Rcd problems

[MickkNipfler]

I'm having exactly the same problem an this:

-With only the supply cable connected, the test button does nothing
-If I connect the lighting circuit with a pull switch and 11w LE bulb, as soon as I pull the switch, the RCD trips
- If I connect the ring main and plug a drill in, plugging the drll in is fine but as soon as I ull the trigger, again the RCD trips
- I only hve a single nuetral bar
- The unit is badged 'CTI'

 

[ban-all-sheds]

Who installed the CU?

How come they've gone off and left the job only part-finished?

When are they coming back to finish the testing and issue the EIC?

 

[MickkNipfler]

Don't ask silly questions...... the word 'I' should give a clue

If only the supply cable is connected, surely the unit should trip when the 'test' button is pressed?

 

[ban-all-sheds]

What readings did you get from your RCD tester?

 

[MickkNipfler]

I'm only using a multimeter.

-I have taken a spur off my main consumer unit to feed this small unit
-I only have a light circuit and a small ring main.
-If I temporarily take the main live feed out of the main feed RCD and and connect it to the live for one of the 2 circuits, both the lightand power sockets work fine

 

[bongos]

I'm only using a multimeter.

-I have taken a spur off my main consumer unit to feed this small unit.

What exactly do you mean by "spur" in this sense? You would usually split the main tails with a Henley block or use a spare way to power a second CU.

You will require more than a multimeter to test this work. How will you be able to test the RCD operates properly within time limits/current limits?

Post a pic of your exisiting setup. It might help others work out where you're going wrong...

 

[ban-all-sheds]

Don't ask silly questions...... the word 'I' should give a clue

Sorry - my mistake - I assumed that you would have given the task of something as non-trivial and important as a new CU and new final circuits to someone competent and with the right tools etc...

 

[MickkNipfler]

Bogos - I've taken a feed from the main house CU so effectively am trying to use 2 CUs. My main reason for doing this is that it's a lean to shed and if get any problems with rodent damage or anything, it may be easier to isolate. It really is a very simple installation.

ban-all sheds - sorry, I wasn't being rude but let me tell you a story - 6 months ago, I had a problem with my Central Heating. I called in the experts who charged me a considerable sum of money to change the mid control valve. During their work, apparently, the CU kept tripping and they 'diconnected something' according to my wife. Next week, she took a belt off the toaster, then the dishwasher, then I took a belt off a radiator. I had a look at their 'professional' work myself and could clearly see that that the CH fee was putting 240v on my ring main earth everytime it tried to switch the heating on. I then checked the ring main earth and found that I didn't have continuity back to the CU earth bar. I called the CH company who then sent another electrician who rectified the fault and told be what was the fault was (confirming my own conclusions).

I don't have 17th edition qualifications (or whatever they're up to now) but have worked in telecommunication systems all my life so consider myself competent to at least carry out reasonable safe work.

I have by-passed my 2nd CU for the moment and both circuits are functioning fine. I'm wondering whether either the CU is faulty or whether maybe my earth isn't 100% (We are overhead fed). Should I be able to trip the CU by shorting out the Earth bar to the neutral as it doesn't trip whe I press the button?

 

[flameport]

The most likely answer is that the new RCD is wired wrongly.

Please post a picture of the unit (inside, so the wiring can be seen), and one showing the general area (the other CU, meter, incoming cable, etc.)

 

[Spark123]

From above it sounds like you have the supply neutral connected to the neutral rail instead of to the RCD.
Can you upload a pic of the CU?

ps, it might have been better to have started a new thread!

 

[bongos]

Bogos - I've taken a feed from the main house CU so effectively am trying to use 2 CUs. My main reason for doing this is that it's a lean to shed and if get any problems with rodent damage or anything, it may be easier to isolate. It really is a very simple installation.

I have to admit to still being a little confused by your description, sorry! Am I right to assume that the new cable runs from a spare way in the main CU?

As suggested it sounds like you possibly have the neutral wired to the wrong neutral bar for the relevant live. I'm guessing from your description with your concern of nuisance tripping that you don't want it RCD protected at the house CU? You will need to protect at least the sockets (possibly the lighting too dependant on installation method) at the shed end if this is the case and the supply cable must be of the appropriate type and intsalled in the correct way to avoid having to RCD protect it from your house CU.

Post a pic of your existing setup and im sure people will be able to help further.

Also have a look at part p.

 

[electronicsuk]

Not trying to belittle you, but you really should at least get someone to check your main earth and bonding are up to scratch. You say that the CH system was causing a L-E fault and the CH engineers had disconnected the ring final's CPC at the consumer unit. I would still have expected parallel paths through bonding and pipework via the boiler to have caused protective devices to operate under these circumstances.

As they did not and both you and your wife received a shock, that could suggest lack of main earth to the house, TT supply without correct RCD protection, or any number of things. Just as well it didn't happen while you were touching a metal tap in the bath, connected back to the heating system via copper pipework.

 

[ban-all-sheds]

From above it sounds like you have the supply neutral connected to the neutral rail instead of to the RCD.
Can you upload a pic of the CU?

ps, it might have been better to have started a new thread!

Thanks Spark, that was exactly the problem. All working fine now. I've learned how to do it....easy when you know innit.

Do you not think that it might have been more responsible of you to learn how to do it BEFORE you tried to do it?

And learn about the testing you need to do, for which a multimeter is wholly inadequate?

I don't have 17th edition qualifications (or whatever they're up to now) but have worked in telecommunication systems all my life so consider myself competent to at least carry out reasonable safe work.

You should reconsider, before you kill someone.