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Stupid electrical questions

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tingwc
1st Mate

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31 Posts

Initially Posted - 05/06/2007 : 14:59:58

Forgive me, but I have a few stupid electrical questions. I know these must be pretty obvious for the most of you. I did buy and read Don Casey's Electrical book, and that helped a little.

1) I bought a 20 amp double-pole circuit breaker. From the shore power inlet, the hot and neutral go into this breaker, correct?

2) Does the ground go directly from the shore power inlet to the AC plug (and not through the circuit breaker)?

3) Does the circuit breaker need to be in an actual physical box or can i just glue it to wall in the locker?

4) Any tips on how to make a hole to house the AC receptacle?

Wallace Ting
Queens, NYC
1988 WK

Edited by - on

dblitz
Navigator

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240 Posts

Response Posted - 05/06/2007 : 19:09:07

Can't help you with the electrical wiring details but I can tell you that the ac receptacle should actually be a GFI outlet. Doesn't your boat have 2 outlets for shore power???
When I took out the standard 120v outlets that my boat had, the GFI's didn't fit. I was able to make those holes in the fiberglass larger relatively easily with a rotozip type tool.
Wear a mask and safety glasses when you use the tool. I once read a tip that shaving cream helps to cut down on the amount of fiberglass that goes airborne, a tip that I didn't know about and thought might have been very helpful because the glass goes all over the place.

Edited by - on

Oscar
Master Marine Consultant

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USA
2030 Posts

Response Posted - 05/06/2007 : 20:50:08

1: Correct. But, are you plugging into a 30 Amp outlet? The big round yellow plug, or a 20 amp outlet? Regular three prong Edison (as in household) plug? If you are plugging into a 30 amp service, you better have a 30A breaker.

2: Also Correct, or to a bus where assorted grounds meet.

3: NO! to taping.....YES! to building it in.

You'll notice things are a bit exposed......hot (as in electrically charged) exposed metal is a no-no. Electrical wiring needs to be secured, with HARDWARE not tape, Elmer!!! Also. you may wish to limit your outlets to, say. 10 amps. 20 is a lot. You may also wish to install other appliances at some time... like a battery charger. These would need separate circuits. So, I recommend installing the AC Main breaker in a panel, or in a box if you have to, and then installing a three breaker distribution panel.

4:I use a dremmel tool on slow with a zip-bit in it......

Regarding electrics, if you are not sure about what you're doing, get help. It is unforgiving of serious mistakes.

Edited by - on

ct95949
Captain

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Aruba
300 Posts

Response Posted - 05/06/2007 : 21:36:50

Wallace-
If you look in the West Marine catalog you will find quality marine electrical parts and a lot of good info on what you need. I just installed what you are asking about and it went like this: Marinco 30 amp shore power cord and inlet, 10 gauge Ancor triplex wire, Blue Sea 30 amp main breaker, Blue Sea 3 position breaker panel, 12 gauge Ancor triplex to three 20 amp GFI outlets and battery charger. Blue Sea makes ABS covers for thier breakers and panels and a Dremel will cut the holes in the bulkhead to set them.
I'm not an electrician but I've done all the electrical work on my own house for many years so I'm comfortable. If you're not I'd do what Oscar suggested and get an expert. It has to be done right, no gluing stuff to the wall.

Edited by - ct95949 on 05/06/2007 21:41:59

johnsonp
Admiral

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USA
606 Posts

Response Posted - 05/07/2007 : 00:42:54

Some stupid pictures to stimulate some thought.

110volts in

110volt cutout

110volt panel

panels in

wires going forward to 110 outlet

110volts out

paulj C310

Edited by - on

ajniemira
Deckhand

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18 Posts

Response Posted - 05/08/2007 : 15:06:43

Only the "hot" goes thru the breaker. Since this is 120 VAC you only need a single pole breaker and you connect the hot to the breaker. It is against the National Electrical Code to either switch or put a breaker in a neutral. The neutral needs to be run to the neutral bus on your 120 VAC distribution panel.

Edited by - on

ct95949
Captain

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Aruba
300 Posts

Response Posted - 05/08/2007 : 20:05:55

Let me repeat that I'm not an electrician but...the Blue Sea 30 amp main breaker ( model 8077 )is rated at 120V AC and has two poles. One side is labeled HOT with copper colored terminals and the other side has silver terminals which I assumed were for the neutral leads. If not then what is the second pole for?
I've never switched a neutral wire on my house wiring but I figured the two poles were because of the marine application.

Edited by - ct95949 on 05/08/2007 20:11:28

ajniemira
Deckhand

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18 Posts

Response Posted - 05/10/2007 : 12:01:00

I stand corrected. I am an electrical engineer but have never designed boat electrical systems. If you look in the NFPA 302 figure 8-7.3(b) is basically what we have on our C25s. The best I can acertain is that the pole for the neutral is to prevent fire and / or electrocution due to a reverse polarity condition. If you have a fault in a reverse polarity condition the fault curent is on the neutral and with no breaker in the circuit the neutral could burn up or cause an electricution in faulty appliances. Since you are not an expert in this (and neither am I) you really need to have an electrician who has experience in marine electrical systems do this for you. Saving money dosen't mean much if you are dead.

Edited by - on

tingwc
1st Mate

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31 Posts

Response Posted - 05/13/2007 : 22:07:20

Thank you for all of the advice. Those pictures were pretty helpful.

However, I am not looking for something that complex. I am just looking to have ONE ac outlet that connects directly to the shore power inlet. According to Don Casey's Electronics book, I don't need to have an AC switch panel.

The book says I can just use a 15 amp double-pole breaker and connect the breaker from the inlet to the plug outlet. Is that correct? If I use this setup, does the neutral then go into the breaker and the ground directly from the inlet to the outlet?

Edited by - on

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 05/13/2007 : 22:14:57

Hey Wallace - if you are looking for JUST ONE AC outlet - consider a shorepower cable adapter at the shore power box with a 100 foot outdoor extension cord. You'll avoid any holes in the boat, it will be cheaper and you won't need to worry about correct wiring and you have extra functionality with it.

Edited by - on

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 05/13/2007 : 23:44:58

"consider a shorepower cable adapter at the shore power box with a 100 foot outdoor extension cord"

IMHO: That's potentially dangerous. The shorepower box will probably have a 30 amp breaker which will be over-rated for the downstream wiring. A short inside the boat or in the cord will send them up in smoke before the dock breaker trips.

Shorepower cords should match or exceed the rating of the breaker on the dock and any circuits on the boat should have a properly sized breaker to protect their wiring.

Standard breaker size for a 120 VAC 12 GA circuit is 15A. There should be a breaker on each circuit run from the shorewpower termination.

Go here: www.marinco.com/docs/guides/Boater'sGuidetoACElectrical.pdf

Look at the diagram on page 19 for a nice schematic. There is lots of other good information on that page too.

Another good read: uscgboating.org/recalls/pdfs/BSC81.pdf

Edited by - on

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 05/14/2007 : 06:35:05

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by ClamBeach
 "consider a shorepower cable adapter at the shore power box with a 100 foot outdoor extension cord"

IMHO: That's potentially dangerous. The shorepower box will probably have a 30 amp breaker which will be over-rated for the downstream wiring. A short inside the boat or in the cord will send them up in smoke before the dock breaker trips.

<hr height="1" noshade id="quote"></blockquote id="quote">

I was thinking something like this that is made for the application and would knock the straight blade extension cord down to 15 amps

Edited by - on

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 05/14/2007 : 08:55:30

"I was thinking something like this that is made for the application and would knock the straight blade extension cord down to 15 amps"

120 VAC shorepower doesn't have a split-ciruit configuration. It supplies the full amperage on a single leg.
So if you plug a conventional extension cord into the adaptor the problem remains... the rating on the upstream breaker exceeds the capacity of the downstream wiring. Notice how heavy the wiring in the adaptor is... probably 30A rated wire. that's how the mfg covered their 'bacon'. Their adaptor wont' burn up... but your extension cord might.

I used to have a setup like that feeding the shorepower connector on my boat (via a second adapter) until I realized what a chance I was taking over spending about half a BU for a proper shorepower cord.

The coastguard link has some good commentary on using 'consumer' power cords in the the marine environment in addition to some important safety practices. IMHO: Worth a read for everyone.

uscgboating.org/recalls/pdfs/BSC81.pdf

Edited by - on

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 05/14/2007 : 12:03:08

I see where you're coming from - I would think that if it is listed as a 30 amp to a 15 amp there is something in box end that would handle that. The wire guage is 12 on that pigtail, the bulkiness is most likely from a thicker insulation. Most of your quality extension cords are 12 guage. I've personally went this route without problem.

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 05/14/2007 : 12:46:14

I use 10 gauge extension cords.

Edited by - on

John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 05/14/2007 : 15:44:32

Could you put some kind of 15 amp fuse in line. I was thinking that Frank's solution was all I really needed at least for this year but the electricians of the group have me nervous.

Edited by - on

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 05/14/2007 : 18:18:54

I think there is something on the 15 amp end to only allow 15 amps. The documentation for that product is a bit sparse

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 05/14/2007 : 20:43:49

That pig tail is intended to let you plug a 30 amp cord into a 15/20 amp service, not the other way around. Our club is crawling with them and they are all plugged into the dock 20 amp flat blade outlets so people can use their 30 amp cords to the boat.

Edited by - Frank Hopper on 05/14/2007 20:46:27

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 05/14/2007 : 21:07:49

Take a look at that cord again Frank - big end is the male - that is dockside. Little end is female. That would actually require a dockside station that had the prongs sticking out of it.

That is definitely a 30 amp to 15 amp unit, not the inverse.

Edited by - on

frog0911
Master Marine Consultant

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USA
1349 Posts

Response Posted - 05/14/2007 : 23:12:17

The 30 to 15 pigtail means only that one end is designed to plug into a 30 AMP receptacle and the other is designed to plug into a 15 AMP receptacle. In the case of this type of pigtail a 15AMP extension cord. There is no voltage reducer incorporated into the pigtail. Alan, can probable confirm this, but if I remember correctly, 30AMP service requires 10 gauge wire, 20AMP = 12 gauge and 15AMP = 14 - 16 gauge. The 15AMP difference is the length of the run.

Edited by - frog0911 on 05/14/2007 23:19:59

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 05/15/2007 : 06:55:32

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by fhopper@mac.com
 That pig tail is intended to let you plug a 30 amp cord into a 15/20 amp service, not the other way around.<hr height="1" noshade id="quote"></blockquote id="quote">

Duane's right. That pigtail plugs into a dockside 30A outlet.

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 05/15/2007 : 08:05:12

My bad, we use the inverse model.

Edited by - on

danandlu
Navigator

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USA
175 Posts

Response Posted - 05/16/2007 : 09:54:11

I use an extension cord with a pigtail adapter. I put a waterproof GFCI breaker, 15 amp I believe, just after the pigtail. I bought the GFCI at Home Depot or Lowe's, can't remember which.

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