Ok, here goes. I just figured out how to post pics so I hope this works!


On a previous thread I said I would post pics of an added fuse panel I was working on with a brief explantion of
the installation. The idea was brought up about having a separate fuse panel wired in to use for added
accessories (rad. fan, A/C, extra guages, etc.). The reason was to clean up the 'clutter' from extra wires used to tap
into the factory fuse block, and to prevent overloading it as well. I wanted the panel to be 'Hot' with 'Ign On', so I used relays
to do this.

I purchased a six (6) circuit fuse block which allowed for adding circuits off the side, and crimped/soldered a 10g wire to power
the 'feed side'. Then mounted it to the factory panel using 1" wide double-sided moulding tape (the grey stuff). It
doesn't budge!
http://www.chevelles.com/showroom/data/500/New_Fuse_Panel1.jpg

http://www.chevelles.com/showroom/data/500/12V_10g_feed_wire.jpg

http://www.chevelles.com/showroom/data/500/Panel_Attatched.jpg


Next I made a bracket to mount the two(2) 30a relays I'm wiring 'in parallel'. (metal straps & screws purchase at Home Depot)
http://www.chevelles.com/showroom/data/500/Relay_Bracket.jpg


I mounted the bracket on top of the e-brake pedal assy using the mounting bolt to the dash to hold it
in place, then wired the relays in parallel leaving extra wire and mounted them to the bracket.
http://www.chevelles.com/showroom/data/500/Relay_Location.jpg

http://www.chevelles.com/showroom/data/500/Bracket_Mounted.jpg

http://www.chevelles.com/showroom/data/500/Relays_mounted.jpg


I ran a 10g wire with a fusible link from the buss bar +Bat (on horn relay) through the firewall at an existing hole, ran it down behind the new
panel, under the factory panel and wired it to the relays (+bat in). Then wired the (+bat out to acc.) to the +bat feed
on the new fuse panel, and soldered the +control wire (to switch relay ON) to terminal (Hot with IGN ON) on 'Back'
of factory fuse panel. I did this to keep a 'clean' look.
http://www.chevelles.com/showroom/data/500/Connecting_wires.jpg

http://www.chevelles.com/showroom/data/500/Relay_trigger_to_Ign_Hot.jpg

Continued --->>>

I ran the relay 'ground' wire with the others behind the new panel and out the right side, and attatched it to the upper
screw for the steering column mouting plate. I covered the wires with a nylon braided spit loom for a clean finish and
held it in place with a wire tie to the factory fuse panel.
http://www.chevelles.com/showroom/data/500/Wire_Loom_Installed.jpg

http://www.chevelles.com/showroom/data/500/Fuse_Panel_Finished.jpg

With the extra terminaled wires removed, the fuse boxes don't look 'cluttered' anymore. I changed the ATO fuses
for those new smart fuses that glow when the fuse blows, just to make it easier to pinpoint. Next, I'll add those
extra circuits I removed, to the side of the new panel from up and over the steering column using some more
split wire loom to keep things neat under there.
http://www.chevelles.com/showroom/data/500/Finished_Panel_2.jpg

To sum it up, the new fuse panel is OFF until the IGN or ACC is ON. The relays support the load to the added panel, and
only use the factory panel to 'switch on' the relays drawing about 1/8 - 1/4 amp. The added circuits on the side of the new
fuse panel will be used primarily to power relays or toggles for relays of other components. If you notice two (2) wires (red/blue)
sticking out the right side of the panel, those are connected to the feed side of the panel to use if a large circuit
is needed. (just incase)

I hope this info is helpful/useful to others on this site. There are many other ways to accomplish what I did, this
is just how I chose to do it.

Enjoy!

Nice job!

Note that he soldered critical wiring joints too... your regular crimp on terminals are really not very good power handlers without soldering. The soldering seals the connection reducing resistance and thus heating.

I have tried to use plastic split loom with a vinyl tape wrapping when I am trying to look OEM. But that nylon braid looks nice too. How well does it do with larger bundles?

Nice job :thumbsup:

Very nice job! I also added a 6 fuse panel, only it's underhood, and not nearly as nice looking as yours!

I also like the trick using the relays to power up the panel. I hadn't thought of that....I might just try that sometime.... :)

Snazz-ola!

This is really a dumb question but why 2 relays to power it up? dan w

Wow very professional work. I hate wiring so I will just keep my ghetto rigged setup.

that looks excellent!!! do you have this on a website somewhere that i could bookmark? i have other issues to address right now, but somewhere in the future i will be doing this to clean up my factory fuse panel.....
thanks again for the info

This is really a dumb question but why 2 relays to power it up? dan w
Rather than one say 60A monster relay he used two 30A common cheap relays to provide more power to the supply. In electric circuits it is common to build in some excess capacity as this goes a long way towards reducing failures.

Rather than one say 60A monster relay he used two 30A common cheap relays to provide more power to the supply. In electric circuits it is common to build in some excess capacity as this goes a long way towards reducing failures.

Yes, that is why I chose this route.


Jay,
I don't currently have a website, just these pics and a few others in my
showroom. If you want more info later, shoot me a PM or Email, no problem!

Thanks for the compliments, guys!

Thanks for the explanation on the 2 relays. Now I get it


thanks dan w

Yes, that is why I chose this route.


Jay,
I don't currently have a website, just these pics and a few others in my
showroom. If you want more info later, shoot me a PM or Email, no problem!

Thanks for the compliments, guys!


i will do just that.....thanks!!!

How did you find out how to list pictures with your Thread?

How did you find out how to list pictures with your Thread?

http://www.chevelles.com/forums/view.php?pg=showroom

http://www.chevelles.com/forums/showthread.php?t=139748&highlight=posting+pics

http://www.chevelles.com/forums/showthread.php?t=110527&highlight=posting+pics

Wow, very impressive.

Would you mind telling me which relays you used and where each wire on each relay went to.

I am still pretty new to electrical work, but this would work perfectly for providing a keyed 12 volts to my gauges.

Al,
How about putting his pics/text in the Tech Reference section.

Everything there is old and could use a new article.

DG

Rather than one say 60A monster relay he used two 30A common cheap relays to provide more power to the supply. In electric circuits it is common to build in some excess capacity as this goes a long way towards reducing failures.

That is fine as long as either the new fuse panel is split into two different sections (each section powered by a different relay) OR If the panel can be run without problem off of only ONE relay in the event of a failure.

Both relays should not provide power to the same point (run the entire panel) if the panel REQUIRES more than the rating of ONE relay....
In the event of a failure of one relay, the other would be overloaded and cause a fire hazard. This is the same reason that it is a bad idea to run two little wires to power a load instead of one big wire!

That is fine as long as either the new fuse panel is split into two different sections (each section powered by a different relay) OR If the panel can be run without problem off of only ONE relay in the event of a failure.

Both relays should not provide power to the same point (run the entire panel) if the panel REQUIRES more than the rating of ONE relay....
In the event of a failure of one relay, the other would be overloaded and cause a fire hazard. This is the same reason that it is a bad idea to run two little wires to power a load instead of one big wire!
Good point.

When I was writing that I was thinking more along the line of preventing the relays from failing at all. Much of this also depends on the failure mode: is the circuit simply overloaded or is it shorted. Most shorts will take out the fuses quicker than the conductor (wire or relay) even if the conductor is under-sized. Overloads are much more interesting though...

Good point.

When I was writing that I was thinking more along the line of preventing the relays from failing at all. Much of this also depends on the failure mode: is the circuit simply overloaded or is it shorted. Most shorts will take out the fuses quicker than the conductor (wire or relay) even if the conductor is under-sized. Overloads are much more interesting though...

You are right! Overloads would be what could get you in trouble!

For those that arent following the issue....
For example, lets assume the following scenario:
1. Panel is rated at 60A
2. Two 30A relays apply power to entire panel in parallel.(output of both relays is tied to the same input on the fuse panel)
3. The actual load from all your accessories is 50A (I know thats high, but this is just hypothetical)

Now imagine one relay fails due to bad contacts, coil wire breaks from vibration, is defective from the factory or any number of issues...

The remaining relay will continue to supply power, but will be running 66% above its rated current capacity!....
Then the driver says, "hmmm... whats that smell???"

I am learning as I go when it comes to dem electricimical thingies, so bear with me.

Is the consensus here that it is better to just run a 60amp relay as opposed to 2 30amp relays like the original poster has done?

I am learning as I go when it comes to dem electricimical thingies, so bear with me.

Is the consensus here that it is better to just run a 60amp relay as opposed to 2 30amp relays like the original poster has done?

IMHO,
Unless you want to split the panel into 2 different sections, then I say YES!
If one 60A relay fails it will be obvious... If one of the 30A relays fail, it will not be obvious unless a potentially dangerous situation developes!

Also it's just easier to wire one 60A!

Having said all that, the original poster did a beautiful and impressive install....
A great idea and well executed, as long as the total load on the panel stays less than 30A (at any given time) he will be fine...
I just would have done it slightly different...

This would be one way to modify for safer use with two relays..

Note.... neither half should have a load of more than 30A!

Well that solves that. i will get one 60Amp relay to accomplish what he did there.

For one thing, it will be easier to wire :), secondly it will be safer. Those are two very convincing reasons for me.

Now, is there a certain type of 60amp relay that one should get? And will the local parts stores cary them?

Well that solves that. i will get one 60Amp relay to accomplish what he did there.

For one thing, it will be easier to wire :), secondly it will be safer. Those are two very convincing reasons for me.

Now, is there a certain type of 60amp relay that one should get? And will the local parts stores cary them?

I dont know about local....
But these folks got all kinds of relays!
http://www.weisd.com/store2/nterly/nterlyfulllst12.html

here is a 70A!!
http://www.weisd.com/store2/nterly/R51-1D70-12.html

A few minor counterpoints...

Of course one drawback to the high current relay approach is cost. You can often get the two 30A relays for less than a single 60A relay just because they are so common. I think this was why the original approach was taken.

It is also much easier to find supply fuses for 30A circuits than it is for 60A circuits and the supply should be fused here.

Another drawback is the much larger gauge wire required to support a 60A circuit as compared to a 30A circuit. Larger wire is more difficult to route and make connections on. The basic soldering iron that works great with 16g wire might not work very well on the 10g or 8g wire required for the high power circuit.

And finally in most applications it will take several loads to fill the capacity of either a 30A or a 60A circuit. If there is a problem and a fuse blows, that is a lot of stuff to not work. It is often better to split large circuits into smaller circuits each with their own supply fuse. This can also make troubleshooting much easier. Consider if you have 6 devices all hooked up to one fuse and the fuse blows. You have to look at the wiring and such for all 6 devices. If you split it you only have to look at wiring for 3.

There is a lot to say for that picture showing how to split the supply side of the fuse block up into two circuits and using dual 30A relays.

Definate advantages to each approach!
Fun conversation!

Jim,

My compliments on your electrical design and fabrication skills. Not only did you come up with an appropriate way to add circuits, but you did it with simplisity and style. Grade A+

Mike

What size supply wire would you have to use for the 70a relay? Pete

Well i drove around for 5 hours today going from store to store and finally would up in a fast and furious tuner store in koreatown. I was able to pick up 2 30/40 amp relays from them. i still need to find a fuse panel to use.

I will go down to UPS tonight and pick up my gauges. My plan is to have the fuse panel wired and everything ready by the time my dash shows up this weekend.

The plan as i see it is to run the 4 small autometer gauges off of the original factory dash harness pink wires for the power. maybe adding a fuse on each one which will also increase it's length. Then the tach and the speedo will get power from the new fusepanel like seen in the first thread. i will also run the electric choke off of there as well. That way I have a switched 12 volt fusepanel on relays and I also am making use of dash harness wires as well.

My question is what wires go to what? All i have is numbers on the back of my relays and have no idea where to start, but I want to do this right and want to do it once.

I figure some of the wires connect to each other on the relays. Then some go out to the fuse panel and some go to the junction block, but have no idea where to start.

But I got inspired by the other Jim's work and want to do the same thing myself.

Any help is greatly appreciated.

Jim 2

What size supply wire would you have to use for the 70a relay? Pete

The Amp rating of the relay doesnt determine the size of wire...
The maximum expected total load on the fuse panel does!

In the example above we talked about expecting the panel to run about 50A, so we wanted to use a relay that had at least a 60A rating.(Always better to over engineer just a bit!)
It wouldnt matter if you used 60A, 70A, or 200A relay... the load will still be around 50A just the relay would be able handle much more than the job you are asking of it...

To answer your question better....
You must realize that wire size ratings are not absolute!
The quality of the wire being used, whether it is bundled with other wire or left in the open, and the length of the run all impact it's capacity.
In the relative short runs in automove use, it is my opinion that 10 gauge would be fine.....

Wire sizing... Allengator has the basics.

Really it comes down to wire resistance which causes both voltage drops and wire heating.

For maximum efficiency you want all the electrical power applied to the load. But the resistance of the wire becomes part of the circuit load and thus consumes some amount of power, which we see as a voltage drop at the load. As current loads increase, the resistance of the load decreases, making the wire resistance a larger portion of the total. That is given the same size wire. If we increase the wire size we reduce it's resistance thereby keeping it relatively small compared to the load resistance.

We can actually put numbers on the power, in watts, consumed by the wire. When we do we find that it is the resistance of the wire X current X current. If we have 1 ohm of resistance in the wire, it will consume 1 watt with 1 amp and 2500 watts with 50 amps. We can heat a small room with that kind of wattage in a heater!

Note that for a 50A current in a 12V system the load resistance is only 0.24 ohms. If our wire was 1 ohm it would consume 3x as much power as the load.
Fortunately most wire has a lot less than 1 ohm resistance (but it made the math easier).

So choosing a wire size depends on mechanical factors (structural strength of the wire, ability to route), thermal factors (how much power/heat can be dissipated), and efficiency factors (how much voltage drop is acceptable). Lots of stuff to figure out... but fortunately there are some tables out there to simplify this for us. I often do a net search for "wire current capacity" or something like that and find a few. Here is one example:

http://www.rallylights.com/other/wiring.htm

For relay wiring:

http://www.the12volt.com/relays/relays.asp

Is this simplified diagram correct schematically? I know two relays were wired in parallel and the diagram I made only uses one. This diagram would use ignition "on" power to energize the new fuse panel using the relay. Is this correct?
http://members.cox.net/edhale/relay.jpg

edhale,

That's how I wired it. I used a fusible link at the connection to the horn relay, too.

A few minor counterpoints...


Another drawback is the much larger gauge wire required to support a 60A circuit as compared to a 30A circuit. Larger wire is more difficult to route and make connections on. The basic soldering iron that works great with 16g wire might not work very well on the 10g or 8g wire required for the high power circuit.




With respect to soldering larger wires ( the purple "S" wire to the starter for example) I have had good luck using generous amounts of non-acid flux. It serves two purposes, it cleans and it accelerates heat transfer. I have a 100/150 watt Weller gun and it has never failed me yet for any car wiring project. :)