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Old 04-07-2022, 14:38   #1
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30 amp to 50 amp adapter???

My boat has 30 amp shore power. If I connect my 30 amp cord to an adapter in order to plug into a 50 amp shore power station, do I now have 50 amp service available on my boat? Note: I would only do this if in a transient slip that only had a 50 amp outlet available. And... is this safe to do? Just curious.
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Old 04-07-2022, 14:49   #2
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Re: 30 amp to 50 amp adapter???

Suspect you have a 30 amp main breaker on the boat. So that would dictate max amp draw.
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Old 04-07-2022, 15:02   #3
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Re: 30 amp to 50 amp adapter???

There’s all sorts of scary and gross adapters that are somehow acceptable for sale because it’s for boats. I’ve got 15A to 30A, 20A to 30A, and worst of all, a 30A twist lock to 15A socket adapter. But they’re all useful to have on the boat.

In my case, I have a 32A Inlet RCD breaker, and then use my inverter/charger to make up for weaker supplies (say I plug into 15A).
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Old 04-07-2022, 15:05   #4
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Re: 30 amp to 50 amp adapter???

Just to be clear in an answer to your question - No. you can use an adapter that allows for a physical connection from 50 to 30 but it doesn’t magically make 50 amps available to your boat in a safe manner. As was previously noted your input circuitry will limit you to 30 amp draw.
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Old 04-07-2022, 20:23   #5
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Re: 30 amp to 50 amp adapter???

Quote:
Originally Posted by BozSail View Post
My boat has 30 amp shore power. If I connect my 30 amp cord to an adapter in order to plug into a 50 amp shore power station, do I now have 50 amp service available on my boat? Note: I would only do this if in a transient slip that only had a 50 amp outlet available. And... is this safe to do? Just curious.
No, it is not safe. The wiring inside your boat is only designed to handle 30 amps. 50 amp wiring is a much heavier gauge wire. Yes, your main breaker is designed to trip at 30 amps, but on the slim chance is doesn’t, you are inviting an electrical fire.
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Old 05-07-2022, 03:54   #6
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Re: 30 amp to 50 amp adapter???

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No, it is not safe. The wiring inside your boat is only designed to handle 30 amps. 50 amp wiring is a much heavier gauge wire. Yes, your main breaker is designed to trip at 30 amps, but on the slim chance is doesn’t, you are inviting an electrical fire.
At the point one considers a circuit unsafe if it would cause a fire when the circuit breaker fails, nearly every electrical circuit everywhere is unsafe. For example, like most boats my 30 amp service goes to a panel which serves several 15 amp circuits served by circuit breakers. The wire in the 30 amp circuit is much heavier gauge than the 15 amp circuits, so if any of those 15 amp breakers failed closed while the circuit was trying to pull more than 15 amps, then under the above logic those circuits would be unsafe. Heck, in most houses you have 200+ amp service feeding 15 amp breakers, so on the slim chance any of those breakers failed closed you could pump 200 amps through wire sized for 15 amps!

As an electrical engineer I have a 50 to 30 amp plug for use when I'm in a location with no 30 amp service and use it without reservation. The only edge case where this is any less safe than using a 30 amp plug in a 30 amp service is the extremely rare case where you have some kind of short between the 50 amp shore power breaker and the 30 amp breaker at the entrance to the boat AND the short is of the very unique kind that is more than 30 but less than 50 amps (since an actual short would trip the 50 amp shore breaker). At which point the shore power cord might catch fire. If that happens I figure it's my time to go, there are thousands of much more likely potential safety issues I'm better served worrying about
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Old 05-07-2022, 06:31   #7
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Re: 30 amp to 50 amp adapter???

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Originally Posted by redneckrob View Post
At the point one considers a circuit unsafe if it would cause a fire when the circuit breaker fails, nearly every electrical circuit everywhere is unsafe. For example, like most boats my 30 amp service goes to a panel which serves several 15 amp circuits served by circuit breakers. The wire in the 30 amp circuit is much heavier gauge than the 15 amp circuits, so if any of those 15 amp breakers failed closed while the circuit was trying to pull more than 15 amps, then under the above logic those circuits would be unsafe. Heck, in most houses you have 200+ amp service feeding 15 amp breakers, so on the slim chance any of those breakers failed closed you could pump 200 amps through wire sized for 15 amps!

As an electrical engineer I have a 50 to 30 amp plug for use when I'm in a location with no 30 amp service and use it without reservation. The only edge case where this is any less safe than using a 30 amp plug in a 30 amp service is the extremely rare case where you have some kind of short between the 50 amp shore power breaker and the 30 amp breaker at the entrance to the boat AND the short is of the very unique kind that is more than 30 but less than 50 amps (since an actual short would trip the 50 amp shore breaker). At which point the shore power cord might catch fire. If that happens I figure it's my time to go, there are thousands of much more likely potential safety issues I'm better served worrying about

tldr: your breaker limits this
no you will not catch fire
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Old 05-07-2022, 07:15   #8
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30 amp to 50 amp adapter???

In industry, we are speaking of tolerance to “single fault” failures. We can safely tolerate a likely fault; but likely only one at a time. As device, or user, reliability decreases, that philosophy may not be good enough.

If the pedestal 30 A breaker is locked-up/corroded, you have used up a fault already.
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Old 05-07-2022, 08:05   #9
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Re: 30 amp to 50 amp adapter???

Plugging into a source with 50a available does not mean you are suddenly drawing any more than you do plugged into a 30a source. Your devices DRAW what they need, it is NOT forced upon them. Unless your boat is tripping its main breaker all the time, your boat does not draw more than 30a. Yes, there can be Worst Case scenarios that result in a fire, but if the boat is well maintained and the wiring is solid it will be safe.

Check out SmartPlug.
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Old 05-07-2022, 08:08   #10
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Re: 30 amp to 50 amp adapter???

Doesn't make it 50 amp as wiring , breaker etc are sized for 30 amp. Will work fine for normal loads below 30 amp though.
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Old 05-07-2022, 08:29   #11
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Re: 30 amp to 50 amp adapter???

Quote:
Originally Posted by Chuck34 View Post
No, it is not safe. The wiring inside your boat is only designed to handle 30 amps. 50 amp wiring is a much heavier gauge wire. Yes, your main breaker is designed to trip at 30 amps, but on the slim chance is doesn’t, you are inviting an electrical fire.
A 30 amp breaker trips at about 37 amps. This is stated on the breaker.

I would be careful about using too much current using a 50 to 30 amp adaptor.

In addition Marinco 30 amp inlets are rated for 24 amps continuous, 30 amps for 3 hours only.
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Old 05-07-2022, 09:53   #12
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Re: 30 amp to 50 amp adapter???

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Originally Posted by solana707 View Post
tldr: your breaker limits this
no you will not catch fire
Time to go back to electricity basics folks. A breaker at your boat can't protect your shore power cord against a short before the boat's breaker. So yes, if your shore power cord shorts and the shore power breaker is larger than your cord is rated for or frozen closed, your shore power cord could catch fire. But as I explained, if one could be bothered to read an entire two paragraphs, that's an edge case.

BTW, turns out complicated topics like electrical safety might take two paragraphs to explain, perhaps even several years of dedicated education or apprenticeship. If two paragraphs is too long for one to read I would submit one has no business making any comments about electrical safety! Saying tldr and then pontificating on what one just admitted they couldn't be bothered to read is.... incredibly annoying at best and certainly doesn't paint one in the best light.
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Old 05-07-2022, 12:39   #13
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Re: 30 amp to 50 amp adapter???

When I plug into 50amp it’s always a 240V connection. The 30A is 120V. A physical adapter doesn’t solve this issue. There may be some 50A 120V but it’s not the norm at marinas I visit
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Old 05-07-2022, 12:56   #14
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Re: 30 amp to 50 amp adapter???

A 50/240 male to 30/120 female adapter merely connects ONE of the two hots on the male end to the hot on the female end (along with the neutral and ground).
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Old 05-07-2022, 13:10   #15
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Re: 30 amp to 50 amp adapter???

Makes sense
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