On a TT circuit there is a split load CU where the main incoming RCD trips for no reason, even when house empty, even overnight; its a Wylex WRMT 100A 100MA of uncertain age! Suspected earting loop initially - can remain ok for weeks on end, then trip off 4 times in an hour!
RCDmain incoming tripping unexpectedly
- Thread starter Mickelo1
- Start date
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Hi,
I have come across this before, can be caused by earth faults upstream from your system ( someone else in the street) . the first thing to try is to have the rcd tested fully including a ramp test ( this tests how much fault current is needed to trip). Also does the test button work??
I have come across this before, can be caused by earth faults upstream from your system ( someone else in the street) . the first thing to try is to have the rcd tested fully including a ramp test ( this tests how much fault current is needed to trip). Also does the test button work??
If it is a true TT, and there are no parallel paths between neighbours (galv gas pipe, lead water etc) then a fault in a neighbouring property cannot cause operation of your RCD. It is known to happen mainly on TN-S systems, although has been seen with TN-C-S too.
You need to start with testing all your circuits, and every part of the circuit - Test the insulation resistance. Remove all neutrals from the CU bar when you do this. If you find no problems here, then you ramp test, or even just swap the RCD, even if temporarily. Reason being, the RCD may be faulty, but intermitantly.
well as you say there can easilly be paralell paths between two properties and with a TT a fault in one property could easilly drive substatial current down a N-E fault in another.
Surges on the mains (potentially caused by equipment used in other properties) can drive more current down virtually any fault.
as lectrician says a RCD ramp test and insulation resistance tests are a very good idea. So is measuring the actual total leakage with everything turned on. If it is more than a third of the RCDs rating normally it is probablly time to start splitting the load accross more RCDs.
Surges on the mains (potentially caused by equipment used in other properties) can drive more current down virtually any fault.
as lectrician says a RCD ramp test and insulation resistance tests are a very good idea. So is measuring the actual total leakage with everything turned on. If it is more than a third of the RCDs rating normally it is probablly time to start splitting the load accross more RCDs.
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B
baz1968
Lectrician wrote
"You need to start with testing all your circuits, and every part of the circuit - Test the insulation resistance. Remove all neutrals from the CU bar when you do this".
NO!
Why go to all the trouble of testing every single circuit first??? Eliminate the simplest and most likeliest cause, the RCD.
"You need to start with testing all your circuits, and every part of the circuit - Test the insulation resistance. Remove all neutrals from the CU bar when you do this".
NO!
Why go to all the trouble of testing every single circuit first??? Eliminate the simplest and most likeliest cause, the RCD.
What nonsense!
Of all the RCD faults I've been to over the years, nearly all of them are down to a fault on the fixed wiring ? appliance.
It is rare for the fault to be the RCD its self.
An IR test proves whether the wiring is causing the problem, swapping the RCD doesn't, especially on a random intervals intermittant fault.
Of all the RCD faults I've been to over the years, nearly all of them are down to a fault on the fixed wiring ? appliance.
It is rare for the fault to be the RCD its self.
An IR test proves whether the wiring is causing the problem, swapping the RCD doesn't, especially on a random intervals intermittant fault.
B
baz1968
I'm talking about a ramp test first which in an earlier post Lectrician seemed to think was the last test that should be carried out
So rather than do a simple ramp test why would anyone go to the trouble of isolating, disconnecting and checking for equipment sensitive to insulation tests BEFORE ruling a simple fault of a dodgy RCD.
How is that Nonsense????
So rather than do a simple ramp test why would anyone go to the trouble of isolating, disconnecting and checking for equipment sensitive to insulation tests BEFORE ruling a simple fault of a dodgy RCD.
How is that Nonsense????
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Well, swapping out an RCD may be simple, but it is costly.
Why not use the test equipment to do a few simple (and free) tests on the fixed wiring first?
As RF says, it is unlikely to be the RCD.
They can go faulty and I've had them faulty straight out of the box before now, but never with an intermittent tripping fault.
If you get clear IR tests on the wiring, then you can point the finger of blame more in the direction of the RCD.
B
baz1968
Where did i say that? Why go to the trouble of swapping an RCD before testing it?
Why not use the test equipment to do an even simpler ramp test first.
But not impossible that it is.
So your saying that if it's not faulty out of the box it will never be faulty?
All i said was that by carrying out a simple ramp test first you can reduce the possibilty of the RCD as the cause of the problem.
Why do you and RF instantly dismiss this as "Nonsense" ???
B
baz1968
Only difference is Plumbers have more manners
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