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Post by 998automan on Nov 9, 2014 21:00:12 GMT
Hi All. Am thinking of upgrading my original fuse box (4 way with glass fuses) for an after market blade type. I have had a look around and they all have a single terminal each side of the fuse rather than the twin type as on the original. As nearly all the terminals on the original are being used is it just a case of buying an 8 way box and splitting these down? Would be grateful to hear from anyone else who has done this and find out if there are any other pitfalls I should look out for?
Thanks Mike.
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Post by 998automan on Nov 22, 2014 20:55:58 GMT
Hi, a bit weird to be answering my own question but thought this might help someone else! :DIn the end I bought `piggy back` spade connectors and this has worked well and has also meant that I could stick with a 4 way fuse box - much simpler for wiring everything back up! Hope this helps anyone doing the same thing.
Cheers Mike.
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Post by mra-minis on Nov 14, 2015 11:39:45 GMT
As long as you got your electrical load calcs right you will be ok, however if not and you could easily have yourself an under bonnet thermal event !
Remember people the fuse is there to protect the wiring not the unit that is being powered... and the wire has be capable of taking the maximum load that can be applied to it plus a safety factor of 1/3 in open air or 2/3 if in a bundle and double or more if the bundle is a long run ... all of these factors have to be catered for to keep you or your loved ones (including your Mini) safe
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Post by 998automan on Nov 14, 2015 14:42:33 GMT
Hi, yes I totally agree. One of the reasons I swapped the box was due to the lack of availability of the glass fuses & the confusion over their continuous & instantaneous blow ratings. After a bit of research it seemed that a good rule of thumb was if replacing glass with blade the blade fuse should only be half the rating of the glass one it replaces. For example in my hand book it states that fuse 1 should have a rating of 17/35amps (lower figure is the current rating & higher is the blow rating) so I replaced with 15amp blade (as there is no 17 amp available). However I am no expert in auto electrics and would always advise seeking out those with the required expertise first if in doubt!
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Post by mra-minis on Nov 18, 2015 15:00:21 GMT
Hi, yes I totally agree. One of the reasons I swapped the box was due to the lack of availability of the glass fuses & the confusion over their continuous & instantaneous blow ratings. After a bit of research it seemed that a good rule of thumb was if replacing glass with blade the blade fuse should only be half the rating of the glass one it replaces. For example in my hand book it states that fuse 1 should have a rating of 17/35amps (lower figure is the current rating & higher is the blow rating) so I replaced with 15amp blade (as there is no 17 amp available). However I am no expert in auto electrics and would always advise seeking out those with the required expertise first if in doubt! Hi the different rating f fuses is due to the way they are rated.... for instance glass is the blow rating and blade tend to be the maximum operating current |
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Post by notamini on Nov 18, 2015 17:26:00 GMT
If the 15A is not blowing under FULL circuit load, you can stay with that. It is safer than an over sized fuse. I am surprised you are finding glass unavailable. We use them regularly in more than just cars and they are readily available. Did you source out an electronics supplier?
Things like motors, solenoids and relays can cause a fuse to blow prematurely and are often fused with what is referred to as a slow-blow fuse. These have a visible 'spring' in them to allow movement before breakage like a shock absorber and will allow 'surges' but still blow if the excessive load is constant. Now keep in mind that the difference is in milliseconds. These are only available in glass as far as I know. I'm wondering now if the blades react in this same manner and therefore have these extra ratings.
Mark
ON,Canada
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Post by mra-minis on Nov 19, 2015 1:28:27 GMT
If the 15A is not blowing under FULL circuit load, you can stay with that. It is safer than an over sized fuse. I am surprised you are finding glass unavailable. We use them regularly in more than just cars and they are readily available. Did you source out an electronics supplier? Things like motors, solenoids and relays can cause a fuse to blow prematurely and are often fused with what is referred to as a slow-blow fuse. These have a visible 'spring' in them to allow movement before breakage like a shock absorber and will allow 'surges' but still blow if the excessive load is constant. Now keep in mind that the difference is in milliseconds. These are only available in glass as far as I know. I'm wondering now if the blades react in this same manner and therefore have these extra ratings. Mark ON,Canada Never seen a slow blow blade, but I have seen resettable or trip blade fuses.... Also keep in mind the fuse is the weak link, don't ever put a bigger fuse capacity in the system or the wire will become your fuse.... thermal event here we come. |
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Post by notamini on Nov 19, 2015 18:48:10 GMT
I agree entirely. The fuse must be low enough to protect whatever device is attached. I always look for the current rating of a device add a small fudge factor and this will guarantee the device is properly protected. i.e. Current rating of 2 Amps, fuse should not exceed 3 Amps. Again, add more for a motor, solenoid or wire wound device. They can take more abuse than say a car stereo.
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Post by 998automan on Nov 19, 2015 20:29:58 GMT
Hi guys, thanks for your comments. I did manage to track down some glass fuses but no-one selling them could tell me if the rating displayed was the load or blow rating. Consequently I didn`t want to put a glass fuse in rated at 35amps not knowing if that was the load current or the blow rating! According to the original handbook Fuse 1 (on my 86 Mayfair) is rated at 17/35 amps, I would be interested to know what rated glass fuse everyone is using here?
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Post by notamini on Nov 20, 2015 16:18:36 GMT
I just use the 3AG35's right off the shelf. I actually have the 1969 originals tucked into the 'spare' pockets of the block. They are good but the adhesive has dried out and the glass is now loose. They actually have a paper label in them showing the ratings.
Mark
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Post by mra-minis on Nov 21, 2015 1:52:19 GMT
I agree entirely. The fuse must be low enough to protect whatever device is attached. I always look for the current rating of a device add a small fudge factor and this will guarantee the device is properly protected. i.e. Current rating of 2 Amps, fuse should not exceed 3 Amps. Again, add more for a motor, solenoid or wire wound device. They can take more abuse than say a car stereo. Sorry chap, the fuse is only there to protect the wire not the item hanging off the end... The fuse is the wires weak link and is not there to protect the device. This is an industry recognised statement. |
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Post by mra-minis on Nov 22, 2015 15:45:32 GMT
Hi guys, thanks for your comments. I did manage to track down some glass fuses but no-one selling them could tell me if the rating displayed was the load or blow rating. Consequently I didn`t want to put a glass fuse in rated at 35amps not knowing if that was the load current or the blow rating! According to the original handbook Fuse 1 (on my 86 Mayfair) is rated at 17/35 amps, I would be interested to know what rated glass fuse everyone is using here? They should be colour coded.. Glass fuses used to have both the blow rating and the continuous useage rating |
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Post by notamini on Nov 23, 2015 17:46:09 GMT
That's a new one on me. Must be specific to the auto industry. I've been in the field of electronics for 40+ years and have always been told that the device is what is protected by the fuse and the feed wire should be rated accordingly. i.e 15 amps/#18 AWG wire. Obviously, this way, both are protected.
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Post by mra-minis on Dec 2, 2015 18:28:32 GMT
That's a new one on me. Must be specific to the auto industry. I've been in the field of electronics for 40+ years and have always been told that the device is what is protected by the fuse and the feed wire should be rated accordingly. i.e 15 amps/#18 AWG wire. Obviously, this way, both are protected. It is definitely a Space, Aeronautical, military and auto industry thing for sure, however I am being told it is getting applied across more industries such as white goods where a fire in a washing machine could easily kill... Can I ask which field of electronics you are in ? how many devices that plug in to the mains have you seen that have a fuse on the plug and a fuse at the device ? for instance my soldering iron has both, one to protect the mains cable and one to protect the device in this case my soldering iron... |
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Post by notamini on Dec 3, 2015 13:34:36 GMT
Here in Canada, we do not have this method of protection. Fusing is determined by the expected draw from the device or the load rating of wire in the case of house wiring. I have not seen many devices with plug or cord fused, only for UK and Europe. It is likely not a bad idea. The only other application I've seen is where the device has fused input and output load protection.
My experience is in military communication devices (including antenna design), weather radar, weather instrumentation )mostly electronic), remote control design, electric fireplace design and now aquatic research equipment, including high voltage electrofisher design and service. I have a degree in both analog and digital engineering technologies. I have also served as an electromechanical tech for a variety of devices and industries. And the list goes on...
Mark
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Post by mra-minis on Dec 3, 2015 23:54:56 GMT
Hi Mark,
That is impressive, I guess we do things differently in the UK and Europe... with all the new legislation coming in the auto industry has been applying the same system for years now... since at least 1999 with the Jaguar S type.
I can see what you are saying, I was responsible for the wiring design and manufacture of the Wheel barrow Mk9 electrical wiring system and that was done by each device having a fuse or fuse type device internally that was rated to the wire size and length.. ie the fuse was still to protect the wiring not the device, if the device failed it failed so what ? it meant that part didn't work anymore, however if the wiring failed without a fuse, then the wire became the fuse and then it became a thermal event with £15 million worth of damage to an otherwise repairable bomb disposal robot.
Yes in the UK we have fused plugs.... not sure if your system is that much different to ours, but in a building we will have a fused mains cable single or 3 ph coming in to the building, this will then go to the meter then to the fuse box, in every case the fuse is a lower rating than the wires to protect the wires, then for example it goes to a ring main and a single phase ring has to be capable of supplying 32A minimum per side then onto a 13A plug, lets say you plug in 5 x 3KW heaters ... that is 65A of draw, this would not blow each individual fuse at the plug because each heater is only drawing 13A but the total is higher than the wiring can cope with, and the fuse being below the capacity of the wiring would then blow first .... this is why you must never fit a fuse above the rated size.
Until Harmonisation a few years ago Britain had the best by far electrical safety record.
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Post by mra-minis on Dec 4, 2015 0:00:00 GMT
Come to think of it I was also responsible for wiring on the NP Aerospace Mastiff, Mastiff EOD, Wolfhound, Ridgeback and Buffalo and they where wired exactly as you mentioned, but the first job we did was get it all ripped out and applied latest system specifications to bring them up to date.
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Post by firept on Jun 15, 2016 20:12:03 GMT
I thought I would add to this, I found this info on the net when researching some time ago, apologizes if it has been plagiarized :-
"Lucas Glass Fuse Rating x .6 = ATC (Blade) Fuse Rating... then go to the next smaller value.
For example Lucas 35 Amp x .6 = 21 Amps. There is no 21 Amp fuse so use a 20 Amp ATC fuse
The "Randall table" on the page reflects what most of us in the U.S. have followed for years. You will notice that the .6 multiplier I mentioned works with Randall's table except for the 50 Amp fuse.
Like so many other things about our Triumphs, the British did things just a little bit different than the Americans, including what the ratings marked on fuses mean. The British Standard that Triumph used rated fuses by the current that was guaranteed to make them blow instantly while the American (and now international) standard rates fuses by the current that they will carry forever. Fuses work on heat, so a small overload may take a long time to build up enough heat to melt the fusible element and blow the fuse. How warm the fuse was to begin with plays a large role too. So the carry rating winds up being quite a bit lower than the blow rating... the difference is roughly 2 to 1!
So, what this means to you is that, if you elect to use common American standard fuses (Bussman is one maker, there are others) in your Triumph, you need to use a much lower rated fuse than what your Triumph documentation says to use. There have been cases reported where a restored Triumph has caught fire from a short, because someone used American fuses with the Triumph recommended rating marked on them... the short did not blow the fuse but instead set the wiring harness on fire!
Here is a conversion chart, lifted from a long-ago Bussman fuse catalog:
Bussman Conversion Chart
English Type American Standard Replacement
50 amp AGC 30
35 amp AGC 25
30 amp AGC 20
25 amp AGC 15
20 amp AGC 10
10 amp AGC 7 1/2
5 amp AGC 3
Personally, I feel even this chart results in fuses rather larger than needed, so for example I use an AGC 20 to replace the original "35 amp" fuse in my TR3A. My conversion chart would go more like :
Randall's Recommendations
English Type American Standard Replacement
50 amp AGC 25
35 amp AGC 20
30 amp AGC 15
25 amp AGC 15
20 amp AGC 10
10 amp AGC 5
5 amp AGC 3
Tim Buja and Glenn Merrell put on a good visual demonstration of the difference in fuse ratings at VTR this year, where they first put in a "25 amp" Lucas-equivalent fuse and applied enough load to blow it. Then they installed a "25 amp" American fuse and applied the same load. The fuse did not blow, but after just a minute or so the wire started visibly leaking smoke...
"
Ahh……… Lucas prince of darkness strikes again. Anyone remember the part number for loom smoke mine seems to have run out.
Paul.
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