Rcbo trip test

[Doc Hudson]

but that's like saying the brakes on your van work when you are parked on the drive but not when doing 70 on the motorway so I will test them on the drive don't you agree

No, You are suggesting by your assumptions that your electrical knowledge is greater than the combined knowledge of the IEE who publish BS7671 and the on site guide and the various guidance notes. I personally consider myself reasonably knowledgeable but not more knowledgeable than the IEE. I think they have a few members with higher qualifications than I have attained.

Doc H.

 

[frankie310581]

now one is saying that but you must see the point being made

 

[Sidewinder]

OK,

Your Megger is well made and an expensive bit of kit, as is my Fluke 1653 to us anyway, in the realms of test equipment it is cheap tat really as is my Fluke!

To test an RCD in a fully connected circuit then you can move the decimal point about 6 places to the right of where it is in the price of either of our meters.

The limits on cost infer that the meters apply an overload current to the device being tested, they also sart a timer, and measure the mains voltage at the point of test.

Once this voltage begins to cahnge and drops to a predetermined level they deemthe circuit to be de-energised thus the rcd has tripped.

Now you have conductors going around your circuit in the form of copper wires, these are insulated.

An insulated conductor has what properties?

Think electronics.

Also you have all the other kit attached.

One of the theories of Heisneberg is that you cannot simltaneously measure the position and velocity of a particle, commonly known as you can't measure it without changing it.

e.g. when you measure a voltage at the output of an rcd, the meter takes a minute bit of current from the supply for the measurement.

This is negligible in normal circumstances.

However, by ohms law, that diverted current has the affect of reducing the measured voltage.

Are you there yet?

 

[Doc Hudson]

now one is saying that but you must see the point being made

Not really no. If the guidance is there in industry recognised publications, but electricians are not following that guidance, it is hardly surprising that the results may not be within the recommend values given in the same guidance. I think Sidewinder has tried to offer a lot of hints to science behind some of the reasons.

Doc H.

---------- Post Auto-Merged at 23:34 ---------- Previous post was made at 23:30 ----------

The question has to be, Why follow and accept the recommend operating times of the wiring regs, but not the recommend test procedure?

Doc h.

 

[frankie310581]

lol think so but going to look this up interesting

 

[Sidewinder]

OK,

keep asking and I'll keep asking until the light comes on, mind remember the forum light will be going out for a bit soon as I understand things, but, stick with us!

 

[ianmacd]

Not really no. If the guidance is there in industry recognised publications, but electricians are not following that guidance, it is hardly surprising that the results may not be withing the recommend values given in the same guidance. I think Sidewinder has tried to offer a lot of hints to science behind some of the reasons.Doc H.

---------- Post Auto-Merged at 23:34 ---------- Previous post was made at 23:30 ----------

The question has to be, Why follow and accept the recommend operating times of the wiring regs, but not the recommend test procedure?

Doc h.

While I agree with you Doc that it should be tested in isolation (mainly due to the shortcomings of our metres), the issue surrounding testing RCD's in circuit does have some weight with other people (and even members on here) and I do understand their concerns but, at the end of the day, we follow the regs and guidance for a reason, defence from prosecution.

If you test an RCD in isolation and it passes but then kills someone by not tripping when attached to the circuit, you can fall back on the defence of 7671 and associated guides. If you follow another procedure, then you have no such defence and may well be binning working RCD's when they do not pass testing with circuits still connected.

 

[Sidewinder]

ian,

It's not just load though is it!

 

[ianmacd]

No its not, possibly a bad choice of word there.

 

[Sidewinder]

OK!

 

[ianmacd]

Fixed

 

[nsbs]

why dont you test the RCBO at its terminals. you should be testing RCD's & RCBO,s with the load disconnected. i test mine at the CU.