Low Voltage

[captbuddy]

Found out this weekend I had low voltage on our boat. Ice maker wasn't working right. Checked voltage and had 102 to 105 volts. Checked the dock it was OK. Repaired my dock 50 plug and checked it at boat side of cord. OK. Took panel off outside of boat where you plug in shorepower and we noticed someone has clipped the large white ground wire into. The plug housing is grounded to a smaller green wire which is run to a nut on the back side of the housing. Checked behind the main AC panel in salon. White wire is also clipped in there. Can anyone tell me why someone would have done this and if this would cause me to have low voltage? My friend has taken all my prints with him to see if he can figure out the electrical system. He is a aircraft electrician by trade. Any help.
captbuddy

[captbuddy]

I just found out from my friend that the prints shows that it suppose to be cut. The shore power goes through a isolation transformer and not directly to the panel. He said the prints show it is hard wired for 50Hz/60Hz. No rewire of the tranformer has been done. Does anyone know where the transformer would be located? Is there a switch somewhere where we can switchfrom 50Hz to 60Hz. We are getting 123 volts at the plug into the boat. But in the AC panel we are only getting like 108volts. Can't figure out where we are losing the volts.
captbuddy

[yachtsmanbill]

Not a lot of help, but its probably buried. On my '74 58' TC its under the deck on the starboard side under the cardox bottle. Check the voltage at the ISO trans. Mine saw underwater service and still runs perfectly. Not to make a bigger project out of what you have, but you can rig a "tap switch" to change the voltage/freq. See pics. ws

[SKYCHENEY]

Look for the large gray box in the engine room. That is your isolation transformer. The prints show how to wire it for 50hz, but you don't want to change that. You can, however, hook to some other taps on the transformer to increase the voltage. Several have added a selector switch for just this purpose. Search the archives for isolation transformers.

[captbuddy]

Thanks for the info guys. Did the search and found more info. Is there parts of the isolation transformer that can go out or are they indestuctible?
captbuddy

[yachtsmanbill]

Usually they are wound then sealed with a dielectric resin of various types. It would be a real mess to rewind one. I picked up a 7 kw unit for my Roamer about 15 years ago and it was about $350... Its anyones guess now with copper prices the way they are !! Mine weighs in at 275 lbs and most of that is windings. Have you checked all the connections. Resistance is a real killer. Does the unit get any more than "kinda warm"? (depending on load, of course.) ws

[captbuddy]

We've checked the voltage from the dock to the AC panel in the boat. We can get 123 volts in both legs of the fuses which are just to the right of the plug in on the boat. So I know we have it throught the shore power hookup and through the shore power cord and into the panel at the hookup on the boat. It appears we are losing it from the panel on the outside of the boat where we plug in and the AC panel in the boat. When we pulled the panel off of the AC panel and checked the leads coming in we got 108 volts.
captbuddy

[SKYCHENEY]

Is this voltage loss with a load on it or with no load too?

[captddis]

Was the voltage checked after the fuses? They can be troublemakers.

[Pete]

I suspect that you are plugged into a marina that has a 120/208 volt three phase electric system. The easiest way to confirm this is to go to the on dock shore power receptacle and measure the phase to phase voltage, not each leg individually. Assuming you have a 50 amp/250 volt receptacle, you will have three female ports on shore receptacle. One will have a straight opening (actually a slight curve), and the other two will have small 90 degree angle to the openings at one end. The ones with the 90 dergee openings are your hot legs. The one without the 90 degree opening is your neutral. Use your meter to measure between the two openings with the 90 degree ends. I will wager a cold diet coke that you read somewhere below 220 volts, within a few volts of what you are seeing at your Hatteras electric panel. Let us know your findings and we can go from there. Be careful probing the receptical, lots of power there, and you will have to wiggle the meter probes deep in the receptacle to make contact.

Pete