AC Wiring

[Charlie]

The next item I want to tackle on my boat is the AC wiring. I come from a backround of house building and when running AC circuits we daisychain the wire -- that is we run one home run to the AC panel and then take our power off that box and continue on. Sometimes it is run in series and sometimes in parallel. On my boat the AC circuit neutrals were all run back to the AC negative bus bar and the positives were all homeruns back to the breakers. My thought is that I would run new wire to the circuits and was wondering if there is any logic/reason for running the hots all the way back to the circuit breaker. The reasons I have against it are: 1)Extra wire and wiring and 2) extra GFCI's needed for every outlet whereas one GFCI can cover the entire circuit. Comments with reasons for or against running homeruns are much appreciated.

[knottybuoyz]

Hi Charlie

30 or 50 amp service? Inverter or generator capacity?

I know the ABYC electrical standard was under review and can check for updates at work next Tuesday. Until then I think that running the circuits in parallel is ok as long as you have adequately sized breakers for each branch, knowing the loads you're most likely to put on each branch. I've planned for 3 outlets with one being a GFCI at the end of each branch. I've also planned separate circuits and breakers for the big loads such as hot water heater and microwave etc. ensuring breakers sized accordingly for the expected loads. As long as you're not likely to plug in the toaster, microwave, coffee maker, blender and table saw into one branch to run concurrently you should be ok!

I just hauled a mess out of our old boat and removed 8 redundant outlets along with the associated household wiring. Our little boat doesn't have a large demand for AC appliances so we're now down to two outlets. Rationalizing the number of oulets saves wire and wiring as well. I ran all home runs back to the panel using the multi-conductor cable which I like a lot with the added protection of the binding insulating cover.

[Charlie]

Thanks Rick:

I'd appreciate it. I have generator on the boat. I'm going to remove the inverter. The boat has a 30 amp service. I do have to watch the number of circuits that I put on each breaker. The other 120v items that I have are a 120 v water heater and a battery charger. When the charger is running full bore I can't use much else.

[Lancerbye]

Being a qualified electrician with marine endorsement, the above postings scare the hell out of me. There should only be one circuit on each breaker. The breaker which is located at the distrubution point is there to protect the down stream wire from burning up and burning your boat. If you do not wire according to NEC your insurance will be null and void when your boat burns up. Breakers are sized according to the wire they protect regardless of the load you apply to the circuit.

[LtBrett]

Originally Posted by Lancerbye

There should only be one circuit on each breaker.

Agreed, but does that mean one receptacle per circuit? I think all Charlie wants to do is run several receptacles in series, with the first receptacle from the breaker box being a GFCI. I don't see anything wrong with that.

Brett

[GordMay]

There seems to be a little semantic confusion about terms.

A “Circuit” is comprised of all loads fed from an Overcurrent Protective Device (OCD), such as a Fuse or Circuit Breaker. Each OCD shall supply only a single circuit.

An “Outlet” is any load device, such as a receptacle (plug) or light fixture. Providing the capacity of the OCD is not exceeded, there may be up to 7 outlets on a single circuit. Outlets are always wired in parallel to each other - never in series.

HTH,
Gord

[Charlie]

Thanks for the replies:

Lancer -- Brett is correct in that I want to run multiple oulets off of one circuit breaker as is typically done in residential construction.

Gord: your information is exactly what I wanted to know. In a house on a 15 amp circuit I might run 8 to 12 outlets on a circuit. On the boat I think that 5 will be the max. I am going to run #12 w/grd wire. I'm thinking of running the circuits w/ a 20 amp breaker b/c that is what I would do in a bathroom or a kitchen and the wire is rated at that amperage. Your comment on always running parallel would cause me to put a GFCI receptacle in for every outlet. I am not a master electrician but I can not see the advantage of running parallel circuits except that if a recetacle should go bad the downstream receptacles would continue to function whereas in series I would know where the connection had failed b/c eveything downstream would not be working. What is the reasoning for running AC circuits parallel?

[btrayfors]

Charlie:

A semantics problem, again. You don't run multiple outlets in series because that would reduce the voltage to each outlet (like in a series-wired christmas tree light string).

You always wire multiple outlets in parallel, i.e., with the black or hot wire always attached to the black or hot connection on the previous outlet...or the breaker...and the other wires similarly connected to their upstream mates.

So what you wind up with is a series of parallel-connected outlets on the same circuit :-)

Bill

[Charlie]

Thanks Bill:

Showing off my lack of knowledge. Sometimes I will do a pigtail in a box so that the upstream and down stream wires are spliced together and a third pig tail wire is connected to the receptacle.(What I meant as parallel) When I do this the GFCI only protects the one outlet. Other times I connect the upstream wire to the GFCI and then the downstream wires are also GFCI protected.(What I meant as series)

[GordMay]

Wiring a GFI Receptacle:
http://www.cruisersforum.com/gallery...p?i=1898&c=517

[hellosailor]

Guys, I think part of the confusion over "parallel" and "series" outlets is that people are confusing what we usually call "daisy chaining" outlets, with other terms. In home wiring it is common to "daisy chain" outlet boxes so there is only one wiring run to the breaker panel.

As opposed to running each box individually back to the breaker panel.

BOTH of those runs are PARALLEL wiring runs. The way that socket, etc. allow for daisy chaining may appear to be serial wiring--but it is not, it is still parallel wiring. Each box is still on a "T" or drop circuit, you just don't see it because the "drop" is just some metal between the screws, so it looks like you are wiring the BOXES in SERIES. But they are not in series, that's just an illusion.

IIRC for marine AC wiring you are required to have a GFI within 18" of the point where the AC feeds into the boat, and for typical installations that one GFI would cover all the AC wiring in the boat.

Still, given that GFI outlets are so damn cheap these days, I would go with redundantly installing a GFI-protected outlet at each location, not a plain one. Sure, that might waste an extra $4.50 per outlet. That's still cheap protection in case "the" main GFI doesn't failsafe one day.

And Charlie, if your outlets have the simple "stick the wire in here" contacts so you don't have to use screws? Forget it, use the screws, they make a better more durable contact, especially in the marine environment.

[Lancerbye]

Well I am relieved to see that all that got straightened out. Remember that a GFCI recepticle is a special recepticle that provides downstream protection. This does not mean that the downstream load is in series with it just that the ground current sensing circuit will trip if a ground current is sensed disabling everything from the GFCI(including it) downstream. Hellosailor's comment is very correct especially in a marine environment. I don't know how many times I was asked to check a none working recepticle only to find a corroded push in connection. Use the screws. Another point to remember: Do not use the recepticle as a connection point, except on a GFCI that is protecting downstream, pigtail junctions which means at a common recepticle, that is not the end of a branch, you should have two main wires and a pigtail (which is connected to the recepticle) for each color. The ground will have two pigtails one to the recepticle and one to the box. Use good quality wire nuts (Marettes)

[btrayfors]

Originally Posted by Lancerbye

... Use good quality wire nuts (Marettes)

NO. Wire nuts are generally NOT approved for marine use and are very dangerous.

Use captive ring terminals for connections and positive locking screw-type connectors only.

Bill

[GordMay]

Originally Posted by btrayfors

NO. Wire nuts are generally NOT approved for marine use and are very dangerous.
Use captive ring terminals for connections and positive locking screw-type connectors only.
Bill

Bill was too diplomatic - Twist-on wire nuts are specifically prohinited
for use on boats.

Targeted to the shoreside user, Chad Reynolds provides some good information at:
Testing for safe and efficient branch circuits:
http://www.accurateinspections.com/vdrop.pdf