New Boat: Inverter Question

[jayslu]

Hello all,

I have a new Nordic Tugs 34. The boat features a Kisae Inverter/Charger, which charges the house battery from shore power and also acts as an inverter. (There is a separate Kisae battery charger for the start and thruster batteries.) Should I keep the inverter functionality turned off while I'm on shore power? There is something in the instruction manual about leaving it on in case shore power is interrupted, but that doesn't seem important to me.

Thank you.

 

[ranger58sb]

Depends on how wired and whether there's an automatic internal transfer switch.

Ours has the latter, and we can usually leave it on all the time... mostly because of the AC-only fridge and freezer. And then we hope any potential shore power outages don't exceed 36 hours or so...

-Chris

 

[Xlantic]

I turn mine off as I want to know if the shore power has been interrupted and I don't want to draw-down the batteries if i can avoid it.

 

[Bmarler]

I prefer to leave the inverter function turned off. I don’t want it to drain my batteries if I’m not there to watch them.

 

[Iggy]

I think it depends on your set up. I turn mine off, but I do not have any important AC loads.

My inverter has a low voltage cutoff that can be set. As not to kill the house bank.

 

[ranger58sb]

My inverter has a low voltage cutoff that can be set. As not to kill the house bank.

Hmmm... there's a good point, thanks. I need to check our setting...

-Chris

 

[rslifkin]

I leave mine on and let it auto transfer. There aren't any big AC loads that it powers when we're not on the boat, but it'll keep a few basic things running. And we have solar to keep the batteries up, so no reason to switch it on and off every time instead of just letting it take over whenever shore power isn't available. I also have remote alerting if the house batteries get drawn down to 40%, so I'd have some warning of an issue.

 

[jayslu]

Thanks for all of the replies. I'm leaning toward turning the inverter off while I'm away. I would worry about it drawing the house batteries all the way down if shore power were lost for some reason.

Jay

 

[guy with a boat]

Leaving the inverter on provides clean 120v power to whatever needs it. Some marinas have mediocre power and the voltage sags to a point that is hard on refrigerators etc., so that can be a benefit.
Also, leaving the inverter on gives backup power in the event of shore power loss, until the house bank is depleted. That might be important if you have a refrigerator and/or freezer left on. Ideally you would have some type of remote monitoring that would let you know you have lost shore power and give you a chance to deal with it before the batts are dead.
We leave our inverters on for both of the above reasons when we are away from the boat.

 

[Bacchus]

As mentioned some inverters automatically sense shore power and pass it through avoiding running off DC.
For newly built / rebuilt marinas the recent GFCI/GFP codes can be troublesome for some boats. My understanding is the neutral & ground need to be separated when powered by shore but combined when DC bank is the power source. Apparently some inverters handle the above automatically and others not which can create fault tripping issues.
Helpful to know your boat will handle new marina power systems even if only for cruising.

 

[SteveK]

Inverters have a setting to shut off if the house batteries get to a certain voltage to avoid killing the battery

 

[jayslu]

I will look for that setting on my Kisae. Thank you.

 

[dhays]

Most of the time, I don't even think about it. When I do think about it, I turn the inverter off. My refrigerator will switch from 120v to 12v on its own if power is disrupted. There aren't any critical 120v systems that run when I am away from the boat.

 

[slowgoesit]

As mentioned by Don above, you need to know whether your inverter allows "Pass Through" voltage or not.

Ours does. By this I mean it runs the 120vac appliances off of shore power unless the demand is greater than shore power can provide.

For Example: In our boat, we have a 12/5000 Victron Quattro inverter charger. It allows pass through voltage. In our case, our boat only has 30 amp, 120vac shore power. That is small for our size boat and power consumption. Pre-refit, we were always doing the CB dance, "Okay, I'm going to use the microwave, so turn off XXX, then remember to turn it back on after I finished with the microwave so I didn't exceed the shore power 30 amp input." We were planning on changing over the 50 amp service . . . .

Then we refit the boat with the new inverter, LiFePO4 house battery bank, etc. The Victron inverter charger allows the user to set how many amps you pull from the "pass through" before you begin supplementing with inverted 120vac from the house bank. In our case, I set the "pass through" at 28 amps. So once my 120vac power draw exceeded 28 amps, the inverter would automatically kick in, supplying 120vac up to 41.6 amps (5000 watts/120vac + 41.66 amps) from the LiFePO4 house bank. Then once the draw reduced below 28 amps again, the inverter stopped supplying 120vac from the house bank and goes back to solely using shore power, with the inverter charger recharging the house battery bank.

30 amps (or in our case, 28 amps allowable) of 120v is really a LOT of power, if continually supplied. But often the load will exceed that, but we designed/installed our system to account for that.

We still would have probably switched over to a 50 amp service (2 legs of 50 amps each, 120vac) but we couldn't source a 50 amp isolation transformer anywhere. However, having the system we do now, we've never really needed the 50 amp service after all.

Hope this helps!

 

[tiltrider1]

I operated a Uniflite 42 with a supplementing inverter for 15 years in the PNW. With the water heater and electric heaters running in the morning we would pull 30 amps. All was good until the wife turned on the hair dryer. Fortunately, the Trace inverter would supplement the 10 additional amps needed for the 10 minutes. I had a 1400 Ah bank on that boat.

 

[jayslu]

As mentioned by Don above, you need to know whether your inverter allows "Pass Through" voltage or not.

Ours does. By this I mean it runs the 120vac appliances off of shore power unless the demand is greater than shore power can provide.

For Example: In our boat, we have a 12/5000 Victron Quattro inverter charger. It allows pass through voltage. In our case, our boat only has 30 amp, 120vac shore power. That is small for our size boat and power consumption. Pre-refit, we were always doing the CB dance, "Okay, I'm going to use the microwave, so turn off XXX, then remember to turn it back on after I finished with the microwave so I didn't exceed the shore power 30 amp input." We were planning on changing over the 50 amp service . . . .

Then we refit the boat with the new inverter, LiFePO4 house battery bank, etc. The Victron inverter charger allows the user to set how many amps you pull from the "pass through" before you begin supplementing with inverted 120vac from the house bank. In our case, I set the "pass through" at 28 amps. So once my 120vac power draw exceeded 28 amps, the inverter would automatically kick in, supplying 120vac up to 41.6 amps (5000 watts/120vac + 41.66 amps) from the LiFePO4 house bank. Then once the draw reduced below 28 amps again, the inverter stopped supplying 120vac from the house bank and goes back to solely using shore power, with the inverter charger recharging the house battery bank.

30 amps (or in our case, 28 amps allowable) of 120v is really a LOT of power, if continually supplied. But often the load will exceed that, but we designed/installed our system to account for that.

We still would have probably switched over to a 50 amp service (2 legs of 50 amps each, 120vac) but we couldn't source a 50 amp isolation transformer anywhere. However, having the system we do now, we've never really needed the 50 amp service after all.

Hope this helps!

Wow, I didn't know that inverter/chargers could do that! That's a great feature. It applies to us because if our air conditioning is running, we can't turn on the microwave without exceeding 30 amps of shore power.

Thank you!

 

[Lepke]

I use a Magnum inverter that supplies 120/240v and is on 24/7. The inverter bank is 48v. More output than the 12v model, the inverter can be far from the batteries, and I can use smaller cabling. The boat is wired like a house with house appliances. It's a pass thru when on dock power. When the shore power is disconnected it automatically switches so no loss of AC power, no surge. If the bank gets low it starts a generator. Underweigh I have 48v alternators on my mains that keep the bank full, so I rarely have to run a generator.

 

[tiltrider1]

Wow, I didn't know that inverter/chargers could do that! That's a great feature. It applies to us because if our air conditioning is running, we can't turn on the microwave without exceeding 30 amps of shore power.

Thank you!

Not all can. For Magnum only the hybrid line will do this. Victron has a line that will do this but most of their inverter/chargers will not.