I have 2 mains downlighters over the sink. The are connected to
socket that is in the lighting circuit, using a 3 amp fuse. Every tim one of the mains downlighters blows, usually when switching on the ligh switch, the mcb trips and all the lights go out. The idea of the fuse i so it will blow first. Shall I use a 13 amp fuse or will it make n difference at all?
TI
-- Hands On
Is it an MCB or RCD, and what's the rating ?
RCDs quite frequently "nuisance trip" when a lamp blows.
The fuse should allow for discrimination and should be rated at less than the one in the consumer unit so it blows first under fault conditions, so I wouldn't consider changing that.
How many downlighters are there - are they halogen ? mains / LV ?
The fuse won't blow first -- the MCB is faster. You could try changing the MCB from a Type B to a Type C, but it may not make any difference. Replacing the MCB with a 5A BS1361 HRC fuse cartidge would solve the problem.
Err, wrong way round.
An MCB will beat a fuse when you get into the fault current part of the tripping curve, which is what happens when a lamp blows sometimes.
On Wed, 26 Jan 2005 23:17:54 -0000, Colin Wilson strung together this:
Ooh, 50\50 chance of getting the right one and you got it wrong!
The tripping characteristics are different for fuses and MCB's. If there are an identically rated fuse and MCB on the same circuit the MCB will usually trip before the fuse blows. To get around the problem use a 1A fuse in the spur and change the MCB for a Type C, or an HRC fuse.
On Wed, 26 Jan 2005 23:17:54 -0000, Colin Wilson strung together this:
Could we all possibly set up kill filters for that bunch of fuckwits at diybanter? I'm only getting replies and it's annoying.
Its late and i`m drunk :-}
Not sure if this was aimed at me ? I`m not on diybanter...
On Thu, 27 Jan 2005 09:23:26 -0000, Colin Wilson strung together this:
No, I just replied to you as I don't see the original question coming from there, just the replies. It just so happens that you replied so I could only reply to you.
No worries, I was wrong anyway, so perhaps the comment would still apply :-}
I have two 50w downlighters on a 3 amp fuse. The mcb, not main RCD trips when one lamp blows and the 3 amp fuse blows too. It is a wast of time. Is it better to have a 13 amp fuse in the plug, then only th mcb will trip
-- Hands On
Which plug is this? It is likely that the downlighters can be wired directly into a lighting circuit with no fuses at all. Are they currently wired off a socket circuit or something? What is the rating of the MCB that trips?
Christian.
First off, Lurch already suggested you'd do better to hunt down a source of 1A fuses (two 50W downlighters will draw about 0.5A steady-state, allowing for losses in any transformer); that way the cable supplying the mains to the lights/transformer is adequately protected (which it might not be with a 13A fuse), and the lights-specific fuse will blow leaving the rest of the lights on. Change the lighting MCB for a Type C (widely available at any electrical trade counter or mail-order leccy-bits supplier) or an HRC fuse-carrier (harder to source) to make it that much more likely it'll be the local fuse that blows.
Secondly, what's with this 'plug' supplying your downlighters? Do you mean you have a 'standard' 13A socket on the lighting circuit? *Not* a good idea - some numpty'll plug in a hairdryer or similar, overloading the lighting circuit enough to overheat the cables without necessarily making the 6A MCB blow. It's possible you've done this to use some 'wall-wart' supply for the downlighters (transformer built into a 13A plugtop-style case) - if so, at least put the 13A sockets well out normal reach and sight, and cover them with warning labels... and feed the sockets themselves off an FCU with a 1A fuse!
Stefek
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I have two 230v mains downlighters over the sink. The are connected t a socket that is in the lighting circuit, using a 3 amp fuse. Th socket is switchless, out of sight and cannot be used for anythin else. This is normal practice. Every time one of the main downlighters blows, usually when switching on the light switch, the mc trips, not the RCD, and also the 3 amp fuse blows, and all the lights g out. The idea of the fuse is so it will blow first. Shall I use a 13 am fuse so that the fuse does not blow, or will it make no difference a all and even the 13 amp fuse will blow as well?
Is there an mcb that is opn a plug, so the lighting mcb does not trip? If nothing is suitable is it best to use a round 3-pin socket without fuse?
The mcb rating is 6 amp. It is a Legrand B6 mcb
-- Hands On
Trouble is your 1A fuses will pop regularly. To avoid this you'd need
1A antisurge fuses - and those are slow blowing enough that your mcb will trip instead.The 1 realistic solutions are:
NT
It would be best to simply wire the cable from the downlighters into the lighting circuit using a circuit box and don't use a plug/socket at all. Provided the transformers are happy at being protected at 6A instead of 3A.
Christian.
No it isn't.
I guess you can't see the answers already posted. You might want to change the way you access this newsgroup to use a proper newsreader and news server. In the interim, use groups.google.com to see the whole thread.
I posted originally that the downlighters were mains, yet many went o about transformers.
The socket over the lights "is" stadard. It was put in 3 years ago This is a new house. Even houses just built have them. Originally i was LV cabinet lights, which kept dropping out so I bought main downlighters as Homebase only sell them now. They don't sell sets of L fittings any more.
When my candle bulbs pop in the l/room they throw the mcb as well
-- Hands On
"Hands On" wrote | The socket over the lights "is" stadard. It was put in 3 years ago. | This is a new house. Even houses just built have them.
So what. Having a BS1363 13A socket on a 6A lighting circuit is *wrong*.
Owain
*wrong*.
It does contravene the regs but in safety terms it is trivial, and of no real relevance to the OPs problem.
If your mcb keeps nuisance tripping, and not only on these lights, try a C type mcb. Hopefully that will sovle it. But if it doesnt, your next best move is a fuse in the CU instead of an mcb. What fuse you put in the mains plug is irrelevant in this case.
NT
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