HELP!! Wire size recommendations for 4120 cab power circuit

[OtterBrookStables]

I just installed a new cab on my 4120 (VERY nice!). I'll post pics shortly. I'm running power to the cab straight from the battery through a relay activated by ignition on. I need a 40A relay circuit - I have the following to power up: a set of 55W front lights, pair of 55w rear lights, strobe beacon, dome light, defroster fan, front wiper and rear wiper. What size wire should I use???? I already have the 40A relay, switches, fuse holders and all of the components - just need the size of the wire to run from the battery. I think I should run #8, as #10 is only rated for 30Amps. BUT - it is really hard to find crimp connectors for #8 wire - the common ones only go down to #10 wire. Thoughts and ideas?

 

[jenkinsph]

Try Genuinedealz.com for wire and connections


Genuinedealz > 8 awg,Battery lug,terminal lug,cable lug,tinned lugs,solder lugs,crimp lugs


Make sure that you provide a fuse or circuit breaker at the battery end to protect the wiring. I would use 8 ga wire for this, sounds like you could be running a 30 amp load easily.

 

[atschirner]

I'll add my $0.02 to the discussion. With 220 watts of lights you are already using half of your 40 amp budget. Adding blower and wiper motors and all of the other stuff is going to run you plum outa rating on a single relay. Can you split the power buss and use parallel relays, 10 ga wire and fuse holders at the battery? Don't forget to double check voltage drop on your ground path for excesses. Steel frames aren't known for their high current carrying ability.

Sounds like a fun project. Enjoy the finished product.

 

[glc24]

I'll add my $0.02 to the discussion. With 220 watts of lights you are already using half of your 40 amp budget. Adding blower and wiper motors and all of the other stuff is going to run you plum outa rating on a single relay. Can you split the power buss and use parallel relays, 10 ga wire and fuse holders at the battery? Don't forget to double check voltage drop on your ground path for excesses. Steel frames aren't known for their high current carrying ability.

Sounds like a fun project. Enjoy the finished product.

My thoughts exactly. It would be a much more efficient circuit,if you split the work between two relays

Greg

 

[OtterBrookStables]

I'll add my $0.02 to the discussion. With 220 watts of lights you are already using half of your 40 amp budget. Adding blower and wiper motors and all of the other stuff is going to run you plum outa rating on a single relay. Can you split the power buss and use parallel relays, 10 ga wire and fuse holders at the battery? Don't forget to double check voltage drop on your ground path for excesses. Steel frames aren't known for their high current carrying ability.

Sounds like a fun project. Enjoy the finished product.

Not a bad idea - thanks! But with everything on at once, I think I am still under the 40A budget. Need to double-check the current draw on the wipers and fan. The dome light is a very small load. Going to check one more local source for the 8 AWG connectors tomorrow. I need butt, ring, and spade terminal connectors to make the #8 wire work. If I cant find them, I will probably just run twin 30A relays w/ #10 as you suggested. What do you mean exactly by checking the ground path voltage drop? And, what can I do about it?

 

[jenkinsph]

My thoughts exactly. It would be a much more efficient circuit,if you split the work between two relays

Greg

How so? Please explain.

 

[jenkinsph]

Otterbrookstables,

Does your new cab have a fuse block built in that needs a 40 amp feeder for it? Do you have a NAPA auto parts store or a West Marine store near you? These terminals should be readily available for 8 ga. wire.

 

[KB9UDE]

Please post pics and info about your cab.

Merry Christmas to all of TBN...

John

 

[atschirner]

Return path voltage drop.

Keep in mind that the available current is limited by the series resistance of the circuit and all of the voltage drops in the circuit equal the supply voltage at the battery. The higher the current, the larger the voltage drop across a given resistance. This is the short version of Ohm's Law.

The game here is to make all of your accessories think they are snug up against the battery and have access to full battery voltage.

You are engineering the supply side for minium resistance so take a couple of minutes to ensure you hard work and big supply wire is being used to its full advantage.

Connect a digital volt meter between the ground point of the cab and the negative post of the battery. Turn on all of the loads fed by your relay(s) and read the volt meter. It is displaying the voltage drop in the ground, return, circuit. Shoot for a value less that 1.0 volt DC.

If you see greater than 1.0 volt look for a spot to add a ground strap between the cab and tractor frame. Green paint has great insulating qualities so make sure these connections are metal to metal. You can use a automotive jumper cable as a test strap if you need.

Good luck and send pictures, Alan

 

[kennyd]

Another vote here for the twin 30a circuits...