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Inverter vs Genset

Discussion in 'Technical Discussion' started by 3 ROYS, May 6, 2020.

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  1. 3 ROYS

    3 ROYS New Member

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    Newbie Hatteras 53 owner. Just brought boat from LA to SF Bay; bought her with dead 12kw NL genset (found during survey) and evaluating 110AC power options. My cruising is going to be in/around SF Bay; expect to be on shore power most (not all) of the cruising time away from home marina. I have a new 3kw inverter that supplies basic 110AC power needs and am considering not replacing the dead genset but, adding another inverter/batteries to handle off shore loads when cruising.

    I’d appreciate any thought on the trade offs; inverter vs genset power. I looked for a thread on this but didn’t find one.
  2. Pascal

    Pascal Senior Member

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    A 3KW inverter should be good for all loads except air con, water heater, stove and oven

    problem with these loads is the amount of battery you would need.

    what is wrong with the genny? Northern Lights are really and worth repairing. Is it the engine or the electrical side? How old is it ?

    Personally I can’t imagine a boat without a genny. Inverters are great so you can shut off the genny when heavy loads aren’t needed but not a replacement.

    also, unless you have a dedicated battery bank for the inverter, older hatts only have two banks, one per engine with one of them doubling as house duty. Inverter will put a lot of wear on that bank, better make sure your parallel solenoid is working
  3. Capt Ralph

    Capt Ralph Senior Member

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    Pascal is A+ here.

    I have been preaching about inverters for a long time. Luv them.
    There is a line where a generator takes over where an inverter can not go.
    Lets fix that Northern Light gen-set.
  4. Beau

    Beau Senior Member

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    I have had both aboard my Egg Harbor. Inverter is good for nights on the hook when you can have the hatches open, or running over for a quick lunch or dinner - keeps the fridge running, but you may want to turn off the ice maker. Genny is needed for all the heavy work like a/c during the day when anchored out.

    I tended to use my genny in all situations, except at night
  5. Capt Ralph

    Capt Ralph Senior Member

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    Yep
    When we are underway, windows are open and the boat in on inverter. Josie, I and guest are on deck anyway. why run the A/Cs and gen-set if nobody is down below.
    We have had times with a boat load of folk or Josie is in the galley, then all has to run.

    I remember when we first purchased our Bertram. NO gen-sets, No A/Cs, Boat was a mess. An inverter was darn near the first purchase. At least the beer was cool when we left the dock and some lights worked. The first gen-set was not far behind.

    What is that NL not doing?
    Last edited: May 6, 2020
  6. v10builder1

    v10builder1 Senior Member

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    Agree - repair or replace the generator. A suitable size/battery capacity inverter ( like the 3 kW) system, preferably with a dedicated battery bank, is great to have on board - will do much of your day to day stuff (lighting, entertainment, fan ventilation, battery charging) but the list of exceptions (heat and air conditioning, water heating) and gray areas (cooking, refrigeration, bait pumps, etc.) is pretty long, especially for a boat size of yours. Quality inverter systems correctly interconnected are easy to operate, reliable, and low maintenance, but the downside is available battery capacity. A 12 kW inverter system is possible, but a battery set to give you a practical run time for the large loads would be either outrageously expensive or very heavy/impractical for a planing boat. Shore power capacity for quick recharging could be an issue.
  7. 3 ROYS

    3 ROYS New Member

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    Thx for weighing in everyone.

    The NL genset (not sure of age) engine is frozen and inop. Couldn’t even be turned with a bar. It has salt water in it; have to determine source of salt water. Removing genset would require disassembling front & back ends to get it out. My surveyor suggested that buying/installing a new genset is better than repairing one in this condition. Thoughts?

    If I replaced it with a new genset, it’s $10-13k+ for a new one (I’d consider moving up to 15kw; modest price bump for 25% more capacity) plus a few $K for parts and probably $5k labor; $20-25k all in. As an alternative, I could add a 10kw inverter and 20 x 200ah deep cycle batteries for $11k+/- plus $3k parts/labor = $14k all in, and get 12hrs total 13kw load or a whole day at half load, if my math is correct. Remember, I live in SF, how often will I be using max load? Pls feel welcome to shoot holes in this.
  8. Capt Ralph

    Capt Ralph Senior Member

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    An over sized gen-set is almost as bad as an undersized gen-set. Proper loading of a generating engine is important.
    Pascal can help here as he has a sister ship.
    I'm assuming your existing gen set is down forward. I just replaced an original OhNo 20 and installed a NL 20 and 12.
    Yes, they go in / out in pieces. Not an issue for a good yard. I built a stage/ramp to the forward deck hatch. Did most of it my self.
    (I was a service tech/company).
    Your yard may want to come thru and down the stb wheel house door and stair case.

    Where do you think 20 batteries are going to go? There is not any deck on your boat to support 20 batteries.
    200 AH, are you talking golf cart batteries? In what kind of bank? 6, 12, 24, 48Vdc configuration?
    Flooded, AGM or better?
    AND, It's a boat. Don't care what anybody says, boats sit, batteries sit, your batteries will have a short life span.

    A properly sized gen-set for near the same money now will not have a short life if properly maintained.

    My bottom line; In 3 years you can still have a solid gen-set made for the marine environment.
    In 3 to 4 years you replacing all of your batteries.
    AND the electronics in the inverter equipment are subject to fail in a marine environment any day, without warning..

    My first inverter ran for 1 year. The second near 2 years.
    Current inverter has over 6 years installed but the case started to rust up the day it was installed. It's been crumbling apart sense.
    New Magnum PAE should be here tomorrow with all the gizmos including gen-set auto starter. Oh, Did I mention, I have 2 gen-sets onboard.
  9. Capt J

    Capt J Senior Member

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    REPLACE. Do not fix the generator. You need a generator.
  10. rtrafford

    rtrafford Senior Member

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    Meh, Northern Lights are really good pieces of equipment. With the motor seized from salt water intrusion, likely source would be the heat exchanger, but a total tear down of the engine would be required, so the end result is as good as new, in my opinion. Salt water into the engine doesn't bother your power generation side of the unit. But you'll want that tested as well while you have taken the unit apart.

    "Easiest" solution is either rebuild or replace exactly what you have. Don't go larger unless your calculations show that you require to do so. But if you're considering an inverter as your sole source, sounds like bigger is not necessary. So, explore the cost of new like kind as well as the cost of a rebuild.
  11. Pascal

    Pascal Senior Member

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    First your batteries are going to be good for only 4 or 5 years so then it s back to square one. While there is room You re also going to build some shelves and boxes in the genny room to install them.

    But you will still have a boat with limited capabilities. Can’t cook, can’t cool off on hot muggy days... are there mosquitoes or bugs where you are?

    I would have a NL guy look at the generator and if the electrical end looks good I would see about replacing the motor only or rebuilding it if possible

    if that’s not possible a 15kw is best on the 53. I have an 18KW which is overkill but here in so FL we run the AC a lot so underloading isn’t much of concern. It s nice to have extra power when a compressor starts and overall the genny runs a little cooler if loaded 50-60%
  12. Capt J

    Capt J Senior Member

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    I've been that route with a 58' Hatteras YF, which is the same boat as the OP's except has a cockpit. Ironically with a 16 kw Northern Lights. We had to pull the starboard pilot house window to get it in. It is such a ******* to get the generator in and out of that boat to either rebuild or replace it (same with the generator end), it's best to replace with new as the cost was only a tiny bit more than rebuilding it.

    A lot of these older generators you simply cannot get parts for. On a trip, it cost an owner close to $150 to have an alternator bracket on a 1984 NL that snapped welded in Charleston, S.C. and a day's pay Captain and mate, because the $9.87 bracket was nowhere to be found in Northern Lights entire system and NL quoted a 4 week lead time. It's that way for many brands of old generators. Can't find ANY parts for the old ONAN's Hatteras installed in these boats.
    Last edited: May 8, 2020
  13. Pascal

    Pascal Senior Member

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    On a 53 MY or 58 YF, the genny should slide up the steps and then go out the aft deck doors. Plenty wide. I don’t see why you d have to get it out thru a window.
  14. Capt J

    Capt J Senior Member

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    We didn't have the height with the NL to make the turn to go down the steps. I didn't install it, the boat yard did, I just watched.
  15. rtrafford

    rtrafford Senior Member

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    Look, If the heat exchanger is the access portal for salt water, there's a range that the seizure is mild. Lugger is a sleeved engine. The injectors are looking at you, right in the face. Hell, pull the injectors and pour in some Marvelous. Let it sit for 24 hours, lay a heating pad onto the head, and come back the next day and try to turn her over again. If she moves she can be torn down where she sits and rebuilt in a couple of days. If that all works out, you can rebuild the genny AND add an inverter for the price of a new genny.

    If the owner isn't a wrench guy, I'm sure there's help close by that can lead him to a point where more information can provide a more certain path forward.
  16. rtrafford

    rtrafford Senior Member

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    Yes, and you can disconnect the generator from the motor to lighten the load and shrink the dimensions. That galley can quickly become a pretty nice workshop, too.
  17. v10builder1

    v10builder1 Senior Member

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    When rtrafford said repair the genny and add an inverter/charger - got me to thinking. Check out a 12 kW inverter/charger and a small capacity lithium technology dedicated battery set (easy to find room for). My inverter/charger (Outback brand - brand used by Nordhavn) has automatic shore power switching and generator control/interfacing/relay (boat never had a generator). What I like is automatic operation - all I do is plug/unplug the shore power - the inverter/charger takes care of the rest. When in inverter mode (disconnected from shore power) the inverter/charger looks at the battery set state of charge and would automatically start the generator to take the load and recharge the battery set, and then shut down the generator when finished/unloaded/recharged if I had a generator.

    For you, this would give a completely automatic system, and use the generator only when needed. IMHO, this would not be an overly complicated installation task - all the pieces are standard stuff.

    I understand that the experienced folks posting here have had some problems with inverter/charger reliability and battery lifetimes - true - the marine environment, etc. There have been some major brands that have not been too good, but I read of good service from Magnum, and I have had the Outback 3 kW inverter and the Crown lead acid batteries in service for 7 years. The last year annual load test was 90% of the first. I maintain the batteries (twelve 8 volt golf cart batteries 165AH each) properly, and the recharge current is set a bit lower than maximum. Also, the inverter/charger monitors battery temperature when charging and shuts off at 55% state of charge. In my system, both inverter/charger and the batteries are well removed from the engine space heat/vibration/moisture, which is not always possible.

    The way we operate, not usually more than 4-6 hours away from shore power or on the hook maximum of 2 nights (no AC), this works great for us, however, if this boat had had a busted generator when we bought it, I would have repaired or replaced it then.
  18. Capt J

    Capt J Senior Member

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    Not to put this the wrong way, but do you know how many hours you can run a 12 kw generator at 1/2 a gallon per hour? 12 KW inverter bank? What are you going to charge it with?
  19. v10builder1

    v10builder1 Senior Member

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    Thanks for the questions. 1/2 gallon per hour seems like a reasonable fuel burn for a 12 kW generator, so I figure the run hours would be determined by the fuel quantity. To further clarify what I suggested: Note that for both generators and inverters, the kW rating applies to the total nominal power in kilowatts (the load), measured at a specific time - not over a time. kW measured over a time, kWh, is actually a measurement of (total) energy, not power. For example, a resistive (electric heater) load of 1.5 kW which is 1500 watts (120 volts x 12.5 amps = 1500 watts) operating for 1 hour consumes 1.5 kWh of energy(1.5kW x 1h = 1.5kWh).

    My suggestion above called for a 12 kW inverter/charger sized to match the generator kW. The actual battery bank attached would be small. It would operate the system at 12kW load only for, say, 10-15 minutes, but for much of the time (no ac), the typical load is way below 12 kW, so the small battery bank would provide enough energy to operate for a number of hours. Disconnected from shore power/on inverter operation, the small bank begins to discharge, slowly (no ac) or more quickly (ac is on). When the battery bank voltage/state of charge (SOC) decreases to the inverter/charger's generator start set point, the inverter charger starts the generator to pick up the load and recharge the bank to 100%. When the bank is back at 100% SOC (the generator is powering the inverter's charger at this point) and/or the big load has gone away, the inverter shuts down/disconnects the generator, and the cycle repeats until the shore power is reconnected. When shore power is back, the inverter's charger tops off the bank, and shore power carries the loads. Most any modern quality inverter/charger can operate this way right out of the box - folks who live off-grid power their homes in a similar manner.

    On the boat, the generator would have to be operated with control set up for remote start only.

    Thanks. I hope I made it clearer.
  20. cleanslate

    cleanslate Senior Member

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    Get a quote direct from Phasor marine generators ask for Allen.
    Southeastern power products . I've had two of their units , in two of my boats and run great all the time. Easy to install, I did them both on my own.
    A 6 kW and 8kw compact unit.
    12 kW being bigger yes but it can be done on your own.
    They have good numbers $$.

    I would not mess around with the inverter ideas you are thinking up.
    Get the generator.
    Look around for a possible good used unit also. You never know.
    The new generator should reuse most of the parts from the old NL unit. Exhaust is the same, wiring is the same etc. just make sure it is all in good shape. If not you can replace it on your own with like materials . Fuel lines are also the same....
    Last edited: May 9, 2020