Thinking of building my own fuse block with relays to support higher draw accessories like AC, FANS FP and ignition/starter etc. So say you start here https://www.amazon.com/MMdex-Holder...F8&qid=1483591790&sr=1-11&keywords=fuse+block with a distribution terminal. You run 5 30A relays on one side. The other 5 for direct connection to low amp accessories (radio, interior light, For simple math - each of those accessories on those relays is 120W. ~ 10A. [50 AMP] Assume each of the direct run accessories is up to 5AMP. [25 AMP] Questions. 1) What size fuse do you use on the main power wire to battery. If all accessories and relay protected circuits are running thats a potential ~75A draw. 2) I think you need 2 fuses for each wire in the relay. Meaning 1 for the main draw (10A) and then one for the signal wire (say 2A). So then what - get a 15-20 fuse box ? OR - do they just get the 2A trigger/signal wire fused ...... and then protected by the main fuse 3) What if the relay trigger wire is joined/spliced to another circuit - eg for ignition on trigger. What does that do to the calcs and whats required for fuse etc. 4) Anyone got a link thats shows in better detail how it SHOULD be done thanks
fuses are there to protect the wire. However big the wire is, that's how big the fuse needs to be. typical fuse ratings for wire size.... 30A 10 gauge 20A 12 gauge 15A 14 gauge
what he said, but the fuse panel, its the old ceramic fuses , those can be hard to find (at least down here) , look for the more standard glass or modern push in shit. Also that one has screw on wires, sorta looks better than a new one but it could end up giving you poor connections, I prefer soldered. If your struggling (no offence) get a good wring kit from someone. I do all my own in cloth covered and screw on terminals where it can be seen.
Sort of something like this but with more Relays. http://www.turbomr2.com/MR2/HowTo/FusePanel/FusePanel-01.JPG Do you need to fuse (for each ofthe 5 relays) RELAY MAIN DRAW WIRE + TRIGGER WIRE - SINGLE WIRE BACK TO BATTERY or just TRIGGER WIRE - SINGLE WIRE BACK TO BATTERY
you need a fuse on the supply side of everything and should have a FOB fuse/circuit breaker (one that wont blow unless everything shorts so use an appropriate sized feed wire) on the main supply from the battery to the fuse box, you need something that drops out in every circuit to stop the smoke getting out of the wires. Headlights should have a bimetal circuit breaker (whats modern speak for these?) protection so the lights dont just go "poof" in the middle of a corner, at speed, in the rain on a road with huge drop offs (cause thats when they will fail)
That fuse panel looks too light for the loads you're talking. What you really need to do is actually calculate the loads, then size the system to the loads; don't guess... Here's a lot of reading, but this will explain what's involved: http://www.jalopyjournal.com/forum/threads/wiring-101.843579/ As to relay control, that can be done multiple ways. One power circuit for all relays (most typical relay coils only draw about .3 amps) or you can power each relay off the controlled circuit. If you switch the ground connection for the relay coil, you only need one wire to the switch and just ground the other side.
Check out the fab forum on YouTube. He has a video on making a four relay set up. Has links for all the parts too. Sent from my SCH-I435 using The H.A.M.B. mobile app
I'm not interested in reinventing the wheel. I use a Centech fuse panel which has provisions for all 3 busses used in an automobile. Battery , ignition, And accessories. They have ided all the circuits and figured what amperage fuse is needed. I have used them in several wiring jobs I've done. I could sit down and design and build a custom panel but why? Sizing and properly routing wire is enough of a challenge itself. There are so many things to do when building a car that I don't need more. I once watched a friend who owned a body shop take almost three days making a copy of a Gennie shifter to avoid spending the money. When he was done, I asked him how much time in shop production he had lost just to prove he could make a shifter as good as Gennie did . In a pinch I would design and fab one but as good friend once said when I asked him why he had me build 3 cars for him and he was a fair wrench himself but also a busy and successful business man. He Loken at me and said "let the other guy do what he does best and I do what I do best, and everything works out well". So as I see it Centech and others do what they do and I do what I do. The reason I don't use a prefabbed harness is that I go to the boneyard and remove the fanciest harness from the type of car I'm wiring and use the factory color wiring. GM wires for GM cars, Ford color wires for Fords and so on. Getting phynolic block and all the bracket just slows me down when I don't need it.
Thanks Steve. Funny - exactly where I got the idea of correct wiring/fuse control Good video but missing some detail. Reality is I will probably end up buying a multi circuit for my swap. But just want to understand the circuitry better for sizing and safety especially when using multiple device,circuits,relays etc. THANKS GUYS.
So it only needs to be on the supply side - not the trigger side. ? So for example on this picture ... how are the relays used in the circuit. Obviously there are 7 fused circuits ....... do the relays simply just supply power to the circuits on key on so its not constant hot? Basically 1 relay that supports power to each bank of 4 accessories ? http://www.painlessperformance.com/webcat/70118
A relay takes the load off a switch , and supplies the power for whatever. The power wire to the relay (supply wire) has to have fuse between it and the battery. The trigger wire , the one that makes the contacts in the relay close and the "whatever" turn on (or off depending on how its wired and the relay type) comes from the "whatevers" switch and doesnt do any work as such as no real load on it or the switch, this trigger wire will be fused somewhere and can be with the ignition on acc position or could be live at all times. Don't run a wire that has voltage without a fuse , only exception is the wire from battery to the starter and its best not to have anything live with the key out of the car (exception being clocks and some modern wireless's , car alarm that sort of shit)
to help cover the basics get a copy of "How to Wire Your Street Rod" by Jack Sweeden ( do not let title scare you) booklet available through speedwaymotors.com and others - I built my first wiring panel with basic parts from local parts store - even used all black wiring - yikes - car still on the road 25 years later
Note that the starter can draw 150+ amps at start. That is what determines the battery cable size Sent from my iPod touch using The H.A.M.B. mobile app
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