So I'm staying at a private dock for a while, the wiring situation is a little weak. The dock is just wired for lights with regular outdoor wiring, fairly light stuff. I'm using a 30amp 50' shore power cable with a pigtail adapter to plug into an outlet on the main dock. When I hook up the power available led comes on and the rev. polarity light is off ...until I turn something on, even if it is my little 3 amp fridge. But the led is very dim. I found this in the archives: "When high amperage loads are operated in the circuit, enough voltage drop in the length of the Neutral wire can be created to overcome the resistance in the 25K resistor required by ABYC that sufficient current is driven through the LED to cause faint illumination. This situation is not inherently dangerous, however, it can indicate undersized wiring in the dock, shorepower cord or ship’s wiring portion of the AC circuit." Ok, that sounds like the problem but how do I figure it out for sure?
- Status
- Not open for further replies.
electrician
Although I try my hand at everything else on my boat, wiring is one thing I leave to a qualified electrician because I.m afraid of fire. I had slight short in my control panel that was due to improper and defective installation when my Hunter 340 was new. But the short was so subtle, it was hard to detect that anything was wrong. It kept ketting worse and since I had a new boat I presumed it that there was something wrong with the marina's end of the shore power. Bottom line is that by the time I figured it out and got it fixed right, it was out of warranty.
Although I try my hand at everything else on my boat, wiring is one thing I leave to a qualified electrician because I.m afraid of fire. I had slight short in my control panel that was due to improper and defective installation when my Hunter 340 was new. But the short was so subtle, it was hard to detect that anything was wrong. It kept ketting worse and since I had a new boat I presumed it that there was something wrong with the marina's end of the shore power. Bottom line is that by the time I figured it out and got it fixed right, it was out of warranty.
Perhaps I can help...
as I'm a licensed electrical contractor/engineer. It sounds to me like you already have the most likely answer already figured out. Generally speaking, the reverse polarity indicator is merely an LED or incandescant bulb with a resistor wired across the neutral and ground wires. If a true reverse polarity occures, the bulb would see the voltage between the (now hot) neutral and ground, causing it to glow. However, if the wiring on the dock side is of correct polarity, enough voltage could be present on the neutral to cause the light to glow dimmly; this being caused by the excessive voltage drop along the neutral due to either the length of the run or insufficient wire guage, or both. This problem would be more obvious at night, when the dock lighting is ON and loading down the system. There's not much you can do about it (other than convince the marina owner to hire a REAL electrician to re-wire the docks-good luck!) Here's a couple of things to check: using a high quality digital voltmeter, check the voltage from hot to ground, it should be around 112 to 118 volts, check the voltage from hot to neutral, again it should be 112 to 118, now check for voltage between the neutral and ground, it should be close to zero (at least in theory!) Here's what your likely to find: the voltage from hot to ground is about the (nominal) 112 to 118, the voltage from hot to neutral is 5 to 10 volts less and the voltage from neutral to ground is about equal to the difference between the two. That is to say, if you have 118 volts hot to ground and 110 volts hot to neutral, you can expect to see maybe 6-8 volts from neutral to ground. If you find something different, let us know. Hope this helps! Jeff
as I'm a licensed electrical contractor/engineer. It sounds to me like you already have the most likely answer already figured out. Generally speaking, the reverse polarity indicator is merely an LED or incandescant bulb with a resistor wired across the neutral and ground wires. If a true reverse polarity occures, the bulb would see the voltage between the (now hot) neutral and ground, causing it to glow. However, if the wiring on the dock side is of correct polarity, enough voltage could be present on the neutral to cause the light to glow dimmly; this being caused by the excessive voltage drop along the neutral due to either the length of the run or insufficient wire guage, or both. This problem would be more obvious at night, when the dock lighting is ON and loading down the system. There's not much you can do about it (other than convince the marina owner to hire a REAL electrician to re-wire the docks-good luck!) Here's a couple of things to check: using a high quality digital voltmeter, check the voltage from hot to ground, it should be around 112 to 118 volts, check the voltage from hot to neutral, again it should be 112 to 118, now check for voltage between the neutral and ground, it should be close to zero (at least in theory!) Here's what your likely to find: the voltage from hot to ground is about the (nominal) 112 to 118, the voltage from hot to neutral is 5 to 10 volts less and the voltage from neutral to ground is about equal to the difference between the two. That is to say, if you have 118 volts hot to ground and 110 volts hot to neutral, you can expect to see maybe 6-8 volts from neutral to ground. If you find something different, let us know. Hope this helps! Jeff
P
patrick
jeff...
so I wasn't losing it when I found about 10 volts when I checked between the neutral and ground bus on my panel. Thanks!
so I wasn't losing it when I found about 10 volts when I checked between the neutral and ground bus on my panel. Thanks!
10 volts! Whoa!
Patrick- If you're reading 10 volts between the neutral and ground, that system is seriously overloaded/underwired!! No wonder the reverse polarity indicator is glowing!! Have you brought this to the attention of the dockmaster? He really should get a professional to look at this. Jeff
Patrick- If you're reading 10 volts between the neutral and ground, that system is seriously overloaded/underwired!! No wonder the reverse polarity indicator is glowing!! Have you brought this to the attention of the dockmaster? He really should get a professional to look at this. Jeff
10V on shore-side as well?
Did you also check the Neutral to Ground Voltage Drop on the shoreside? Being that it’s only a floodlighting circuit, I wouldn’t be surprised if the shore ground is very corroded, and also shows a 10 Volt drop (N - Gnd). Could also stem from a corroded neutral bar gnd connection at the (outdoor?) panel. Given that the dock is NOT actually set up for shore power, I’d hesitate in offering any advice on remedying the shore side wiring - however if the 10Volt drop is only on the boatside, we (collectively) can probably deal with it... One of the best ‘cheap’ tools a cruiser can carry, is a receptacle analyzer ie: ‘Ideal’ #61-501 or 61-051: http://www.mytoolstore.com/ideal/ide05-08.html ‘Morris Products’ #59080, or ‘GB Electrical’ #GFI-501A, etc.
Did you also check the Neutral to Ground Voltage Drop on the shoreside? Being that it’s only a floodlighting circuit, I wouldn’t be surprised if the shore ground is very corroded, and also shows a 10 Volt drop (N - Gnd). Could also stem from a corroded neutral bar gnd connection at the (outdoor?) panel. Given that the dock is NOT actually set up for shore power, I’d hesitate in offering any advice on remedying the shore side wiring - however if the 10Volt drop is only on the boatside, we (collectively) can probably deal with it... One of the best ‘cheap’ tools a cruiser can carry, is a receptacle analyzer ie: ‘Ideal’ #61-501 or 61-051: http://www.mytoolstore.com/ideal/ide05-08.html ‘Morris Products’ #59080, or ‘GB Electrical’ #GFI-501A, etc.
- Status
- Not open for further replies.