Extending shore power cable

[sailorboy1]

The place to be worried about a shore power connection failing is at the pedestal. Maybe we should hard wire that.

[rwidman]

Originally Posted by sailorboy1

I need a longer shore power cable, will2 standard cables plug together?.

Yes, you can plug two shorepower cables together to make a longer cable and it won't change from a 30 amp cord to a 20 amp cord. There will be an additional voltage drop but no more than if you bought a longer cord to begin with.

I'm not suggesting that someone string three 50' cords together to make a 150' cord, but for reasonable lengths, you'll be just fine.

Theory tells us the shorter the cable from the dock to the boat, the better. I carry two cables, a shorter one and a 50' one. If the shorter one will reach, that's the one I use. Sometimes I need the 50' cable and once or twice I've had to use both as you describe.

[David M]

How much current it can carry depends on how much of a voltage drop you are willing to accept. You won't know ahead of time how much this is until you try it. Some connectors have different amounts of voltage drops than others, even identical connectors.

The voltage drop over a given length of wire is easier to predict, but even that is not 100% predictable.

[Terra Nova]

Originally Posted by rwidman

...you can plug two shorepower cables together to make a longer cable and it won't change from a 30 amp cord to a 20 amp cord. There will be an additional voltage drop but no more than if you bought a longer cord to begin with...

Not true. You can expect a voltage drop at each set of connections.

[transmitterdan]

Originally Posted by rwidman

Yes, you can plug two shorepower cables together to make a longer cable and it won't change from a 30 amp cord to a 20 amp cord. There will be an additional voltage drop but no more than if you bought a longer cord to begin with.



I'm not suggesting that someone string three 50' cords together to make a 150' cord, but for reasonable lengths, you'll be just fine.



Theory tells us the shorter the cable from the dock to the boat, the better. I carry two cables, a shorter one and a 50' one. If the shorter one will reach, that's the one I use. Sometimes I need the 50' cable and once or twice I've had to use both as you describe.

A well designed longer cord will use bigger wire to compensate for the extra voltage drop. So a 50 foot cord is usually not the same as 2 25 foot cords plugged together.

[a64pilot]

I'm all for the silicone grease myself, I keep a tube or two of Dow Corning DC4 on board, I keep shore power cords plugs well greased, cause I'm cheap. Keep them greased and you will only replace them when they get so old and the insulation so hard you can no longer roll them up to store them, not because they overheated and burnt the ends.
Grease prevents corrosion, corrosion is of course high resistance, high resistance obviously causes heat and low voltage.
I even keep my Smart plug greased

[flyingfin]

Originally Posted by sailorboy1

The place to be worried about a shore power connection failing is at the pedestal. Maybe we should hard wire that.

Too many people in this blog seem to be shooting from the hip
Y'all need to read the National Electrical Code Article 555

(1) Enclosures. Receptacles intended to supply shore power to boats
must be part of a listed marina power outlet enclosure, be installed
in listed enclosures protected from the weather, or in listed weatherproof
enclosures. The integrity of the assembly must not be affected
when the receptacles are in use with a booted or nonbooted attachment
plug/cap inserted.

[sailorboy1]

What's that got to do with plugging cords into each other

[rwidman]

Originally Posted by Terra Nova

Not true. You can expect a voltage drop at each set of connections.

Sure. A half a volt perhaps.

We are talking about supplying power to a boat. A practical real life application not an electrical theory question.

[rwidman]

Originally Posted by transmitterdan

A well designed longer cord will use bigger wire to compensate for the extra voltage drop. So a 50 foot cord is usually not the same as 2 25 foot cords plugged together.

None I've ever seen. 30 amp cords are #10 wire.

Consider this: When wiring a house does the electrician use heavier gauge wires for circuits that are further away from the electrical panel?

Now consider this: The wire run from the marina's panel to your slip is already several hundred feet. What difference does another twenty five feet make?

[rwidman]

Originally Posted by sailorboy1

The place to be worried about a shore power connection failing is at the pedestal. Maybe we should hard wire that.

I can't even begin to list the things that are wrong with that idea!

[sailorboy1]

It’s been months now and the connection between the cables hasn’t gotten any moisture in it or had the breaker trip. That’s the fact.

[BlackHeron]

Originally Posted by rwidman

None I've ever seen. 30 amp cords are #10 wire.

Consider this: When wiring a house does the electrician use heavier gauge wires for circuits that are further away from the electrical panel?

Now consider this: The wire run from the marina's panel to your slip is already several hundred feet. What difference does another twenty five feet make?

Yes, in fact we do.

Voltage drop and wire length are taken into consideration when pulling branch circuits (as well as feeder circuits to panelboards.) This is not so much a big deal in houses as most houses are not large enough to have many problems except some McMansions and real mansions when distances start growing quite large. In the commercial world you bet yo buttocks we need to upsize the wire for longer runs. Often we will pull larger gauge wire out to a junction box from the panel, and then run in the walls with smaller wire to achieve minimum voltage drop numbers (see below.) So a 20A circuit that is 150' from the panel may get #10 wire in the "home run" run underground or overhead to a junction box 100' away and then dive into the walls with #12 for the last 20-50 feet to the individual receptacles.

Voltage drop is function of wire size, circuit voltage, distance round trip, and most importantly current as it is a variable that we can only control by maximum fuse size, so we need to size wire for the maximum of the overcurrent device.

The NEC requires that feeders to panels be sized to allow for a calculated voltage drop of no more than 3%, and that branch circuits to be sized to have a voltage drop of no more than 3% as well -but the combined calculated voltage drop of the feeders plus the branch circuits may be no more than 5% in any circuit.

[evm1024]

I once needed to have shore power 200' from the outlet. Rather than buying a bunch of 50' shore power cords I bought a spool of Royal SOOW 10 ga 3 conductor wire and put my own connectors on it.

There was a 6 volt drop when running a 1500 W heater.

I still have the cable is anyone wants to buy some (in the PNW)

[BlackHeron]

For something as long as 200' and for a semi-longterm temporary installation I'd be tempted to get 6-6-6 overhead aluminum triplex wire and run it on the ground in 1-1/4" PVC and then hardwire it at the source and build a temporary pedestal. I might consider running it overhead if there was available structure to string it safely.

Perhaps maybe use a 20A or 30A GFCI breaker in an enclosure at the tap to ensure safety along the feeder if it is a high traffic area.