GFCI + Pigtail = Mystery

[Sababa]

So I went down to Queen City Yacht Club this morning for an electrical check that is required for being on their (eternal) moorage wait list. The club has new GFCI podiums with 30 amp power outlets. I have a Marinco 30>50 amp reverse splitter that came with the boat when we bought it last December and which has worked at several marinas we have visited that lack 50 amp power, even though I have worried that there might be something wrong with it because the LED at the output connector doesn’t light up. The inspector hooks it up to the podium, connects it to my shore power cable, turns on the podium breakers, and they immediately flip. We disconnect my shore power cable, flip the breakers back on, and test the splitter legs for power. There is current on each of the 30 amp legs, but no power on the 50 amp leg downstream of the junction. We drive over to Fisheries and I buy a new reverse splitter. We plug it in to the podium, turn on the breakers, and the light goes on. We test and have power now to the 50 amp connector. Turn off the breakers, connect my shore power cable, flip the breakers back on, and they trip again. Try a different podium, same result. So you’d think I have a ground fault. Except we have an isolation transformer, and we have connected the shore power cable directly to ELCI/GFCI protected 50 amp service without problems. Any thoughts why we would experience this problem only with the reverse Y splitter???

 

[SteveK]

WAG. Your neutral and hot are reversed.
You need to mention if the cables are 3 prong or 4 prong as in 120 or 240

 

[Sababa]

My shore cable is four wire 125/250v 50A. The splitter is two 3 prong 125v 30A to single four wire inlet.

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[SteveK]

Do you have a dual isolator?
IMO, while it works without GFCI, it does not on these pedastals as you have one neutral splitting into two 30A outlets each with its own hot, the balance is off.
TT should be along soon.

 

[Clark]

30A > 50A Reverse splitters will always trip new pedestals with ground fault breakers. There is nothing wrong with the splitter or the pedestal and there is no solution other than not using new pedestals with ground fault protections. This is because the 2 30A neutrals are tied together and because the hot and neutral currents on either of the 30A connections will never balance to satisfy either of the two ground fault breakers.

 

[Delta Riverat]

Yup, that's it.

On a split, the current in the neutral is the difference of the 2 hots. Say you are running 10A on one side and 15A on the other. Current in the neutral is 5A. Yeah, GFCI's don't like that.

 

[Sababa]

So what folks are saying is that reverse splitters just don’t work with GFCI and there is nothing wrong with my boat? Anything authoritative I could point to, as the club’s inspector doesn’t seem to think so?

 

[SteveK]

Did you try plugging in only one of the 30A at a time? That should run one circuit and not give a fault.

 

[luna]

So what folks are saying is that reverse splitters just don’t work with GFCI and there is nothing wrong with my boat? Anything authoritative I could point to, as the club’s inspector doesn’t seem to think so?

I would suggest that the Queen City Yacht Club should call the Electrical Engineering Consultant who designed and specified the project, plus the Electrical Contractor that provided these new GFCI or GFPE protected outlets and ask them if the use of a reverse splitter will always result in a tripped Ground Fault protection device.

This of course begs the next question which would be, why is the marina in a position where it can only offer 30 A @ 120 V to a boat the size of a Maritimo 52, who likely can't accept this power connection without significant modification?
Even if the boat can accept this power, it's too small to be of much use.

Are there any 50A 125/250 V GFPE protected outlets at the Marina? If your boat itself is wired correctly you would not trip this circuit.

 

[ranger58sb]

The club has new GFCI podiums with 30 amp power outlets.

In light of @Clark's post...

Is that the only kind of pedestal the club has? If not, try your shore cord (i.e., without Reverse Y) on a real 50A/250V pedestal. If that's successful, tell them you'll want your slip (once assigned) rewired for an actual 50A/250V pedestal.

-Chris

 

[Sababa]

Did you try plugging in only one of the 30A at a time? That should run one circuit and not give a fault.

The reverse splitter circuitry needs power to both inputs before it will supply power to the output. I have a single 30 to 50 pigtail that came with the boat, but I’ve never been able to get the boat to accept the power input. The LED on the pigtail lights up, but there is no power to the panel when I flip on the breaker on the boat. Another mystery.

 

[Sababa]

I would suggest that the Queen City Yacht Club should call the Electrical Engineering Consultant who designed and specified the project, plus the Electrical Contractor that provided these new GFCI or GFPE protected outlets and ask them if the use of a reverse splitter will always result in a tripped Ground Fault protection device.

This of course begs the next question which would be, why is the marina in a position where it can only offer 30 A @ 120 V to a boat the size of a Maritimo 52, who likely can't accept this power connection without significant modification?
Even if the boat can accept this power, it's too small to be of much use.

Are there any 50A 125/250 V GFPE protected outlets at the Marina? If your boat itself is wired correctly you would not trip this circuit.

Good suggestion, I’m going to reach out to the contractor. They do have 50 amp protected pedestals in some of the bigger slips and at their outstation, which I have plugged into without a problem. I don’t know why they only installed the 30 amp pedestals at the transient/guest dock in front of the club where they do the electrical testing.

 

[tiltrider1]

If your isolation transformer only works on 50a 125/250v or split 30a 125v then you are never going to be able to connect to a 30a 125v GFCI dock. This is why I have set my boat up with two 50a 125v isolation transformers and then I use a step up transformer on the boat for my 220v needs. This allows me to operate At least half the boat on 30a 125v.

My guess is that Sababa’s boat is a 50a 250v isolation transformer set up that will only work when it sees two out of phase legs.

 

[luna]

The fact that you have successfully plugged into a 50 A 125 /250 V Ground Fault protected receptacle should tell the Marina’s inspector that the issue is not the boat.

If you use a Ground Fault protected receptacle the days of using a reverse splitter are over.

You have to question why this inspector would require you to plug into the Marina’s system in a manner that will guarantee a failure.

With the growing use of Ground Fault protected receptacles the bigger boats that used to successfully run 2-30 A 125 V services to acquire 240 V, will now have to use only one 30 A service and using an auto transformer make your own split phase 240 V onboard. This would require that you limit the loads to about 25 A @ 120 V. No dear you can’t use your hair dryer while your curling iron and tea kettle are on.

Lots of other options exist but all require on board power generation of one sort or another. The days of the Marina supplying to a transient customer all of the power, are coming to an end thanks to G. F’s.

 

[twistedtree]

30A > 50A Reverse splitters will always trip new pedestals with ground fault breakers. There is nothing wrong with the splitter or the pedestal and there is no solution other than not using new pedestals with ground fault protections. This is because the 2 30A neutrals are tied together and because the hot and neutral currents on either of the 30A connections will never balance to satisfy either of the two ground fault breakers.

Clark nailed. A reverse Y will NEVER work when plugged into two 30A RCD protected outlets. Each of the RCDs expected to see the exact same (well, within 30ma) line and neutral currents. However inside your Reverse Y the neutrals for the two 30A outlets, and consequently making the neutral current in each outlet essentially random and never matching the line current.

Reverse Ys are becoming dinosaurs, and manufacturer's should be boldly disclosing that they are not compatible with GFCI/RCD shore outlets.

The only way to run your boat off a 30A 120V outlet will be via an isolation transformer that can be configured with a 30A input. Perhaps you will get lucky and find that your transformer has such a capability and it just needs to be wired with a suitable selector switch to a 30A inlet on the boat. Then the 30A shore power will go directly into the transformer, and the transformer will create the boat-side 120/240V