PM
[email protected]
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Andrew Gabriel wrote:
In article .com,
writes:

Testing an RCD (part of a split-load CU) I found that at the rated
current (30mA) it would trip anywhere between 16-17ms to not at all
(even with the meter set to the 2s range). Suspecting the RCD I

swapped
in another from a spare box (same make - Clipsal - but almost

certainly
different batch as I bought them at different times from different
suppliers). However the other RCD showed much the same behaviour.

Both
tripped reliably at 50mA.
Is this typical, or are both faulty? (Is Clipsal crap? :-)



It's not typical -- I normally find they trip within
20ms at the rated trip current (not used Clipsal though).


Each & every time? It tripped within 16 or 17ms first couple of times,
but trying repeatedly I got non-operations. Maybe the RCD was getting
tired? ;-)
As I say though, I did test on different samples.

Whitfield says "100% of rated ... must ... trip within 200ms" and
"150mA ... 40ms" which suggested to me that a (say) 30mA 30ms RCD
should trip at 30mA, but doesn't have to do so within 30ms, but would
trip within this time at higher currents.

Is your RCD tester calibration out of spec?


Just recently been calibrated so I'd hope it'd be OK. Will try again on
other RCDs (like this house cct, after I've logged off :-)

  #7  
Old November 27th 04, 05:47 PM
Stephen Dawson
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Posts: n/a
Default


"BigWallop" wrote in message
. uk...

wrote in message
oups.com...
Testing an RCD (part of a split-load CU) I found that at the rated
current (30mA) it would trip anywhere between 16-17ms to not at all
(even with the meter set to the 2s range). Suspecting the RCD I swapped
in another from a spare box (same make - Clipsal - but almost certainly
different batch as I bought them at different times from different
suppliers). However the other RCD showed much the same behaviour. Both
tripped reliably at 50mA.
Is this typical, or are both faulty? (Is Clipsal crap? :-)


When was the test meter last calibrated? Is the battery still good, or is
it a mains operated test meter? It could be your meter and not the RCD's
you know. The most reliable test gear is connected across the supply and
doesn't rely on a battery.

The mains operated test meters have crimp ends which connect with main
supply leads to the RCD switching. Then the test leads are connected
across
the consumer side of the same switch. It then slowly increases the
current
to a point where it causes the RCD to trip out. They then store the info'
on the display for easy reading after they're disconnected. They do have
a
battery to make the display work and keep the NVM chip working after
disconnection, but they don't rely solely on a battery for the full test.

They're also very expensive, especially if you have to buy three like we
did.



The question is very loose.

Climbing up on to high horse :-)

If you do not know how to carry out the test that you are doing, then you
will have no idea how to understand to results and whether they are good or
bad.

This is why you should employ a competent electrician to carry out this kind
of work. If you were competent to do this work you would not be asking this
question.

Climbs off high horse.

Stephen Dawson


  #9  
Old November 28th 04, 03:12 AM
John Rumm
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Default

Stephen Dawson wrote:

The question is very loose.


Which one? The OPs description seemed to contain all the detail required.

Climbing up on to high horse :-)


If you do not know how to carry out the test that you are doing, then you
will have no idea how to understand to results and whether they are good or
bad.

This is why you should employ a competent electrician to carry out this kind
of work. If you were competent to do this work you would not be asking this
question.


What a spectacularly useless comment.

ISTM that the OP had the right test gear, knew how to use it, and knew
what results to expect.

Climbs off high horse.


Looks a bit like an ass from this angle....


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

 




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