Puzzling RCD Problem After Replacing old Garage Consumer Unit


Postby BenB1980 » Sun May 07, 2017 3:57 pm

My first ever post here! I hope someone can help. I've normally got all answers to all problems, but this one has baffled me.

So I've just replaced my old garage consumer unit with a new one. Basically it was in the wrong place and the previous owner of the property had done a REALLY bad job installing it (upside down too?!). So I've taken the opportunity to tidy everything up a bit including installing a nice shiny new unit. At this point I would like to say that, whilst I'm not a qualified electrician, I am happy enough working with it all to know what I'm doing.

So, the problem is basically that everything is now installed, back up and running, except the RCD now trips when I plug the freezer back in.

Yes, it's the age old freezer problem...

The issue I have is that literally NOTHING has changed from when the "old" consumer unit was up.

The old unit itself isn't that old I guess. It's a 40A/30mA RCD. One 32A and one 6A MCB. Nothing unusual. The new unit is exactly the same spec. 40A/30mA RCD, 1x 32A MCB and 1x 6A MCB. I've checked and double checked the wiring. All sockets tested and light up correctly with the tester.

If I plug in something small (battery charger, work light, etc) all systems stay on. As soon as I go to plug in the freezer, it trips.

Is there something glaringly obvious that I'm missing?

Should I simply reinstall the OLD consumer unit and live in ignorance? (because I can only assume that if the old unit doesn't trip but the new one does, then there's potentially something wrong with the rest of the garage electrics which I never knew about! - and therefore need to sort out pretty sharpish!)

Is the issue simply that the newer RCDs are more sensitive and that simply upgrading the RCD to a higher one (Say, 63A or even an 80A one) be the answer?

Sorry for the long discussion start... I like to make sure I've explained the situation properly that's all!

Thanks in advance,

Ben
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Postby kbrownie » Mon May 08, 2017 6:17 am

What electrical testing did you do before and after the alterations made?

May I add as an unqualified and what seems an unskilled person, this is work you should not be undertaking and the work very likely requires building control permission prior to work starting, as the work cannot be verified as safe, you have performed illegal activities.

If you performed none the correct testing procedures, before or after the installation, you have been very foolish!
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Postby ericmark » Mon May 08, 2017 7:05 am

What is the reading you get with the installation tester when you test earth to neutral? And did you use a proper tester with 500 volt?

In electrics never assume, you test. If you can't test, you should not do the job.

I would unplug everything and try one item at a time.
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Postby BenB1980 » Mon May 08, 2017 9:13 am

All sorted!

Traced everything back and found another spur which I never even realised existed! It had never been terminated properly!

Anyway, just to make sure, I unplugged everything, re-checked all junctions and wiring, tested all components again and everything is working absolutely fine!
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Postby collectors » Mon May 08, 2017 10:30 am

Seems like its the freezer. If you can get hold of one, i would PAT test the freezer & also test the wiring in the garage.
Not quite a legal thing know days, but we used to install the freezer socket off the RCD because we had two clients came back from their hols to best steak & smoked salmon floating around in ice cream because the RCD had tripped off to an unrelated fault on the same circuit as the freezer.
But best bet is test to find the fault.
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Postby BenB1980 » Mon May 08, 2017 5:04 pm

collectors wrote:Seems like its the freezer. If you can get hold of one, i would PAT test the freezer & also test the wiring in the garage.
Not quite a legal thing know days, but we used to install the freezer socket off the RCD because we had two clients came back from their hols to best steak & smoked salmon floating around in ice cream because the RCD had tripped off to an unrelated fault on the same circuit as the freezer.
But best bet is test to find the fault.


Thanks Collectors... It's all been tested now. It was an old rogue cable which wasn't doing anything other than not being terminated properly!
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Postby kbrownie » Tue May 09, 2017 6:18 am

What testing took place?
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Postby BenB1980 » Tue May 09, 2017 8:59 am

kbrownie wrote:What testing took place?


I had an electrician come out and he certainly did continuity, polarity, IR and an RCD test. Maybe some others but not entirely sure. I didn't stand and watch over him as I don't think that's fair. He was here for about two hours in the end.

But even so, I'm still going to make a point of saying that he was happy with all that I'd done (although did also give me a lecture about Part P). He even commented on how very neat it all was!

Happy? Can we all move on now?
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Postby kbrownie » Tue May 09, 2017 6:07 pm

We can move on, now you have had a lecture on safe methods of installation and complaints to the laws of the land, I can not advocate illegal activities, nor should this website. The question regarding test was the very first thing I mentioned, on very first reply to your post. Moving on would have been much quicker, had you replied to that with some speed.
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