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Introducing Carling Contura V-Series rocker switch bodies only! SPST and DPDT

You've asked and we answered!  New Wire Marine is now offering genuine marine grade carling rocker switch bodies.  We have always offered great deals on our custom labeled switch and actuator packages, but now you can order just the bodies separately in either Single Pole Single Throw or Double Pole Double Throw!  

Our SPST switches are great for normal loads, while DPDT are ON-OFF-ON switches that can be used for things like Nav/Anc lights and left and right wiper motors.

We are increasing our product line in the coming weeks and months so check back in often for new New Wire Marine product offerings.

www.NewWireMarine.com

One rule to rule them all: Ohm's Law - it cannot be violated

To a brand new electrical engineering student, the first thing you must learn is a law of physics called Ohm’s Law.  It was names after the German physicist Georg Ohm, who published the theory in 1827.  Very simply the law states:

V = I x R

Or, Voltage (V) equals Current (I) times Resistance (R).  It means that the voltage drop across a resistance is equal to the amount of that resistance (ohms) times the current traveling through the resistance (amps).

So what does this mean to the average boat owner?  Well… one application is that the higher current (amps) a load carries, means a higher voltage drop you will have in the cable.  Think about these steps as you look at the formula above:

1)      A large electrical load means high amps

2)      High amps means high “I” in the formula above

3)      With a fixed resistance (R), this means voltage drop (V) must increase proportionally with the current

4)      As voltage drop in the cable increases, it lowers the operating voltage of the equipment

What conclusion can we draw from this?  That to keep voltage drop (V) in your cable constant, while increasing current (I), you must decrease resistance (R).  And you decrease R by… wait for it… GET A BIGGER CABLE!  AH HA!  That is why larger loads need larger cable… large cable has less resistance.

A second application is that as cable length increases (R increases), with a constant current, the voltage drop also increases.  This is why when you run a long cable to a device far away from your battery; you should step up your cable size decrease resistance and voltage drop.

Boat / Marine wiring color codes

What color wire should you use on your boat, and is it important?  First of all: YES it is important.  Just like in your house, using the incorrect color wire when re-wiring your boat will be confusing to anyone working on it in the future and risks short circuits (or faults) that could cause serious damage to you and your boat.

In most small boats there are two main types of power distribution cable... 12Vdc positive, and 12Vdc negative, or + and -.  The colors you MUST use to identify the difference between these + and - are red and black respectively... I repeat:

Positive (+) = RED
Negative (-) = Black (or yellow)

Also, DC grounding conductors should be green... but for many small boats you will not have any grounding conductors on your boat.  These color codes are established by the American Boat & Yacht Council (ABYC), and are standard throughout the industry.  Please, don’t buy all one color wire to re-wire your boat.

Also note that the ABYC has established a more detailed standard of more than 10 different colors to identify what type of positive wire you’re dealing with.  Brown for instance should be used for all pumps, and Pink should be used for a fuel gauge.  These are recommendations only, not Coast Guard regulations, and while useful… having to buy 15 different colors of wire for a DIY job may be impractical. 

So remember… Red is + and black is –

Excerpt from ABYC standard E-11 “AC and DC Electrical Systems on Boats” :

Automatic Bilge Pump Switch - Should I use ON/OFF or ON/OFF/AUTO?

A common question our customers ask is: "Can you give me a labeled BILGE switch that is ON-OFF-AUTO?".  Our response is: "Absolutely we can provide the switch and good choice on adding an automatic bilge pump, but do you really want to put a switch on it?"

On New Wire Marine custom switch panels, we default to providing an ON/OFF switch only.  We DO recomend every boat have an automatic (float switch) feed for the bilge pump, BUT we prefer the "auto" float switch lead be run directly from + on your battery (fused of course).  This method of bi-passing your battery switch and switch panel makes certain that your float switch will turn on your bilge pump if it ever begins to fill up with water.  If you ever leave your boat at the dock, this could keep your boat from sinking if you forget to turn your "auto" switch on, or even if you have your battery switch OFF. 

 

The reason typically cited to NOT connect devices straight to the battery is that a trickle current (like from a GPS, or VHF) could drain it.  BUT, there is little to no risk of this when a device (like a bilge pump) is connected with a physical disconnect switch (like a float switch).

 

Furthermore, even if you trailer your boat how do you compare: 1) the risk of draining a battery because you left the plug in and the bilge pump had to pump rain water out all night - 2) with the risk that you decide to unexpectedly leave your boat at a friend's dock for the weekend and return to find it swamped, or worse... sunk?

 

In conclusion, You DO need an automatic bilge pump, but there is little justification for putting a switch on the "automatic" feed, and there is substantial risk reduced by NOT putting the auto feed on a switch.

 

...but that's just our recommendation, it's your boat, and New Wire Marine is here to help.

 

Here's a wiring digram of what we're talking about: