Replacing AC wiring to outlets

[dhandzy]

I have a short in the cable between two of my outlets that are connected in series (the forward most starboard outlet [near forward end of galley counter] and the forward most port outlet [in V-berth]). That cable is a nightmare to replace as it goes through a number of small holes in bulkheads and is zip-tied to other cables. So I cannot currently get power to any of the port side outlets. I've also begun replacing all outlets with marine grade GFIC outlets.

To get power to the port side, I'm thinking of tapping into the existing cable that currently feeds the first outlet (in the after cabin just off the electrical panle) from the electrical panel. I'd add a bus bar in the electrical panel and attaching the existing hot cable to the bus bar. The two outputs of the bus would be to the first outlet (aft cabin) and I'd add a new cable under the floorboards to the port side to power the outlet in the V-berth. That means that two outlets would be in parallel (aft cabin and v-berth) and all other outlets would use the factory installed cables and be downstream in series from those first two.

Does anyone see a problem with this approach? Any recommendations on what kind of bus bars to get (I'll need one for power, one for neutral and one for ground)?

 

[jssailem]

I have a short in the cable between two of my outlets that are connected in series

AC circuits are almost always wired in parallel. This allows the failure of one plug not to affect the rest of the plugs.

If you have a GFCI set up, the GFCI come first and the rest of the plugs are in parallel but in series to the GFCI.

I suggest you check carefully the actual set up before adding or changing your electrical systems. This would include all of the wiring for the affected circuits. It is not uncommon for a wire to chafe and get shorted on a protruding screw on a boat.

 

[Ralph Johnstone]

I've got to agree with @jssailem on this one but I'll go one further and say that outlets are ALWAYS connected in parallel, never in series. In series, none of the outlets would work until every outlet had a load plugged into it and then the resistance would be so high, nothing would work anyways.

With all due respect, I strongly suggest you review the theory of series and parallel wiring (AC or DC, house or boat) before you even think of getting into your own boat wiring. Once you understand the difference, hire a licenced electrician to do the work for you as this is not your specialty and electrical work is positively the "LAST" thing you want to screw up on a boat. The positively, certainly, absolutely, unquestionably "LAST" thing you want to screw up."

 

[colemj]

I've got to agree with @jssailem on this one but I'll go one further and say that outlets are ALWAYS connected in parallel, never in series.

Except for the specific case @jssailem mentioned - all paralleled outlets downstream of a GFCI are wired in series with the GFCI.

@dhandzy - you don't need to replace all outlets with GFCI ones. You only need to replace the first outlet in any string of outlets with a GFCI, and that single GFCI provides fault protection to the entire line of outlets.

Or go further (and arguably simpler) by replacing the breaker on the main panel feeding the outlets with a RCD type of breaker. Then everything beyond that breaker has ground fault protection.

Mark

 

[dhandzy]

@Ralph Johnstone and @colemj - you're absolutely right about the parallel vs. serial. I was using the language too loosely and I caused confusion with that. I'm not changing the configuration from the existing setup: all outlets are being run in parallel with the standard 3-wire cables with line/load lines appropriately attached. What I'm changing is how they are fed from the source in the electrical panel. Sorry for the confusion.

Prior to any change, the panel fed only one outlet (in the aft cabin) but that outlet wasn't GFIC. The next outlet in line (in the cabinet above the stove) was GFIC and the 3rd outlet on the starboard side was also GFIC. All other outlets in the boat were not GFIC. I doubt that Catalina set it up this way (the first outlet should be GFIC) and one of the previous owners must have replaced the first outlet for some reason. I've begun replacing all the outlets with GFIC (I know it's overkill) and I've tested all the cables for shorts between power, neutral and ground. The short I found between outlet 3 and 4 (outlet 4 being on the port side in the v-berth) is prompting me to power #4 directly from the electrical panel in its own new line rather than from outlet #3.

My intention is to take the power in the panel into a bus bar that then powers two separate lines of outlets, feeding the starboard and port outlets each directly from the bus, just as @jssailem's diagram (reproduced below) shows. In my case, I will have two such 3-outlet lines, one on each side of the boat, where each of them has their power source (as shown on the left of the diagram below) being the bus bar I intend on installing in the panel. That bus bar would be powered by the current cable that today powers just that first outlet.

 

[Johnb]

You also need to ensure that a 30 amp main panel breaker is not the only protection the outlets have.

 

[Ralph Johnstone]

@Ralph Johnstone and @colemj - you're absolutely right about the parallel vs. serial. I was using the language too loosely and I caused confusion with that.

"Jeez Louise, that's a relief," he said as he wiped his brow. "Now I can exhale."

But maybe as others have said, just fit the first first outlet on the port and starboard outlet legs with a GFCI as shown in post #2. Whether you've got one GFCI only at the start of the starboard leg and one on the the port leg or one on each outlet, they'll do the job of sensing the different amps between hot and ground (~5 ma.) so just use the one. Cheaper.

In my case, I will have two such 3-outlet lines, one on each side of the boat, where each of them has their power source (as shown on the left of the diagram below) being the bus bar I intend on installing in the panel.

A bus bar ? ? ? You're only splitting one wire into two wires, port leg and starboard leg. Put the two black wires on the load side of the breaker if you want. Split the black wire coming off the load side of the breaker out in the field (use a box) if that makes it any easier. Run the ground wire to the existing ground buss and the same for the white neutral wire to its buss. I think you're obsessed with buss bars for some reason. You don't need it for one extra wire on a retrofit.

You mention a PO may have done some work with this 110V AC wiring. Check all of the wiring sizes used in these two legs and ensure the breaker protects the smallest wire on each side.

 

[Ralph Johnstone]

It is not uncommon for a wire to chafe and get shorted on a protruding screw on a boat.

I'd be willing to bet the short is inside an electrical box. Stranded marine 3 wire cable is tougher than tough and incredibly resistant to abrasion. As you've said, a PO may have gotten into this wiring and god knows what he's done, probably with marettes .

Check this before anything else.

 

[Leeward Rail]

Stranded marine 3 wire cable is tougher than tough and incredibly resistant to abrasion.

That's assuming it's not solid NMD Cable.

 

[leo310]

On our 310 we have only 2 GFI that protects the 110 system. 1 for Port other Starboard side.

 

[jssailem]

Ralph… there is always the possibility that someone used Wire Nuts on the AC cable connections.