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Old 05-08-2021, 12:46 PM   #1
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Weak 120v system on one half of one breaker

So, the other morning on the boat I wake and see my phone did not charge. I check it, yep, not charging. So I get a power indicator that lights up on AC power and I get a light. So, ok I'll put in a new receptacle. Still no charging. Break out the multi tester and I find that I have 99v across the receptacle and 120 hot to ground. That was on the stb side of my aft stateroom. So, Ok lets check the next closest receptacle, also bad. Ok what about in the stb head. Also bad. Port side is no problem. Both sides are on the same breaker. Port and stb salon are good. I checked for corrosion and neutral wire tightness on all affected receptacles and they look clean and tight. All read 99v.

I pulled down the main breaker panel and of course the 30 year old rats nest is just mind boggling to me. I looked at and wiggled all the white wires and most every thing looks clean enough and solid for 120v.

By the way, I get about 4v from neutral to ground. Might that be a separate problem? Or is that normal?

Any suggestions for a novice to look for beyond hiring a qualified marine electrician? My guy charges $120/hr with a 2 hour minimum and he is 3-4 weeks out.
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Old 05-08-2021, 01:22 PM   #2
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I bet your shore power is 50A/220V/120V. Could it be that you have lost one of its legs and that is why half of the receptacles don't work. The 99 volts you are seeing is probably leakage from the good leg but not enough to support a device plugged in.

Check out your shore power supply. Maybe its double pole breakers aren't tied together and one side tripped off but left the other side on. Could be at the pedestal or maybe the main breaker in the boat.

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Old 05-08-2021, 01:31 PM   #3
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I bet your shore power is 50A/220V/120V. Could it be that you have lost one of its legs and that is why half of the receptacles don't work. The 99 volts you are seeing is probably leakage from the good leg but not enough to support a device plugged in.

Check out your shore power supply. Maybe its double pole breakers aren't tied together and one side tripped off but left the other side on. Could be at the pedestal or maybe the main breaker in the boat.

David
Thanks David but all my other receptacles are working fine. Only one half of the ones on the Aft cabin circuit. Also, I have power reading of both legs of my 220v system. Also, I have the same problem when off of shore power and running off of the inverter or generator.
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Old 05-08-2021, 03:03 PM   #4
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Ok, if part of the receptacles on one breaker are working and others aren't then there is probably a loose connection at one of the receptacles. Receptacles are usually wired in daisy chain fashion and the one with the bad connection and all downstream ones will be dead.

The only way to deal with it is to open up each one and tighten up the connections. Receptacles with the push the wire in the hole type connections are particularly bad at coming loose or making bad connections.

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Old 05-08-2021, 03:49 PM   #5
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Ok, if part of the receptacles on one breaker are working and others aren't then there is probably a loose connection at one of the receptacles. Receptacles are usually wired in daisy chain fashion and the one with the bad connection and all downstream ones will be dead.

The only way to deal with it is to open up each one and tighten up the connections. Receptacles with the push the wire in the hole type connections are particularly bad at coming loose or making bad connections.

David
Yes, as I explained in my original post, I checked all of those connections. I did not include a light switch. Not sure if that would be included but I'll check it next time I'm on the boat.

Tracing the neutral back to the main panel would be tough as there are bundles of wires. I did do a look and feel but I suppose I may have to disengage all of the neutrals from the buss bar and check continuity to find the right one, but then what? If I reattach it and everything works, great, but if the connection doesn't look corroded and the wire is tight, why would there be a problem.
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Old 05-08-2021, 03:56 PM   #6
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If some of the receptacles on one breaker work and some don’t, it is probably a connection issue at one receptacle. You need to figure out what receptacles are on the circuit and then figure out the order they are wired in the circuit. Find the first failing receptacle and that is most likely where the issue is. It could also be the last working receptacle on the outgoing side. Check both the incoming wiring and the receptacle itself. The problem is figuring out what order the receptacles are wired in. Good luck.
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Old 05-08-2021, 04:08 PM   #7
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If some of the receptacles on one breaker work and some don’t, it is probably a connection issue at one receptacle. You need to figure out what receptacles are on the circuit and then figure out the order they are wired in the circuit. Find the first failing receptacle and that is most likely where the issue is. Check both the incoming wiring and the receptacle itself. The problem is figuring out what order the receptacles are wired in. Good luck.
All stb aft stateroom receptacles and head exhibit the same symptoms. 99v from hot to neutral, 120 from hot to ground. Like I said it can't be a problem with the breaker because the port receptacles are on the same breaker and have no problem and anyway the breaker breaks to hot lead. It can't be a problem with any of the receptacles because I'm bypassing their internals with the multimeter. Its in the line and I'm not happy about the degree of difficulty in sourcing this fairly unimportant issue.
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Old 05-08-2021, 04:33 PM   #8
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I suspect a bleed from neutral to ground. Start by unplugging everything, then check again. I use one of these, works faster than multimeter.
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If problem persists then look for a GFI plug, that should be the first plug from the breaker. Confirm breaker is off and pull it out, disconnect (if any) load lines out of it, then power on check if it works correctly alone.
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Old 05-08-2021, 05:29 PM   #9
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This situation isn't painting a super consistent picture in my mind, so I probably need more information.

Was the phone previously charging and abruptly stopped? Or was the last time it was known to work never or a long time ago?

Do you have an old school incandescent 120V light or even a corded electric drill? What happens if you plug it in and turn it on?

If you carefully remove the outlet from the wall and measure at the back of the outlet-- with a load plugged into the outlet -- what voltage do you measure?

This problem can be caused both by loose connections and also by bad wire, where the strands become black and brittle and won't conduct well -- even if tightly crimped or otherwise attached. Normally this is easily curable by trimming a little off of the edge to get to good wire and going from there.

But, I was on a boat a few weeks back where feet of the wire had gone bad, so the whole run needed replaced. In other words, especially if this isn't a new problem, it is possible it is a cumulative effect, not a point effect.

But, my real question is if that~99v is "real" or just the result of coupling in the wires or at some device. Hooking a simple analog device like an incandescent lamp or corded drill up will tell us that. If it can't make those devices go, we're looking for a disconnect, not a high resistance situation.
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Old 05-08-2021, 05:48 PM   #10
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This situation isn't painting a super consistent picture in my mind, so I probably need more information.

Was the phone previously charging and abruptly stopped? Or was the last time it was known to work never or a long time ago?

Do you have an old school incandescent 120V light or even a corded electric drill? What happens if you plug it in and turn it on?

If you carefully remove the outlet from the wall and measure at the back of the outlet-- with a load plugged into the outlet -- what voltage do you measure?

This problem can be caused both by loose connections and also by bad wire, where the strands become black and brittle and won't conduct well -- even if tightly crimped or otherwise attached. Normally this is easily curable by trimming a little off of the edge to get to good wire and going from there.

But, I was on a boat a few weeks back where feet of the wire had gone bad, so the whole run needed replaced. In other words, especially if this isn't a new problem, it is possible it is a cumulative effect, not a point effect.

But, my real question is if that~99v is "real" or just the result of coupling in the wires or at some device. Hooking a simple analog device like an incandescent lamp or corded drill up will tell us that. If it can't make those devices go, we're looking for a disconnect, not a high resistance situation.
All receptacles were working recently, like a couple weeks ago.
I have a heater I tried and no good. Also, a drill battery charger, no go.
I'll try to plug in something and take a reading but not sure what that will do unless maybe it is a light like you suggest where it would just be dim. I can try.

There is something rotten in Denmark that is for sure. If I was bleeding from neutral to ground wouldn't I have a higher voltage than 4v from neutral to ground?
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Old 05-08-2021, 07:25 PM   #11
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Do you have a GFI plug in one of those not working now, like in the head? GFI have gone bad. I would start there.
The daisy chain mentioned before will likely start there and make all the rest a GFI outlet. it is possibly the closest to the breaker panel.
Find the first one from the breaker, disconnect the downstream load and test there.
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Old 05-08-2021, 10:50 PM   #12
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You will need to break this down into smaller units. First test from the circuit breaker to the neutral buss. This should show fine based on the info you have already given. Next, follow the circuit to the first outlet. Disconnect the power and neutral and test just the wire. If it passes reconnect and disconnect the rest of the circuit beyond the outlet. Then retest the outlet. Keep following the circuit until you find the faulty wire or outlet. I suspect what you will find is an outlet with a strange corrosion trail short on the backside between the power and neutral wire.
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Old 05-09-2021, 08:29 PM   #13
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No one picked up on the 4V neutral to ground...... assuming the multi meter is accurate. I don't like that. Sounds like there's a "leak" somewhere.

The other comment I have is to make sure NOTHING is plugged into the circuit while trouble shooting to rule out any appliance being the culprit.
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Old 05-09-2021, 10:10 PM   #14
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Yes, there is a leak. It is very common to find an outlet that has a salt trail on the back side that allows leakage. I can’t guarantee it is the socket, it could be corrosion in wires or even a chaffed wire. By taking this one segment at a time we can locate the area of leakage.
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