Joining both main circuits

G

gregarious

New Member
Nov 6, 2013
19
Savannah
Boat Info
440 EB 1996
Engines
Cat 3116
For when I only have a single 30 amp choice on the dock, can I jump the two on the boat? I know I can buy a kind of reverse splitter for $175 which does that, but it seem it would be cheaper and simpler to combine on the boat with a 30 amp two pole switch. 1996 44 EB
 
No.........it won't work and isn't safe.

No matter what you do on the boat, the single 30A service will only supply 30A of current. That means that all the circuit protection and wiring between the source and the boat are designed to only carry 30A. When loads for your jumped connection add your AC, refrigerator, icemaker, pumps, etc. together, and total more than 30A, the breaker in the power pedestal, or the panel that feeds it will trip, or worse, you will over heat the conductors in the power cable, the plug or the receptacle on the boat.
 
My last cruiser came from the factory with a parallel switch. It effectively took the power from shore power one and fed it into shore power two side of the breaker box. When parallel was selected, it mechanically blocked the shore power 2 breaker from being able to be turned on so you didn't back feed the power cable or accidentally connect both sources. Perfectly safe as the main breaker (30 amp) was still in control of all incoming current. So yes, there would be a way to do it safely but likely not easily.
 
I have that adapter and use it at my home marina. However, some marinas do not allow them because they can overload the 30amp shore connection and if you pop a breaker on shore you may impact other boaters.

On thing I did though was switch over the accessories to the same side as the microwave so that if I have to use only one side I have most of what I need.
 
I use the same adaptor, when I am unable to run two separate cords, and have not had a problem at any marinas. You do, obviously, need to keep an eye on the power consumption so as not to exceed 30amps in total. I also recently picked up (from EBay) a 50amp / 240 volt to twin 30 amp splitter, just in case I don't have access to 2 separate 30amp plugs.
 
h_gerry said:
I use the same adaptor, when I am unable to run two separate cords, and have not had a problem at any marinas. You do, obviously, need to keep an eye on the power consumption so as not to exceed 30amps in total. I also recently picked up (from EBay) a 50amp / 240 volt to twin 30 amp splitter, just in case I don't have access to 2 separate 30amp plugs.
Click to expand...


I do this as well and have never had a marina present an issue. If they did have an issue with it you could always run one 30amp from the pedestal to the boat and then hook up the adapter on the boat side where no one could see it.
 
What is on ebay is what we have. Works well. I would never purchase a used electric cord or splitter as the plug ends may be defective and the damage they could do to your boat are far greater than the cost of a new cord. One needs to watch the draw on the boat. We try to keep total amp draw to 25 when on 30 shore power. Where we go some marinas have 15 or 20 AMP power. With these we use two cords one to each leg of the panel.
 
I bought the very ebay splitter posted below. I can check out the resistance easily to tell if there is an issue. And yes your total amp draw has to be monitored. I took the smoked plexi doors off my power panel so I can always see it. Unless we have a 50 amp service, we only run one A/C, the rest don't amount to much. The water is always hot after an hour of running, etc Thanks.
 
Frank,

I gotta ask the question as I have seen it done on several boats. Single 50 amp cable run to the boat then split into the (2) 30 amp plugs on the back of the boat. I've also seen the same set up connected to a single 50 amp dock connection as well as split at the dock end to (2) 30 amp power supplies. The reason giving was it was easier to handle (1) 50 amp cable vs. the (2) 30 amp cables. What type of issues would be of concern?
 
The 50 amp cable is a 240 volt cable. When you use the 50 to 2 30 plug split you are still 2 complete circuits going to each plug. Like a dryer plug having 2 120 volt legs a 50 amp circuit has the same.
 
John,

I don't have a problem with the single 50A cord supplying 2 -30A inlets as long as there is a splitter outside the boat and it is a true 50A service.

My issue with the OP's idea of jumping or connecting the 30A circuits inside the boat is that one could connect a single 30A service to the boat then draw much more current than the service, the power cord, the inlet receptacles and the wiring between the inlet on the boat and the jumped connection could carry, thus creating an overloaded situation which would quickly overheat. The result could easily be burned connections or worse, a fire.

I would much rather lug 2 30A power cords around when we are traveling away from our marina than I had a single 50A power cord........those boys are heavy!
 
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