| T O P I C R E V I E W |
| KiDa |
Posted - Mar 09 2012 : 17:40:23
I finished tearing out the upper galley on Saint Max today. I was checking the wiring while I have it apart. I think I have a problem but not being an electrician, I don't know.
In the receptacle for the microwave the following occurs:
White to black - 125 VAC
Black to green - 125 VAC
White to green - ~0.9 to 1.0 VAC
Is there a problem?
If so, how do it trace and fix it?
The microwave is the only electrical draw on this circuit.
TIA. |
| 20 L A T E S T R E P L I E S (Newest First) |
| D. Andrews |
Posted - Mar 13 2012 : 19:10:28
Any test results yet Kida?.........D............ |
| pdecat |
Posted - Mar 13 2012 : 07:31:22
That is what I mean by the main panel, the marina master panel. I stand by my comment try the meter on both AC and DC scales.. |
| rawidman |
Posted - Mar 12 2012 : 17:49:20
quote:
Originally posted by pdecat
not a great mystery. The white and green are indeed connected at the main panel. The green goes to the water via the shafts and zincs that create a low voltage on the system thence through the earth to the same main panel.. I'll bet your meter reads the same voltage on the DC as the AC scale. That seems an artifact of the diode bridge at the front of the meter in the ac circuit.
The white and green wires should not be connected at the main panel.
As I posted above, they are connected together at the marina's service panel. |
| pdecat |
Posted - Mar 12 2012 : 12:21:50
not a great mystery. The white and green are indeed connected at the main panel. The green goes to the water via the shafts and zincs that create a low voltage on the system thence through the earth to the same main panel.. I'll bet your meter reads the same voltage on the DC as the AC scale. That seems an artifact of the diode bridge at the front of the meter in the ac circuit. |
| KiDa |
Posted - Mar 12 2012 : 11:38:23
quote:
Originally posted by Shadowcruzr
Sell the boat and buy a new CHaparral....
The name is D. Paul, not J. Paul!  |
| Shadowcruzr |
Posted - Mar 12 2012 : 10:54:12
Sell the boat and buy a new CHaparral. Quit dealing with second rate merchandise. You dont shop at walmart, why shop at searay. Get with the program Soldier! |
| rawidman |
Posted - Mar 12 2012 : 07:08:53
There should be no connection between the neutral and the ground wire on the boat unless there's a genset or inverter and in that case, there should only be a connection when the genset or inverter is operating.
The neutral and ground are connected together at the service entrance of the building or dock (the place where the utility connects to the customer's equipment. In some cases. this could be several hundred feet from the boat. With a very sensitive meter, an induced voltage will be shown when wires carrying AC current are in close proximity to each other (like in a cable or conduit).
The first thing to do is make the same test at the shore power outlet where you are receiving power for your boat (with the boat disconnected). I'll bet you get the same reading.
In my opinion, it's nothing to worry about. If you're still worried about it, hire a qualified marine electrician to check your boat's wiring.
As for meters and phanto readings, in the old days with analog meters, this was seldom a problem. Most digital meters are so sensitive, they can read induced voltage in a wire, especially around transformers or sources of RF. |
| pdecat |
Posted - Mar 10 2012 : 08:41:50
Probably the zincs in the bonding system since the white wire is gonnected to ground at the main panel.The zincs are inthat circuit as a voltage source. My meter has the strange performance of reading small dc on the ac scale as well. |
| D. Andrews |
Posted - Mar 10 2012 : 07:28:58
Kida, 200vac is fine, that should provide plenty of resolution. If it is actually there, I would not tear the boat appart trying to find it, I would start looking for electrolissys just to be on the safe side, and keep an eye on the isolaters just as a precaution. I really do not feel there is an issue, but as mentioned above, in a house, not a big deal, on a boat or around water it could be depending on the source. With electricity on a boat, best to be sure than sorry.
.9 volt reading, on a fluke, with shorted probes indicates it is ready for calibration. All my meters that are used for work and testing are sent each year for calibration. when you measure in the ma range this is a must. Should read 0v and 0 ohms with a new set of probes attached..........D....... |
| JimPend |
Posted - Mar 09 2012 : 20:21:37
My Fluke will bang around on .9 to 0 volts when I short the leads out. |
| jpowell |
Posted - Mar 09 2012 : 19:49:39
Jim Pend
I am an enginee AND a master electrician. I would not be worried about 2 VAC on a neutral inside a home, but around a pool or a boat it can cause problems. This leakage on boat is probably a reversal,of a hot or a neutral. On a boat it can cause electrolysis and be a safety problem. |
| KiDa |
Posted - Mar 09 2012 : 19:45:10
quote:
Originally posted by JimPend
I'm an engineer and there is no problem the voltage he has between the common or neutral and the ground it is his meter tolerance.
Is there a particular setting I should be using? The lowest AC setting IIRC is 200VAC. |
| KiDa |
Posted - Mar 09 2012 : 19:32:33
quote:
Originally posted by D. Andrews
Turn every other breaker off in the panel except the main and this one. Un plug every thing plugged into this circut and retest. It is likely some where on that circut or on another circut to that panel there is something with a coil or winding in it and your reading the bleed over across the neutral. If you return to pretty much zero, then slowly start adding things back on, one at a time untill it reappears, then see what the source is. If it does not go away, check your shore power outlet with the boat unplugged and see if it is there, could be some place else along the dock. If all that fail, check your meter, it could be meter fade, not uncommon..........D..........
I shall do that next time I am at the boat. The only load on that circuit is the microwave. I took it out at the end of the season to plug in my goldenrods and caframo dehumidifier. My ER heater is on the "outlets" circuit and adding all the other dehumidification devices was too much for the "outlets" circuit. The microwave is on the 2nd 30 amp leg of shore power.
Thanks.
I shall keep you posted.
In the meantime, if one volt proves to be valid, is there a worry? I have a galvanic isolator on each leg.
There is so much wiring shy of a complete tear down I cannot get to I really don't know where to start if the one volt violates safe conditions for my boat, passengers, marina.
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| D. Andrews |
Posted - Mar 09 2012 : 19:30:32
That's very possible. Take your voltmeter home and see if you get reading between the neutral and ground. I just went out to my van and brought in my voltmeter; got a reading of 0.56 volts.
Very possible, and probable and can be much more depending on if you have a bonded neutral panel or not (bonded neutral is a buss going from the neutral to ground esecentially giving them the same potential) or if you are measuring on a circut that has an electric motor (fridg) mechanical clock (stove) dryer or washer running, stove on, etc. Anything with a "resistive" load can cause you to read higher than expected voltage from neutral to ground in either type panel, depending on the distance to the panel and if bonded or not, not bonded will give higher as the link to ground is away from the house.
I did bring the meter home and will check it tomorrow at home. My fear (unfounded due to lack of knowledge) is stray current "electrifying" the surrounding waters and causing electrolysis on my boat as well as my dock mates. I was under the impression the white to green was supposed to be 0.0 VAC.
Good idea to verify the meter, but, the test will not be valed if any of the above conditions are present. You could perform the same test at home, but will have to be done the same way as there is no way to turn off the neutral or ground and any circut with a resistive load that is active will give you some reading. Be very carefull, you can get seriously hurt doing this, a neutral will kill you if you become the path of least resistance to ground in a circut with a resistive load. Electrolysis would be my only concern as that does not require much voltage to happen.............D............... |
| KiDa |
Posted - Mar 09 2012 : 19:12:53
I did bring the meter home and will check it tomorrow at home. My fear (unfounded due to lack of knowledge) is stray current "electrifying" the surrounding waters and causing electrolysis on my boat as well as my dock mates. I was under the impression the white to green was supposed to be 0.0 VAC. |
| Pa Mikee |
Posted - Mar 09 2012 : 19:07:40
quote:
Originally posted by JimPend
I'm an engineer and there is no problem the voltage he has between the common or neutral and the ground it is his meter tolerance.
That's very possible. Take your voltmeter home and see if you get reading between the neutral and ground. I just went out to my van and brought in my voltmeter; got a reading of 0.56 volts. |
| JimPend |
Posted - Mar 09 2012 : 18:21:45
I'm an engineer and there is no problem the voltage he has between the common or neutral and the ground it is his meter tolerance. |
| Radioactive |
Posted - Mar 09 2012 : 18:08:13
The official color coding has:
Black = "hot"
White = "neutral ( the other half to the hot circuit between white and black )
Green = Earth ground.
I'm no electrician, but it looks fairly good to me. It is not uncommon to have a slight voltage difference between "neutral" and "Ground". I am unqualified to determine if the approx. 1 volt difference is too high or not. If it were my boat, I would inspect wiring to confirm good, clean, solid junctions through out. But that's on my boat.
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| D. Andrews |
Posted - Mar 09 2012 : 17:56:07
Turn every other breaker off in the panel except the main and this one. Un plug every thing plugged into this circut and retest. It is likely some where on that circut or on another circut to that panel there is something with a coil or winding in it and your reading the bleed over across the neutral. If you return to pretty much zero, then slowly start adding things back on, one at a time untill it reappears, then see what the source is. If it does not go away, check your shore power outlet with the boat unplugged and see if it is there, could be some place else along the dock. If all that fail, check your meter, it could be meter fade, not uncommon..........D.......... |
| JimPend |
Posted - Mar 09 2012 : 17:52:30
Looks good to me now put the black on the brass. Wire the rest to the others, white on the other screw on the receptacle across from the black and the green to the one in the corner of the receptacle. |
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