Twin 30 amp Vessel on single 30 amp Shorepower

[RossWilson]

Hello Everyone:
I've reviewed countless posts on this general subject, but have yet to find an answer to my quandary. Maybe my challenge is too simple?


My 2006 Mainship 34T features twin 30 amp power cords for a total of 60 amps with corresponding input receptacles on the transom. And when I have double 30 amp shore power outlets, I've obviously no problems. But when I'm faced with a town harbour that refuses to install another outlet, what can I do to properly power my boat?


I have a "splitter", along with a few other adapters (the purpose of which I have no knowledge), but does this not just divide the 30 amps into 2 x 15 amp circuits? And will this be sufficient to power all the heavy draw equipment aboard, including 2 C/A units, a 2-burner electric stove, water heater and assorted other pumps, chargers and inverters? Would the double 15 amp sources combine to provide the power on demand?



Are there any other solutions or ideas? Thanks.

 

[Comodave]

The splitter just enables power to flow to both inputs. It does not split the 30 amps in half evenly unless the power demand just happens to be 2 15 amp draws. Basically you have 30 amps to use across your whole panel, but only up to 30 amps. Your boat most likely can draw much more than 30 amps with 2 A/Cs, battery charger, refer, stove, etc. you will have to manage your power usage so that you don’t draw more than 30 amps. You will have to turn things on and off to keep it under 30. Really you should not be using the full 30 amps for any length of time as the connections will overheat. You are really limited to about 24 amps for long term usage in order to be safe. We have 2 30 amp inlets and even with both we still sometimes have to manage our power usage if both A/Cs are running.

 

[Bacchus]

Does the marina also have 50A outlets?
If so you can get a splitter from either 50A 120V to 2 - 30A 120V or if 50A 240V you can get a different splitter 50A 240V to 2- 30A 120V
If not and all you have available is one 30A 120V that's all you get is 30A. I run my '08 34HT on one 30A cord much of the time. I have to watch my loads but can run 1A/C along with water heater & charger. Turn WH off and I can run 2 A/Cs but not much else. Stove or microwave are normally short duration and I shut down ACs.

 

[RossWilson]

Thanks, Dave, for your rapid reply. That's good to know. So, instead of 60 amps (2x30) to power my boat with 2 shore power outlets on the dock, wherein any given piece of equipment can draw the needed power, I have only 30 amps total. Careful management indeed!

 

[O C Diver]

Does the power pedestal have a 50 amp outlet? If so, there is a Y splitter that gives you two 30 amp outlets with full amperage for your 30 amp cords.

If you use a Y adapter that that splits a single 30 amp outlet into two 30 amp outlets, the total amperage combined is only 30 amps. With the Y adapter you can pull 30 amps through one or the other cord, but not both at the same time. You can draw some amps from each cord, but the combined total can't exceed 30 amps.

Ted

 

[RossWilson]

Hey Don: Good to hear from you. The town provides only one 30-amp outlet. So, that's what I get. The clerk said he'd try to facilitate my need once the docks are back in the water, but couldn't guarantee it.


I have several adapters aboard, the purpose of each I have no clear idea. But by the end of this string, I hope to be a little wiser.


It's just careful management or power use. Thanks.

 

[RossWilson]

Thanks, Ted. I understand. Apparently, the pedestal has only one 30 amp outlet. It's a public marina (with security), and maybe they aren't accustomed to accommodating the growing needs of the boating public?

 

[DavidM]

I owned a 2006 34T for a half dozen years. On the main A/C panel there is a combiner switch that ties one of the two shore power inlets to the other (and properly isolates the other one so it doesn't shock anyone) and supplies that 30A power to both AC busses. I didn't have A/C or an electric stove so it worked fine and easily lived with 30A.

There isn't an easy solution for your power problem given you only have one 30A outlet on the marina's power pedestal and your AC loads are much higher than 30A with two A/Cs, an electric stove and a water heater. All I can offer is to carefully manage your power to stay under 30A total.

One A/C probably draws about 15A and one of the stove's burners probably draws almost that much. So first never use more than one A/C at a time. Do you need two A/Cs in Ontario? Do your cooking with one burner and heat your water when you are finished cooking. If the 30A main panel breaker trips with the stove and A/C on, shut down the A/C while you cook. The water heater draws about 12A so you should be ok with that on while the A/C is on.

A good solution would be a 50A/240/120V power socket at the marina with a Y splitter that would split the 240V power into two 30A circuits to feed your boat. Talk to your marina manager. If you are a long term customer they may wire this up for you. Depending on how the marina is wired it may not be hard to do. But if not,......

David

 

[High Wire]

All manual load management when going 2-30s down to one.
Make a table of loads with different combinations that add up to 30 amps.
For example:
1-16 Kbtu ac, blower, and water pump 16 amps
1 stove burner- 10 amps
Total = 26 amps = ok
Etc, etc.
What you don’t want is to flip on loads and go over. Permanent damage happens quickly and is dangerous.

 

[caltexflanc]

If so, there is a Y splitter that gives you two 30 amp outlets with full amperage for your 30 amp cords.

Um, no, If you exceed 50 amps total draw on that, the breaker at the dock will trip. Plus, at 50 amp rating, it will not protect your 30 amp cord either.

On these matters, it more advisable to consult a source like Calder's "Boat Owners Mechanical and Electrical Manual" than querying a bunch of us anonymous folks on an internet forum.

 

[syjos]

I don't know why boat builders split the AC panel and wire it to two 30 amp inlets instead of installing a selector switch to either run each panel from two separate shore cords or parallel from one cord.

To save a few bucks?

On Sandpiper, I have the AC panel split (A and B) with selector switches to:

1. Operate both sides A and B from one 30 amp shore power, 5.5 Kw generator or 3000 watt inverter.

2. Operate side A from one 30 amp shore cord and side B from a second 30 amp cord.

3. Operate side A from 30 amp shore and side B from inverter or generator.

I also have Sandpiper wired with shore inlets at the front of the PH and cockpit to be able to plug in a combination of cords at the front and back of the boat.

Since installing a Victron Inverter with Power Assist, I don't use the third option any more. The inverter when on shore power automatically reduces charging when max power is required. If more power is required, the Victron automatically switches to invert mode, matches the shore power wave form and combines the inverter power and shore power to create around 50 to 55 amps.

I don't run in the combined mode for long because of the battery drain, but it's handy to be able to operate high demand things like the microwave and Keurig without turning other things off.

 

[caltexflanc]

I don't know why boat builders split the AC panel and wire it to two 30 amp inlets instead of installing a selector switch to either run each panel from two separate shore cords or parallel from one cord.

To save a few bucks?

On Sandpiper, I have the AC panel split (A and B) with selector switches to:

1. Operate both sides A and B from one 30 amp shore power, 5.5 Kw generator or 3000 watt inverter.

2. Operate side A from one 30 amp shore cord and side B from a second 30 amp cord.

3. Operate side A from 30 amp shore and side B from inverter or generator.

I also have Sandpiper wired with shore inlets at the front of the PH and cockpit to be able to plug in a combination of cords at the front and back of the boat.

Since installing a Victron Inverter with Power Assist, I don't use the third option any more. The inverter when on shore power automatically reduces charging when max power is required. If more power is required, the Victron automatically switches to invert mode, matches the shore power wave form and combines the inverter power and shore power to create around 50 to 55 amps.

I don't run in the combined mode for long because of the battery drain, but it's handy to be able to operate high demand things like the microwave and Keurig without turning other things off.

One of many things I liked from the start on our old Hatteras was the main panels were set up just like that. 50amp/240 to be sure, but the same flexibility.

 

[Bacchus]

Syjos
Mainship at least the later years including Ross's has the transfer switch to allow running off one cord and manually managing loads. It is handy when draws are manageable and only one cord needed.

 

[Pau Hana]

Hello Everyone:
I've reviewed countless posts on this general subject, but have yet to find an answer to my quandary. Maybe my challenge is too simple?


My 2006 Mainship 34T features twin 30 amp power cords for a total of 60 amps with corresponding input receptacles on the transom. And when I have double 30 amp shore power outlets, I've obviously no problems. But when I'm faced with a town harbour that refuses to install another outlet, what can I do to properly power my boat?


I have a "splitter", along with a few other adapters (the purpose of which I have no knowledge), but does this not just divide the 30 amps into 2 x 15 amp circuits? And will this be sufficient to power all the heavy draw equipment aboard, including 2 C/A units, a 2-burner electric stove, water heater and assorted other pumps, chargers and inverters? Would the double 15 amp sources combine to provide the power on demand?



Are there any other solutions or ideas? Thanks.

We were in the same boat (metaphorically speaking) on our boat: being liveaboards, doing the amp dance was getting old. I replaced our twin 30A inlets with a single 50/250 inlet, and split the incoming power into 2 50A/125v legs via an isolation transformer.

The install was very simple- change the wires feeding the 2 power panels (from the isolation transformer) to 6 gauge, change the main breakers on the panels from 30A to 50A, and that’s basically it.

Benefits- we now have 2 50A panels, and we’re electrically isolated against steamy current in the water. We also don’t trip ELCI dock breakers.

 

[Comodave]

But he said his dock only has 1 30 amp outlet per boat. So 50 amp isn’t a solution for him. His solution is either convince the marina to install more power or learn to live with it.

 

[wkearney99]

I have a "splitter", along with a few other adapters (the purpose of which I have no knowledge), but does this not just divide the 30 amps into 2 x 15 amp circuits? And will this be sufficient to power all the heavy draw equipment aboard, including 2 C/A units, a 2-burner electric stove, water heater and assorted other pumps, chargers and inverters? Would the double 15 amp sources combine to provide the power on demand?

Are there any other solutions or ideas? Thanks.

If the dock post has only a 30A socket then that's all you can pull at one time. You can use a 30A splitter, but that's not going to magically increase what the dock can provide. It'd then be up to you to manage your on-boat power consumption.

As in, turn off the breaker to the AC when you need to use something else. It's a good practice anyway to keep high-wattage devices off when they're not in use. Learn how long it takes for your water heater to get up to temp, plan for that and keep it off otherwise. There's no point in wasting the power keeping the water hot when it's not needed, especially when it might conflict with powering other things on board.

One thing you want to avoid is exceeding the dock breaker's capacity on a regular basis. As in, tripping the breaker all the time. This opens the door to the bad habit of accepting electric problems, as opposed to being concerned about them and eliminating the problem. Because electrical fires are among the many reasons boats and lives are lost.

 

[SteveK]

Was wondering if twin 30 amp cords are each running the same 120V feed line or a different 120V lines to produce a 240V outlet onboard.
I note two separate panels suggests no 240.

Then a 50A/240 cable does have 240 available, so with two panels does one feed line go to each panel.

I guess wondering why two panels in any application, why not same as a house panel which can balance loads from the 2 incoming lines, and allows 240 too.

 

[DavidM]

Was wondering if twin 30 amp cords are each running the same 120V feed line or a different 120V lines to produce a 240V outlet onboard.
I note two separate panels suggests no 240.

Then a 50A/240 cable does have 240 available, so with two panels does one feed line go to each panel.

I guess wondering why two panels in any application, why not same as a house panel which can balance loads from the 2 incoming lines, and allows 240 too.

Your question is mostly theoretical since the OP's boat (of which I owned one several years ago) only has two 30A panels. All of the wiring to those panels is designed for 30A (probably 10 gauge) so it would not be suitable to feed it from a 50A/240/120V source and feed one buss with one leg of 120V and the other buss with the other leg. The wire isn't big enough to carry 50A although it might not be that big of a chore to rewire it all for 50A.

Marinco makes a 50A/240/120V splitter that feeds two 30A/120V cables and I believe that these have a 30A internal breaker that protects the 30A cable, but not sure.

David

 

[Comodave]

Your question is mostly theoretical since the OP's boat (of which I owned one several years ago) only has two 30A panels. All of the wiring to those panels is designed for 30A (probably 10 gauge) so it would not be suitable to feed it from a 50A/240/120V source and feed one buss with one leg of 120V and the other buss with the other leg. The wire isn't big enough to carry 50A although it might not be that big of a chore to rewire it all for 50A.

Marinco makes a 50A/240/120V splitter that feeds two 30A/120V cables and I believe that these have a 30A internal breaker that protects the 30A cable, but not sure.

David

But he said he only has 1 30 amp outlet on the dock so a 50 amp splitter is a moot point.

 

[DavidM]

But he said he only has 1 30 amp outlet on the dock so a 50 amp splitter is a moot point.

Like I said, my answer was theoretical and wasn't meant to reflect the OP's circumstances.


We do this all of the time on this and other forums I visit. An OP asks a question and it quickly diverges to what might be rather than what is. Nature of the beast.


David

 

[rgano]

Like I said, my answer was theoretical and wasn't meant to reflect the OP's circumstances.


We do this all of the time on this and other forums I visit. An OP asks a question and it quickly diverges to what might be rather than what is. Nature of the beast.


David

Sticking relentlessly to the OPs' questions, which are often adequately answered in short order, would make for less interesting thread following IMHO.

 

[syjos]

Sticking relentlessly to the OPs' questions, which are often adequately answered in short order, would make for less interesting thread following IMHO.

I agree 100%

 

[FF]

To live well on 30a , either a bunch of CB flipping ir a load shedding system is required .

Load shedding is simply a relay that opens a circuit when a different circuit operates.

An example is a hot water heater that gets its power cut when the air cond thermostat switches it on.

Grainger used to have NO (normally open) ad NC (normally closed) relays that could be used either way for about $60.00 , but its been a while since I have had a catalog.


Good hunting,

 

[syjos]

To live well on 30a , either a bunch of CB flipping ir a load shedding system is required .

Load shedding is simply a relay that opens a circuit when a different circuit operates.

An example is a hot water heater that gets its power cut when the air cond thermostat switches it on.

Grainger used to have NO (normally open) ad NC (normally closed) relays that could be used either way for about $60.00 , but its been a while since I have had a catalog.


Good hunting,

The Victron Multiplus inverter has that feature. It has a separate output that is live when on shore power/generator and automatically turns off when on inverter.

I run the hotwater tank on that output.

 

[DavidM]

The Victron Multiplus inverter has that feature. It has a separate output that is live when on shore power/generator and automatically turns off when on inverter.

I run the hotwater tank on that output.

That is an interesting feature. Do you run that circuit through a breaker on the main panel that feeds the hot water heater. The water heater is typically on a 20A breaker and I suspect that the separate output on the Victron can source 30A.

Also if it is a breaker on the main panel, I presume that you have cut the buss to isolate it from the main AC feed or set up a separate breaker on the panel.

David

 

[syjos]

That is an interesting feature. Do you run that circuit through a breaker on the main panel that feeds the hot water heater. The water heater is typically on a 20A breaker and I suspect that the separate output on the Victron can source 30A.

Also if it is a breaker on the main panel, I presume that you have cut the buss to isolate it from the main AC feed or set up a separate breaker on the panel.

David

You are correct, the auxiliary output is rated at 32 amps.

Yes, I have it wired to the water heater breaker on the main panel, which is isolated from the AC bus.

It is a very handy feature.

 

[OldDan1943]

I have a 34AT with 2 30 amp cables. One is dedicated to the 2 A/Cs.
That leaves me with a 30 amp service to support the rest of the boat.
I have a an electric 3 burner stove with electric oven, HW heater, microwave and the usual galley 120vt outlets. Start cooking and plug in toaster.... the 30 amp breaker trips. The amp meter is in the pilot house.... I also have a 1800 amp inverter... I can put the microwave OR the 120 vt galley outlets on the inverter. A little cumbersome but, it works.
Load shedding is the only way to make this system work well for me.
I actually had a another amp meter installed in the galley area so I can easily keep an eye on the amp usage and shed loads via the electric stove or shutting down the electric water heater. This has worked out well for me.
Trying to run the washer/drier .... Not going to happen until there is very little power usage.
Another point for concern, the coffee pot uses lots of amperage too so, timing is important.

 

[syjos]

I have a 34AT with 2 30 amp cables. One is dedicated to the 2 A/Cs.
That leaves me with a 30 amp service to support the rest of the boat.
I have a an electric 3 burner stove with electric oven, HW heater, microwave and the usual galley 120vt outlets. Start cooking and plug in toaster.... the 30 amp breaker trips. The amp meter is in the pilot house.... I also have a 1800 amp inverter... I can put the microwave OR the 120 vt galley outlets on the inverter. A little cumbersome but, it works.
Load shedding is the only way to make this system work well for me.
I actually had a another amp meter installed in the galley area so I can easily keep an eye on the amp usage and shed loads via the electric stove or shutting down the electric water heater. This has worked out well for me.
Trying to run the washer/drier .... Not going to happen until there is very little power usage.
Another point for concern, the coffee pot uses lots of amperage too so, timing is important.

This is where an inverter with Power Assist will come in hand, adding additional power to the shore AC. It reduces load shedding requirements.

 

[diver dave]

I have a 34AT with 2 30 amp cables. ....... the 30 amp breaker trips. The amp meter is in the pilot house.......timing is important.

Here is the portable option for measuring AC current.

https://store.ncd.io/product/wifi-ac-current-monitor-android-ios/

ps: I have two late teen daughters. If its not on a phone, it doesn't exist.

 

[RossWilson]

I owned a 2006 34T for a half dozen years. On the main A/C panel there is a combiner switch that ties one of the two shore power inlets to the other (and properly isolates the other one so it doesn't shock anyone) and supplies that 30A power to both AC busses. I didn't have A/C or an electric stove so it worked fine and easily lived with 30A.

There isn't an easy solution for your power problem given you only have one 30A outlet on the marina's power pedestal and your AC loads are much higher than 30A with two A/Cs, an electric stove and a water heater. All I can offer is to carefully manage your power to stay under 30A total.

One A/C probably draws about 15A and one of the stove's burners probably draws almost that much. So first never use more than one A/C at a time. Do you need two A/Cs in Ontario? Do your cooking with one burner and heat your water when you are finished cooking. If the 30A main panel breaker trips with the stove and A/C on, shut down the A/C while you cook. The water heater draws about 12A so you should be ok with that on while the A/C is on.

A good solution would be a 50A/240/120V power socket at the marina with a Y splitter that would split the 240V power into two 30A circuits to feed your boat. Talk to your marina manager. If you are a long term customer they may wire this up for you. Depending on how the marina is wired it may not be hard to do. But if not,......

David

Thanks, David. I don't suppose you have a photo of this "combiner switch"?


I normally don't use both AC units simultaneously. So, it may indeed be manageable. Since the slip is in a town harbour and not an actual full service marina, I can't depend on their accommodating me with an additional 30amp outlet, though the manager said he would discuss the issue with their electrician. He claims that if there's sufficient power to the dock, he'd have another installed.