LED anchor light AWG requirement

[Richard19068]

I'm getting a new LED anchor light and running new wire for it.

The lowest amp draw I can find a voltage drop calculator for is 1 amp. That's on the Blue Seas Systems DC Circuit Wizard.

Using a 1 AMP draw and a 120 foot round trip from mast head to power source calculates to 14 AWG for a 3% voltage drop and 18 AWG for a 10% voltage drop.

The West Marine adviser recommends using the 3% for running lights.

So, sticking to the 3% factor can I reasonably use something less than 14 AWG because the LED will draw probably less than 1/2 an AMP or should I just stick with the 14 AWG ?

I'm not looking to save $10 or so on the cost. Just thinking that the lighter wire would be easier to run and support.

Thanks for your any opinions and input.

 

[Brian D]

Don't overthink this. You might be able to get by with 16AWG or 18AWG. I wouldn't go any smaller. But if you want to use 14AWG you should do alright. What was being used before? Your anchor light probably was a 2W before so you will be drawing less current for the LED.

 

[smokey73]

I'm not sure I'd worry too much about the 3% or 10% voltage drop. Most of these LED lights are rated at 10 volts if I remember the specs I saw and will operate over a fairly wide range of dc voltages. Assuming you don't routinely draw your batteries below 11 volts a 10% loss would still give you the 10 volts. I'd be more worried about pulling the smaller gauge wire and taking a chance on overstressing or parting the wire on the path from the panel to the mast base during the pull. Are you puling single, individual wires or a duplex wire (which will be larger and stronger?)

 

[garymalmgren]

Well Richard.
As Brain and Smokey have said, Don't overthink this one, But if you have a mind to..

You have a theory and a theoretical outcome.
Time for a bit of experimentation.
Get yourself an LED anchor light.
Get yourself 60 feet (plus a little extra to be safe) of 14# duplex wire.
Hook one end to the light and the other end to a 12 volt source.
Take a photo of the illuminated light.
Connect the light to a 12 volt source with 1 foot of wire and take a photo of the illuminated light.
Compare the photos.
If you are satisfied by what you observe, away you go with the installation.
You can add a fuse to the line just to check voltage drop across it, but I wouldn't bother.

have fun
Gary

 

[Davidasailor26]

There is a calculator at Voltage Drop Calculator that takes fractional amps. Looks like 16 gauge would be around 2% and 18 gauge would be 3.2%.

 

[dlochner]

Don't go smaller than 16 ga. On mast wiring the limiting factor is the weight of the wire. It needs to be strong enough to support its self and big enough to easily work with. Larger wire will add weight aloft which may or may not be a concern. On my 55 foot mast I used 16 ga and the light is plenty bright.

If I recall correctly, LED lights are current driven not voltage driven, meaning that light output is a function of the current available. If voltage is low, it will draw more current to produce the same light, in contrast to an incandescent light that is voltage driven, lower voltage, less light. That's why standard dimmers don't work well with LED lights. A standard dimmer is just a variable resistor that lowers current to the light. Dimmable LED lights need to reduce the current.

 

[kappykaplan]

A standard dimmer is just a variable resistor that lowers current to the light. Dimmable LED lights need to reduce the current.

?? Your statement says that both reduce current. My head hurts!

 

[LakeOntario270]

For a long run you never want to use anything smaller than 16 gauge. You need 16 for the strength of the wire. For a LED anchor light you will have plenty of current.

 

[Maine Sail]

ABYC Standards for voltage drop = Max of 3% for nav lights
ABYC Standards for min wire gauge = 16GA

I would not advise 16 GA in a spar however...

 

[LakeOntario270]

"I would not advise 16 GA in a spar however..."
You left us hanging, why?

 

[dlochner]

?? Your statement says that both reduce current. My head hurts!

The traditional incandescent dimmer switch is a variable resistor, it increases the resistance in the circuit which lowers the voltage at the lightbulb so the light is not as bright.

After a cup of coffee and a quick internet refresher, dimmable LEDs work differently. One version is a Pulse Width Modulation, the electronics switch the LED on and off to achieve a dimming effect. It happens rapidly so that the eye doesn't see the flicker.

The other version is similar to the incandescent dimmer, the current is reduced which affects the light. And I don't quite understand that just yet and have an appointment to make in a few minutes.

 

[CYQK]

Talked to the person from marinebeam about this at the Annapolis show last fall. He said voltage drop for their leds is no problem they operate fine at a reduced voltage. Personally i oversize all wiring but you dont need to in this installation

 

[kappykaplan]

The traditional incandescent dimmer switch is a variable resistor, it increases the resistance in the circuit which lowers the voltage at the lightbulb so the light is not as bright.

After a cup of coffee and a quick internet refresher, dimmable LEDs work differently. One version is a Pulse Width Modulation, the electronics switch the LED on and off to achieve a dimming effect. It happens rapidly so that the eye doesn't see the flicker.

The other version is similar to the incandescent dimmer, the current is reduced which affects the light. And I don't quite understand that just yet and have an appointment to make in a few minutes.

Looking forward to the next installment! Your first statement in this post matches my understanding of what a resistor does. Enjoy the coffee.

 

[Brian D]

Interesting enough, I looked at my boat manual and it indicates the mast lighting wire gauge is 10AWG. But this is for a standard light bulb, not an LED.

 

[Project_Mayhem]

In most cases current increases linearly as voltage rises. Resistors are used to limit the current flowing through the LED. LED drivers often adjust voltage to maintain constant current. PWM is more appropriate for dimming rather than limiting current. The reason being is that it sends full voltage pulses. The timing of those pulses (duty cycle) is adjusted to make the LED appear brighter or dimmer. The other method of dimming an LED involves changing the voltage. Current would go up or down accordingly.

As for wire gauge, 20-22 would be OK for most LED's you'd find on a boat. However, you should always check your amperage requirements

 

[Brian D]

I don't think that is correct. If the load (R) does not change, then if voltage (V) increases then current (I) decreases. Conversly if the demand for (I) increases then (R) has changed with means (V) drops: now we have the voltage drop issue. Hence the use of 240vac vs 120vac, or 24vdc vs 12vdc. Also, in the case of PWM, the end result would be RFI if the package is not well built. This is a very common problems with solar controllers. They may work well controlling the solar panel production but kill the use of some electronic on the boat.

For wire, I would not recommend anything less than 16-18AWG with leanings toward 16AWG or better.

Of course, all this is JMHO.

 

[dlochner]

In most cases current increases linearly as voltage rises. Resistors are used to limit the current flowing through the LED. LED drivers often adjust voltage to maintain constant current. PWM is more appropriate for dimming rather than limiting current. The reason being is that it sends full voltage pulses. The timing of those pulses (duty cycle) is adjusted to make the LED appear brighter or dimmer. The other method of dimming an LED involves changing the voltage. Current would go up or down accordingly.

Thanks, that is how I understood it, but couldn't explain it clearly.

ABYC Standards for voltage drop = Max of 3% for nav lights
ABYC Standards for min wire gauge = 16GA

I would not advise 16 GA in a spar however...

Using the calculator here I calculated a 2.5% voltage drop over 75 feet for a 1 amp draw at 12 v for a 16 ga wire. The tricolor at my masthead draws about .6 amp and the anchor light draws .18 amps, the actual loss should be much less than 2.5%. I used 16 ga duplex wire for the tricolor with a strain relief at the light. For most of the run, the wire is in a conduit. So, I'm left wondering what makes this inadvisable.

I can understand that a single 16 ga wire without strain relief and connected with a screw connector might be problematic. In a duplex wire the sheathing helps protect and support the wire.

 

[Project_Mayhem]

@Brian D For simple circuits such as a diode and resistor it generally rings true. A simple example of where this does not apply is a device that uses a transformer. Assuming for this example the transformer has 100% efficiency watts in equals watts out. Utilizing a transformer you can alter the relationship between current and voltage. Most devices using a transformer have a 120/240v switch. The primary is center tapped to accommodate a secondary voltage input.

With more complex circuits and some other components this relationship isn't always linear. I recently converted an audio DSP for use in 12v. During testing I analyzed current draw at various voltages. At 12v the device drew 200mah. At 6-9v it drew slightly more. When I dropped down to 4.5v the draw was slightly less than 200.

Current–voltage characteristic - Wikipedia

 

[rgranger]

.... If voltage is low, it will draw more current ...

Ohm's law

V=IR

Where V= voltage, I = Current and R = resistance.

How does an LED "draw more current" if the voltage is regulated by the battery? I don't know everything about LEDs so I'm happy to be schooled but if what you suggest is true, the LEDs must have the ability to vary their resistance as a function of applied voltage. I do know a little about band-gap theory and I don't ever recall any discussion about variable resistance in a diode.

 

[smokey73]

All good info but back to the basic question of the OP. I think we've concluded that a 16 gauge would probably work fine as far as voltage drop is concerned but the real question is pulling the wire and supporting the wire. I really can't see that "weight aloft" between 16 gauge and 14 gauge would be that significant a difference. I am assuming the OP will need to pull the new wire through some "obstructions" from the panel/breaker to the base of the mast to some sort of a connector and then up the mast. Depending on the clearance for the pull and the type of wire it might be advisable to pull bare insulated single wire from the panel to the connector to reduce frictions and clear obstructions in the path and then duplex from the connector up to the light. If the OP can use the existing wire from the panel to the connector at the base of the mast, then that part of the pull question is out of the picture. I'd then just pull duplex to the top of the mast with strain relief at the top of the mast. But then again, what do I know?