110 shore power

[Hookster57]

The dock slip I'm soon going to only has a standard 110 outlet. Where can I find a plug that that has the right ends to hook into the Grady shore power? And how many amps does 110 put out? I want to run the battery charger at least, and more if able.

 

[seasick]

The dock slip I'm soon going to only has a standard 110 outlet. Where can I find a plug that that has the right ends to hook into the Grady shore power? And how many amps does 110 put out? I want to run the battery charger at least, and more if able.

You will need an adapter and the specific model depends on which connector you have on the shore power cord.
Here is one to convert a 30amp standard shore connector to a standard 110v 15 amp receptacle
http://www.wholesalemarine.com/p/MAR-83A/

With regard to amps, a standard 15A circuit can supply 12 amps continuous and a 20 amp will supply 16 amps cont. Your 110 service could be 15 amp or 20 amp normally. A 20 amp 110v receptacle has a T shaped slot on one of the plug holes. Even if you have a 20 amp receptacle, the circuit may not be sized and/or fused for 20 Amps. If you can get to the breaker, check its rating.

Your 30 amp was rated for 24 amps so (although not exactly correct), you will have half the power available that you had before but definitely enough for a charger and small small loads.

 

[ocnslr]

If a voltmeter really shows 110VAC, then you might ask the marina to check their system for losses, as the voltage is supposed to be 120VAC on either side of the usual 240VAC feed.

 

[seasick]

If a voltmeter really shows 110VAC, then you might ask the marina to check their system for losses, as the voltage is supposed to be 120VAC on either side of the usual 240VAC feed.

The nominal voltage can range from 110 to 120 or so. It can be lower too depending on drops, utility source voltage etc. The actual expected voltage depends on the power distribution configuration. For example if your dock has 220 single phase service, the leg to neutral voltage will be 110 nominal. On the other hand if the service is three phase 240V , nominal voltage will be 120v, leg to neutral.

 

[Legend]

There are many marinas that have the setup you referenced - when I am visiting other marina I always have my pig tail adaptor just in case it is a 110 setup . Got mine at West MArine

 

[JeffN]

The amperage of your 120 volt circuit will be determinded by the size of the circuit breaker or fuse protecting it. The wire feeding the receptacle will be sized for the amperage of that overcurrent device. Generally speaking the breaker size will be either 15 or 20 amps for a 120 volt circuit. A 20 amp breaker will supply 20 amps and a 15 amp breaker 15 amps. The mention of continuous loads (a constant load for three hours or more) above is for sizing circuits for fixed equipment and is allowed for at the design and installation phase and not for a general use circuit - the breaker does not know if the load is continuous or not. If it is a 20 amp breaker it will supply 20 amps.

If you have a 20 amp receptacle and at your slip the breaker and circuit conductors would be sized 20 amps if the installation was done properly. It is against the code to install a 20 amp receptacle on a 15 amp circuit.

 

[seasick]

. The mention of continuous loads (a constant load for three hours or more) above is for sizing circuits for fixed equipment and is allowed for at the design and installation phase and not for a general use circuit - the breaker does not know if the load is continuous or not. If it is a 20 amp breaker it will supply 20 amps.

quote]
This is not true. Breakers use bi-metal thermal mechanisms that actually heat up with the load. The more the load, the more they heat up and at some point the bi-metal strip bends enough to trip the breaker. You can pull a lot more amperage than 20 amps through a 20 amp breaker as long as it is for a short period of time. Generally breakers will carry 80% of rating forever. 110% may work for 5 minutes or an hour depending on the design and intended use.
For example, a large compressor type load could spike several times its continuous draw but you would size for the smaller draw and not the start up peak current.

One other factor to consider is voltage drop. Even with properly designed distribution, there is a designed voltage drop figured in the wire sizing. When you have long service runs, add extension cords etc., you may add more resistance and under load more voltage drop. For resistive loads like lights, that results in dimmer lighting, no big deal, but for constant load devices like compressors, low voltage due to drop results in higher current. That can lead to breaker trips at best and burned out motor windings at worst.
A lot of DIYers assume that for a 20 amp service you need a 12 gauge wire but that it true up to a length limit(about 50 feet). It is not uncommon to see undersized wires for longish runs. Note that a 12G extension cord is a hefty cable. A 10 G is really bulky. Your run of the mill extension cords are usually sized much smaller

 

[JeffN]

. The mention of continuous loads (a constant load for three hours or more) above is for sizing circuits for fixed equipment and is allowed for at the design and installation phase and not for a general use circuit - the breaker does not know if the load is continuous or not. If it is a 20 amp breaker it will supply 20 amps.

quote]
This is not true. Breakers use bi-metal thermal mechanisms that actually heat up with the load. The more the load, the more they heat up and at some point the bi-metal strip bends enough to trip the breaker. You can pull a lot more amperage than 20 amps through a 20 amp breaker as long as it is for a short period of time. Generally breakers will carry 80% of rating forever. 110% may work for 5 minutes or an hour depending on the design and intended use.
For example, a large compressor type load could spike several times its continuous draw but you would size for the smaller draw and not the start up peak current.

One other factor to consider is voltage drop. Even with properly designed distribution, there is a designed voltage drop figured in the wire sizing. When you have long service runs, add extension cords etc., you may add more resistance and under load more voltage drop. For resistive loads like lights, that results in dimmer lighting, no big deal, but for constant load devices like compressors, low voltage due to drop results in higher current. That can lead to breaker trips at best and burned out motor windings at worst.
A lot of DIYers assume that for a 20 amp service you need a 12 gauge wire but that it true up to a length limit(about 50 feet). It is not uncommon to see undersized wires for longish runs. Note that a 12G extension cord is a hefty cable. A 10 G is really bulky. Your run of the mill extension cords are usually sized much smaller

Circuit breakers have a time delay function to allow for spikes of starting current etc. I would direct you to NEC aticle 100-I for a definition of continuous load. Then go to article 210-19 (A) and 210-20 (A), in the 2008 Nec, for more info about sizing a circuit for continuous loads. These factors are used for sizing continuous loads that are fixed/known loads. Who knows at the time of construction what equipment a boat will have that happens to tie up in that slip? How will you size for a continuous load on a receptacle when you don't know what willl be plugged into said receptacle. In addition there is an entire section in the NEC, article 430, for motors like for the compressors you mention above. In a motor application the the over current protection is permitted to be increased to allow for current surges. This information is available in table 430.52 again in the 2008 NEC my 2011 book is out in the van currently. The breaker can be oversized because the motor is protected by the heaters in the motor or motor controller. In the case of a single phase motor an inverse time circuit breaker can be increased 250% after you have done your motor calculations. Thats why you will see 12 gauge conductors on a motor feed protected by a breaker larger than 20 amps. You can't just throw a larger circuit breaker on a circuit with a unknown load, like on at a dock. The dock receptacle the OP mentions I would guess is sized for either 15 or 20 amps, perhaps 30 amps and the conductors are matched to that overcurrent device. If it is protected and sized for a 20 amp overcurrent device he will have 20 amps available. The 16 amps (or 80% of 20 amps) you mention is part of a continuous load calculation that no one is able to complete as the receptacle in question does not have a fixed known load.

Voltage drop, conductor size and other factors are all part of the calculation of course but there is more to it than that.

 

[seasick]

. The mention of continuous loads (a constant load for three hours or more) above is for sizing circuits for fixed equipment and is allowed for at the design and installation phase and not for a general use circuit - the breaker does not know if the load is continuous or not. If it is a 20 amp breaker it will supply 20 amps.

quote]
This is not true. Breakers use bi-metal thermal mechanisms that actually heat up with the load. The more the load, the more they heat up and at some point the bi-metal strip bends enough to trip the breaker. You can pull a lot more amperage than 20 amps through a 20 amp breaker as long as it is for a short period of time. Generally breakers will carry 80% of rating forever. 110% may work for 5 minutes or an hour depending on the design and intended use.
For example, a large compressor type load could spike several times its continuous draw but you would size for the smaller draw and not the start up peak current.

One other factor to consider is voltage drop. Even with properly designed distribution, there is a designed voltage drop figured in the wire sizing. When you have long service runs, add extension cords etc., you may add more resistance and under load more voltage drop. For resistive loads like lights, that results in dimmer lighting, no big deal, but for constant load devices like compressors, low voltage due to drop results in higher current. That can lead to breaker trips at best and burned out motor windings at worst.
A lot of DIYers assume that for a 20 amp service you need a 12 gauge wire but that it true up to a length limit(about 50 feet). It is not uncommon to see undersized wires for longish runs. Note that a 12G extension cord is a hefty cable. A 10 G is really bulky. Your run of the mill extension cords are usually sized much smaller

Circuit breakers have a time delay function to allow for spikes of starting current etc. I would direct you to NEC aticle 100-I for a definition of continous load. Then go to article 210-19 (A) and 210-20 (A), in the 2008 Nec, for more info about sizing a circuit for continuous loads. These factors are used for sizing continuous loads that are fixed/known loads. Who knows at the time of construction what equipment a boat will have that happens to tie up in that slip? How will you size for a continuous load on a receptacle when you don't know what willl be plugged into said receptacle. In addition there is an entire section in the NEC, article 430, for motors like for the compressors you mention above. In a motor application the the over current protection is permitted to be increased to allow for current surges. This information is available in table 430.52 again in the 2008 NEC my 2011 book is out in the van currently. The breaker can be oversized because the motor is protected by the heaters in the motor or motor controller. In the case of a single phase motor an inverse time circuit breaker can be increased 250% after you have done your motor calculations. Thats why you will see 12 gauge conductors on a motor feed protected by a breaker larger than 20 amps. You can't just throw a larger circuit breaker on a circuit with a unknown load, like on at a dock. The dock receptacle the OP mentions I would guess is sized for either 15 or 20 amps, perhaps 30 amps and the conductors are matched to that overcurrent device. If it is protected and sized for a 20 amp overcurrent device he will have 20 amps available. The 16 amps (or 80% of 20 amps) you mention is part of a continuous load calculation that no one is able to complete as the receptacle does not have a fixed known load.

Voltage drop, conductor size and other factors are all part of the calculation of course but there is more to it than that.

There once was a man from Nantucket
Who went up a pole in a bucket.

Never mind


In general I think we are on the same channel. What I see in many cases as I expect you do also is that the design guidelines for conductor sizing, especially when it comes to overall run including accessory cord sizing are not accurately followed.
Now, how do you manage to quote so many sections of the NEC. My code book is buried in the basement and I suspect due to its age, often references Thomas Edison

 

[JeffN]

Nope not a lineman - I work my mischief on the ground or as close to the ground as possible.

Yeah who knows what someone will plug into a receptacle. Like you we see some beautiful creations. At least with a boat most of the shore power cords are pretty good. It is the home made ones that get creative. Lots of people can make their wiring work, not everyone can make it safe.

I have to keep the code book close as we have a good inspector, he keeps us on our toes. Plus I kind of enjoy it.