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Old 06-03-2016, 11:15   #1
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Converting twin 50 Amp 125v to one 50 amp 250?

Hoping I could get some "expert" advise

I am not an electrician but have lots of electrical experience! Here is my question. I have a 1987 51' Bluewater Coastal Cruiser that came from the factory (i believe) with (2) 50 Amp 125 volt shore power connections (3 wire). Inside there are AC power group "A" breakers and AC power group "B" breakers. Both have their own 2 pole (double) 50 Amp main breakers. It appears that each main breaker has the hot (black) wire on one pole, and Neutral (white) on the other. I thought it was odd the neutral was on the breaker/ switch, but they are definitely 125 volt. I have (2) 50 ft, 50 Amp shore power cords running from the boat to the dock.

Since 50 amp 125 volt service is not that common at marinas, somewhere along the line someone replaced the dock side ends of the shore power cords with 50 amp 125v/250v ends (4 wire). The second hot leg or (4th) wire is just not used still providing 125 V to each shore power cord. All works fine, other than the fact that havong (2) super heavy shore power cables to lug around at 50 lbs. each is not really my idea of a good time I also think this is a weird setup by today's standards. Most of the marina's I have gone to provide 50 amp 125/250 (4) wire hookup and a 30 amp 125v hook up at each pedestal (if you lucky) or just a single 50 amp 125/250 or single 30 amp 125v. When I tell the dock master I need (2) 50 amp connections or one 50 and one 30 to plug into they look at me like...are you for real? LOL

My question is this... Can I convert the (2) 50 amp 125v shore power to ONE 50 amp 125v/250v? I would get a 50 amp 125v/250v 4 wire standard shore power cable (using both hot legs). On the boat I would use only (1) 50 amp 125v/250v receptacle. I would accomplish this by taking the two existing receptacles wires and combine the neutrals together and the grounds together into the single 50 amp 250v. One hot lead to would go to AC group "A" and the other hot lead go to AC group "B". Does any of this make sense? LOL

Thanks in advance for any advice!
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Old 06-03-2016, 11:34   #2
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

https://marincofaq.wordpress.com/category/shore-power/
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Old 06-03-2016, 12:33   #3
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

Quote:
Originally Posted by watermart View Post
Hoping I could get some "expert" advise

I am not an electrician but have lots of electrical experience! Here is my question. I have a 1987 51' Bluewater Coastal Cruiser that came from the factory (i believe) with (2) 50 Amp 125 volt shore power connections (3 wire). Inside there are AC power group "A" breakers and AC power group "B" breakers. Both have their own 2 pole (double) 50 Amp main breakers. It appears that each main breaker has the hot (black) wire on one pole, and Neutral (white) on the other. I thought it was odd the neutral was on the breaker/ switch, but they are definitely 125 volt. I have (2) 50 ft, 50 Amp shore power cords running from the boat to the dock.

Since 50 amp 125 volt service is not that common at marinas, somewhere along the line someone replaced the dock side ends of the shore power cords with 50 amp 125v/250v ends (4 wire). The second hot leg or (4th) wire is just not used still providing 125 V to each shore power cord. All works fine, other than the fact that havong (2) super heavy shore power cables to lug around at 50 lbs. each is not really my idea of a good time I also think this is a weird setup by today's standards. Most of the marina's I have gone to provide 50 amp 125/250 (4) wire hookup and a 30 amp 125v hook up at each pedestal (if you lucky) or just a single 50 amp 125/250 or single 30 amp 125v. When I tell the dock master I need (2) 50 amp connections or one 50 and one 30 to plug into they look at me like...are you for real? LOL

My question is this... Can I convert the (2) 50 amp 125v shore power to ONE 50 amp 125v/250v? I would get a 50 amp 125v/250v 4 wire standard shore power cable (using both hot legs). On the boat I would use only (1) 50 amp 125v/250v receptacle. I would accomplish this by taking the two existing receptacles wires and combine the neutrals together and the grounds together into the single 50 amp 250v. One hot lead to would go to AC group "A" and the other hot lead go to AC group "B". Does any of this make sense? LOL

Thanks in advance for any advice!
===

The easiest solution is to get one of these: Hubbell 64CM55 Y Adapter

Hubbell 64CM55 Y Adapter

Each side of the Y goes to your shore power inlet connectors, the other end of the Y goes to a 50 amp shore power cable. That's how I do it on my boat and it works fine. You can frequently get good deals on EBAY for both cables and Y adapters.
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Old 06-03-2016, 15:48   #4
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

On boats, and on houses really, you always break both hot and neutral with the main breaker. My boat came with two 30amp shorepower inlets. One goes to the main panel and the other to a second panel which is dedicated to the air conditioner and an AC heater. You might not be able to run those off of the same cord as they could easily exceed 30amps. There is a 1-2-all switch to be able to use which side shorepower is coming in to the other panel, or both at once. But you wouldn't and shouldn't put 60amps to a panel or circuits designed and built for 30 amps, or 50 amps and then expect to draw 60. Everything should go through the main breaker for the circuits they feed. So you might actually have two main circuit breakers on each side. One near the inlet (per ABYC) and one on your panel(s) for each shorepower inlet. That is how mine is wired.
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Old 07-03-2016, 05:57   #5
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

Unless you have 220V appliances/systems on board, I doubt converting the boat would be worth the effort.

Out here, common service is two 30s per pedestal, one 50/250V per pedestal, or more likely two 30s and one 50/250 per pedestal.

Quick guess, but I'd have thought a 30-to-50/125V adapter for each of your power cords would be quickest/easiest solution. Assuming twin 30s would run most of your boat most of the time.


Another idea is that splitter adapter thing: one 50/250V to two 50/125Vs.


We find we usually have to carry a variety of adapters anyway, mostly just in case our assigned power pedestals (while traveling) are for some reason "challenged."

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Old 07-03-2016, 11:19   #6
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

I've done many that way. It will work fine. That way you only have one cord. You will have to tie the two neutrals And the two grounds since you only have one of each coming in but that will be fine.
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Old 07-03-2016, 14:43   #7
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

What you describe will work just fine.

Just remember, the (2) groups are now 180 degrees out of phase wrt each other, meaning you will measure 240v from hot to hot of the 2 groups.
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Old 07-03-2016, 18:56   #8
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

Thank you everyone for all your input...greatly appreciated! I like the idea of Wayne B's suggestion of using a Hubbell 64CM55 Y Adapter. I have found one for $300.

but I am leaning towards the advice from Monepit & DonDun about combining the neutrals & grounds as I originally questioned and using the (2) hot legs to feed each AC group. I do understand each leg will be 180 degrees out of phase

Monepit or Dondun....or if anyone else would would like to chime in. Is there any disadvantage of doing this way...having the "hot" wires out of phase? For example.....what happens if I go to a marina that only offers two separate 30 amp receptacles. One would "assume" each outlet would be on a different phase...but are they? Is there any advantage of keeping the (2) 50 amp 125 Volt receptacles and dual shore power cords?? Just want to make sure :-)

You guys are great...thanks again!
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Old 07-03-2016, 19:06   #9
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

I don't see any. When you have 2 125 cords. They are always out of phase. As are 30s. The neutrals and grounds are always tied in the box. One cord has the same capacity but is just one cord. Much easier. I've seen may use the y. Including my brother, but I would much rather only have to deal with one cord. I am an electrician by trade and have done boat wiring for 30 years. This works well. I usually put a phone cable plug to replace the other cord input. Although with cell phones and sattillite they aren't used a lot any more.
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Old 07-03-2016, 19:41   #10
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

Not sure you are getting good advice, you will be trying to run 2 50amp 125v services via single cord rated at 50amps with a single neutral, your panels are rated at 50amps I don't think Mr. Ohm agrees with that, you could potentially overload the cord and cause a fire.

I would have to draw it out, but it sounds suspect.
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Old 07-03-2016, 19:49   #11
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

There's no issue with overloading the cord. His panels are each 50 amps at 110 which is exactly what he'll be feeding them. The only issue is the disconnect. Under the proposed installation one panel (ie. one 110 amp leg) can trip without tripping the second panel. I think to be strictly code compliant there should be a master panel ahead of the two existing panels with a single 50 amp 240 volt breaker which then feeds each sub panel through individual 50 amp 110 breakers. I think the code issue is that there needs to be a single point that disconnects both legs of the 240 volt service.

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Old 07-03-2016, 20:05   #12
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

How is the outlet configured on a standard 220v 50amp outlet? Are both hot legs on a 2 pole 50 amp breaker with the nuetral leg direct? By splitting it woudln't you be able to apply excess amperage via nuetral leg feeding both 50amp 110 service, but not trip the dock side breaker? IE if both panels were pulling 30amps wouldn't the single combined nuetral leg see 60?
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Old 07-03-2016, 20:24   #13
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

Quote:
Originally Posted by Cruisingscotts View Post
How is the outlet configured on a standard 220v 50amp outlet? Are both hot legs on a 2 pole 50 amp breaker with the nuetral leg direct? By splitting it woudln't you be able to apply excess amperage via nuetral leg feeding both 50amp 110 service, but not trip the dock side breaker? IE if both panels were pulling 30amps wouldn't the single combined nuetral leg see 60?
===

No, the two 120 volt legs are 180 degrees out of phase so if both legs are drawing equal power, the neutral is actually at zero amps.
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Old 07-03-2016, 20:27   #14
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

What you are proposing will work easily. Do not buy the Y-adapter as someone else said, all it is doing is exactly what you will do at the panel. The price and the extra connections of the Y-adapter are not needed or desired. The price of the 50A/250V cord will be enough, by itself, to take your breath away.
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Old 07-03-2016, 20:32   #15
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Re: Converting twin 50 Amp 125v to one 50 amp 250?

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What you are proposing will work easily. Do not buy the Y-adapter as someone else said, all it is doing is exactly what you will do at the panel. The price and the extra connections of the Y-adapter are not needed or desired. The price of the 50A/250V cord will be enough, by itself, to take your breath away.
===

But using the Y adapter has the advantage of not requiring any changes to the existing boat wiring or shore power connectors. It's possible to save a great deal of money on cables and adapters with some careful shopping on EBAY.
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