Power Panel cross over switch

[gjrylands]

On my 1979 F36, Trojan installed a cross over switch on the power power. This switch allows the panel to be operated with either 1 or 2 shore power lines. I try to make things fool proof. The engineers of Trojan didn't when it comes to that switch. They placed a warning label on the panel, but who reads labels. If the switch is in the wrong position when both shore power lines are connected a direct short can results. (If each shore power line is coming off different legs of the shore panel, which they usually do.) The panel explodes with a bang and the breakers blow. I didn't think it to be that much of a problem until I opened the panel. Inside the panel there is a common bus bar for the neutrials. The short acted like a lightning bolt inside the panel, cracking the bus and almost melting the neutrials off.

I replaced the bus terminal and replaced the crossover breaker with a 30A single pole double throw switch. (A single pole double throw switch is used when you power a single device with 2 different power sources. This would be the same type of switch that would be used to back up your house with a generator, although that would be a double pole double throw since that is 220V. It is an on/on switch.) When installed it is fool proof. In one position the panel is supplied with only one power cord. In the other position the panel is powered by two power cords. If interested I can email you a drawing of how the switch is wired.

[oldsun]

gjryland, I would like to see your drawings. I am new to power boats and my F-32 has 2 power cords and 2 receptacles. I have been dealing with bilge issues and will move to electrical next.

Thanks,

Scott

[Peter]

I also have 2 shore power receptacles . My selector switch just says shore power/off/generator. Underneath the selector switch is a toggle switch which must be in a certain position when both shore power cords are plugged in [the labels are worn off] or the circuit breakers all pop. with one shore power, I can supply all a.c. components if that toggle switch is in the up position. I assume this is the same layout [76 F36] that you have, you think I should pull the panel and look for signs of arcing? It seems to work okay, and I have not smelled any electrical smells.?

[prowlersfish]

gjrylands , You should have just poped a breaker . Something may been wrong with your boat or someone may have rewired somthing in the pannel . the way the boat was wired at the factory it would have just poped a breaker . your boats almost 30 years old a lot of things could have been change over the years .


One other thing whats to say the shore power on the dock is done correctly ? I have seen many marinas wired wrong .

[gjrylands]

No Paul, Nothing on the boat was changer and the dock power was wired correctly. Trojan's circuitry is the problem. I am a licensed electrician and know my way around a power panel. The way Trojan wired the boat's power panel crossover switch can cause a direct short. When both power cords are plugged in, and the crossover switch is in the position to feed both sides of the panel with one power cord, a direct short results. Even though there is a warning label advising that the switch must be in the proper position when both cords are connected, there is nothing from keeping it from happening. With the type of switch I installed a direct short is imposable. If you don't believe me try throwing your crossover switch with both cords connected, and see what happens.

The way I discovered the problem was the first time I plugged in the boat with 2 power cords. I bought the boat during the off season while the boat was in winter storage. While in storage I was using only one power cord. I never thought of the crossover switch until I arrived at Burnham Harbor Chicago, where I keep my boat. (For sure, there is nothing wrong with the dock wiring.) I did what I have been doing for the last 25 years. I set up my mooring lines, hooked up the dock water, ran the power cords, and got ready to start the season with my new boat. All was well until I plugged the second power cord in. When I did the panel seamed to explode. The crossover switch was in the wrong position and the circuit breakers blew. I threw the crossover switch and reset the breakers and the power was restored. It wasn't until later that I had an occasion to open the panel that I found damage caused by the arcing. One of the neutrals from one of the power cords was almost burned off. Another terminal had cracked from the heat. I replaced the terminals, and wires, and then looked for the cause. I traced the problem to the design of the crossover switch. No attempt was made to isolate the two power feeds of the power cords. In fact, it caused a direct short. The crossover switch that Trojan used is a 30 amp circuit breaker. I think it was Trojan’s intention that the short would blow this breaker. When 2 - 30 amp circuits are shorted a lot of power is unleashed.

The excessive arcing in my panel could have been caused by a poor connection on the terminal strip. This could have been caused by a loose connection or corrosion, but because of the damage a definite cause was not found. The bottom line is, the short should have never been allowed to happen.

The switch I installed is fail safe. It makes it impossible to short out the system. When the switch is in the one cord position both sides of the panel are powered by a single power cord. This is the primary cord. Only the primary cord will power the panel even though the other cord is connected. When the crossover switch is thrown, the panel is powered by both cords.

[jimbo36]

I also have the same power panel and the two cord setup. I have never used two cords as everything works fine on one, including the a/c. When would I need two 30 amp cords?

Thanks, Jim.

[prowlersfish]

Jerry ,I can tell you what happens when I hit the switch it trips the breaker . Like its made to . I have done it several times . Nothing has changed in 30 years ? bet the breakers are not what they used to be time can be unkind . The system works if all parts are in good working order .

With that said they are better ways to do it . the best way I have seen sliding lock out on the pannel . I am sure your system is a improvment Also


Jim,
Why would you use 2 cords ? 30 Amps can't handle 2 A/C's a hot water heater micro wave and stove . Let the better half lose wire Her hair dryer and curlers 2 30 amp cord don't cut it .

[gjrylands]

During the boating season I'm a live aboard. I wouldn’t conceder operating the boat with only one power cord. My primary cord powers the half of the panel that controls the outlets, stove, hot water heater, refrigerator, ice maker, and the 120v lighting that I added. The second cord operates the 2 ac units, and 2 - 1500 watt built in heaters.

The primary cord is the side of the panel that has the larger draw and blows regularly. Each morning I have to turn off the hot water heater before I make breakfast. Even with the heater off I can blow the breaker. I never blow a branch circuit, it’s the main. The typical load that is powered is 1 or 2 burners on the stove, a coffee pot, the TV, lights, and the straw that breaks the back, the toaster or hair dryer, along with every thing else that is running. Now on top of all that, if I had to run an ac unit or 2; breakfast would be a long time coming.

Yes, the boat can be run with only one cord, but not everything at once. Does Green Acers come to mind?

[prowlersfish]

You have both A/C units on one power cord ? I have one one each and I belive the heaters are also .

[gjrylands]

I think the 2 ac units and heaters are on the same side of the panel. I'll have to check. If I split the units I could also divide up some of the other circuits and keep from blowing the breaker as offen.

My thinking was that since there was only one water pump for the 2 air conditioners they would both need the run off the same power cord. I guess that was silly since the water pump runs when either unit is on, but must be tied to only one of the 2 air conditioner circuits. There is an atomatic shut off if the water pump isn't running. If the power cord feeding the pump was off the air conditioner unit on the other line would shut down with out damaging it. I'll look to change that next year. The to do list keeps growing.

[prowlersfish]

Gerry , My water pump for the a/c runs off the same curcuit as the front A/C there is a relay/triger box box that contols the pump . this is very common . the old type box had 2 relays in it (spaces for 4 ) I replaced my relay box with a updated box that used trigers ( I still think thier relays) the resone I changed they stoped makeing the relays and very few left so I looked ahead and updated. I got a box with 3 trigers so I mave a spare.


BTW I think I have the wiring diagrm for a 78 F36 if you what it .

[gjrylands]

It's a fairly simple job to add a relay so the second unit. It would still have it's own breaker, but only get power fed to it if the relay was energized by the primary unit. Again I like fail safe.

[Rich Schwochow]

gjrylands, I have a F-32 with the same crossover, and duel power plugs. I've forgotten the crossover switch a few times when using two power cords. All that has ever happened was a tripping of the crossover breaker. It was designed to do just that. With everything in proper working order this is what should happen. There are ten F series boats at my club, and no-one has had any issues, (so far) Rich

[gjrylands]

I'm glad to hear that Trojan owner are not having the same problem that I had. As I stated in an earlier thread, that was the first time I plugged the boat in with 2 power cords. There must have been some previous damage to the panel that I was unaware of. At the time I thought that the problem was with the design. All I know is that when I plugged my boat in the panel went off like a bomb. I knew I never wanted it to happen again.

It good that the switch I bought in is not really needed. It was expensive. An old Grainger catalog lists the switch at $72.95. There are plenty of other ways to spend your money.

[prowlersfish]

Gerry . your a/c will have the relay box for the pump ( they hide it very well )