what AWG for mast head light?

[CharlieJ]

@DeValency #45
Circuit length is defined as the length of conductor from source to load and the return from the load back to the same source.

[GordMay]

Originally Posted by DeValency

... You calculate it one way, so 70’.

You calculate voltage drop on the TOTAL WIRE LENGTH, so Round Trip = 120'.

[DeValency]

Well, as an electrical engineer the rules of a circuit are quite known to me too . However, the conductor to load practical installation charts refer to a wiring from the source to the load, e.g. one way.

As such and considering the masthead led is max 500mA and the allowed voltage drop can be (for a LED) up to 10%, theoretically, you can use 20 AWG conductors cable. To be on the safe (and frankly, overkill) side, I would use AWG 18-16 for a distance of 70’.

[GordMay]

Originally Posted by DeValency

... the conductor to load practical installation charts refer to a wiring from the source to the load, e.g. one way.
... and the allowed voltage drop can be (for a LED) up to 10% ...

Show me one such chart. Every chart, I've seen, states round trip length.

The maximum recommended voltage drop, for a navigation light (LED, or Inca.) is 3%.

General convenience illumination is permitted 10% Vdrop.


Note, the engineer's specification, below.

[CharlieJ]

@ DeValency

For DC circuits the circuit length is defined as Gord and I have defined it upthread.

To be compliant with ABYC and the CFR, AWG 18 cannot be used in this application. In fact, to be CFR compliant, AWG 14 or bigger must be used.

[thruska]

Originally Posted by BAD ORCA

Thanks. according to that chart i can use 16 AWG wire.

5 watt bulb / 12 volts = .41 amps * 140ft = 57.4

Yes .
Just be sure to use marine grade tinned wite. Solder the connections, waterproof the connections with shrink tubes with the inside sealants.

(10awg would be for your washer/ dryer ) no ?

[thruska]

Originally Posted by CharlieJ

@ DeValency

For DC circuits the circuit length is defined as Gord and I have defined it upthread.

To be compliant with ABYC and the CFR, AWG 18 cannot be used in this application. In fact, to be CFR compliant, AWG 14 or bigger must be used.

I believe that correct.
I used 14 on a 35’ mast in consideration of the weight of the run.
And a timber hitch on the nylon line ater the splice to secure the setup.

[DeValency]

Originally Posted by GordMay

Show me one such chart. Every chart, I've seen, states round trip length.

The maximum recommended voltage drop, for a navigation light (LED, or Inca.) is 3%.

General convenience illumination is permitted 10% Vdrop.


Note, the engineer's specification, below.

Yeah, the old and very true cartoon of a corporate communication common failures. I’ve been (and still) in tech corporates all my life.

As for the charts, sure you’ll find these by a simple online search.

Voltage drop: LED lights normally operates internally on 5V, while the internal diodes rated voltage is 1.8-3.2V. Meaning, whatever supplied above 5V is internally dropped in the led circuit or simply a resistor to the required operational voltage. Many LED fixtures are protected in a way that the voltage will cut off at 8V or below.

As I recently ran new wiring in my own 17 meters (56’) deck stepped mast, for spreaders up and down lights, masthead dual light - all LED based ranging from 1W to 18W per fixture (9 LED units on the mast), I had the opportunity to test the actual consumption and voltage drops.

The 3% rule drop is mostly anachronistic based on old electrical technologies or non-brushless high power motored devices (winches, windlass etc), not advanced electronics that operate on lower voltages and can support a wider range of power supply voltage. For example, Raymarine’s Axiom MFD, a much heavier device than a led fixture is rated for 8-16VDC supply @ a 12V system. That’s more like 30% tolerance, not 3%...

Enough said for a cold Sat morning.

[CharlieJ]

@ DeValency #53

I apologize for continuing to beat this dead horse but:

You stated your qualifications and that circuit length is the length of the wire one way. There are readers here that are novices and that is why the horse beating will continue.

DC circuit length is calculated using the total length from source to load and from the load back to the same source. Period. Your post #53 is interesting but does not correct your mistaken premise that circuit length is only from source to the load.

You owe it to the less experienced readers of this thread to correct yourself.

[darylat8750]

Two thoughts:

At some points the phrase "5 strand" wire was used when I think they meant "5 conductor".

When talking about pulling the wire bundle and having to get past a bunch of rivets that impeded progress, it made me think that the post about making up a wire loom and wrapping it all with a protective cover would make sense. Even it the initial installation was more difficult.

[darylat8750]

I doubt a mast head light is a 5W LED, 1W is an awful bright LED.

"5 strand 16 ga cable $1.26 a foot
https://www.showmecables.com/16-awg-...xoC8hUQAvD_BwE"



That cable doesn't appear to be tinned conductors....

[DeValency]

Originally Posted by CharlieJ

@ DeValency #53

I apologize for continuing to beat this dead horse but:

You stated your qualifications and that circuit length is the length of the wire one way. There are readers here that are novices and that is why the horse beating will continue.

DC circuit length is calculated using the total length from source to load and from the load back to the same source. Period. Your post #53 is interesting but does not correct your mistaken premise that circuit length is only from source to the load.

You owe it to the less experienced readers of this thread to correct yourself.

Indeed beating a dead horse. But to be practical. The tables are considering two conductors supply from source to load. Hence the cable length is of the distance between - the theory you discuss is already taken into consideration in the tables calculation.

And for the simple question of the OP and other non pros, this is why I recommended a specific (still overkill) range of 16-18 AWG conductors cable to well support up to ~300 mA load @ 70’.

You may recommend even 1 AWG, I’m sure vendors and service providers will make, as usual, good money on that. I’ve seen too much of it over the years.

My boat is Lloyd’s of London Certified vessel built by one of the world’s best builders, with Selden Ocean type 3 mast and rigging - by all means way more vigorous than the ABYC old books. The original wiring to the 5W masthead incandescent bulb is 14 AWG. The new Hella masthead light is 1W. So clearly the ABYC recommended is anachronistic for this use case.

But what can I say. My companies design critical care medical equipment and I believe in science not in the “conservative” overkill downgrading of a boat maintenance life (and life in general ). Maybe it is a Boston innovative, ultra progressive thing

[GordMay]

Originally Posted by DeValency

Indeed beating a dead horse. But to be practical. The tables are considering two conductors supply from source to load. Hence the cable length is of the distance between - the theory you discuss is already taken into consideration in the tables calculation ...

If "such a simple online search" will find such tables, please provide one.
I've searched, and NEVER seen such a table. YRMV.

[CharlieJ]

#57 @ DeValency

And yet you continue to obfuscate.

I do not give a fig about how well your boat is built or what you design and build outside of your boating hobby.

What I do care about is your false statement that a circuit is measured by one way length.

[Cadence]

The wire gauge round trip or not is about a moot point with the load presented by an LED. Wire strength and insulation for abuse in the mast might be a larger consideration.