Shorepower

O.K. I'm stuck. Would a knowledgeable marine electrician please step up to the plate.

1.) I know about what the average 30 yr. home/boat owner knows about electrical work.

2.) Here's the scenario. I am establishing a shore power connection at my boat's new location. (120VAC/30A).

The breaker box I installed below the meter base on the pole has 1 30A single pole breaker and 2 15A single pole breakers. I brought power into the enclosure (2 hots and a Neutral) from the meter base. I connected this neutral conductor to the enclosure's ground bar. I also connected the bare ground wire from the ground rod next to the pole to this same ground bar.

Next I installed a 30A 120VAC shorepower outlet below the breaker box enclosure. I wired it (in conduit) to the enclosure with #10 boat cable. Black from brass terminal on outlet to 30A single pole breaker. White from silver terminal to the ground bar inside breaker box. Green from ground terminal to ground bar inside breaker box. This is where I'm STUCK!

Sorry about all this tedious detail, but I want to make sure I'm clear about what I've done.

Neither Don Casey's "Sailboat Electrics Simplified" and Charlie Wing's "Boatowner's Illustrated Handbook of Wiring" Address this very well.

Even though the ground and neutral are not connected together on the boat, I see that the boat's ground IS connected to the neutral through the connection between my shore power cord and the shorepower outlet box. Do I have this wired correctly or not, and if not could someone Puuleez straighten me out.

P.S. Polarity indicator inside boat indicates ok, but is somewhat dimmer than normal.

Thanks,
Terry

 

do you have a fire extinguisher.??? Black is hot white is neutral and green is ground. If you ground to the neutral you are introducing AC to DC. Drop a voltmeter negative into a bucket of water to see if your currents floating across somewhere

 

Your question, I think, is...

Do wiring runs leaving the breaker box have both the ground and neutral wire going to the same ground bus inside the box?

That is how my home is wired. There is continuity between the neutral wire from the street and my water main via that ground bus. I've also scratched my head over that question. I think it would be a bit safer to keep the neutral and ground busses separate, but this won't affect performance in the least ( you were concerned about a dim bulb). I think you did fine.

I don't see a difference with regard to on-board electrolysis with either wiring scheme.

Mike

 

I'm not a marine Electrician, but I do have an A-level in the subject and an amount of theatrical and house wiring behind me.

Basically, we start with three bus bars, Live, Neutral and Earth. There are no connections across these bars!!!

At one end connect the L/N/E connections that you are taking from the marina.

Assuming you have single-pole breakers (2 terminals) connect the consumer N/E to the N/E bus bars. Connect the breaker input to the live bus bar, and the consumer live to the breaker output.

If you have double-pole breakers (4 terminals) Consult the installation instructions. They may not all be the same.

Inside the boat, there are a thousand and one ways to get the power to a usable form. Personally, I like the idea of isolating the batteries for charging from 240v/120v when you connect to shore-power and then everything else being run through a large 12 volt power supply. This is unusual.

Suitable power supplies are ATX computer power supplies. Several can be used in parallel depending on the required current output.

Most of the time the 120/240v to boat power is direct connection to any 120/240v circuits and basically a big battery charger for 12 volt power.

If you have 24 volt on-board power then the parts for a 240/120v to 24v system are a little harder to get hold of, but they are available.

Whatever you end up with, Keep it seperate, keep it neat.

Tim B.

 

Hey Swimpy
First question:
Are you bringing 240 or 120 to the box?

 

He said he's got 2 hots, so he's got 240 at the box (120 times 2). His single pole breaker delivers 120 to the boat. His description of colored terminals sounds correct.

I think he is doing fine... don't see the problem.

Mike

 

Now that everyone can see how I have it wired, let me see if I can explain my concern a little better. The two books I mentioned (and ABYC) state ground and neutral MUST be connected together at the source, but NEVER on the boat. It is obvious there is a connection between boat ground and shorepower neutral when shorepower cable is plugged into shorepower outlet.
Is this right and proper? Perhaps this is considered an indirect connection and is of no consequence?


Terry

 

That is American regs. When you go to a foriegn marina you will be very popular when you blow the earth trips.

AC means alternating current, it come up one wire and goes down the other, then it does it the other way round (alternating) 50 time a second. You will get a shock if you touch iether wire. As Bilge boy said how the hell can you connect your neutrals to ground???

On my boat I have 240 AC NO GROUND just 2 wires in and out.
Most appliances are 2 pin plugs any way and plastic insulated bodies.

You may have neatly wired up a ground to your boat but is the ground in the marina working, if not you dont have a ground. Or if not you could be connected to your neighbours boat, you can use him as a ground,-- or him you.

Now if he has connected all his skin fitting to his ground as well and your micro wave shorts out you will sink him Or him sink you.

I dont like grounds on boats and in any case 110 wont kill you. I thought thats why US uses 110.

 

can you post drawings from the equtment you bought?

 

Two inputs at 110 volts is 110 volts but twice as much power. Only when you look at voltages between phases does the voltage change.

Also, 110 volts will kill you almost as hapilly as 240 volts, especially if there's water involved.

The voltage is not actually very critical, you just need breakers that are correctly rated.

Tim B.

 

Bilge Boy, you have just about got it nailed.

I cn't post drawings from here, maybe when I get home next week.

Terry

 

Could the problem posed above be solved by installing an Isolating Transformer on the boat as follows:

1. Hot and neutral (120 V) - or hot and hot (240 V) - shorepower connections to the Isolating Transformer primary, due allowance afforded by transformer tap-changer;

2. Isolating Transformer secondary connections to hot and neutral on the boat´s AC electrical panel;

3. Isolating Transformer case and boat´s AC electrical panel case connected to the boat´s grounding plate;

4. Ditto (as per 3 above) for the Green Wire that is wired to the 3 rd pin on the boat´s AC electrical outlets.

 

OK, here is the rub;

North american power is 440 V, 3 phase, Y-wired.

The middle node of the Y is the "neutral", the zero potential "earth return" identically equal to the "ground", so each arm of the Y to the middle is 120V. Potential between two arms is 240 v and beweeen any two gathered arms is 440. Check the phasing (+120,0,-120) and you will see this.

In normal house or pole wiring, you get 2-phase 240v power. This is accomplished by bringing in any two phases (specifically selected by the power company to balance the phase loading at that point), and the neutral. The neutral is then sent to the "earth return" through a dedicated grounding wire. This wire has to be be unspilced, of sufficient cmils to carry the TOTAL maximum current in BOTH phases, and attached to a grounding stake of sufficient length to carry the "earth return" load. In normal operation, power goes out the hot and comes back down the neutral to the "earth return". The neutral and ground should never touch, except at the grounding bus/stake, in normal wiring and operation.

Now the grounding wire is only for fail safe only, it should never carry any load. If a "hot" line was to "leak" current to say a motor case or metal switch box cover, the ground line would carry that current back to the earth return instead of going through the shortest path....i.e you when you touched the switch or any thing in touch with the "earth return" (like the hull). Everything powered by AC on the boat should have both a neutral to carry the load back, and a ground to carry any "leaked" current back. Amping the ground with power on should show zero current. This is how a GFI works....if amperage is detected in the ground, then the breaker blows because there never should be amperage in the ground

It seems to me that you have it wired correctly, but if you are getting dim lights/low power, then is suspect that there is some increased resistance somewhere. First check that the powere cable is of sufficient cmils for its length, then I would look at my cable connections and the length/size of my earth return stake and cabling.

Now if you want to talk about how ships are wired...that is 440 V, 3 phase Delta....which is whole other kettle of fish....

 

Hi Jehardiman,

I'm not sure you are completely correct of your assessment of North American grid power. I think we should look at the two major areas that power is used; industrial (3 phase) and 'home or small business' (single phase) .

Most industrial settings will have three phase power to supply big loads. These phases are 120 degrees apart (as you mention), but also come in a variety of voltages. I'd like to just focus on one voltage level in an industrial setting that will be used most of the time (to provide 120VAC). Each leg of the 3 phase, y wired will indeed have 120VAC, but the voltage across one leg to another is actually 208VAC as this is just a trigonometric function of the 120VAC phases (square root of 3 * 120VAC). No industrial settings have 240VAC, unless they are stepping up one of the 120VAC phases.


Here's the part that will always cause arguments. Homes in North America are only supplied with single phase. Everybody is now going to cry out that they do indeed have two phases of 120VAC supplying their homes. Ok, there ARE two phases, but they are 180 degrees apart – NOT 120 degrees apart like our industrial and grid power. The transformer that steps down the power from the grid to run it into your home has a center tap on the output , which becomes the neutral and thus referenced to ground at the neutral-ground bond. These two phases 180 degrees apart are tapped off a single phase of three phase power – not two as you suggested.

I'd like to point out one other thing – GFCI's don't monitor for ground leakage current, they trip if there is a current imbalance on the line/return of a circuit.

I hope this helps clear things up

Cheers,
Mark Ovenden

 

Swimpy,

Following up my previous post, plus contributions by Hardiman and Ovenden in response to your query:

"Even though the ground and neutral are not connected together on the boat, I see that the boat's ground IS connected to the neutral through the connection between my shore power cord and the shorepower outlet box. Do I have this wired correctly or not, and if not could someone Puuleez straighten me out."

it would appear that your connection is CORRECT, as per Technical Papers available for on-line consultation on the Blue Sea Systems site.

In fact, AYBC requires you to automatically establish connection between neutral and ground on your boat, should you disconnect from shorepower - thereby breaking the link to remote earth ground - and resort to using your boat-based inverter or genset.

Look it up - well, worth it ! There is also an article on why the Reverse Polarity light can come on FAINTLY, even if all connections are supposedly correct

The whole issue may be side-stepped by installing an Isolating Transformer. A costly item, upwards of 500 US$, specially if it has a marine label attached to it !

But breaking up the windings and re-making connections on, say, a 1 to 1,5 KVA, 110/117 to 220/240 V AC Auto-transformer of good quality for RV or home use, and then adding some turns if need be based on the actual numbers on the name plate, will furnish satisfactory results in a relatively thrifty manner.