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Some Inverter install questions...

Discussion in 'Technical Discussion' started by Prospective, Jun 16, 2017.

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  1. Prospective

    Prospective Member

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    Sep 27, 2016
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    Location:
    New England
    I get mixed results with wiring questions because some folks who know the answer are afraid I'm going to burn my boat down. So as a full disclaimer, I haven't even done this yet and will likely contract an expert to do the parts I don't feel comfortable with. But I 'd still like to understand. My questions surround tying the AC from the inverter back to my main panel.

    Currently the AC side of my boat is a 125/250V shore connection. My understanding based on inspection and research is that the 250v is split in two to feed 2 rows of 125v circuits. What I'd like to do is have one of those legs fed by an inverter/charger with a typical internal transfer switch so when on shore, the inverter would pass thru 125v to the inverter-load leg, and when not on shore it would feed those circuits via inverter power. My understanding is this is pretty typical and I like the idea as it allows me to isolate certain things like the water heater and Air con that I don't want to accidentally try to feed from the inverter.

    I have two basic questions. I know the charger/inverter can't "feed it's self". So it can't be on the same leg as the inverter loads. But it seems to me that if I put it on the "non-inverter" side of my panel I'm essetially losing a leg of 125v power so when on pass-thru one leg is now powering both the inverter AND non-inverter legs. Since I want to keep my full capacity of A/C shore power I am assuming the inverter-charger breaker needs to be fed independently from one leg of the 125/250. Am I right and if so, how? Can I do this by putting the inverter charger on the inverter load side but cutting the buss bar so that the inverter-charger breaker is isolated from the rest?

    Second question is, it looks like all of my AC neutrals are tied together on a buss behind my panel which makes sense. But in reading my Caulder book it says that if an inverter doesn't power all the loads on the boat, then the inverter and non-inverter neutrals should be seperated to their own buss bars. Is this correct, or am I miss-understanding? Separating out the hots is obvious and the circuits are easy to identify. But the neutrals are unlabeled so finding which is which would be a challenge.

    Thanks for any clarification you can offer...
  2. bobhorn

    bobhorn Member

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    Kemah, TX
    The last inverter I installed a couple of years ago switched both the hot and the neutral, so you will have to separate the neutrals for the circuits fed by the inverter and those not fed by the inverter.
  3. Pascal

    Pascal Senior Member

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    I ve installed a couple of them over the years, on my boat or on boats I ran. You pretty much described the process fairly accurately.

    The details depend on the inverter model and on your panel payout.

    I finally your inverter only has one input and one output then you will only be able to feed one of the two 125v legs so any lost on leg nr 2 won't be inverter powered. Not a problem if leg two is only used for air con as is the case on some boats.

    If you have loads on leg nr 2 which you want to power thru the inverter then you will need to get an inverter with twin inputs and outputs (like the Magnums)

    In either case you will need to split leg and likely move some beakers around. Basically you group the non inverter loads together, at the top, and the inverter loads at the bottom. Non inverter loads will be air con, water heater, battery charger and any heavy loads like ovens, stoves, etc... you also add a breaker to power the inverter. Run a wire to the inverter input from that breaker

    The inverter output will feed the second group of breakers. So when on shoe or generator, power goes to the first group, pass thru the inverter and to the second group.

    On inverter, only the second group is powered by the inverter.

    Two things to be aware of. Typically the inverter input will be limited by a 20 to 30 amp breaker so even when on shore power you will only be able to power 20 or 30 amp to the pass thru loads. It may or may not be a problem depending on your needs.

    When using an in error with a single input, both your pass Thru loads and charging will be limited by that 20 or 30amp breaker greatly reducing charging rate and or pass thru loads. That's why I prefer twin inputs, twin outputs inverter. One of the input can be dedicated to charging

    As to the neutrals, I ve done it both ways. I prefer splitting the neutrals if they can be easily identified but sometimes it's just not feasible.

    It's is important to use a marine inverter which will automatically bond ground and neutral when running in inverter mode but keep them separate when I need charging mode as per abyc standards

    Finally, and obviously, make sure whoever does the work uses only tinned marine wire and mArine connectors. No homedepot romex and wire nuts. No laughing... I ve seen this on a Viking 63 MY where the owner had paid a good amount of money to a reputable yard...
  4. Prospective

    Prospective Member

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    Location:
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    Pascal, thanks for the quick feedback. I've actually read several of your inverter posts so was hoping you'd chime in.

    I believe I understand what you've described but want to clarify a couple of things.

    On powering the inverter... My concern is that if I power it from the non-inverter leg by putting the inverter/charger on that leg, then on pass-thru mode, I am effectively powering the whole boat with only one leg of 125V. To avoid that I want to power the inverter with the leg that is being "replaced" by the pass-thru. Seems to me, that way the inverter/charger and inverter load leg at least get their own 125v leg? If I'm correct on this I'm wondering if I can just insert an appropriate breaker on the inverter load leg buss but cut the buss so it's not connected with the rest of the leg. Or should I cut a new space for a brand new breaker. The former would obviously be easier/cleaner.

    On the neutrals.. sounds like it's "better" to seperate the neutrals but not "required or necessary". Is that correct. I'm guessing their are 20+ neutrals and they are all unlabeled. Identifying and moving the neutrals would significantly up the complication level.

    No question I'll have to move some circuits between legs so I can separate what I want on Inverter from what I don't.
  5. Pascal

    Pascal Senior Member

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    Neutrals. I ve gotten conflicting info but both work so I ve stopped loosing sleep over it :)

    Let s make sure we re on the same page. When I say "leg" I mean the two 120v legs in the panel.

    This is leg 1

    Shore/Gen
    |
    B1
    B2
    B3
    BI --------- inverter in 1

    B1----------inverter out 1
    B2
    B3
    B4
    B5

    The top breakers would be non inverter powered loads like charger, water heater, air con, etc

    The second group would be inverter powered like lights, outlets, fridge etc

    BI is a new breaker used to feed the inverter

    If you have loads that need to be inverter powered on leg 2 you would need an inverter with tow inputs and two outputs and wire that leg the same way but to in 2 and out 2
  6. Prospective

    Prospective Member

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    I'm with you on the diagram and the use of "Leg". Mine are side by side but same deal. But my issue with what you illustrate is... Currently I believe each of those legs is being fed by it's own 125v hot. On the leg that I want to handle inverter loads I would need to disconnect that hot since it will now be powered via pass-thru from the other leg while on shore power. So far correct?

    If so, then if I put the inverter's breaker on the non-load side it would seem to mean that in pass thru mode the whole boat is being powered by a single leg of 125v? ie.. in your example isn't one leg now powering both the top and bottom. Rather than that, wouldn't I want the new inverter breaker to be powered by the 125v hot I removed from the inverter-load leg?
  7. Pascal

    Pascal Senior Member

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    In my crude diagram 125v comes in at the top and flows down

    First set of breakers powers AC, wh, etc. the last breaker (BI) send power to the inverter which pass it thru the bottom set

    When shore power is disconnected and genset is off, the top breakers including BI are not powered. Power from the inverter out put only powers the bottom ones.

    Onviously there no link between the top group and the bottom group

    As to leg 2, if there are loads you want to power with the inverter it would motor leg one except you re using the second set of inputs and outputs on the inverter.

    If leg 2 doesn't have any load that you want to be inverter powered then you would only connect the inverter input 2 to a new breaker and not use the output. This way you get more power to the inverter to recharge the bank

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