|By Jay (jayc) on Saturday, April 08, 2006 - 9:08 am:
|I have a roll of twin core 16 gauge cable and thought it would be good for my tower lights. |
Got 6 lights at 55W so I'm guessing they need cable that will handle 27amps.
Is it going to handle it?
|The chart at this link http://www.skingco.com/portable_power/wiring_size_chart.htm doesn't have 16 gauge wire. But to handle 27 amps you need at least 10 gauge wire. |
Depends on the length of cable. #16 cable will drop 1.65 volts over 15 feet with a 27amp load.
|The numbers on the link above seem a little off to me. I checked my books and here is what it recommends: assuming approximately 15-20 foot run you will need a minimum of 12 ga. for 25 amps. To be safe, I would go with what George suggested and use 10 gauge if you want to run all the lights on one circuit. Or divide the lights up into 3 circuits (2 lights on each) and use your 16 ga. |
|....the first link......|
|I didn't mean to imply that 16 ga is sufficient. I was showing what would happen, should he use 16ga. |
Realistically, you want to target under 1/2 volt drop -- Which points you to 10ga cable as per my link. (Personally I'd use 12ga as it'll perform fine)
|Watts divided by volts equals amps so at 14 volts, each 55 watt light will draw 4 amps. I have six 55 watt lights also and ran 14 guage wire with three 20 amp rocker switches, one switch for each pair of lights. Since two lights only draw 8 amps on one 20 amp switch, no breakers needed. 16 guage might be fine but if was me, I would go 14. 12 or 10 is overkill but always better to error on the bigger side when it comes to wire size. |
(Message edited by wake upppp on April 08, 2006)
|You have to understand that there are two considerations regarding the wire size. |
The first consideration is the ability of the wire to withstand the current. This is a function of the amps it is carrying and the ambient temperature. The current flowing through the wire heats the wire, and at some point the heat will cause the insulation to melt and bad things happen.
Obviously, the type of insulation on the wire will determine the maximum temperature it will be able to withstand.
A typical maximum capacity, for 16 awg wire in an open ambient (plenty of fresh air to cool it) is 21 amps. This is not enough for the 27 amps that you need.
In most cases you will experience an undesired voltage drop well before you need to worry about the insulation melting. The voltage drop is a function of the size of the wire, the current, and the length of the wire.
If you want those lights to be bright then you will not want any more than a 10% drop in voltage to them, which means instead of 12 volts they will only be getting 10.8. You need to get the positive wire up to the top of the tower and a ground wire back, so I would guess that you would have a run of 20 feet (10 up, 10 back). To keep the voltage drop less than 10% at 27 amps you will need 12 awg wire.
If you want only a 3% drop you will need 8 awg wire.
Here is a good web site with all this information:
go to "techinical information" then "Wire Calculator"
You might want to consider grounding the tower (put a big cable to one of the bolts holding the tower to the boat) and use the tower as ground. That will cut out half the run as you will only need to run the plus wire up the tower and not a ground.
|By Jay (jayc) on Sunday, April 09, 2006 - 2:32 am:
|I did consider grounding the tower but as it has a few moving joints and is used in saltwater I thought it may cause problems. |
I'll just get some more cable.
|By Bob (bob) on Sunday, April 09, 2006 - 4:45 am:
|Rod ,speaking of grounding towers...Has anyone thought about grounding their tower to their engine for lightning protection like sailboats do with their mast? One person I spoke with that did some weather experiments in the past, professionally, says you wouldnt want to do this as it would assure the lightning sees you as a good ground but the sailboat folks swear by running a ground off the mast with some large plates under the boat for the charge to bleed off in the water. With all these wakeboard towers on boats now i'd have thought this subject would have been discussed but I havent seem anyone post on it. Oh yea, just call me the hijacker|
|How are you arriving at 27 amps? A 55 watt light at 14 volts will only draw 4 amps. You only need to run one common ground wire for all six lights, and then a seperate power wire for each light.|
|Sparky: Depends on the voltage that the 55 watts was rated at. If it was rated at 12 volts it is 4.6 amps per light, or 27.5 amps total. |
Why would you run a separate power wire to each light? Individual switches? If you are going to turn them all on or off together then it will be a lot less bulk to run one large rather than four smaller wires.
A sailboat is generally a significantly different case than a wakeboard boat. First off, they tend to get a long way from home and are unable to run for shelter so they have to deal with whatever comes their way. Second, thier mast is a whole lot taller than a wakeboard tower. Third, a sail boat tends to be out on a large body of water far away from trees, hills, buildings, etc. hence a 30 foot mast can be the tallest thing for miles.
Even if you connected the tower to "ground" it is very unlikely that you or the boat would survive a direct strike. Current surges of that magnitude don't like to follow the tortorous paths you provide, it will branch out and burn a hole right through the hull.
|Rod, I wanted the ability to turn on only the front facing pair, either pair of the rear facing four, or all six at once. If I'm just loading up some stuff, I sure ain't gonna want all six lights running. If I'm just running across the lake, I don't want the rear lights on. I also wanted the ability to take the light bar down. I don't know of a 9 pin quick connect plug that would accept 10 or 12 guage. lol|
|Hey Rod - What do you think about using the tower itself as the ground wire return? For instance: Run the heavy 8ga up the inside of the tower. Then run an 8ga ground from neg(-) through the hull and Terminal bolt it to the tower. Then on the topside (without going through any tower pivots or other tower connectors) terminal bolt the light's ground wire to the tower. |
My motivation for this would be to reduce the amount of wire running through the tower so that the drilled holes are smaller.