Question - Multiple wires through hull

[sionnach]

Hi everyone -
I am in the process of making a wiring harness and need to pass multiple wires(6x12AWG) in one bundle through the hull.

Obviously I am concerned about water penetration. The high flow heatshrink I have doesn't seem to penetrate all the gaps between the inner wires.

Does anyone have any suggestions on how to accommodate this? And on what product would be good for the through hull hole?

I'll be passing 57amps through the wires (if everything is on) and will be making a slight turn then terminating the ends of the wires with 3 metripack 630 series connectors. (6 wires = 3 separate circuits)

Thanks all for the advice.

Best,
Todd

 

[John Nantz]

Above or below waterline?

Todd - just curious, where through the hull would this bundle be going? Like above or below the waterline?

More curiosity is getting the best of me, what kind of a project is this?

 

[kloudie1]

700 Watt fishing machine that may electrocute fishies??

 

[RAD]

700 Watt fishing machine that may electrocute fishies??

It's called an underwater Telsa Coil fish eliminator.....but the 700 watt unit dosn't work as well as the 1500 watt unit

 

[RAD]

Oh...to answer the question

http://www.defender.com/product.jsp?path=-1|328|49758|112306|316467&id=1351907

 

[sionnach]

I really like the idea of the tesla coil.

I actually have two projects - one is wiring my SUV with tons of lights for camping.
(I'm using all marine grade product for this)

The other is helping a friend rewire his boat and add a ton of lighting to it as well.
12v system with 3 circuits. 170w, 330w, 165w. (roughly)

Above waterline for both situations (especially - hopefully - the truck!).

I'll take a look at the product you linked to.

Speaking of tesla coils - check out Arc Attack at Maker Faire this last weekend. YouTube should have some videos.

 

[Maine Sail]

I really like the idea of the tesla coil.

I actually have two projects - one is wiring my SUV with tons of lights for camping.
(I'm using all marine grade product for this)

The other is helping a friend rewire his boat and add a ton of lighting to it as well.
12v system with 3 circuits. 170w, 330w, 165w. (roughly)

Above waterline for both situations (especially - hopefully - the truck!).

I'll take a look at the product you linked to.

Speaking of tesla coils - check out Arc Attack at Maker Faire this last weekend. YouTube should have some videos.

It will be very, very difficult to seal those six wires. Perhaps the most watertight solution is to use "round", not flat, duplex marine grade wire and a cable clamp for each. I don't know of any 12GA three pair. The round jacketed duplex wire seals significantly better in a cable clam than does the flat duplex.

 

[Smithy]

I'm thinking stuff the bundle with butyl tape, then heat shrink the bundle tight. Then use your caulk of choice on the heat-tape interface.

 

[Old Skool Neil]

I'm struggling with your 330 watt circuit on #12 wire.

There is a sealing compound used in the electrical trade in conjunction with EY explosion proof conduit fittings that renders a conduit with multiple conductors absolutely vapor tight. Might consider a variation of that system.

 

[sionnach]

I'm struggling with your 330 watt circuit on #12 wire.

There is a sealing compound used in the electrical trade in conjunction with EY explosion proof conduit fittings that renders a conduit with multiple conductors absolutely vapor tight. Might consider a variation of that system.

330w @ 12v = ~27A right?

12AWG should carry up to 30A for a 10' run I think,
so if I have a feeder run of ~10' then split to a left run and a right run for lights then that should be ok right, as the full amp is only on the feed line and then well beneath that on either side.

Am I thinking about this wrong?

 

[tommays]

I think your into the 10 AWG range with the 27 amp draw

 

[Forrest15112]

I was thinking about a waterproof bulkhead connector attached to the hull. Something like this - ( http://www.route66supply.com/store/product12.html ) I suppose there are "marine" grade bulkhead connectors somewhere.

 

[Old Skool Neil]

Regarding wire size, the following comments are based in the alternating current world but the principles apply to DC as well. By the way, your amperage calculation is correct.

Issue #1: Conductor heating. The conductor size along with the insulation rating (unknown in your case) limits the current carrying capacity due to temperature rise. Exceeding the current carrying capacity as specified in a table of ampacities increases conductor temperature and in this case could affect the proposed sealing system as well. Further, bundling conductors of different circuits in close proximity beyond a certain length requires derating the conductor's allowable amperage. This may or may not be a factor for you, length being the determinant.

Issue #2: Voltage drop. You are correct that length is a factor even if you are within the wire gauge specified by the table of ampacities. The table does not account for wire length and voltage drop, that is handled by a separate calculation and always results in a negative figure, a derating of the wire's amperage capacity. Exceeding the rated amperage of a conductor aggravates voltage drop.

A rule of thumb that addresses both above issues is to design your system so that a conductor never carries more than 80% of its rated amperage. This is a basic tenet used in the engineering of electrical circuits. Following this principle, even #10 wire is a little small for your 330 watt circuit.

 

[sionnach]

@Neil - I am using the ancor wire.

Looking at this table the insulation is rated to 221F outside the engine.

What would you advise when running through conduit - 1" steel square tubing?
I was thinking 6 wires in and then split the the 4 locations.
2 wires for the rear.
2 wires running to the right side
4 wires running on the left side for the left lights and up to the forward lights.

I am new to wiring so all this is a learning experience.

 

[Bill Roosa]

Can you add a panel after passing trhough the deck? Then all you have is 2 wires to power the panel that have to pass through the deck.
baring that can you add a junction box after the passing through the deck? As you are adding lightining is it all going to be on one switch or do you want to have 3 sets of lights that you can turn on/off independantly?

 

[sionnach]

@bill - 3 separate switches.

1 for forward
1 for left and right nav lights
1 for rear lights

 

[Old Skool Neil]

My previous comments may have caused undue alarm, particularly in terms of the current carrying capacity of conductors. I just researched the ABYC Standards on wiring and their ampacity table is way different than the values I've used in the electrical industry for 35 years and way different than the National Electric Code. Here's a link to the ABYC table: http://www.acbsphl.org/Tips_and_hints/ABYC_Wiring.htm

Using their values (I wouldn't be able to sleep at night if I did but I admit to being a product of my industry) 12 gauge will be fine for your project but I've got to say it really sticks in my throat. According to their table, 45 amps on a #12 wire? Oh Lordy!!

I still stand by the properties and design principles I offered earlier but that ABYC ampacity table affected my sphincter!!

 

[Maine Sail]

My previous comments may have caused undue alarm, particularly in terms of the current carrying capacity of conductors. I just researched the ABYC Standards on wiring and their ampacity table is way different than the values I've used in the electrical industry for 35 years and way different than the National Electric Code. Here's a link to the ABYC table:http://www.acbsphl.org/Tips_and_hints/ABYC_Wiring.htm

Using their values (I wouldn't be able to sleep at night if I did but I admit to being a product of my industry) 12 gauge will be fine for your project but I've got to say it really sticks in my throat. According to their table, 45 amps on a #12 wire? Oh Lordy!!

I still stand by the properties and design principles I offered earlier but that ABYC ampacity table affected my sphincter!!

Neil,

Please don't confuse E-11 Table VI Ampacity Ratings with what you can or should pass through the wire. That table is for sizing over current protection not "general duty go ahead and run 45 amps through 12GA" sort of stuff. You still need to calculate your length and VD to size it correctly and that is a different table. As I mentioned before 20 feet round trip @ 27A for a 5% voltage drop is 10GA wire. However his circuit total length will be far greater than 20 feet....

I use this one as it is much easier than doing it "free hand".

Wire Gauge Calculator

 

[Old Skool Neil]

Thanks Maine, now I can get some sleep tonight.

 

[sionnach]

Gotcha - thanks Maine.

Like I said this is pretty new to me.
I talked with the guys at Fisheries Supply and they had a chart to show amps when running in a bundle, 6 wires 12AWG each wire is then rated at 23A (on the low end).
With 10AWG the rating is 33A.

So on the boat I have room to run larger wiring and can definitely do that since the runs will be longer and I'll need to account for drop as you mentioned.

However on the truck I have limited space, luckily the runs are not that long.

from the rear hatch to the plug for the roof rack is probably 6 - 8 feet then:
front lights = ~6 feet
left lights = 2, 4, 6 feet (space from the quick disconnect plug)
right lights = 5, 7, 9 feet (again from the quick disco)
rear lights = 1, 2, 3 feet (from the disco)

So the plan is to run the wiring to a blue sea 5025 fused distorbution box in the rear hatch.
bundle the wires from it to the top of the truck and terminate them with 3 Metripack 630 2 conductor connectors.
then run a bundle from the connectors into the roof rack and jumper the wires as appropriate the branch for the left and right nav lights would be ~1.5 feet from the Metripack connector and would branch left and right at that point.

would it make sense to run 10AWG for that circuit up to the connector, then from the connector to the branch and then 12 AWG from there given that those runs are shorter and (I think) fit within the voltage drop and temp rating.

Thoughts? I'm basically doing the same setup on my friends boat (without the roof rack) as I am doing on the truck

Thanks guys!