Have 240 vac shore power, but only 120 vac used

[jr_spyder]

Wow, all this input is wonderful. Thanks.

I'm back on the boat Monday and I'll confirm exactly how I'm wired. It's been a while since I focused on this, because it ain't broke, but I know it's flawed. It was an article about a boat fire started by a shore power inlet corrosion problem that woke me up and made me start asking these questions (I know that issue is mostly a maintenance issue - but if I split the load on my 240v legs I'd have less chance of heat).

An isolation transformer is a whole new education for me. Been reading all morning so far. It might be overkill for my needs, but giving it careful thought. In the few cases when I can't get the right/enough shore power the genset and a mooring is a fine alternative. My only issue with my genset is that it's not well insulated and it's in the center of the boat so it puts heat into the cabin. Running it so I can run aircon is almost counter productive, especially once I'm cool and I can turn it all off, but then the genset just bleeds out it's heat for hours.

A lot to think about. Thanks again for all the input. More from me with the facts when I can confirm them.

[HappyMdRSailor]

Great tool for the price... Not a Fluke, but damn close... I have 2...
Clamp to your heart's content...

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[foufou]

It might be a good idea to follow the wires. By that I mean look at the incoming (power off if you don't like living dangerously) wiring. If it is in fact 240v 4 wire then usually in the US it is white (neutral), green (ground), black (120V), red (120V). Between red and black =240. Between either red or black and neutral is 120. A house panel may use either "hot " leg to power a 120V circuit. In your boat you have to determine if both hot legs are utilized. Follow the wires. If they are not both used then there should be a wire that goes nowhere behind your incoming power plug. Good luck

[Zil]

Could be a PO found most marinas had 50 amp services. So they made a modified shore cable but only wired 1 leg with 120 volt. If that is so, you would be well served to have a new panel using both legs.

[Thumbs Up]

I agree with Zil. I think the previous owner changed something. Probably because their dock only had 110v. It might be as simple as switching a wire back. Look for a stacked connection and an empty post over by those big fuses or behind your panel.

[jr_spyder]

Hi all,

I got on the boat today and dove into the facts.

The 50 amp inlet only has three wires coming out of the back and into the boat. Black, white and green; so 1 hot leg, neutral and ground. There is a forth lug for another hot leg wire but nothing is connected to it. All the wires are 6 awg.

The AC breaker in my main panel is only wired for 120v. Also the safety switch that selects power from either shore or genset is wired for 120v. Its quite clear this panel has never seen 240v.

I agree with the notion that a previous owner changed the inlet to a standard 50 amp setup for ease of plugging in at marinas, but kept the rest of the boat at 120v.

I understand the idea but have no plans to change the system to a properly wired and balanced 240v. I've never had a single problem with any of this so don't see the need for what would be a very extensive change. Also, I've been reducing power usage on board, not increasing it, which is a better overall course and investment I think.

I'll add the correct ELCI breaker at the inlet and a galvanic isolator and sleep better for having these safety features that I don't have now.

Thanks again for all the help here. I've learned a few things and now have a good plan.

JR

[DotDun]

Originally Posted by jr_spyder

Hi all,

I got on the boat today and dove into the facts.

The 50 amp inlet only has three wires coming out of the back and into the boat. Black, white and green; so 1 hot leg, neutral and ground. There is a forth lug for another hot leg wire but nothing is connected to it. All the wires are 6 awg.

The AC breaker in my main panel is only wired for 120v. Also the safety switch that selects power from either shore or genset is wired for 120v. Its quite clear this panel has never seen 240v.

I agree with the notion that a previous owner changed the inlet to a standard 50 amp setup for ease of plugging in at marinas, but kept the rest of the boat at 120v.

I understand the idea but have no plans to change the system to a properly wired and balanced 240v. I've never had a single problem with any of this so don't see the need for what would be a very extensive change. Also, I've been reducing power usage on board, not increasing it, which is a better overall course and investment I think.

I'll add the correct ELCI breaker at the inlet and a galvanic isolator and sleep better for having these safety features that I don't have now.

Thanks again for all the help here. I've learned a few things and now have a good plan.

JR

Sounds like a good plan!

[Kentb]

In typical homes, there are two legs coming into a breaker box. Most circuits are 120V, but a few high-load circuits are double-width breakers that combine the two legs to power items such as Air conditioning, heat, hot water, electric range, dryer, etc.
On your boat, it is apparent that there are no devices that demand a 240V input.
So what you will probably want to do is have all of your Air Conditioning on one leg, and Battery Charger, and all other necessities on another. This way the load is not all on one hot wire in your shore power cord. If you only have a 30 amp outlet to plug into, you may have to continue to regulate when you turn on air conditioning or your charger.
As all others say, of course consult a professional. There are always some things that should be verified, like polarity, bonding, etc... And you need somebody good at using a meter and troubleshooting and who knows what to look for.

[ranger58sb]

Originally Posted by jr_spyder

Hi all,

I got on the boat today and dove into the facts.

The 50 amp inlet only has three wires coming out of the back and into the boat. Black, white and green; so 1 hot leg, neutral and ground. There is a forth lug for another hot leg wire but nothing is connected to it. All the wires are 6 awg.

The AC breaker in my main panel is only wired for 120v. Also the safety switch that selects power from either shore or genset is wired for 120v. Its quite clear this panel has never seen 240v.

I agree with the notion that a previous owner changed the inlet to a standard 50 amp setup for ease of plugging in at marinas, but kept the rest of the boat at 120v.

Good feedback; always useful to close the info loop on issues like this...

-Chris

[HappyMdRSailor]

Originally Posted by jr_spyder

Hi all,

I got on the boat today and dove into the facts.

The 50 amp inlet only has three wires coming out of the back and into the boat. Black, white and green; so 1 hot leg, neutral and ground. There is a forth lug for another hot leg wire but nothing is connected to it. All the wires are 6 awg.

Originally Posted by HappyMdRSailor

Jr-

Sounds like you have an empty terminal on the backside of your 250V/50A inlet...

And if you have 6 AWG all the way to your main panel, you're probably good... Still suggest you get a clamp on ammeter... The info gleaned can be invaluable...