Compact Waterproof Relay Box

[kndrewa]

I was inspired by this thread to improve the wiring for various powered accessories I've added to my Jeep over the years (fog lamps, etc).
Switches activate relays in the engine compartment using Cat5 Ethernet cable to save space and keep the larger accessory wires out of the passenger compartment.
I am satisfied with the modular design enabled by the use of Cat5 Ethernet cable.
It will come in handy if I ever need to service a specific part of the assembly, or should I want to move things around in the future.
I had two main goals for my switch and relay box project.

* Compact
* Waterproof

I don't have a lot of electrical experience and would like to improve, so please alert me of any areas which may be a cause for concern!

 

[kndrewa]

I housed 6 relays and a fuse panel in a residential electrical enclosure.

 

[kndrewa]

The relays are grounded to and routed through the metal armature.

 

[kndrewa]

I added a Cat5 jack and a ground terminal to the fuse panel.

 

[kndrewa]

The fuse panel pivots back for access to the relay wiring.

 

[kndrewa]

I added an external fuse for the main power going into the relay box.

 

[kndrewa]

I painted and mounted the housings between the battery and PDC.

 

[kndrewa]

Organization and simplicity were important for meeting the compact space requirements.

 

[kndrewa]

I wired a second fuse panel and Ethernet jack in the interior to connect and power the switches.

 

[kndrewa]

I added 2 switches and created a detachable wiring harness for easy removal.

 

[kndrewa]

Wanting to maintain a stock appearance, I chose black switch housings with various LED configurations which illuminate when powered on.

 

[fallacist]

sexy. nice work!

 

[kndrewa]

Thanks!
I do have a few questions about choosing the proper fuse sizes for my circuits. I'll get my information together and post it here later for some advice!

 

[LYKOS]

I'm curious as to how you're powering these switches.

Are you using a dead ground (what I call it) system where all the switches do are connect or disconnect the ground to the relay?

Or are you actually running power through the switches and the cat5e?

Cat5e is what, .25 mm copper wire? How many amps can it safely handle?

I have five switches mounted beside my shifter, one in the dash beside the wiper switch and four more to go in the dash beside the gauge cluster. cat5e would be a great way to wire these without the mess but I wonder if it will handle any amps...

 

[bdahlg]

the relay handles the amp load, which is why you need a relay to power headlamps. Cat5e is just the signal wire to the relay, which is rated for like 30amps or so. NO relay closes, powering the high amperage load. Only needs a few miliamps of current to switch it

 

[LYKOS]

Okie dokie, I'm learning this as I go along. I've never found exactly how many amps it takes to activate a relay. My search skills are weak in the area.

 

[bdahlg]

Everyones here to learn, and a great place to do so; and not only for XJ's!

That's a good thread though. Give it a read.

 

[kndrewa]

I'm curious as to how you're powering these switches.

Are you using a dead ground (what I call it) system where all the switches do are connect or disconnect the ground to the relay?

Or are you actually running power through the switches and the cat5e?

Cat5e is what, .25 mm copper wire? How many amps can it safely handle?

I have five switches mounted beside my shifter, one in the dash beside the wiper switch and four more to go in the dash beside the gauge cluster. cat5e would be a great way to wire these without the mess but I wonder if it will handle any amps...

Hello! I'm not sure the exact characteristics for load and diameter on each strand in the cat5 - but it isn't carrying any accessory loads. Each strand of cat5 is used to power on the relays under the hood, which completes their internal circuits; the relays are rated at 40amps.

As long as you only use your switches to power some relays either under the dash or hood (wherever you choose to put them!) I think cat5 would be a great way to clean up the bulky wiring going up to your dash. Your larger accessory load wires would then run to the relays, rather than all the way into the dash beside the gauge cluster.

 

[X E Ryder]

Info

Well the ampacity of 24awg wire is about .5 amps, and the load of a typical Bosch relay with a 75ohm coil is .16 amp. This means you can safely run 3 relays at continuous duty on a 24awg cat 5.

Because this load is so small, you can use most multimeters in the Amp scale, in series with one of your relays to test the actual load of the coil to verify it is .16

If you run 1 new larger wire to supply all switch legs inside, you should be safe for the single .16 amp load returns to each single relay. I have to admit I'm concerned about the thin jacketing of the cat 5, at least put some 1/4" split loom over it to give it a bit more protection from incidental damage. It's pretty warm under an XJ's hood!

As another poster mentioned, you can drop ground to provide contact closure, but that does mean you have +12 through the coils on All switch legs until you drop them to ground.

In a 4 relay system, I prefer to run 6 wires to the cab. Ground, a 1 amp fused +12v for coil closure, and my 4 hot returns to the relays. I've actually considered mounting them in the glovebox this time, because I don't use it anyway and it would be cake to work on or service if a problem, even in bad weather! You could jump out any failed relay in like 1 minute.

What you have done there is a good idea, and I like the hoffman box too, just a little fine tuning to keep you safe is all I'm suggesting. Hopefully you see this is constructive feedback.

 

[kndrewa]

Re: Info

What you have done there is a good idea, and I like the hoffman box too, just a little fine tuning to keep you safe is all I'm suggesting. Hopefully you see this is constructive feedback.

Thank you for the feedback! This is my first big electrical project, I'm learning, and your input is very valuable to me.

Well the ampacity of 24awg wire is about .5 amps, and the load of a typical Bosch relay with a 75ohm coil is .16 amp. This means you can safely run 3 relays at continuous duty on a 24awg cat 5. Because this load is so small, you can use most multimeters in the Amp scale, in series with one of your relays to test the actual load of the coil to verify it is .16 If you run 1 new larger wire to supply all switch legs inside, you should be safe for the single .16 amp load returns to each single relay.

My relays don't have their power chained. Instead, each switch powers a single relay on a single strand of the cat5. I have incorporated a fuse panel at the relay box which is powered with 10 gauge right off the battery (and through a large fuse before powering the fuse panel). Does this make sense, and is it safe? Perhaps I need a larger lead from the battery?