Adding Inverter to Boat Electrical system

[capt jgw]

Originally Posted by LostDog88

So......right now my question is this:

How the heck do ya'll wire in an inverter so that the outlets you use when plugged into shore power work when you are not on shore power?

The idea is when I leave the dock and unplug the shore power line I will have an inverter and be able to use the outlets in the boat off of the batteries.

So...I can't figure out how to wire it. Every way I see to wire in the inverter ends up looping the charger back to the batteries. Seems silly to charge the batteries while using the batteries.

Not only silly and resulting in dead batteries, it would eventually kill the inverter. It would try to put back all the amps it's consuming, so it runs WOT all the time. Not good.
You can't turn your charger off? Every one I've seen had it's own breaker which you turn OFF when you turn the inverter ON, along with the water heater and anything else you don't want on the inverter. Any yes, you need a transfer switch. Two double throw breakers with a sliding lock between them that only allows one to be ON at a time. If you back feed the inverter you'll make smoke. Blue Sea and others make the parts.
An inverter/charger makes this a little easier as the transfer is built in. And you get a new charger that may be more powerful than the old one. Any loads you don't want to invert still need to be turned OFF or on their own subpanel. The subpanel option is pretty much automatic, when you unplug the inverter will kick in and power your loads, and automatically go back to shore when you plug back in. Loads are only interrupted for the second or so it takes the inverter to switch over.
On my sailboat I only have three AC circuits: water heater, charger and outlets. Plus the two DT breakers for the transfer switch. Before I throw the transfer switch I turn the charger and WH off. Inverter is powered off a breaker on the DC panel, adjacent to the AC panel so it's all quick and easy.
I've since installed an inverter/charger, running the incoming AC line through it. The manual transfer switches and charger breaker are no longer connected so all I have to do is turn the WH off before unplugging.

[stormalong]

You should not have to "be sure to turn off the WH" before unplugging shore power. Your inverter is wired in to the wrong position in the electrical system. The inverter should be wired just to the outlets breakers, not the whole AC electrical system. A simple change will prevent accidental big loads on the inverter/batteries.

[capt jgw]

Originally Posted by stormalong

You should not have to "be sure to turn off the WH" before unplugging shore power. Your inverter is wired in to the wrong position in the electrical system. The inverter should be wired just to the outlets breakers, not the whole AC electrical system. A simple change will prevent accidental big loads on the inverter/batteries.

That's how I'm going to connect the inverter/charger on my new to me trawler. AC panel is split in two banks, each with it's own master breaker. IC will be wired in between one of the master breakers and it's side of the panel. I'll also have to split off the neutrals for those circuits too, but there's an unused buss in the panel I can use for that. Lights and outlets will be on the inverted side, WH and air conditioners on the shore/gen only side.

Doing that on the sailboat would not have been a simple change. The incoming AC line runs within a couple feet of the batteries so that's where the IC is located, to keep the battery cables as short as possible. The AC and DC panels are 12 feet further forward. Splitting the loads at the panel would have involved running a lot of new wire. The way it is now just needed short DC cables and cutting the incoming AC at the inverter/charger.

[mitiempo]

Originally Posted by LostDog88

So......right now my question is this:

How the heck do ya'll wire in an inverter so that the outlets you use when plugged into shore power work when you are not on shore power?

The idea is when I leave the dock and unplug the shore power line I will have an inverter and be able to use the outlets in the boat off of the batteries.

So...I can't figure out how to wire it. Every way I see to wire in the inverter ends up looping the charger back to the batteries. Seems silly to charge the batteries while using the batteries.

Buy an inverter/charger such as the Victron 12/2000/80. It is sine wave, has a built-in transfer switch, and an 80 amp charger.

Wire the AC from a breaker on your AC panel to the inverter - 30 amp breaker.

From the inverter go to a sub-panel like this :https://www.bluesea.com/products/8058/AC_3_Position

Wire the outlets to this panel.

This arrangement means that you cannot forget to turn off a battery charger or water heater and drain the battery bank by mistake. When on shore power the inverter will pass through to the outlets. When away from the dock the inverter will power the outlets only.

[Madehn]

just finished doing this job on my boat- 3000 watt pure sine inverter- 110 amp charger-- here are a few things i learned along the way---
1) split the ac into two panels- one for non inverter loads- power that panel from the main panel but the sub panel needs to have a separate breaker that can turn that entire panel off. on that breaker, both neutral and hot wore need to be on the breaker (both interupted)
2) pay attention to the grounds- not getting them cross connected to the neutral is VERY important
3) ground wire for the inverter if it has a charger in it needs to be quite large as you can only come down one size from the charger wires in order to be compliant with ABYC standards
4) get an inverter with an auto transfer switch-- incidently when on shore power you MUST apply power to the auto transfer switch prior to turning on the battery charger- failure to do so will void your warranty and damage your inverter.
5) physically locate the inverter/charger close to the batteries so that you cable runs will be shorter. put a class T fuse in the positive line going to the batteries and make sure you have a disconnect switch in that line also
6) placard your AC panel to let anyone working on it know that there may be live AC power even if the shore power cord is unplugged
7) make sure that you get an inverter with a remote panel so that you can turn it on / off without going to the main unit- really handy! mine burns a couple of amps just sitting there idling so i wanted to be able to turn it on and off easily.
8) inverters/chargers can produce a lot of heat- make sure area is well ventilated and that nothing can get jammed up to the heat sink.

The wiring for doing all this was fairly complicated- i was adding a second shore power at the same time as well as putting in the wiring for a generator, another AC unit, and watermaker so that added time but plan on a couple of days and several trips to the parts store of your choice.

[Captain Anthony]

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[StuM]

Originally Posted by Captain Anthony

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[chrisr]

we have seperate power outlets for inverter (labelled "inverter") and shore or generator power (labelled "shore")

shore & gennie goes through the A/C switchboard. Inverter just has an isolating switch to connect / disconnect to house bank

keeps it simple and fool proof

cheers,

[MerMike]

Simple is better. However, if an inverter is required, look for a marine rated inverter with an internal transfer switch and ground relay to connect neutral to ground when running on inverter power. I'll add the usual warning about AC on a boat. Please study up and know what you are doing. A mistake can be deadly.

[Cliffhanger]

Originally Posted by LostDog88

So......right now my question is this:

How the heck do ya'll wire in an inverter so that the outlets you use when plugged into shore power work when you are not on shore power?

I struggled with the same question. The solution I used was to simply have 2 separate circuits. All outlets(except one) run off the inverter. Shore power runs the charger and fridges when connected.
You lose a few percent through the inverter but only on shore power where it doesn't really matter.

[Emouchet]

Is your boat is on 12v DC batteries ?
For a 2500w inverter, that will draw at full load about 200 amps.
You will need beefy cables between the battery and the inverter.
Even a 50% load, 100 amp is not something to neglect.

[sailcrazy]

We wired ours a little differently. I use a rotary 3-pole, On-Off-On switch to connect either shore power or genset to my AC Dist panel. Then I used another rotary 3-pole On-Off-On switch to power only those AC circuits I want the 2000w inverter to power. I chose the outlets and the m/w circuits to be on either AC (shore power or genset) or Inverter. And I also have a remote Inverter On/Off sw, just to make sure I select Inverter only when I want to run it....it really draws alot of amps and will quickly flatten your house bank!....but its a good backup. My batt charger is on its own circuit, and can easily be turned On/Off. A note: now some 16 years later, we rarely use the inverter! We typically run our genset about an hour in the morning (batt charging, coffee, breakfast/electric stove, AC refer system, m/w, etc), and about an hour in the evening(AC refer, stove, AC watermaker when needed, etc). Our computer plug-in, TV, printer, etc all run on separate, small(350watt) inverters dedicated just to that use; we turn each one on/off as we need that specific item, and its dedicated outlet. System works good!

[Nate24]

A couple of things to consider that many people miss according to surveyors. The ground for the inverter box should be sized appropriately. People assume that an AC rated wire will work. However, the ground has to be a DC cable that is no more than one size less than the properly sized DC circuit for the inverter battery cables. It is important that the ground wire is connected to a buss bar that is sufficient size to handle a ground fault.

It is important that the AC neutrals for the circuits running off of the inverter be segregated on their own buss bar.

If you have a gas engine and intend to have the inverter in the engine room, then the inverter must be ignition protected. The only ignition protected inverter I know of is made by ProMariner.

Hope that helps. Good luck with the install!

[rslifkin]

I finished up my inverter install the other day. To help out the others in this thread, here's a post-install photo of my panel.

The selector switch at the top (not pictured) controls the main panel feeds, selected before the L1 and L2 bus main breakers (not pictured). Switch has 3 positions, generator, shore power, and single inlet (I have 2x 50A/125V inlets, so that position feeds both buses from inlet 1). The inverter is wired with 6ga and has a 50A transfer switch, so it draws from the L1 main breaker and L1 neutral bus. I added a third neutral bus for inverter output.

The bottom left group of breakers is fed from the inverter, so I disconnected the hot jumper going to that group and connected the inverter output instead. And then moved the neutrals for those circuits from the L1 neutral bus to the inverter neutral bus. All works perfectly and it was a fairly easy change to the panel.

[MVDarlin]

I changed my 3 way Blue Sea 120 power switch from 3 way, off, shore , gen. To a four way that added an inverter setting. It was spendy. $350 10 yrs ago. Water heater, AC and charger are on separate breakers. These are switched off when using inverter.