AC Main Power?

[ssullivan]

Wheels, you are absolutely correct. I'm going to trace this out this AM and see what I get. (hoping for the receptacle (the hull fitting) being bad, so I can just buy a new one and replace.

[CaptainK]

Mark S (Coot)

You said you're tied up at a dock. So you own a boat. I noticed on your profile that you didn't list, that you own a boat?

What type of boat do you own?

And Sean.

I think what Mark was saying around the latter half of his post said.

Coot once whispered in the wind

I'm not saying "don't inspect the wiring" -- just if you find anything, replacing the burned up part is not enough to fix the problem.

I believe he means, that if you find a burnt wire. You should replace the entire wire that has burned. And replace with a new wire?

[ssullivan]

Wanted to follow up. Thank you all for the replies so far. They have been helpful. I just want to let you all know that I have a semi-decent understanding of electricity (remember... Physics degree and computer science - worked for NASA and built electronic components that are in space today aboard the ACE, FAST, and CLUSTER missions).

Not trying to sound snooty, but I want to emphasize that things like the shore power cable are not the problem. I have thoroughly tested voltages throughout the system, and here is where I am, unfortunately:

1. Shore power cable works fine. 118VAC is coming out of the end of the shore power cable.

2. No signs of any burnt wires yet.

3. Looking in from the back of the shore power receptacle on my deck (I am looking at it from inside the hull), there is no evidence of any fried wires.

4. NEW DEVELOPMENT! I have found that there is ~85VAC between the hot and neutral bus (on the AC Main panel). I measure the same voltage between the hot and ground bus. I got a better meter that auto-adjusts. The old meter didn't pick up this strange, low voltage. This is current coming in from line connected to the shore power receptacle on deck.

5. Also new - When I take the 80V and run it through to an outlet somewhere by turning on an outlet's breaker, I am getting 2VAC out of the outlet (touching meter between hot and neutral). This is indeed real juice, since turning off the breaker to the outlet results in 0VAC.

I'm going to head into taking apart the shore power receptacle now to see if I'm getting 80V out of the back of it, or the normal 118V.

Anything in #4 or #5 indicate a problem to any of the electrical experts?

I'm not sure about that plumbing comment! ha ha ha. I re-plumbed the entire boat in about a week. Soup to nuts. One little short circuit, and I'm pulling whatever hair I have left out.

[GordMay]

118 Volt Source at Shore Power Cord (Boat End), reduces to 80V at Distribution Panel = High-Resistance Connection between them.
80V At Distribution Panel reduces to 2V at branch circuit outlet = high-resistance connection between them.
The common thread seems to be the distribution panel.
Voltage between Hot & Neutral, and Hot & Gnd should be equal (as you indicated). No Voltage Neutral to Gnd.

[Alan Wheeler]

Well it isn't hard to do an inspection of terminations, so I suggest you go there first.
But to add to Gord, that 80V could also be a red hearing in the respect that it maybe just a residual voltage being picked up via induction. Hence why the massive drop to nothing (2Vac)when you turn on a breaker. There is simply no "guts" to the leakage.
Continue to test the main cable in. But do I understand you can not get the test probes into the recepitcle? I would have thought you would test there first, before you pull it apart. But then you guy's have strange plugs at times.

OK, just to ensure your on the right path, Neutral and Earth should be tied together, hence why you get the same measurement to Hot. Ensure you have NO reading between Earth and Neutral.

Another test.... on the back of the circuit breaker, can you get to the wires going in? so you can test for AC there. Test you have AC of correct voltage on both sides of the breaker when switched to on and only one side when switched to off. It could be possible that the breaker is OC. You may find the mains is apparent on the in leg and not on the out leg. There are two types of breakers. Magnetic triping and heat tripping. The heat tripping uses a small element. This element could be leaking enough voltage to give you your 80V reading. Just a thought.

[colemj]

Hi Sean,

I don't remember from other posts, but do you have an inverter with an automatic transfer switch? If so, these are often wired between the shore power inlet and the main panel (through a separate circuit breaker).

Mark

[By Invitation]

Sean,

A simple test, I would recommend that you disconnect your AC "in" to your main panel and see it you have your 115 available. You have one hell of voltage drop and you need to isolate where that drop is happening. Start with the basics and go from there. Just make sure to don't "short" out your wires while testing unless you really want to wake yourself up.

If you have 115 at the wire, the problem is at or after your panel, if you have 80 at the wire your problem is before the panel.

In most cases, the solution is easy so just take it one step at a time.

[Jon D]

Alan Wheeler once whispered in the wind:

It could be possible that the breaker is OC. You may find the mains is apparent on the in leg and not on the out leg. There are two types of breakers. Magnetic triping and heat tripping. The heat tripping uses a small element. This element could be leaking enough voltage to give you your 80V reading. Just a thought.

Don't dismiss this out of hand. I had a similar issue on power to my refridgeration last year. Pulled my hair out trying to figure it out. Breaker was giving false power indication got 12v but no amperage. Replaced the breaker on a fluke solved the problem.

[ssullivan]

Hi everyone,

Thanks for the help in diagnosing the problem. After I read Gord's post, I spend the afternoon focused on the wiring running from the shore power receptacle to the AC Main breaker panel.

I had just cleaned all the contacts, when BINGO. Half way though the wire run, there was a fuse. It was tucked away up inside the rear corner of the hanging locker in the master stateroom.

How it continued to transmit 85V is beyond me, but there is a resistor and a little light in the assembly the fuse is attached to. I replaced this extra fuse, and everything is back to normal.

This is a great thread. Maybe, someone else will have an issue like this sometime and will be able to find this thread useful.

[GordMay]

Sean:
Glad you located your problem.
You say a resister & light along with the fuse ... could you post a photo’ (or additional description) ... doesn’t immediately ring any bells /w me (unless it's a home-made Reverse Polarity* Indicator (Resistor & Light connected in series 'twixt Neutral & Gnd.)?


* FWIW: In N. America, Reversed "Polarity" is the correct term for Hot-Neutral Rreversal. A "phase" reversal would apply to polyphase circuits, where two Hots are reversed.

Gord

[ssullivan]

Hi Gord,

Here is a photo of the weird fuse-thing. It's got a dim glowing red filament (like an incandescant bulb with too low a current/voltage), and a resistor.

You unscrew this little jobby from the wooden box (and a plastic housing it sits in) and out pops a 30amp fuse.

This was hidden up in the back corner of the hanging locker in my master stateroom.

Now how this little thing let 85V through is beyond me, but that's what happened.

BTW: It is actually INLINE in the hot line running from my shore power receptacle to the AC main breaker panel. There is no neutral or ground entering it. Only hot in and hot out. It's a real head-scratcher to imagine how this thing lights up with no neutral or ground. ???

I guess it shows how much current you are drawing by lighting up more... maybe.

Here's the link to the image:

http://cruisersforum.com/photopost//...sort=1&thecat=

[GordMay]

I don't think this little "jobby" is likely to be in series with your #10AWG shore power "Hot" supply (inlet to panel).

INLET>..BLACK #10 ..>"JOBBY">.. BLK #10..>PANEL

[ssullivan]

It is in series. There are 2 terminals on this item. Terminal #1 is wired directly to my shore power receptacle (a 24 inch run - black hot 10AWG power cable). Terminal #2 is wired directly to my AC breaker panel (same black 10AWG hot cable). Taking the item out of the circuit (and bridging the terminals) resulted in perfect power flow to my AC main panel.

I first discovered this item was the culprit when I touched one probe to the neutral on my shore power receptacle, and the other to Termainal #1 on this unit. Terminal #1 read 118VAC. I then touched the probes to the neutral on the shore power receptacle again, but this time to Terminal #2 on this little unit. Guess what? 85VAC on termainl #1 of this unit.

The voltage drop was inside this thing. So... I played around with it and found a way to unscrew it. A 30 amp fuse popped out. I decieded to have some fun and bridge the terminals now that the fuse was out (knowing that nothing was wrong downstream anymore) .

Result? Perfect 118V power throughout the boat.

So, I replaced the fuse inside this little thing, and everything is back online.

[CaptainK]

That's great to hear Sean.

You know it's one thing about electronics. If you don't have a ditigal mutlimeter. It's one hellva pure nightmare trying to figure out where the problem is!!

But, with one. That just makes life more easier to figure out what the hell is going on?

[Alan Wheeler]

Dang, the name has gone right out of my head. But it is a form of lightbulb and if you look closely, it has no filament. It has two probs inside that stand parrellel to one another. When it operates, the light flickers around one of those probs. Often seen as indicator bulbs on all sorts of AC equipment and were very common in the old days on Valve operating equipment.Theywork on AC only. They are a lower voltage than the mains and the resistor is to drop the voltage son it doesn't self destruct. This thing will indeed be in series with the Hot wire and is wired across the breaker/fuse. When the breaker is on, the light will be off. When the breaker trips, the circuit is now flowing through the bulb/resistor and it will light. If the bulb lit is indicating the circuit is in fault interupt. OR in otherwords, the fuse/breaker has gone OC. Of course, the only way it will light is to have a load on at the other end, so if you isolated the main panel, it would not have worked. The 85V is just a no load leakage current flowing through this little device. They use almost no current.