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Old 10-12-2014, 19:53   #1
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Shore Power

I liveaboard and always anchor out except presently while visiting a friend and in this area only option is to dock which has 20 amp and 30 amp shore power outlets which have those short adapter plugs available so one can plug in a 3 pronged extension chord. The extension cord I have looks fairly typical and is rated 16 awg. I want to plug into their shore power using their adapter and run my extension chord back inside my boat to use for a few things...computer, lamp. Can I use my 16 awg extension chord for their 20 amp shore power and not fry anything anywhere? ... thanks
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Old 10-12-2014, 20:19   #2
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Re: Shore power

20 amp circuit breaker is supposed to be wired with 12 AWG or larger wire on load side. 30 Amp requires 10 AWG. 16 AWG cords should not carry more than 13 Amp current (up to 50 foot). Note: Larger AWG number means smaller wire.

If your boat panel does not allow more than 13 Amp total you should be OK. If total load in any case is less than 13 Amp you should be OK. If more than 50 foot from 20 A outlet (and within reason), limit is like 10 Amp.

10 or 13 Amp is not a very large load for a boat. Make sure you know what total load is plugged in. Over that you will be seeing excessive voltage drop (less than 110 volt at load end) and will over heat the extension cord. You can get into big trouble before the 20 A breaker at the dock trips.

Frankly, people connect with undersized extension cords all the time with no bad results as long as load is within the cord's limit. Be careful.

16 AWG is a punk extension cord (for like plugging in a Christmas tree). Really should use 12 AWG minimum in any case (contractor grade).
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Old 10-12-2014, 20:52   #3
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Re: Shore power

I suggest your go to Harbor Freight or Home Depot & get a 12 or preferably 10 ga extension cord. With a cord rated for the max breaker you are risk free. The worst that can happen is shore breaker trips.
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Old 10-12-2014, 21:10   #4
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Re: Shore power

Larger AWG number means smaller wire.

If your boat panel does not allow more than 13 Amp total you should be OK. If total load in any case is less than 13 Amp you should be OK. If more than 50 foot from 20 A outlet (and within reason), limit is like 10 Amp.

.... thanks for the info. My boat does not have a panel (i.e., interior wiring for shore power). I am wired only for 12 volt. I just run an extension cord out of the boat and plug into shore power. My use is just a lamp and my lap top pretty much if I dock somewhere that has power.
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Old 10-12-2014, 21:24   #5
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Re: Shore power

Everything we do has some risk. The short answer to your question is that you will not damage your lamp or computer by plugging your light gauge extension cord in the the 20 amp dock outlet. As others have pointed out there are other risks but if I was you I'd plug in and get on with my life.

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Old 11-12-2014, 17:11   #6
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Re: Shore power

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Originally Posted by bobofthenorth View Post
Everything we do has some risk. The short answer to your question is that you will not damage your lamp or computer by plugging your light gauge extension cord in the the 20 amp dock outlet. As others have pointed out there are other risks but if I was you I'd plug in and get on with my life.

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I have to agree with that, especially if you are only running a couple of light loads. Wort that can happen is the cord gets warm - but probably not.
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Old 11-12-2014, 17:21   #7
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Re: Shore power

It's a "cord". not a "chord".

You didn't say if your boat has a built in shore power system but I'm assuming from the wording of your post that it doesn't.

While you can "get away" with your 16 gauge cord for a lamp and a computer, I agree with the advice to go buy a 12 or even 10 gauge extension cord and use this. They are not that expensive and you will find uses for it in the future.
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Old 11-12-2014, 18:07   #8
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Re: Shore power

16-ga is fine for those 2 small loads.
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Old 12-12-2014, 10:58   #9
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Re: Shore Power

You can do that with the 16ga cord but you really should get a good quality 12ga cord. It will last like forever, so don't try to go cheap on this. Ideally you would also make an enclosure with a house receptacle outlet or two, a GFCI breaker, and a ground wire. Even better, install a proper shore power breaker, a breaker box and a couple of outlets, and a shore power cable receptacle. If it is done right it improves the value of the boat. I strongly suggest, insist even, that you have a marine electrician check your work. It is nice to have proper wall outlets and breakers, and a heavy duty shore power cable instead of just an extension cord.

Whatever you do, don't leave an energized 16ga extension cord unwatched with a load on it. Think fire and electrical shock safety. I saw the aftermath of a guy who ran a space heater unattended on a cheap extension cord. It wasn't pretty.
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Old 12-12-2014, 11:35   #10
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Re: Shore Power

Don't run a heater with it. I've fried two cords in the past year. One was an appropriate shore power cord and the end pugging into the boat fried and melted the metal prongs. The other was a cord connected to a brand new heater. The end got hot and melted and fried the plug and outlet inside the boat. (Two separate occasions). Those were both factory made and properly rated products. Both could have caused fires if breakers hadn't tripped. You are talking below rated, and so much more likely to have a problem with a heavy load.
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Old 12-12-2014, 11:45   #11
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Re: Shore power

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Originally Posted by Terra Nova View Post
16-ga is fine for those 2 small loads.
Yes, but with a twenty amp circuit breaker on the dock the 16 gauge cord can melt and catch fire before the breaker trips. $15 for a proper cord is cheap insurance.
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Old 12-12-2014, 12:25   #12
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Re: Shore Power

I'd suggest replacing the cord with a heavier one, which will cause less voltage drop and allow a brighter lamp and faster laptop charging, along with having less risk of overheating.


BUT.


Since you are on a boat and cords often wind up having some moisture or condensation on them, I'd buy a cord with a GFI or similar shock protection device BUILT INTO IT. Yes, they exist, yes, they often cost a bit more. Yes, the power post on the dock is supposed to have one. "Supposed to".


You'd be surprised to find out how easily you can be shocked by the moisture on an outdoor extension cord. Having a GFI built in is cheap insurance. If you can't find one built in, you can buy one pre-wired in a one or two foot extension cord, sold for that purpose. Just tie it onto your other cord, so it can't walk away.
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Old 12-12-2014, 12:52   #13
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Re: Shore power

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Originally Posted by rwidman View Post
Yes, but with a twenty amp circuit breaker on the dock the 16 gauge cord can melt and catch fire before the breaker trips. $15 for a proper cord is cheap insurance.
You ain't getting a 50' 10 or 12 ga cord for $15,
This one at Lowes is $100, less tax.

Shop Utilitech 50-ft 20-Amp 110-Volt 10/3 Yellow Outdoor Extension Cord at Lowes.com

I'd say bigger is always safer, but for a lamp and laptop, 16Ga is fine, not heater, coffee pot etc though.
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Old 12-12-2014, 16:13   #14
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Re: Shore Power

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Originally Posted by hellosailor View Post
I'd suggest replacing the cord with a heavier one, which will cause less voltage drop and allow a brighter lamp and faster laptop charging, along with having less risk of overheating.


BUT.


Since you are on a boat and cords often wind up having some moisture or condensation on them, I'd buy a cord with a GFI or similar shock protection device BUILT INTO IT. Yes, they exist, yes, they often cost a bit more. Yes, the power post on the dock is supposed to have one. "Supposed to".


You'd be surprised to find out how easily you can be shocked by the moisture on an outdoor extension cord. Having a GFI built in is cheap insurance. If you can't find one built in, you can buy one pre-wired in a one or two foot extension cord, sold for that purpose. Just tie it onto your other cord, so it can't walk away.
The voltage drop on a 16 gauge power cord used to power a laptop computer and a small lamp would be pretty insignificant. I agree with you that a GFCI equipped cord or a separate adapter would be a very good idea.
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Old 12-12-2014, 16:16   #15
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Re: Shore power

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Originally Posted by a64pilot View Post
You ain't getting a 50' 10 or 12 ga cord for $15,
This one at Lowes is $100, less tax.
Doesn't matter. If you can't afford to be safe, it would be best to get off the water.

Once the boat has electric power it's just too much of a temptation to plug more things in. The power cord should have the capacity of the overcurrent protection supplying it. In this case, it seems to be 20 amps so that's a #12 cord.

I think the OP plans to be at a dock so it's unlikely a 100 foot cord would be needed.
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