Electrical Problem too much voltage!

[whaler23]

I have 50AMP service on my 1968 Constellation. It's pretty much all original. Today I went to check on the boat and when I stepped aboard and turned on the lights I noticed they were way too bright. About 10 seconds later they started to pop and blow. I quickly cut the power but heard what sounded like a fuse popping and the smell of burnt electrical and a whiff of ozone.

The boat has a 50AMP and 2 30 AMP inlets on each side, I almost always use the Single 50.

I first checked the shore power inlet and all wires intact and properly secured (I disassembled the connector and visually checked all). Next, the main panel, on the Chris Craft there are two large selector switches one is the 115/230V and Light Plant selector, the second is the 115V Dockside Power on one side and a Thru Transfer on the other.

None of the panel circuit breakers were tripped. I checked everything and turned power back on briefly and noted that 250V was measuring on the voltmeter, however, nothing will work. NO more smells either.

NOt sure if I have a bad ground some where that burnt off, a bad common that would allow too much voltage into one side or what? Any advice appreciated.

I'm not aware of any type of isolation transformers on the boat.

Thanks.

 

[captddis]

You most likely lost neutral.

 

[Canuck Dennis]

Seems odd, is your boat set up for 230 V input by using the 2 -30 amp inputs ?

That would only work if the 2x30's are fed from opposite sides of the shore distribution panel/

Disconnect the 2x30's at the dock pedestal, check across the hot of each outlet on the pedestal, and if you get 230 v, then you must have somehow combined them inside the boat, if you only get 115 across them then something else really weird .

 

[whaler23]

The boat is set up to use 2 30's to get 230V, the range/oven is the only appliance on the boat using 230V. The dock is only 50AMP. There is a series of circuit breakers to control the 2 30's on both sides of the boat as well as the 50's. There is a Main selector switch for the 115v/230V and Light Plant, you select one. Then the second main switch that is 115V dockside or Thru Transfer, I'm assuming this thru transfer would give me the 2 30's combined to provide 230V.

The normal set up on the boat has been shore power 115v/230v and thru transfer on at all times. THis has been the norm for over 2 years now.

How wouldl I check for a lost neutral? Do you mean I burnt a neutral off somewhere? One bit of information I forgot to add is that when power was on I flipped the battery charger the outlets on one side of the boat when from bright (over volts) to dim with the flipping of the charger switch. Not sure if this helps.

 

[whaler23]

"When you lose the neutral, or have a poor connection, you lose the centering point for the relative voltage to neutral.

The 120 volt / 240 volt service is really just a 240 volt service with a common center point (the neutral) which is used as a reference to obtain the two 120 volt legs (from the neutral) - there still is 240 volts across the entire service.

The neutral serves to keep the center of the circuit at 120 volts to each leg. With loads applied to circuits with that centered common point, the volts will remain the same and the current changes.

When the neutral is lost, the center common point is lost, and then the voltage is 240 volt across two loads (two loads normally intended to see 120 volts). Now, the voltage is free to fluctuate across each load and the current is free to fluctuate based on the total of the two loads placed across 240 volts instead of each load being placed across 120 volts.

That means that one load could conceivably have 90% of the 240 volts with the other load having the remaining 10% of the 240 volts, which calculates out to 10%=24 volts and 90%=216 volts.

You could easily have any voltage combination which totals to 240 volts. I have personally seen 186 volts and 54 volts with an open neutral, which changed as soon as the loads were changed"

Found the above answer on another forum which agrees with Cannuck above.

I have an electrician coming to the boat Monday but want to learn as much about the cause/effect of this condition as possible.

 

[GOLE IV]

I have experience this also on a house when the neutral is lost,
In you post mention you measure the voltage Inside the boat, Did you measure the voltage on the pedestal?
Did the marina made any changes to their installation?
In three phase delta installation there is a weird phase when taking out single phase voltage of, this is call "teaser". If the marina did any changes to their electrical installation you may be getting this phase in your boat. On this phase the voltage is very unstable, very complicated to explain here.
Check with the marina

 

[REBrueckner]

Whaler's Post #5 is good advice, either check the voltages yourself or have the marina do it and record the findings. If dockside voltages are ok, an open neutral is likely aboard or in your shore cable.

Such a situation can even happen, briefly, when inserting or removing a shorepower plug when plugs make contact at different moments....that's why your electric panel circuit breakers and ideally the shorepower pedestal circuit breakers on the dock should be OFF when connecting or disconnecting power.

AVOID MAKING POWER CONNECTIONS OR DISCONNECTS TO HOT OUTLETS

 

[whaler23]

Follow UP:

The neutral was lost on the dockside connection between the meter and the boat. Repaired. All is well again.

Thanks for the replies, everyone was right on.