@ Apache (or other electrical Gods)

[MudSurfer]

Hi mate - when you wired your roof bar - what wattage bulbs did you use, and what size fuse did you put on the relay???

I've just put a load of 100W bulbs in and blew the 15A fuse I had in the relay POP!!!

What is the best size to fit?? - is it 30A or higher???

TIA

[gwh200]

how many lamps andy ?

[MudSurfer]

how many lamps andy ?

Four lampth thir!

[gwh200]

goth,thath loadth !!

so a 15 w fuse is no way gonna be enough.
i have no idea either,but as im still wired for spots i am going to use that feed from a piaa relay and hopefully apache will tell you and i will steal the info (if you get what i mean)

[mark g8awo]

!00w bulbs using ohms law calculators will give you 10A each bulb so you will need at least 20A fuse for 2 bulbs.


http://www.hydrogenappliances.com/oh...alculator.html

[MudSurfer]

Cheers Mark!

Well - I worked it out at 33.3A - and tried a 30A and that blew too hahahahahahahaha - so it's off to Halfrauds tomorrow to see if there is a 40A fuse or online to buy a BFO relay and big old fuse for it - or a second, smaller relay and 2 x 20A!!

[The Lovely Boyo]

Mud - 40A is a lot of 'letric!

You'll need wiring to hold that much current too - otherwise it may melt and cause other issues, ahem.

[MudSurfer]

Mud - 40A is a lot of 'letric!

You'll need wiring to hold that much current too - otherwise it may melt and cause other issues, ahem.

The spots are wired with 20A cable to each one, then it goes down to two wires - so should be OK to take that to the relay...I think!

If the best route is two relays, then I'll wire another one up at the weekend.

[Apache]

AHEM!!!

I think this question was directed at me (though Mark has answered with some obvious engineering knowledge)

With engine running - 30A fuse is the nearest at just over 27A

Without engine running (and you're gonna flatten your battery quickly!) - just over 33A

40A is the correct value whatever.

[nero279]

I'm gonna get for this but:-

40Amp relay, 35 amp wire (could maybe get away with 27 but it would get warm over extended periods, only reason I say is coz 27's more readily available than 35) protect it with a 30 amp fuse, and don't use em without the engine running, should cope.

400 / 14.4 = 27.7

35A wire and fuse would theoretically be the correct rating at 12v (works out to 33.3A), but realistically with the engine off you'll be running closer to 11v which would put the current up to 36A. Which means using whatever the next guage up wire is, all the time putting up the cost for the sake of being able to flatten your battery quick by running 400w of lighting with the engine off, when probably you aint ever gonna need to have em on with the engine off anyway.

If it were me on my car i wouldn't be bothered if it was only done with 27A wire and a 30A fuse. I don't think it would cause any problem at all. Then again, my 4 x 55w lights are currently wired with 35A cable but only coz i got it free.

See, clear as mud mud now eh?

[MudSurfer]

So my 20A wire is no good then?????

Off to buy a 40A fuse on the way home!

[nero279]

Mate, do not use a 40A fuse and 20A wire -

the wiring will be melted or worse still the car on fire before the fuse blows.

[MudSurfer]

Mate, do not use a 40A fuse and 20A wire -

the wiring will be melted or worse still the car on fire before the fuse blows.

Looks like I'm rewiring the lights on Sat then!

[MattF]

Looks like I'm rewiring the lights on Sat then!

Just run a second wire. Whether you do it via one large capacity or several smaller capacity cables is irrelevant.

Btw Graham, how big is a 15W fuse then?

[lord lucan]

Cheers Mark!

Well - I worked it out at 33.3A - and tried a 30A and that blew too hahahahahahahaha - so it's off to Halfrauds tomorrow to see if there is a 40A fuse or online to buy a BFO relay and big old fuse for it - or a second, smaller relay and 2 x 20A!!

if you blew a 30A fuse you have a short