Date:         Mon, 9 Sep 2002 16:49:48 -0500
Reply-To:     Chris Mills <scmills@TNTECH.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Chris Mills <scmills@TNTECH.EDU>
Subject:      Re: Headlight upgrade questions
Comments: To: Jack <john.cook58@VERIZON.NET>
In-Reply-To:  <3D7CA484.27586.E3C8DF@localhost>
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I do have a pretty good understanding of electricity as I was a Navy EM for
several years but it's also been a few years since I had to regularly worry
about breakers and fuses.

Yes that was my assessment - just fuse it heavy enough to cover the loads
and a little more. Now to find out what those relays pull.

I think I can borrow a 10A current meter at the University where I work.

>You can certainly drop the size of the fuse as long as you accommodate
>anything else which might be on the same circuit plus the relay coils plus
>a healthy margin.
>
>Fuses are not usually precision devices and they can fail from repeated
>temperature cycling if they are rated too close, so I'd guess (roughly)
>you should at least double the actual (worst-case) current for the fuse
>rating for a reasonable trade-off between circuit reliability & safety.
>(There may be a better rule for how much margin to provide available
>somewhere but it would depend upon a lot of factors & IMHO not worth the
>effort to pursue it.)
>
>The existing 8 amp fuse should blow long before there's any risk of
>melting wire (or its insulation) in the case of a hard short, but it's
>still a good idea to reduce it.  Hard shorts (low resistance) will pop
>almost any good fuse quickly and safely.  It's the higher resistance
>"shorts" which are dangerous (e.g., arcing, carbonized connection areas).
>This probably isn't intuitively obvious unless you already have a good
>understanding of electricity.  But this is why fires in home wiring can
>occur even with proper & functional breakers/fuses.
>
>//Jack
>'85 GL

Chris M. <"Busbodger" of "TEAM SLOWPOKE">
Cookeville, Tennessee

ICQ# 5944649
scm9985@tntech.edu

'78 VW Westfalia (67 HP -> that is...67 Hamster Power)
'65 Beetle - Type IV powered
'99 CR-V AWD station wagon
'81 CB900 Custom moto-chickle
2.5 Corvair engines for my Trans-vair Conversion