Can you connect 30 amp and 50 amp service at the same time?

[Circledog]

Hello Guys, we recently took
possession of our new to us 49 Gulfstar Motor Yacht. This is our first big boat and live aboard. It seems that the boat running a 39k air condition, water heater, and dryer at the same time will trip the 50 amp service at the pedestal.
I was wondering if I could connect the 30amp plug to increase the amount of power coming in. I have a 30 amp service plug and cord. The boat was rewired
In 2018, but the previous owner made no mention of the 30 amp system.
Thanks for your input guys.
Paul

 

[psneeld]

Till you or someone else understands thr wiring behind you main electric panel ...I don't suggest it.l

 

[Comodave]

Till you or someone else understands thr wiring behind you main electric pane...I don't suggest it.l

+1. Get a certified marine electrician to check it out. Probably not though.

 

[High Wire]

It all depends on how it’s connected inside the boat. Agree you should get a professional opinion or at least talk to the previous owner.

 

[psneeld]

Not sure it has to be a pro to figure it out, it could be very simple. But someone has to trace some wiring. A very experienced fellow boater might be of some help.

After looking at it, gotta be better than guessing here....

 

[Comodave]

It is probably either one or the other. The 30 amp is most likely there for use to get some power at docks that don’t have 50 amp service.

 

[Comodave]

Not sure it has to be a pro to figure it out, it could be very simple. But someone has to trace some wiring. A very experienced fellow boater might be of some help.

After looking at it, gotta be better than guessing here....

Probably not, but there are a lot of boaters out there that don’t understand the electrical system. I usually recommend a certified marine electrician because it is the safer way to go than trusting someone that may or may not know what they are doing with electricity.

 

[Bacchus]

Do you even know if the 30A inlet is connected to anything aboard or was simply abandoned when the 50A inlet was added?
If you are comfortable and able to trace & diagram what exists you might be able to get a marine electrician to comment or provide options at lower cost.

 

[Comodave]

Do you even know if the 30A inlet is connected to anything aboard or was simply abandoned when the 50A inlet was added?
If you are comfortable and able to trace & diagram what exists you might be able to get a marine electrician to comment or provide options at lower cost.

Good point.

 

[AlanT]

Hello Guys, we recently took
possession of our new to us 49 Gulfstar Motor Yacht. This is our first big boat and live aboard. It seems that the boat running a 39k air condition, water heater, and dryer at the same time will trip the 50 amp service at the pedestal.
I was wondering if I could connect the 30amp plug to increase the amount of power coming in. I have a 30 amp service plug and cord. The boat was rewired
In 2018, but the previous owner made no mention of the 30 amp system.
Thanks for your input guys.
Paul

Congratulations!

It is unlikely that your boat is wired to accept both 120v and 240v simultaneously (also will the marina give you both outlets?).

If you are new to liveaboard it is worth mentioning that many liveaboards are used to load shifting. Ie: we know we can run the A/C and the water heater but not the Washer/Dryer. So we load shift and turn off the water heater for the period that the W/D is running. No big deal, the residual hot water in the tank will be enough to complete the washer cycle and when the washer is done the heater goes back on.

I have load shifted for years on a Bayliner 4788 and prior to that a 49' sailboat. It was manageable. Even when we ran 3 a/c units in the Caribbean/Med.

Good luck ~A

 

[tiltrider1]

First, we are missing some information. Is your Pedestal a 50a 125v arrangement or is it a 50a 125v/250v arrangement. This makes a difference. Second, The code on the Pedestal assumes an either or arrangement and not both. By using both you will be exceeding the safe limits of the wiring on the dock. Now, if your pedestal is a 50a 125/250v and a 30a 125v then it is safe to take one leg off the 50a side and also use the 30a 125v socket. Don't get confused, if the pedestal is a 50a 125v and 30a 125v then you can not safely use both sockets at the same time.

Then as mentioned above there is the on the boat side. While not common I have seen boats that used a 30a for house and a 50a for heat, these set ups use only one leg of the 50a 125/250v socket. These boats were wired this way for a very specific type of cruising and it would be uncommon to find this set up.

If you are already using both legs of a 50a 125/250v set up and it is not enough power then you have a serious problem. That is a 100 amps of power and if you need more then you need to learn how to load shed.

 

[OldDan1943]

Running all those things at the same time?
I suggest you leave the dryer off. (you have a house size dryer?)
Pipe the engine coolant to heat the hot water.
You have an electric stove? It sucks a lot of amps
The fridge is 120vt?
Why even consider a 30amp service? Sort out the wiring and loads. Put the ACs on a separate 50amp service and schedule the other loads on the other newly installed 50amp house service. You may still have to load shed a bit on the house 50amp service a bit but, you should be fine.
On my N46, I had 2X50amp service. The only time I had to worry was when using 3 electric stove burners and oven.... the microwave wouldn't fit. The hot water heater wouldn't fit either.
2x50amp serice will be ideal and you will get use to shedinng/cycling the loads one the house 50amp service.
I am talking theory based upon my experience with my N46 BUT, YOU NEED to get a marine electrician out to design, sort out, replacing wires as necessary and install the 2nd 50amp service. Dont even consider a 30amp service.
The electrician may have to rework the breaker panel.

 

[bglad]

Assuming you have 240/50 service check how the loads are distributed between the two phases. If one side is loaded beyond 50-amps and the other has extra capacity see if it makes sense to rebalance your loads. This means moving 120-volt circuits from one buss to the other.

Hello Guys, we recently took
possession of our new to us 49 Gulfstar Motor Yacht. This is our first big boat and live aboard. It seems that the boat running a 39k air condition, water heater, and dryer at the same time will trip the 50 amp service at the pedestal.
I was wondering if I could connect the 30amp plug to increase the amount of power coming in. I have a 30 amp service plug and cord. The boat was rewired
In 2018, but the previous owner made no mention of the 30 amp system.
Thanks for your input guys.
Paul

 

[psneeld]

Not sure it takes an experienced, qualified marine electrician to figure out the wiring in question, but in my experience, it usually does to understand the advice given about electricity on the internet.

 

[Bmarler]

Wouldn’t a properly sorted power inlet have some sort of interlock to prevent energizing more than one source?

 

[Circledog]

Thanks for the input guys. Was looking for some starting points, and now have them. Thanks

 

[Datenight]

Not sure it takes an experienced, qualified marine electrician to figure out the wiring in question, but in my experience, it usually does to understand the advice given about electricity on the internet.

+1

Rob

 

[BigTime]

Not sure it takes an experienced, qualified marine electrician to figure out the wiring in question, but in my experience, it usually does to understand the advice given about electricity on the internet.

Scary, isn’t it !

 

[OldDan1943]

I strongly suggest a qualified marine electrician just incase 'something' happens down the road, you will have documentation indicating how it was accomplished.

 

[psneeld]

If someone looks behind the 30A power inlet and there are no wires going to it...paying a "qualified marine electrician" to tell you the answer is gonna feel pretty silly.

If not a simple sight to behold...sure bring in the pros.... THEN.

 

[SteveK]

If someone looks behind the 30A power inlet and there are no wires going to it...paying a "qualified marine electrician" to tell you the answer is gonna feel pretty silly.

If not a simple sight to behold...sure bring in the pros.... THEN.

common sense approach has no place in this discussion, so stop it.

 

[tpbrady]

I would think that with two power inlets, there is a switch matrix at the AC panel that allows the 120V service from either the 50A source to power the 120v loads or the 30A source to do the same. In this situation they can’t be used at the same time as the switch won’t let you. I have two 30A shore power connections and to use both, there is a switch which separates the 120v loads into two independent busses. If you connect shore power to the wrong input, it won’t power anything until the switch is thrown and then it only powers some of the loads. Connected to the other input with the switch in the other position combines both 120v busses.

A picture of the AC panel may answer the question. If there is no switch, then call an electrician.

Tom

 

[Osprey69]

Thanks for the input guys. Was looking for some starting points, and now have them. Thanks

Circle we are on our new to us 49' Gulfstar in JAX. PM me and we can chat.

 

[jgwinks]

If someone looks behind the 30A power inlet and there are no wires going to it...paying a "qualified marine electrician" to tell you the answer is gonna feel pretty silly.

If not a simple sight to behold...sure bring in the pros.... THEN.

I doubt it is hooked up, but I'd definitely check that the terminals aren't hot when the 50A is connected. Better to have an open, empty hole where the 30 was than to have live AC terminals waiting to bite somebody.

 

[Ric]

System configuration

The electrical system needs to be configured to handle dual inputs, and it doesn't sound like yours is. We have 30A and 50A shore power terminals. Each feeds its own 120v distribution panel with the heaviest loads on the 50A circuit. You cannot cross-connect/combine the feeds but you can supply both circuits from one input or the other (or from the generator onboard). If your boat does not have separate panels for the separate feeds and a selector switch (ours has Off/Shore 1/Shore 2/Shore 1+2/Genset/Inverter) then you will only be able to draw power from one or the other input.
I suppose you could have a single panel but fed from the rotary selector switch but only if you don't have an inverter on one of the circuits. Our inverter is 4kW and it only supplies the 30A circuit panel.
Setting up the system compliant with ABYC regs is important. A good marine electrician is key. Be warned, there are a lot of "marine electricians" in name only, and their work can literally be dangerous. We had one who wired the hot lead to a ground terminal. Fortunately we were cruising in fresh water at the time and we didn't fry anyone before we sorted that out.

 

[Avalon36]

You can add additional 30 amp service but you will need to install a second panel and split the breakers between the two panels. I have dual 30 amp service with main breakers for each service (A & B) that feed breakers on the main panel. Split big loads.HVAC is fed by A, HW is fed by B and so on. Works well and also provides a level of redundancy.

 

[Circumnavigator]

The short answer is "NO!" The slightly longer answer is that there should be an interlock to prevent using both shore inlets to power the boat.


It is possible, and is common on larger boats, including Fintry, to have an A bus and a B bus with the loads split between the two. When using one shore power inlet, you feed the B bus from the A bus. When using both, you feed the B bus from the second inlet. Of course this requires interlocks so that you can't have both shore power inlets energized while the B bus is connected to the A.


In short, as advised often above, consult someone who knows what they're doing.


I should add that Morning Light, our new to us boat, when purchased, had a 30A and a 50A inlet wired together just downstream of the entrance breakers. That's an invitation to having a 240V short. If the two had both been connected to shore power, on opposite sides of the 240V line (50/50 chance). the breakers should just pop, but I (and the various electrical codes) don't like relying on things that should happen, so it's prohibited to do that and now removed from Morning Light.



Jim

 

[Steve DAntonio]

Normally, you can't connect two dissimilar inlets simultaneously. generally, if it's ABYC compliant, in a set up like this there is a selector switch to switch between the 50 and the 30 (I'm assuming the 50 is a split phase, 120/250, or is it a 50A 120 VAC?), either or but not both, and it's highly unlikely you have what's known as a "split bus" that can accept both at the same time. If they were both 50s, that would be different. Share a photo of the panel and any selector switches for shore power.

Having said that, 50 amps, 120/240, 12 kW, seems like it would be OK for a vessel of this size to run most loads, with maybe some moderate load management.

 

[monti]

30 amp

New to boating… I have a Glen-Denni 65 foot 50 amp. Will I still need a 30 amp cord cruising the Gulf Islands, BC?

 

[SteveK]

New to boating… I have a Glen-Denni 65 foot 50 amp. Will I still need a 30 amp cord cruising the Gulf Islands, BC?

Most every dock has 50A but not enough. Best to carry a 30A adapter, there is one 30 for each berth 99% of the time.
IF your 50 is 240 then start planning on splitters