GFCI + Pigtail = Mystery

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Spike said:
I believe the statement that the reverse Y will "never" work is not quite true. I carry one 50' 30 amp cord along with a smart reverse Y and have been able to get both legs to work using 2 different pedestals. I assume this is because it's using different neutrals. I have also come across a few marinas that understand the problem and have each pedestal wired with different legs on each side so the smart Y will work here also. I realize this is a bit cumbersome and not always possible but it has allowed us to run the AC in marinas with gfci and 30 amp only.

I'm no electrician so I'm not really sure how the magic works but it does.
Click to expand...
It will work with out of phase 30A in an old marina but not with newer marina meeting current codes... big difference.
How could the Y adjust /;split the amps returning on the single ( 50A 125/250V) leg to the 2 30A 125V legs and match exactly the amps delivered from that recepticle? Possibly if everything is off and there is zero amps being drawn??? but once a load is applied the 125V hot and neutral will be unbalanced.
I have no interest in continuing any disagreement only trying to assist the OP answer his question. Only / best? Way it to find a friend / acquaintance with a 50A 125/250V pedestal and connect directly from pedestal to boat with a 50A cord while he is out of his slip... or haveva marina allow you to try connecting with a 50A cord.
 
Notes: 1) The reverse Y can never work if there is working ground fault sensing present on either of the 30A circuits. Technically, they are called EPD (equipment protection devices). It trips if the imbalance is more than 30ma. GFIs trip at around 5ma but the idea is the same. The reverse Y will work fine is one Y leg is on L1 and the other is L2 and both are without GF sensing.

2) The OP stated he had a 240V isolation transformer. They don't normally have a center tap connected to neutral on the primary side. If neutral comes aboard, it is usually not connected. Even if it was was, the current would all be flowing between L1 and L2 and not be returning to the one neutral and back out the other to balance the currents within 30 ma.

Think of the EPD breaker as a clamp on ammeter. For 30A, it clamps around hot and neutral and not ground. The resulting current fliwing in and out must be within 30 ma of canceling out to 0. For 50A, the clamp is around L1, L2 and neutral. If the current is flowing from L1 to L2, it cancels to 0 as in the 240V isolation transfomer or 240V load case. If is flows from L1 to N or L2 to N (or any combination), it again cancels to 0.

Consider two 30A EPD breakers with the isolation transformer or even a 240V load. Current flow from one EPD breaker but returns to the other one. Both are unbalanced and one if not both will trip. (It's a race.)
 
Spike said:
I believe the statement that the reverse Y will "never" work is not quite true. I carry one 50' 30 amp cord along with a smart reverse Y and have been able to get both legs to work using 2 different pedestals. I assume this is because it's using different neutrals. I have also come across a few marinas that understand the problem and have each pedestal wired with different legs on each side so the smart Y will work here also. I realize this is a bit cumbersome and not always possible but it has allowed us to run the AC in marinas with gfci and 30 amp only.
Click to expand...


That may be bypassing the part about trying a Reverse Y with new GFCI pedestals (the "never work" part)? Did those places have the new GFCI pedestals?

-Chris
 
Clarification: I am are not talking about convenience outlets with the GFI buttons, I am referring to new "to code" EPD 30A outlets.
 
Bacchus said:
I think the only way to confirm whether your boat has any issues is to connect to a 50A 125/250V GFCI Pedestal and see if it trips. You will never be able to do this with the reverse Y.

Basically... in layman's terms... GFCI measures and ensures there is no imbalance in amps in the system (leakage out of the system).
With 30A 125V that means amps in via the hot matches (within milliamps) the amps returning via the neutral.
With 50A 125/250V system you have 3 wires... hot line 1, hot line 2 and a neutral and the neutral only carries the amps that are out of balance on L 1 + L 2.

The reverse Y will be useless in recently rebuilt marinas that meet current (no pun intended) codes.
Click to expand...
I just got through to Marinco technical support and they have confirmed that this is the correct answer. You cannot use a reverse Y adapter with GFCI/ELCI protected podium because of the mismatch on the neutral line, full stop. Thanks everyone, this mystery is solved.
 
Sababa said:
I just got through to Marinco technical support and they have confirmed that this is the correct answer. You cannot use a reverse Y adapter with GFCI/ELCI protected podium because of the mismatch on the neutral line, full stop. Thanks everyone, this mystery is solved.
Click to expand...
Ask Miguel if you can do the test on a 50A pylon over by the recip dock instead.
 
@Sababa
You said you have a 30A single 125 to 50A dual 125 adapter.
In theory the 2 hots merge into one, one neutral, one ground. If that does not work I would like to know why not. The only other is the isolation transformer that could prevent it from working.
Of course 30A is less than you want.
 
Sababa said:
I just got through to Marinco technical support and they have confirmed that this is the correct answer. You cannot use a reverse Y adapter with GFCI/ELCI protected podium because of the mismatch on the neutral line, full stop. Thanks everyone, this mystery is solved.
Click to expand...
Ian
Thanks for reporting Marinco confirmation. I have never checked w them but have done some digging about GFCI ELCI after our home port marina was upgraded and many transient boaters ran into problems.
 
SteveK said:
@Sababa
You said you have a 30A single 125 to 50A dual 125 adapter.
In theory the 2 hots merge into one, one neutral, one ground. If that does not work I would like to know why not. The only other is the isolation transformer that could prevent it from working.
Of course 30A is less than you want.
Click to expand...
I don't know why the 30A single doesn't work. I'm assuming it has something to do with the isolation transformer but would appreciate any insight.
 
A Thought. Can you do a continuity test on the adapter to eliminate a internal wiring issue. As in ground to ground and nothing else, neutral to neutral then hot split to two 50A hot.
 
Ertyqway said:
Ask Miguel if you can do the test on a 50A pylon over by the recip dock instead.
Click to expand...
Notwithstanding what Marinco says, Miguel insists that he has had other club members successfully use the reverse Y adapters with the GFCI podiums and the hitch must be with my isolation transformer. He seems to be a bit prickly about it so I'm not going to push it. I don't know what to think at this point so I'm just going to figure out where I can line up 50 amp service with an inspector and take it from there.
 
I second the previous comments of you can not share a neutral between two seperate gfci circuits. This would lead one to say you cannot use splitters with Gfcis.
 
Sababa said:
Notwithstanding what Marinco says, Miguel insists that he has had other club members successfully use the reverse Y adapters with the GFCI podiums and the hitch must be with my isolation transformer. He seems to be a bit prickly about it so I'm not going to push it. I don't know what to think at this point so I'm just going to figure out where I can line up 50 amp service with an inspector and take it from there.
Click to expand...
My guess is his comment that's others have used reverse Y w updated ELCI us blowing smoke. He may not understand exactly what others situation or equipment was but Marinco knows and I would truct their reply.
 
Spike said:
I believe the statement that the reverse Y will "never" work is not quite true. I carry one 50' 30 amp cord along with a smart reverse Y and have been able to get both legs to work using 2 different pedestals. I assume this is because it's using different neutrals. I have also come across a few marinas that understand the problem and have each pedestal wired with different legs on each side so the smart Y will work here also. I realize this is a bit cumbersome and not always possible but it has allowed us to run the AC in marinas with gfci and 30 amp only.

I'm no electrician so I'm not really sure how the magic works but it does.
Click to expand...
I think the 30A outlets you are plugged into are not GFCI outlets.
 
So an off the wall comment. Use a single 30a 125v to 50a 125/250v adapter. It won’t fire up your IT but it won’t trip the pedestal. There, you pasted the test, pedestal didn’t trip. Not his buisness if IT can’t work off a single 30a. Just make sure you get Assigned to a 50a slip.
 
I’ve spoken to the Commodore and they are going to let me do the test off the 50 amp connection either at my own slip or at the outstation depending on when and where I can get an inspector lined up. They are all volunteers and don’t charge anything so I can’t get too fussy.
 
Sababa said:
I don't know why the 30A single doesn't work. I'm assuming it has something to do with the isolation transformer but would appreciate any insight.
Click to expand...

Don't know the technicals, but for years owners in our club have confirmed there's no (sane) way to get a single 30A/125V shorepower supply through a 50A/250V isolation transformer.

Most of the those discussions evolved as owners grew into larger boats over the years (with 220V appliances) and as that maker began fitting isolation transformers as a matter of course, starting in circa 2003-ish. Often , this questions were about how to charge batteries while on the hard in winter, with only temporary storage lot power.

-Chris
 
ranger58sb said:
Don't know the technicals, but for years owners in our club have confirmed there's no (sane) way to get a single 30A/125V shorepower supply through a 50A/250V isolation transformer.

Most of the those discussions evolved as owners grew into larger boats over the years (with 220V appliances) and as that maker began fitting isolation transformers as a matter of course, starting in circa 2003-ish. Often , this questions were about how to charge batteries while on the hard in winter, with only temporary storage lot power.

-Chris
Click to expand...
If there's space on board, the way to do it (and I've seen something like this done from the factory on a Tiara) is a selector switch and a separate 120 -> 240V step-up transformer. So you have a single 30A inlet and a 50A inlet on the boat and select which one you're using (rather than using the 50A cord with an adapter). That assumes that the isolation transformer is intended to take straight 240V and make 120/240V split phase from it.
 
This is related to the problem I'm having in this thread. 120V step up to 240V needed

Isolation transformer needs 240V to work. Will not work on single 30 whether GFCI or not. Apparently won't work on dual 30 Amp with reverse splitter if GFCI.

One option is a 120v to 240V transformer. Still won't help with dual 30's but would give me some power.

I guess I could add two 120V isolation transformers and dual 30 amp inputs that would feed the 240V isolation transformer.
 
jhall767 said:
This is related to the problem I'm having in this thread. 120V step up to 240V needed

Isolation transformer needs 240V to work. Will not work on single 30 whether GFCI or not. Apparently won't work on dual 30 Amp with reverse splitter if GFCI.

One option is a 120v to 240V transformer. Still won't help with dual 30's but would give me some power.

I guess I could add two 120V isolation transformers and dual 30 amp inputs that would feed the 240V isolation transformer.
Click to expand...
My isolation transformer takes a standard 125/250v split phase as an input, ie, two 125v legs with opposite phases and a common neutral. So I don’t think a 120 to 240 v step up would work, because if I understand correctly, that would just be supplying 240v AC between a single hot and neutral.

One WAG about why the single 30>50 will not work with an isolation transformer wired for 125/250 split phase but will supply 120v loads if one is not present is that the split 30 A 125v current being supplied to each leg of the 50 A input is in phase instead of out of phase like with a regular 125/250 input. Ie, it’s just the same 125 v current sine wave being replicated in parallel to each of the two legs. Since the different legs are hard wired to different 120v circuits on the panel, the 120v loads on board that are wired to one leg don’t care about what phase power is being supplied to loads wired to the other leg, but you can’t stack the hots on the two input legs to get 250 volt power to run the AC and such like you can when they are out of phase like you do with a standard 125/250 power source. Does that make sense?

 
Arrrg. Here we go off the deep end with a lot of posters being some what right and some what wrong.

Some boats are truly 220v and some are just two legs of 125v. Some can work off of two 30a in phase 125v legs but are unknowingly overloading the neutral. Some are designed to prevent this and will only work on two out of phase 30a legs. By code 50a 125/250v are always out of phase.

So what works or doesn’t work on one boat won’t be the same for the next boat. Just because it works doesn’t necessarily mean it’s safe.

My boat will work on two 30a 125v in phase lines but my splitter won’t. Some splitters will but I purposely chose a splitter that wouldn’t for safety.
 
rslifkin said:
If there's space on board, the way to do it (and I've seen something like this done from the factory on a Tiara) is a selector switch and a separate 120 -> 240V step-up transformer. So you have a single 30A inlet and a 50A inlet on the boat and select which one you're using (rather than using the 50A cord with an adapter). That assumes that the isolation transformer is intended to take straight 240V and make 120/240V split phase from it.
Click to expand...
Some iso transformers can accept either 120 or 240v as the input, The input has a 120v tap. My boat is set up this was with a 30A120V input, if I choose to use it. But not all transformers can do it. Regardless, it’s worth checking.
 
Sababa said:
My isolation transformer takes a standard 125/250v split phase as an input, ie, two 125v legs with opposite phases and a common neutral. So I don’t think a 120 to 240 v step up would work, because if I understand correctly, that would just be supplying 240v AC between a single hot and neutral.

One WAG about why the single 30>50 will not work with an isolation transformer wired for 125/250 split phase but will supply 120v loads if one is not present is that the split 30 A 125v current being supplied to each leg of the 50 A input is in phase instead of out of phase like with a regular 125/250 input. Ie, it’s just the same 125 v current sine wave being replicated in parallel to each of the two legs. Since the different legs are hard wired to different 120v circuits on the panel, the 120v loads on board that are wired to one leg don’t care about what phase power is being supplied to loads wired to the other leg, but you can’t stack the hots on the two input legs to get 250 volt power to run the AC and such like you can when they are out of phase like you do with a standard 125/250 power source. Does that make sense?

Click to expand...
I know it may sound counter intuitive but your isolation transformer is getting single phase 240V on it's primary winding and the secondary is tapped for 120V.

Look at your wiring. You should see that only the Black, Red and Green are needed from the shore power cord. The white or neutral is not used.
 
jhall767 said:
I know it may sound counter intuitive but your isolation transformer is getting single phase 240V on it's primary winding and the secondary is tapped for 120V.

Look at your wiring. You should see that only the Black, Red and Green are needed from the shore power cord. The white or neutral is not used.
Click to expand...
I’m with you—240(250) single phase is what you get when you connect to just the hot wires from the two opposite phased legs and omit the neutral wire per the explainer PDF I posted a link to. So a 125>250 step up transformer should be able to take a single phase 30A 125v source to output 250v 15A single phase to my isolation transformer, which would then supply 125/250v power to my panel?

Still wondering however what that single 30>50A pigtail does.
 
Yes a step up transformer would output 240 across the primary windings. You can get these really cheap on amazon or Victron makes a step up isolation transformer that would cover all situations. I'd probably put a 30 amp plug on one end and a 50 amp socket on the other to make it portable.

30 to 50 just supplies one side on the 50 amp connection. will work one side of service on a boat without an isolation transformer.
 
jhall767 said:
Yes a step up transformer would output 240 across the primary windings. You can get these really cheap on amazon or Victron makes a step up isolation transformer that would cover all situations. I'd probably put a 30 amp plug on one end and a 50 amp socket on the other to make it portable.

30 to 50 just supplies one side on the 50 amp connection. will work one side of service on a boat without an isolation transformer.
Click to expand...
Got it. As a practical matter, I will just leave it alone and continue to use the house batteries, generator, and diesel furnace as if I were on the hook when no 50 amp or compatible 30 amp power is available.
 
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