Liveaboard electrical system

Discussion in 'Boat Design' started by CFMarine, Jun 7, 2015.

  1. CFMarine
    Joined: Jun 2015
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    CFMarine Junior Member

    I am starting the planning of an electrical system for a 50' liveaboard. Until now I've never dealt with appliances such as ovens and dryers in marine applications. I will be consulting engineers over final wiring schematics but still need some ideas on the type of system i will use.

    With the larger appliances I would like to run 240vac but want to maintain versatility with shore power options. For the battery system I am considering all 24v.

    I will be thoroughly reading the "electrical bible" which should give me the ability to complete the task. in the meantime I am trying to predict situations to avoid and could use advise. Also, if anyone has feedback on conveniences that can be incorporated into a new electrical system i will be grateful to hear them.
     
  2. gonzo
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    gonzo Senior Member

    24V will limit the options for electronics and make them more expensive. The first step is an energy audit. That is a list of every piece of equipment, including lights, and add up the power requirements.
     
  3. philSweet
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    philSweet Senior Member

    A budget for the electrical stuff is also a good place to start. If this is a blue water boat that has a 6 figure electrical/electronics budget, that is a bit different from $30K of misc appliances and nav gear for an inland waters boat.

    Concentrate on the big loads first. Anchor winch, autopilot, water maker, water heater, dryer, those 6 little ac compressors, 3 more for the galley, don't forget the 1700W hair dryer and the microwave oven. I helped deliver a 50' Alliaura catamaran, and even at 2am, we would be drawing 84 amps dc @ 12 volts. Never got lower than that in two weeks. On the other hand, my 38'er runs on two solar panels and three Walmart batteries. Like Gonzo said - make a list of everything. List the price and the weight and the location of anything bigger than a shot glass.

    The other thing to get a handle on at the earliest opportunity is the battery charging plan. How much time will you spend on batts? how much charging will come from shore power? How much from on-board gen set. How much from engines. Solar? Wind gens? This is a big factor in the overall scheme of things, and has a large effect on cost and space and overall sophistication of the electrical system. If you can provide the engineer this info for different modes of use or times of the year, they ought to be able to run with that.
     
    Last edited: Jun 8, 2015
  4. CFMarine
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    CFMarine Junior Member

    One of my concerns was the worth of a 24v system once all the factors come to light. I have begun to list electrical equipment. There are some options as for gas/electric utilities and i would not want to run the dryer off auxiliary power anyways. Most of the time the boat will be docked, at least for 1-2 more years. I will have a generator but will integrate with solar closer to travel time.

    So in short, i want to focus on mainly shore power but wan the ability to increase the dependency on batterys.
     
  5. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Of course 24VDC for energy storage only.
    The house wiring layout only 240 VAC, controlled by a CAN-bus system like CAPI-2. That way certain loads can be automatically excluded when the power comes from the inverter(s) or generator. The whole system can be monitored and controlled from an LCD or -touch screen.

    In case there are any 12V items that cannot be avoided, provide these with a small local power supply. The efficiency of such devices is 95%, no need for separate wiring.
     
  6. nzboy
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    nzboy Senior Member

    I think with the technology today and not knowing the future 240ac is the way to go .The centre piece will be your inverter come controller. This is where you need to ask the right questions .Some can accept shore as well as your generator at the same time ( you don't want to be blowing the marinas 20amp fuse etc. My fathers experience (he was the guru )is solar combined with a small wind turbine through a couple of truck batteries with say a 5kw generator is probably a good start .My father proved you do not need expensive deep cycle batteries if you are charging and discharging batteries on a 24hour cycle( eg everyday living) Of course gas oven and top and diesel heating and gas or diesel hot water .The reason why truck batteries are good is they can be charged quickly with generator or alternator from your main motor when running .When running on shore power your generator is unnecessary .So you only draw from the shore when your controller decides your batteries are getting down Most likely these will be charged over night from shore for the next day
     
  7. FAST FRED
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    FAST FRED Senior Member

    IF the boat will liveaboard iin ONE expensive marina ,US 240V is an option.

    Most folks do not use 240V appliance , as 120V units are available and will multiply by 10 the number of marinas you can use.

    Of course using the noisemaker dockside is an option , but for 3 meals a day will get you tossed out of most marinas.

    Refrigeration cruising is the biggest hassle , propane the simplest answer , esp on a new build where it can be done with safety.

    Ranges and ovens are also propane , many months of cooking from a BBQ sized tank.

    Create a system where all you REQUIRE dockside is 15A 120V, then you can add electric goodies to eat the power of a common 120V 30a power hose.

    The US ultimate is (2) 120V legs at 50A , the usual 50A 240V supplied in better marinas.

    This can run multiple air cond or heaters , but in many places its a flat 25c a KW so electric heat can run big bucks for one night.

    An appliance actually requiring US 240V should not be aboard .

    A priority relay for LOAD SHEDDING is only one extra wire and will allow loads selection on small low power marinas.

    The Hot Water heater can be secured when the air cond starts or the range , about $60 at an electric supply.

    12V is far easier to live with and find toys for.Use dimmable LED for internal lights.

    "The reason why truck batteries are good is they can be charged quickly with generator or alternator from your main motor when running"

    "Quickly" is difficult with lead acid batterys.

    Assuming 50% is removed most batt builders suggest a 10% charge rate for refilling , so since a 50% discharge will require electric for a 60% refill its 6 hours or more to 100-% full.2x as expensive batts will help IF the charging system is large enough.
     
  8. philSweet
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    philSweet Senior Member

    Not sure if FF is correct about availability. I would be very surprised to not find 50A available in a 50' slip. I would expect to have 50A available in slips over 30'. A 50'er might have a pair of 50A services.

    I might be getting the cart in front of the horse here, but the subject of load shedding has been mentioned, and it is worth considering from an early stage. I also feel that it is often misunderstood and it's benefits oversold.

    An example of where load shedding is not appropriate IMO is the situation where it is often offered up - setting a current trip at 48 amps to unload the service and keep it chugging along just below the 50A service rating. I deal with these setups in RV's quite a bit. Load shedding simply doesn't work when set at 90% of the service capacity. The reason is that marinas and RV parks are wired based on the assumption that the peak load averaged over a couple hours is less than 50% of the pedestal capacity. If everyone starts load managing at 90%, nothing will work. Load shedding should be controlled by the service provider, not the user. In our area, the power company can disconnect all the residential electric waterheaters during peak demand (or when they can sell the power at a profit to another grid).

    Which isn't to say that it has no role in a boat. For instance, if you had a 50A shore connection, but decided you only wanted a 9kW genset (instead of a 12kW that would match the shore service), you could set the load shedding at 8.5 kW and not have to worry about anything when switching to generator. Generators like a substantial load, shore service doesn't, so the above can be a decent way to get both. The point is, your shore power connection needs a lot of head-room vs the average power consumption. It was already sized assuming the loads were averaged out over a few hours, so you aren't really changing anything by delaying a HWH element for 15 minutes while the third AC is running.
     
  9. nzboy
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    nzboy Senior Member

    The heart of any system today is an inverter/charger 3kw costing 3-5k .This is placed down line from any power source .Just imagine you pull up to a marina and are placed next to a 70ft megayacht and hook up to shore power. At 5pm they turn on their induction oven and hotplates and you are watching tv on your widescreen next minute your tv is fried . With a decent inverter charger this would be eliminated because it would make up for the voltage drop . With a decent inverter charger it can charge a decent truck battery in a hour without cooking it .The limitation is power imput . Also with an inverter charger you can start hooking solar into it as money permits .It also allows you to have a ac generator and also take power from dc source .It sycronizes the sine wave so you can safely run modern appliances Here in nz we only think in terms of240v .All I know is 50amp at 120 is 25amps at 240v which may not even start a medium size aircon if you've got a few other things running
     
  10. FAST FRED
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    FAST FRED Senior Member

    "With a decent inverter charger it can charge a decent truck battery in a hour without cooking it .The limitation is power imput"

    A common truck battery being a LA , (lead acid ), if 50% discharged at a charge rate of 10% will take 5 or 6 hours.

    Even a 10X as expen$ive Lithium battery and complex charge system can not make it from 50% to 100% in an hour.

    The use of a pass thru and current boosting inverter works fine IF the batterys are large enough , and the required boost is modest, in terms of load and duration.

    Much of the worlds power hassles would be solved IF a battery could be fully charged in an hour.

    Closest is a flywheel in a vacuum that spins at 100,000 rpm + and can be spun up depending on the power provided.
     
  11. CFMarine
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    CFMarine Junior Member

    CDK, that's spot on my original idea of what i want, right down to the CAPI-2. However I could not find info on the costs of a CAPI2 system but loved the modularity of the system. I have since been reviewing similar options and would love to incorporate such a system.

    Fast Fred, why recommend against 240v appliances?
    I plan on spending the money on a quality inverter/charger to ensure longevity and adaptability. As far as I know, unless i get both, its either 120v or 240v AC inputs. 240v is what i would want for a liveaboard providing its reasonable accessible.
     
  12. philSweet
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    philSweet Senior Member

    You'll probably answer your own question when you start specing part numbers and checking prices and availability. Just to be clear, we are talking about US 240V split-phase power as a source from both shore and genset. The distribution can be either 120V or 240V anywhere the wires go. You have several options as far as the inverter/controller goes, including running a fancy 120V inverter/charger on one leg and a matching dumb inverter to supply the second in case you get stuck running on 30A 120 shore power through an adapter plug. Such a system may help if you don't need 50A except in the summer. Or if 50A service is unavailable when you are hauled and blocked in the yard. The batteries supply some boost for running 240V appliances for short periods. By the way, you should consider what you need in the yard. Having at least one air to air AC is a real good idea.:cool:

    Whether or not you can set her up to run on both 30A 120V and 50A 240V depends on how much load you can shed if you need too. Yards will have a laundry and shower and maybe a kitchen. But not a portable AC. But for $75, Walmart will sell you one.
     

  13. FAST FRED
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    FAST FRED Senior Member

    In the US about the only item on board that might require 240V is a washing machine dryer .

    The 120v unit does takes longer , which might be a concern if operating on a noisemaker at $5 - $10 per hour.

    Cruising operating it from the main engine alt. with an inverter , 45 min, 90 min who care?.

    Dockside there are far more 30A 120v marinas , and you usually have loads of time .

    A marina bound liveaboard always has the hassle of cost vs future utility.

    Plugged in a cheapo house reefer will set you bacj $150 or so , and when you leave the dock will kill most batt sets ( over 100ah in 12V per day) in a single day.

    A Sun Frost 12V reefer is $1300 and will double the endurance away from the dock.

    If the boat will only leave the slip for weekends , endurance with a generator could make sense, although is costly and noisy.

    If the boat will travel and anchor out normally ( $2.00-$5.00 per ft per night for a marina slip gets tedious) installing a cruising boat system from the start is cheapest in the long run.

    What is the vessel GOAL? Aground in your coffee grounds ? or cruising?
     
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