i have just started a course in electrics, while i was at the college i notice all these test boards that had lamps connected to a ccu, im thinking of building my own board to do some testing; however my ccu will not be connected to my house fuse box; can connect it to 13amp plug socket; if so what is the procedure is the same as fitting a plug?
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- Thread starter rzaxl
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I'm not really sure what you are asking.
Hi
I think hes asking can a 13a plug run a fuse board for test/learning purposes.
If that is the question then I cant see any reason why you cant. Do you mean to build yourself, plug it in, then play about (safely)/learn circuits? Just wire the earth to the earth bar, neutral to the neutral bar and live to the main switch. Obviously you cant exceed the 13a fuse in the plug but you should be fine with the lower mcbs.
If that is what you were asking.
I think hes asking can a 13a plug run a fuse board for test/learning purposes.
If that is the question then I cant see any reason why you cant. Do you mean to build yourself, plug it in, then play about (safely)/learn circuits? Just wire the earth to the earth bar, neutral to the neutral bar and live to the main switch. Obviously you cant exceed the 13a fuse in the plug but you should be fine with the lower mcbs.
If that is what you were asking.
thats exactly what i was asking; but im just trying to figure out the wiring procedure do i connect the switch to the plug and where does the earth come from
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Why not neutral to the main switch also?
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Which switch to the plug and which earth?
Maybe it's best if you tell us what you plan to do then we can advise.
Our trainers wired the earth in the plug to the neutral pin, so any RCD in the training facility didn't trip as we were testing the ones on the board.
Remember that this effectively makes the earth bar a live conductor, but we weren't told that till quite late!
Remember that this effectively makes the earth bar a live conductor, but we weren't told that till quite late!
Sorry secure, I was ment to add that in. 
basically i will have 4 circuit (each connected to a lamp) on the board, then connected by one light switch the circuits will be running from the 6a mcb of the ccu; the ccu then be connected to a 13am plug socket. This is where im a bit nervous
I did this myself many moons ago - setting up a small cu on a board with a live neutral and earth supply from a 13A plug.
The idea was to use it to learn the ins and out of various lighting circuit set ups (1 way, 2 way intermediate etc) and to practice testing.
If that is what you are planning then there is nothing wrong with your set up - all you are doing is effectively creating an appliance that runs off a household plug.
Buy yourself some resistors (various sizes) and put them in your circuit so when you do r1+r2 etc you actually get a useful reading rather than 0.01ohm if you know what resistors you're putting in you can calculate what length the cable would be were it a decent size run not 1m or whatever
Would that be TN-C-S-C earthing?
Wouldn't it be more like "TN-C-S² " - since an earth was derived from the CNE conductor in two different places?!! If it were true TN-C-S-C (actually TN-C-S-C-S, I suppose!), with the earth pin of the plug connected to the neutral (which I assume mfarrow didn't mean), then it would probably cause upstream RCDs to operate immediately it was plugged in, wouldn't it?
Kind Regards, John
Deriving the "earth" for the test board from the neutral to the earth board would simulate the situation provided the "earth" for the test board never came into contact with any other earth. If that happened then the RCD feeding the 13 amp socket would see a Neutral to Earth fault and trip.
Using an isolation transformer would avoid that happening.
Using an isolation transformer would avoid that happening.
Indeed, that was obviously the point in doing it.
Exactly - as I said, if the earth pin of the plug were connected (to N and the load CPC), that's precisely what would happen.
Kind Regards, John
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