British Fuses vs American Fuses...big difference

[Guest]

For those of you out there that may have an American Buss fuse stuck in your fuse block, thinking that they are an ok substitute for the correct British fuse, think again. VTR has a nice article in this month's magazine on just that subject. And how using the incorrect replacement fuse can be fatal to your car. Perhaps one of you out there will get into the meat and potatoes of why this is so (I know but would rather someone with better organizational skills write it out).

Now tell me honestly, surely one or two of you have slipped a 30 amp Buss fuse in that little fuse block, thinking ole TR6Bill wouldn't notice.


I have seen a car torched because of this.




Bill

 

[Geo Hahn]

Re: British Fuses vs American Fuses...big differen

In simple terms (because I can only express 'lectrics in simple terms)... I think the US system rates the fuse based on the continuous load it can handle w/o blowing whilst the British system expresses the load at which the fuse will immediately blow. Comparison/substitution looks something like this...

Lucas 50 amp - continuous 25 amp
Lucas 35 amp - continuous 17 amp
Lucas 25 amp - continuous 12 amp
Lucas 20 amp - continuous 10 amp
Lucas 15 amp - continuous 8 amp
Lucas 10 amp - continuous 5 amp
Lucas 2 amp - continuous 1 amp

Other problem you may encounter is that US fuses are likely a different physical size from the Lucas equivalent.

My preference is to use US 14 amp fuses which are the same (shorter) size as Lucas 35 amp. I open them up and slip in a Lucas paper so they look right and the 'blade' is hidden (Lucas uses a wire). This matters on a TR3 as the fuse block has no cover and the fuses are in plain sight on the firewall.

P.S. Possibly more than you want to know: Anyone wanting Lucas paper inserts can use these images (they look huge but should print small) --

https://www.cybertrails.com/~ahwahnee/fuse%20label%2035.JPG

https://www.cybertrails.com/~ahwahnee/fuse%20label%2050.JPG

35 amp was usually white paper, 50 amp was yellow... use a quick dip in your cup of coffee to give the paper a suitably aged look, cut, dry & curl. The end of a fuse can be carefully removed once hot from a soldering iron and reattached the same way. Test with an ohmeter to make sure you still have continuity.

 

[kodanja]

Re: British Fuses vs American Fuses...big differen

thats great info ((THANKS SO MUCH))!

 

[bobh]

Re: British Fuses vs American Fuses...big differen

Thanks! My spare fuses are all American 35 amp Buss fuses. It's a good thing I haven't used any.

 

[jessebogan]

Re: British Fuses vs American Fuses...big differen

Want a cheap source of lucas fuses? Check out pre 1989 Jaguars in the junkyard. There are fuse boxes under each side of the dash, and at least one under the hood. I "harvest" these from every car I encounter in my infrequent trips to the u pull it place.

 

[Bugeye58]

Re: British Fuses vs American Fuses...big differen

This was my response to a recent question on the Spridget Forum. Dave is an electrical engineer, and knows of what he speaks.
Once again, sincere thanks to Dave.

Bob, regarding your fuse question, this information was provided courtesy of Dave Russell. Dave is about the "Guru-est of gurus" in these parts.

"If you are wondering, you can replace Brit fuses with US fuses. Due to different rating systems, Brit fuses & US fuses will have different numbers for APPROXIMATELY the same ratings.

Brit (Lucas)--------US (SFE AGC)
5-----------------------3
10----------------------5
20---------------------10
25---------------------15
30---------------------15
35---------------------20
50---------------------25
Later Lucas fuses are dual marked to eliminate some of the confusion. An example is the 17/35. In this case the 17 is the approximate continuous current carrying capacity & 35 would be the fast blow rating.
This means that a single marked 35 or a dual marked 17/35 amp marked Lucas fuse is about the same as a 20 amp marked BUSS fuse.
D
Edit:
The US ratings are the continuous current carry ratings. In this case the Lucas fuse marked 35 or 17/35 would have a continuous rating of 17 & the US 20 rating would be close with it's continuous rating of 20.
D "
Thanks, Dave!
Jeff

 

[Brosky]

Re: British Fuses vs American Fuses...big differen

Glad that you posted this. I can't find my latest magazine from them and I'm getting a little upset thinking that I may have recycled it before I read it. Time to check out the bin in the garage.

 

[myspitfire]

Re: British Fuses vs American Fuses...big differen

Well then! question for Dave;By looking at your comparisons
(Brit vs US) WHICH on THAT list would be your BEST choice to use to replace my current Lucas fuses(British Wiring)171/2 35amp continuous.Since most wiring limits on my Spitfire are 10amp rated(headlights etc) would 30ampLucas..15amp US Buss work ok?....I'd like to use US Fuses as they are readily available,& are not that expensive...........ALSO one other question;do you recommend HALOGEN HEADLIGHTS &do they heat up the wiring MORE SO that the standard incandesent. Ken&Whitelightning(alias myspitfire)

 

[Brosky]

Re: British Fuses vs American Fuses...big differen

I use AGC15 in mine and have never had any problems. I carry a stock load on the system, in other words, no extra lamps or big horns, etc.

 

[Guest]

Re: British Fuses vs American Fuses...big differen

I was told by British Wiring that the wiring harness they sold me is capable of handling H4 halogen bulbs. I have on several occasions felt the wires to the headlights and felt no unusual heat, not that that is an accurate test. All my other "high pull" electricals (Delco alternator, halogen fogs {really pull a bunch}, electric fan) I wired totally independant of the stock wiring harness so there is no worries.


Bill

 

[drooartz]

Re: British Fuses vs American Fuses...big differen

I had gotten this wisdom on the Triumphs mailing list once as well, when I was confused about the difference. Very nice chap gave me an in-depth answer on the issue, now posted on my site:

https://www.drooartz.com/index.php?page=29

 

[Brosky]

Re: British Fuses vs American Fuses...big differen

Always a wise choice when adding power accessories to any older vehicle.

 

[Dave Russell]

Re: British Fuses vs American Fuses...big differen

[ QUOTE ]
Well then! question for Dave; By looking at your comparisons
(Brit vs US) WHICH on THAT list would be your BEST choice to use to replace my current Lucas fuses(British Wiring)171/2 35amp continuous.Since most wiring limits on my Spitfire are 10amp rated(headlights etc) would 30ampLucas..15amp US Buss work ok?....I'd like to use US Fuses as they are readily available,& are not that expensive...........ALSO one other question;do you recommend HALOGEN HEADLIGHTS &do they heat up the wiring MORE SO that the standard incandesent. Ken&Whitelightning(alias myspitfire)

[/ QUOTE ]
The Buss 20 amp fuse (a continuous 20 amp rating with a blow rating of around 35 amps) would be a close match to the Lucas 17 continuous/ 35 blow fuse. If you wanted to be a bit more conservative, the Buss 15 amp "might" work.

A fuse is intended to protect the wiring, not the device connected to the wiring. Wiring rated at 10 amps continuous would be adequately protected. In reality, the 35 amp "blow" rating might actually require several seconds to actually blow at 35 amps. The nominal 10 amp wiring would actually require several minutes to damage it at 35 amps so there is adequate margin of protection.

Surprisingly, the newer Halogen lights, in USA legal wattages of 55/60, do not draw noticeably more current than the older Tungsten lights. They would both draw about 4 amps each, maybe slightly more. The increased light output for the same current is obtained by the newer technology. ie- different filament materials & a gas such as Halogen surrounding the filament instead of just a vacuum around the filament as was common in the older designs.

Halogen lamps are available as separate bulbs such as the H4, & as sealed beam units. I personally like the Sylvania H6024XV sealed beam units. A lot more light & no increase in current.

Aside: I tried the "super blue" lights which look very distinctive, but in reality gave less "on the road visibility" than the standard white lights. Something to do with eye sensitivity to various colors? The blues are certainly more annoying to oncoming drivers.
D

 

[swift6]

Re: British Fuses vs American Fuses...big differen

Most of the 'Blue' lights use a dichroic filter on the lighting element. In simple terms the dichroic filter changes the color temperature from the warmish 3800 Kelvin (approx) to the cooler and more like daylight 5500 Kelvin. In doing so though it can reduce the output by a 1/3 to nearly 1/2. So most of them are for show. ( I used to have to deal with a LOT of mixed lighting scenarios for still film and video, Digital has made that part of capture SO much easier.)

HID's tend to be very picky about their lens surface. I've seen a few product warnings stating that if the lenses are dirty the lights will tend to glare more than usual. By dirty they meant anything other than VERY clean. How many newer cars out there do think have VERY claen headlight lenses on a constant basis. /ubbthreads/images/graemlins/smirk.gif

With Modern H4's... I've been using some Cibie's with the 55/60 bulbs in my TR6 for about 7 years now. With no wiring changes. If I want to 'upgrade' to the 55/100 bulbs though I would need to add some relays. /ubbthreads/images/graemlins/grin.gif

 

[myspitfire]

Re: British Fuses vs American Fuses...big differen

Thanks Dave;Very useful informationIt seems my headlights will be Halogen Sylvania 55/60 type;And i intend to start using 15/25-35 amp US fuses,To replace those Lucas 17.5/35amp.Running mostly 10amps on most electrical 15amp should be adequate......just not to split hairs but...the difference between 17.5 & 15 amp fuses would that cause a detriment in operation of the electrical devices? If you follow my thinking. /ubbthreads/images/graemlins/confused.gif
KM

 

[Adrio]

Re: British Fuses vs American Fuses...big differen

If you are replacing a 17.5 amp fuse with a 15 amp fuse in a circuit that is drawing 10 amps (that is what I read of your question) then no there will be no detriment in the operation of electrical equipment.

 

[myspitfire]

Re: British Fuses vs American Fuses...big differen

Thanks my friend;Very good dialog on this issue.I will be buying US made fuses 15amperes 25 amperes continuous for the Spitfire from now on. Which would be better 25amp? continuous or 35 amp? continous.I think this has cleared a lot of uncertainty for TR fans. /ubbthreads/images/graemlins/cheers.gif /ubbthreads/images/graemlins/driving.gif

 

[piman]

Re: British Fuses vs American Fuses...big differen

Hello all,

just to pick up on a point someone made when he said "his wires didn't feel hot".
This is how it should be and if anyone has a hot wire or wires (hot in temperature not what we in the U.K. refer to as 'live') then they are too small in section. This could arise if such things as lamps have been uprated or extra accessories added to that feed.
What will happen is that the device will then have a reduced voltage, as some will be lost in heating the wire, and will not work so well. This is particularly important with headlights as the light output will drop quite noticeably with even a relatively small loss of supply voltage.

Alec