Adrian Simpson writes
It is possible to have an appliance [or eg a shower] which works fine but has a leak of a few ohms between neutral and earth. This may not normally trip the RCD. However, when a nearby kettle and the dishwasher are switched on and draw 20Amps or so, the neutral-to-earth voltage increases enough to cause a trip.
BTW, does anyone have a smooth safe technique for using an automatic PAT Tester on showers and ovens? Yes, I know it's a *portable appliance* tester but...
In article , roger writes
Thanks for the suggested explanation. However as I was the only one in the house at the time, I can say with a high degree of certainty (*), that nothing else got switched on either whilst the shower was trying to be used, or the hob.
(*) the possible exception was the thermostat on the fridge cutting in.
Adrian
Adrian Simpson writes
The last instance I had of this, the offender was a one-year-old Bosch fridge.
An increase in N to E voltage due to load change in a neighbour's house could presumably have the same effect.
If you ever find what it was/is causing your problem, do please post and let us all know.
In article , roger writes
The fridge is out of the ark (It was well past its first flush of your when I got it, which will be 17 years this December), so I suppose that could be starting to shown signs of old age.
If I find out what it was, I will report back.
Adrian
If I recall correctly, 40mA will kill you, therefore RCD's are set to trip at 30mA
The whole purpose of an RCD is to try to prevent people getting killed from electrocution installing a 100mA breaker, IMO is madness
The only reason I can see to use a 100mA breaker, would be to feed it's output directly into several 30mA breakers to keep a handful of circuits separate (for example, mains in ->100mA breaker, then this feeds to house 30mA breaker and another 30mA breaker for another building.
I had a problem with an old MK ELCB - it would randomly trip for no apparent reason Turns out the breaker was knackered - It was replaced with the same make/model/rating, and it hasn't tripped incorrectly since
Just my £0.02
Sparks...
So can 30mA, but not normally within the time it takes for an RCD to trip.
No, that's _one_ purpose. Indeed RCD's used for providing protection against electrocution must not exceed 30mA rating. However, RCD's protecting a whole installation (due to excessive earth fault loop impedance) must be at least 100mA, but cannot be used to provide protection against electrocution. Hence a single RCD cannot do both jobs.
A direct swap is indeed silly. The installation was wrong before, and is now wrong in a different (possibly more dangerous) way.
No, that doesn't work. RCD's don't discriminate on current. You should avoid daisy chaining them at all, but if you have to, the one nearer the supply has to be a time delayed type.
100mA and greater RCD's are for protection again high earth impedance, where a short to earth might not pass enough current to trip the fault current protective device within the required time (or even at all). This is commonly the case where the system uses an earth rod for earthing.
Hmmm, that's interesting.
One of my projects for Q1 next year (ie before the draconian new regs appear and drive the cost up to the point where I won't bother) is to replace my cu rrent CU.
I've read through a number of posts on the matter, and will be getting hold of a 16th edition on-site guide soon, but initial plan was to install an isolator before the CU, and replace the current one with one populated with a mixture of RCBOs and MCBs, possibly splitting my office off onto it's own ring, protected by an MCB due to the amount of computer equipment in there.
I had been uncertain as to whether the CU should have overall protection of a time-delayed 100mA RCD, but from what you say this is probably not necessary nor desireable. The earth is supplied by the provider.
Is this about the size of things?
cheers Richard
-- Richard Sampson
email me at richard at olifant d-ot co do-t uk
One thing to be wary of is that the new regulations don't kick in with a retrospective element.
By this I mean that when you eventually come to sell your house the solicitors may wish you, as the seller, to confirm whether there has been any electrical modifications made during your tenancy - and if so to provide appropriate certification. It is already common for the purchasers solicitor to issue a questionaire to the buyers solicitor requesting confirmation of various services, neighbourhood disputes, etc.
This particular question about the electrical installation could be posed a number of ways, I suppose I would not be surprised if they left out mention of 1st April 2004.
PoP
Yup, noted, thanks.
It should be said that there are also quite a number of ways to answer a question truthfully...
cheers Richard
-- Richard Sampson
email me at richard at olifant d-ot co do-t uk
I spy a budding politician and claim my five pounds ;)
PoP
Public life? I think not! :-)
Just spent rather too much time (and money) in the company of lawyers recently.... think some of it must have rubbed off. I obviously need rehab...
-- Richard Sampson
email me at richard at olifant d-ot co do-t uk
In article , tony sayer writes
Firstly apologies for the amount of quote, but the thread has been dormant for that long, I though it best to retain the context.
Having finally got a sparks in to have a look at it (long story), the circuits were fully checked out, and given a clean bill of health.
The problem was eventually traced to being a touched earth/neutral on the wiring that has been put in place for the oven (which has yet to be fitted). These have now had the ends insulated. Light usage was not enough to cause the circuit to trip, but heavy usage (hob or shower) was.
So thanks again for the replies.
Adrian
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