Main Breaker Trips with Shore Power Outage

[LastChance]

I have a problem with the main breaker on my 120 volt AC panel on our 300 Marlin. When there is a power failure on shore power, the main panel breaker on the boat trips. Trouble is, when the shore power returns, the power to the boat is not restored. Naturally, nothing receives power until I return to the boat and restore the main breaker. I suspect this is the result of a faulty main breaker, which should not trip when it loses power.

Anyone else had this? I am tempted to simply replace the main breaker but it would help to know the manufacturer of the breaker first. Any suggestions?

Thanks for your help.

 

[Lt.Mike]

The breaker most likely trips when the power comes back on as it creates a spike.
The breakers are doing their job protecting what they feed. Dock power isn't as well regulated as what feeds your home.
Consider finding a way to calm down that spike with a auto resetting surge protector, that ain't gonna be cheap though.
This may work, but in a marine environment (???)
http://www.rvupgradestore.com/Progressi ... /pt50c.htm
If you need it adapter plugs are available.

 

[Fishtales]

Hi,
LT. Mike is correct. When power was interrupted by the marina I had the same issue - sometimes, other times it rode through. I noticed the same on my boat end when sometimes the breaker would trip and some times not when I inadvertently removed shore power prior to tripping the breaker on the panel.
Something you can try, is to replace the breaker. There is a possibility that the main breaker is weak, thus tripping more.
The real question is why are the shore power outages occurring. If they are occurring, are their voltage issues at the marina as well. If so, the breaker could be protecting the boat.

tx,
dr

 

[seasick]

It is correct that a surge on powerup could cause the breaker to trip but usually that should not be the case unless you have a higher connected load than recommended or the following: As mentioned, the breaker could be weak. The load at startup depends on what is turned on and what kind of load it is. For example, refrigeration can cause large initial spikes whereas things like lights and electric stoves/heaters do not.
If there is excessive resistance in the power connection, more current will be drawn. You could have an undersized shore power cable, corroded or weak contacts on the plug or receptacle, or a bad receptacle at the shore power service. Measuring the voltage at the supply side and comparing that to the load side when under load will tell you if there is an issue. I would like to see no more than a 5-8% difference under normal conditions.
Low voltage at the shore side can also be a problem since the same demand will call for more current when the supply voltage is low.
Sometimes using a IR contactless thermometer can help identify weak spots in the wiring. A temperature difference ( somewhat subjective) can identify a hot spot which can mean a bad device such as a breaker or connector. Really hot spots can lead to fires.
So the order I would test is:
Visually inspect all cords, plugs and receptacles. Verify that your shore power cable is rated for your load and length.
measure voltage at the source and at the boat both at load and unloaded;look for excessive voltage drops.
Replace the main breaker that is tripping especially if it measure hotter than other similar breakers(that have live loads connected)

If you are connected to 220 volt shore power, there can be other things to look into.

 

[LastChance]

All good suggestions, thanks. I have a 30 amp cable to a 30 amp connection and the startup load consists of the battery charger, hardly enough to generate a spike. The power losses at the marina are caused by power outages in the area. Think I will replace the breaker to start with.

 

[seasick]

All good suggestions, thanks. I have a 30 amp cable to a 30 amp connection and the startup load consists of the battery charger, hardly enough to generate a spike. The power losses at the marina are caused by power outages in the area. Think I will replace the breaker to start with.

Based on your info regarding the type of load, I would replace the main breaker first.
Good luck

 

[Lt.Mike]

All good suggestions, thanks. I have a 30 amp cable to a 30 amp connection and the startup load consists of the battery charger, hardly enough to generate a spike. The power losses at the marina are caused by power outages in the area. Think I will replace the breaker to start with.

The spike isn't caused by your equipment, its from the outside slamming your breaker when the power is restored.
A new breaker is the first & cheapest step to take I agree.

 

[LastChance]

An update: The breaker is a 30 amp 2 pole unit (3 slots wide and ganged with a single lever) which breaks both the neutral and the hot. I have written to Carling Technologies for their suggestions. I suspect the problem may relate to the fact it breaks the neutral as well as the hot.

 

[fishbust]

An update: The breaker is a 30 amp 2 pole unit (3 slots wide and ganged with a single lever) which breaks both the neutral and the hot. I have written to Carling Technologies for their suggestions. I suspect the problem may relate to the fact it breaks the neutral as well as the hot.

The double break design is intentional. Will help protect you against docks/marinas that are wired reverse polarity. You do not want to defeat this feature with a single break.

Just change the breaker. That will eliminate it as the culprit as you cannot do anything about the marina and associated substation causing the outages. It has been said more than once that the returning power to the marina is causing the surge, not your battery charger. If your battery charger was going to trip something, it would be the charger breaker, not the main breaker.

Be careful.

 

[LastChance]

Another update: The breaker turns out to be a double breaker with reverse polarity trip coil. The trip coil is engaged by a 65 volt surge arrestor connected between the neutral and ground conductors, so that the main breaker is tripped if incoming power polarity is reversed. I believe it is the trip coil which is causing the problem when shore power is restored. So as a temporary measure, I have disabled the trip coil by disconnecting the surge arrestor. The double break feature of both neutral and hot has been retained, as has the reverse polarity light.

A functional description of this sort of breaker may be found here:

http://www.google.com/patents/US7012795