Twin 30 amp Vessel on single 30 amp Shorepower

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High Wire said:
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.
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Thanks, Archie. Good advice. Better safe than sorry,
 
caltexflanc said:
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.
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Thanks, George. Better safe than sorry indeed. Nevertheless, it's good to gather assorted opinions so I can more effectively ask the right questions.
 
syjos said:
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.
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That seems logical, Syjos.
 
Bacchus said:
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.
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Hey Don: Do you happen to have a photo of this "transfer switch"? Or can you describe it? In such a scenario, would I still use a Y-splitter cable so as to plug in both transom receptacles?
 
Pau Hana said:
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.
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That's not a bad idea, Peter. However, wouldn't one find 30 amp shore power at marinas (including twin 30's) more prevalent than 50 amp, let alone twin 50's? If so, I suppose I could use some type of adapter to accommodate?
 
Comodave said:
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.
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Agreed, Dave. Thanks.
 
wkearney99 said:
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.
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Good advice, Bill. That's seems to be the general consensus of opinion. Get the marina to install another 30amp outlet for me, or manage the power.
 
DavidM said:
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
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Thanks, David. My 2006 Mainship 34T has 2 panels - one AC and one DC. So, presumably, both 30 amp cables terminate at the one AC panel. Someone else here suggested that there's a "combiner switch" on the panel. I just have to learn how it works exactly.
 
rgano said:
Sticking relentlessly to the OPs' questions, which are often adequately answered in short order, would make for less interesting thread following IMHO.:dance:
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Agreed, Rich. I learn a lot more than I'd planned as a result of the extraneous verbiage. :)
 
FF said:
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,
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Thanks, FF. With such a system, would the circuit that was programmed to open when another was closed, automatically close again when the other was opened? Or would I have to manually re-set the one that opened?
 
OldDan1943 said:
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.
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Thanks for your comments, Old Dan.
 

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Thanks everyone. As usual, this has been most informative. I called (yes - on the land-line) the harbour manager to inquire regarding the possibility of another 30 amp outlet being installed. He had said in his emails that only one was possible since that was all he could guarantee. However, on the phone, he said once the docks are re-installed in early May, he would address the issue with the town electrician. If there's sufficient power at the docks, he said he'd have it installed. Hallelujah!
 
danderer said:
The 34T transfer switch is outlined in the picture below.

It allows the current coming in on shore power line 1 to feed both sides of the panel.

I'd also suggest getting a copy of https://www.amazon.com/Boatowners-Mechanical-Electrical-Manual-4/dp/0071790330/ref=asc_df_0071790330 to understand things better.
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Thanks, Danderer. That appears to be exactly like my own. I seem to recall that it's a horizontal slide that moves from generator to transfer. It's been my understanding (based on the previous owner's brief explanation) that its normally in the "transfer" position, unless I'm operating the generator. Is this correct?


If this is right, then may I assume that since power can be shifted, or transferred from one side to the other circuit, then the side that needs, say, 35 amps, can draw the additional 5 amps from the other side? Or am I way off base here?


The book you recommend looks good. Is it current? Do you happen to know when it was published? I ask because before buying a boat a few years ago (my previous Monk 42), I purchased David Pascoe's "Mid Size Power Boats". Though it was truly educational, I found that since it had been published many years ago, it failed to include newer technology and vessels.
 
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By the way, Danderer, does this mean that I don't really need to use the Y-splitter so that power is fed to both transom recepticles?
 
Ross:

I sold my 34T about ten years ago. But if you post a picture of your AC panel, mostly the top part, I can see if it is the same with a combiner switch and help you figure out how to use it. Mine was a 2006 and so was yours. I would be shocked if they weren't the same, but boat builders have done stranger things.


Also mine had two 30A shore power inlets on the port side inside the transom, with a 30A breaker for each inlet. As far as I can recall, one of the shore power sources would combine with the other panel, leaving the other shore power inlet disconnected. You couldn't do the reverse.


David
 
DavidM said:
Ross:

I sold my 34T about ten years ago. But if you post a picture of your AC panel, mostly the top part, I can see if it is the same with a combiner switch and help you figure out how to use it. Mine was a 2006 and so was yours. I would be shocked if they weren't the same, but boat builders have done stranger things.


Also mine had two 30A shore power inlets on the port side inside the transom, with a 30A breaker for each inlet. As far as I can recall, one of the shore power sources would combine with the other panel, leaving the other shore power inlet disconnected. You couldn't do the reverse.


David
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Your description of the shore power receptacles and breakers on the port inside transom is identical to mine. Unfortunately, I don't have a photo of the AC panel, and it's in heated storage about 3 hours away. I'll snap one when I'm next up there to post here. Thanks again for your help.
 
Ross
I think DAnderer & DMarchand have pointed you in the right direction.
I'll attach what I have re pics of the panel & switches.
To operate on one cord you need to connect it to Shore power inlet #1 turn on #1 breaker, turn off Breaker for #2, slide the transfer breaker cover to the right covering breaker #2 and then turn on the Transfer breaker - you should now have power to both sides of the panel. You need to manually manage loads with the individual circuit breakers. By running individual items and monitoring Amp draw with the A meter you can get a feel for what you can run together. Best to shoot for around 24-25 A for long term running.
To run on the Gen turn off #1 breaker and slide the Gen cover to the left then turn the Gen breaker on. You can power both sides by using the transfer function above.
Best to start the gen w/o a load, let it run for a couple mins and then add the loads. Best to run Gen for 30 - 60 min minimum under load to heat & dry out the gen coils. If charging battys I try to do it while cooking, heating water and/ or heating / cooling with A/Cs / heat pumps to have sufficient load.
Best practice for shut down is to remove the loads and let the gen run for 5 -10 mins to stabilize temps before shutting down.
Any questions on above let us know.
 

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Yep, Don's pic, attached diagram and description of how to use the transfer switch is exactly what I had on my 2006 34T. A little different because I had no generator.

David
 
Bacchus said:
Ross
I think DAnderer & DMarchand have pointed you in the right direction.
I'll attach what I have re pics of the panel & switches.
To operate on one cord you need to connect it to Shore power inlet #1 turn on #1 breaker, turn off Breaker for #2, slide the transfer breaker cover to the right covering breaker #2 and then turn on the Transfer breaker - you should now have power to both sides of the panel. You need to manually manage loads with the individual circuit breakers. By running individual items and monitoring Amp draw with the A meter you can get a feel for what you can run together. Best to shoot for around 24-25 A for long term running.
To run on the Gen turn off #1 breaker and slide the Gen cover to the left then turn the Gen breaker on. You can power both sides by using the transfer function above.
Best to start the gen w/o a load, let it run for a couple mins and then add the loads. Best to run Gen for 30 - 60 min minimum under load to heat & dry out the gen coils. If charging battys I try to do it while cooking, heating water and/ or heating / cooling with A/Cs / heat pumps to have sufficient load.
Best practice for shut down is to remove the loads and let the gen run for 5 -10 mins to stabilize temps before shutting down.
Any questions on above let us know.
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As usual, Dave, great understandable detail. How can I go wrong? When I start the gen in the spring (as I must to check once again for water in the oil - changed twice in fall) to dry it out, I'll follow the advice ya'll have so graciously provided to this relative novice. Thanks again.
 
DavidM said:
Yep, Don's pic, attached diagram and description of how to use the transfer switch is exactly what I had on my 2006 34T. A little different because I had no generator.

David
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Got it. Thanks again, David.
 
DavidM said:
Yep, Don's pic, attached diagram and description of how to use the transfer switch is exactly what I had on my 2006 34T. A little different because I had no generator.

David
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NO generator? Now did you run your heat/AC ????
I am assuming you had a gas stove. What size inverter did you have?
You only had hot water if the main engine was running?
You had an over size engine generator?

What did do with all the extra space in the engine room?
 
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OldDan1943 said:
NO generator? Now did you run your heat/AC ????
I am assuming you had a gas stove. What size inverter did you have?
You only had hot water if the main engine was running?
You had an over size engine generator?

What did do with all the extra space in the engine room?
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I realize that the above comments are mostly tongue in cheek.

But we lived in SoCal and used the boat from San Diego to Catalina Island. Never did we feel like we needed A/C. FWIW we lived about 1/2 mile inland from Balboa Island and turned on the air conditioner at home maybe twice each year for a few days each time. We were never on the boat during those warm Santa Ana hot winds.

Interestingly we needed heat more than cooling where we cruised. So I hooked up a Wave radiant heater to the propane system and that kept us nicely warm in the late evening and early morning.

The stove was propane, with the LPG tank on the fly bridge in a locker. We were usually out for two nights at a time and when we got to our anchorage, often Catalina, the engine had heated up the water just fine. And it would last for at least two nights of showers.

FWIW Mainship didn't plumb the engine into the hot water heater, but a couple of fittings and heater hose got it all hooked up fine. Mainship obviously thinks like you- a generator is essential.

No inverter and only the OEM engine alternator. Never used much DC, maybe a few LED lights, a cell phone charger and a half hour or so of TV for the nightly news is all, although sometimes we watched a movie on DVD. We did have a nice house bank with four golf cart batteries.

And yes the engine room in a 34T with the single Yanmar had lots of room.

It was a pretty minimalist setup but interestingly the purchaser who kept the boat in Newport Harbor immediately put in A/C. Don't know about a generator though.

David
 
DavidM said:
I realize that the above comments are mostly tongue in cheek.

But we lived in SoCal and used the boat from San Diego to Catalina Island. Never did we feel like we needed A/C. FWIW we lived about 1/2 mile inland from Balboa Island and turned on the air conditioner at home maybe twice each year for a few days each time. We were never on the boat during those warm Santa Ana hot winds.

Interestingly we needed heat more than cooling where we cruised. So I hooked up a Wave radiant heater to the propane system and that kept us nicely warm in the late evening and early morning.

The stove was propane, with the LPG tank on the fly bridge in a locker. We were usually out for two nights at a time and when we got to our anchorage, often Catalina, the engine had heated up the water just fine. And it would last for at least two nights of showers.

FWIW Mainship didn't plumb the engine into the hot water heater, but a couple of fittings and heater hose got it all hooked up fine. Mainship obviously thinks like you- a generator is essential.

No inverter and only the OEM engine alternator. Never used much DC, maybe a few LED lights, a cell phone charger and a half hour or so of TV for the nightly news is all, although sometimes we watched a movie on DVD. We did have a nice house bank with four golf cart batteries.

And yes the engine room in a 34T with the single Yanmar had lots of room.

It was a pretty minimalist setup but interestingly the purchaser who kept the boat in Newport Harbor immediately put in A/C. Don't know about a generator though.

David
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The 4 golf cart batteries gave you how many amps??
You live in a unique environment and dont need an A/C. LOL
 
My boat is set up with 2 - 30 amp outlets as well. My panel is divided in half and clearly labeled, with the top half panel running off of 30 amp outlet #1 and the bottom half panel running off of 30 amp outlet #2. I pick what is the most important panel to run (usually just my galley, house lights and forward stateroom AC.
 
Get another 30 amp cord and plug into another leg, I had a boat like this in the nineties and if I couldn’t do that I would run on one cord
 
IF you are going to install a second 30a socket , with a bit of thought you can install switches that could power the socket to create a "buddy plug" to feed power to another boat in a raft up.
 
RossWilson said:
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.
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On the Mainship AC Panel you should have a switch when you plug into Outlet one (the top one) and Then on the AC Panel AC Load group 1 The Cover should be in the down position allowing you to throw the main Breaker then on AC Group 2 Have the shield raised allowing the lower breaker to be turned on this will distribute 30 amps to both panels.
 
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