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Oz34
United Kingdom
2538 Posts |
 Posted - 12/01/2014 : 18:59:08
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Does anyone please know a source of these little (only 1 inch/25mm long) 4.5 amp fuses? Standard glass 5 amp fuses seem easy enough to find however, they won't fit the clips being 30mm.
Cheers,
Dave |
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kimber
United Kingdom
1529 Posts |
Posted - 12/01/2014 : 19:52:01
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quote:
Originally posted by Oz34
Does anyone please know a source of these little (only 1 inch/25mm long) 4.5 amp fuses? Standard glass 5 amp fuses seem easy enough to find however, they won't fit the clips being 30mm.
Cheers,
Dave
If you have a blown one they can be repaired by unsoldering the ends and replacing the wire with new wire of an appropriate rating. |
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Nick Feakes
USA
3372 Posts |
Posted - 12/01/2014 : 21:17:13
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I think I can source these Dave if you cannot find any in the UK
Nick |
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Oz34
United Kingdom
2538 Posts |
Posted - 14/01/2014 : 09:02:30
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Many thanks both of you.
Andrew, how do I know what is appropriate? I had always assumed in my ignorance that 5amp household fuse wire would blow at an entirely different current at 12 volts?
Nick, thank you for your offer which I'll hold open if I may. I have a working one at the moment but.... It would be nice to have a couple of spares available.
Cheers,
Dave |
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i.thomson
United Kingdom
408 Posts |
Posted - 14/01/2014 : 11:52:00
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5amps. is always 5amps. no matter what voltage is specified. The way I understand it, however, and my understanding is somewhat sketchy, is that the difficulty may lie in the way the current value is specified. For instance the current rating on the big, old fuses which our cars use are, as I understand it, the surge current which they will handle without blowing. That is: they will only handle the 30 or 20 amps which are marked on them for a short while, perhaps only milliseconds. This allows for the increased current which flows as devices start up. The steady state current is somewhat lower than this, perhaps half the marked figure. By this reading a 4.5Amp. fuse may only be capable of carrying 2Amps. or so continuously. More modern fuses may be specified differently, perhaps with the continuous current which they can handle. This, it occurs to me, may also apply to any replacement fusewire which is soldered into a blown fuse body. Perhaps someone with some more knowledge of such specs. would like to comment. Do you know any more Nick?
Regards
Ian Thomson |
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Nick Feakes
USA
3372 Posts |
Posted - 14/01/2014 : 15:17:19
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Ian
You are correct.If you pass enough current through a piece of wire its resistance will cause it to heat up and melt (blow). A 5 amp fuse may pass 100 amps for a short period of time (a few milliseconds), it will pass 50 amps for a bit longer, 10 amps for a bit longer still and so on. So here is the difficulty, specification. Automotive fuses in cars of our era are specified to carry half the labeled current continuously but to blow at their rated current. However, as stated above, time to blow is exponentially related to overload. Remember, fuses are there to protect the wiring to prevent a fire. So the issue is really, can the wiring carry enough current to blow the fuse sufficiently quickly?
Nick |
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Oz34
United Kingdom
2538 Posts |
Posted - 14/01/2014 : 18:40:58
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Ian & Nick, if I understand you correctly, if I were to do as Andrew suggested, I could use household 5 amp fuse wire & this would be close enough to 4.5 for government work?
Dave |
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i.thomson
United Kingdom
408 Posts |
Posted - 14/01/2014 : 19:07:35
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Dave. I am sorry if I confused the issue for you by trying to be specific. My point would be that perhaps you need a lower rated fuse if modern specs. are based on continuous current rather than surge current. I don't know enough about specs. to be able to be sure of this however.
Ian |
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LewPalmer
USA
3242 Posts |
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Alan Bertram
United Kingdom
199 Posts |
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Alan Bertram
United Kingdom
199 Posts |
Posted - 14/01/2014 : 22:20:09
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Nick,
I found this site interesting as it gives the original LUCAS fuse rating colour codes and as in your Triple M Electrics book, states that the continuous current rating for the Lucas type glass fuse is half the stamped fuse rating.
What the actual safe continuous working current for a Larger Type Glass Fuse with a blow amperage of 5 amps is not stated?
http://www.car-fuses.co.uk/content/glass-fuses.php
Regards, Alan
PA 0397 |
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Nick Feakes
USA
3372 Posts |
Posted - 15/01/2014 : 00:24:17
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Alan
The site states "Glass fuses are available with a blow amperage of 2a to 50a" so I would assume the continuous current would be half the rated blow current. But as I suggested above, the blow current is dependent on time, so it should really state "guaranteed to blow within 5 seconds when 10A flows continuously" or something similar. Similar to many things, the lack of precision (or understanding) of the specification leads to confusion for the user.
Nick |
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Oz34
United Kingdom
2538 Posts |
Posted - 15/01/2014 : 17:30:29
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Many thanks to all who have replied to this. I have taken the plunge & ordered a 50 pack of the real McCoy as flagged up on Ebay by Alan B.
As I clearly don't need 50 in my lifetime (at least I hope not!!), when I get my act together, I'll offer smaller batches at cost plus postage. This won't be for a while as I'm male & cannot multi-task; at present the focus is getting the car ready for Scotland in May.
Cheers,
Dave
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Edited by - Oz34 on 15/01/2014 17:32:42 |
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Colin McLachlan
United Kingdom
991 Posts |
Posted - 16/01/2014 : 09:15:41
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Dave, bring some up with you in May! I'll take a couple, and I'm sure you'll get rid of a good few to the other entrants.
Colin
PA 0613
MG3242
Register No. 2591 |
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Colin Butchers
United Kingdom
1487 Posts |
Posted - 16/01/2014 : 09:51:21
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Hello Dave,
Count me in for half a dozen, please.
Many thanks,
Colin B. |
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philcoombs
United Kingdom
77 Posts |
Posted - 17/01/2014 : 11:12:37
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Dave, please count me in for at least a couple or whatever number you decide on. Will collect in Scotland or will pick up from you if you would prefer.
Philip Coombs |
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