Fitting an inverter into an existing AC system

[moseriw]

Easy. Have a manual switch for ShorePower/Generator/Inverter/Off and make sure that only one of them feeds the system. The Victron Charger is in the same case but in fact a different unit. Of course it is bloody useless to run the inverter and to charge the batteries from themselves. ;-)

[wrwakefield]

Our current boat came wired differently from what is typically done with an inverter, so I will describe it here as food for thought...

My prior vessels have always had the inverter/charger wired to the AC input as a passthrough/failover. I also always had the AC breakers grouped so the inverter could not power circuits like Air conditioning, water heater, etc.

Our current boat came wired to select which AC input is desired [and only one at a time of course...] This means the inverter is not a passthrough/failover for the incoming AC source. [For reference, the AC sources include: shore power, generator, and inverter.]

In addition, the AC circuits are not isolated for inverter only loads. Instead the breakers are color coded and labeled OK for inverter and not OK for inverter. Therefore it is possible to accidentally power undesirable inverter loads like the water heater, etc. However, since we have to manually select the inverter as the desired AC source, it is easy to switch off the appropriate circuit breakers at the same time as the SOP. [But it is not idiot proof by any means... This is one thing I would consider changing...]

I didn't think I would like this all manual configuration at first, but having used it for a couple of years now, I find I like it better than my previous arrangements. it suits our needs well in part because these days we have no critical AC requirements [e.g., AC powered computer towers, CPAP machines, etc.] that would benefit from a failover to inverter if the primary AC source failed. This means I don't have to worry about the inverter draining the battery bank for some unplanned AC load when shore power is out... I know I can also turn of the inverter failover on the inverter control panel [Magnum inverter] but so far this works well for us.

This arrangements also keeps the galvanic isolator properly wired no matter which AC source is selected.

A somewhat related design feature this boat came with is two 50A shore power inlets on opposite sides of the cockpit- so you can choose which is most convenient. This means you must also select which inlet is switched on. [Options are only one: port, starboard, off.]

If I ever get another boat, I would strongly consider wiring it this same way.

Best wishes completing your project.

Cheers!

Bill

[ramblinrod]

Originally Posted by Jimlad

Hi Folks

My existing shore power set up takes the feed into an RCD protected distibution box and then feeds individual MCB's to sockets, fridge, calorifier, battery charger and galley sockets. All works well.

I now want to install a combi inverter/charger.
I believe I will need to fit an RCD into the feed from the inverter. I will of course disconnect the existing charger feed as this will be redundant and I will need to ensure that the calorifier can never be run from the inverter power.

Someone told me that I will need some 'load-shedding' arrangement within the distribution box, but I'm not sure what is meant by that.

Any other issues that I need to know?
Some pointers from someone who has been down this route on how I should do the job would be much appreciated.

Standard practice is to connect shore power directly to marine inverter charger, and then connect inverter charger bypass to AC distribution panel input.

With an RCD (ELCI in NA) it would be nice if you could go through that before the inverter, then back to the panel. (This way, the inverter is also RCD protected.)

As far as load shedding goes, one should switch off all loads (not required) when leaving the boat. Typically, the charger and refrigerator are the only AC loads that should be left on. With an inverter / charger combo, the charger is ialways on when shore power is connected, and off should it be (event accidentally) disconnected.

If someone nicely (not) disconnects your shore power, the fridge will kill your batteries. Most inverter/chargers have a programmable low voltage cut-off that defaults at 10.5 Vdc. Check the battery voltage under load when at 50% state of charge with the fridge running, and set the low voltage cut-off to that amount (likely between 11.5 and 12.0 Vdc). That way, if you accidentally loose shorepower, the inverter will try to preserve the contents of your fridge, until the point where to do so would start hurting your batteries, which usually have a higher value than perishables.

Ramblin Rod
Marine Service Provider
About Sheen Marine

[Dockhead]

Originally Posted by ramblinrod

Standard practice is to connect shore power directly to marine inverter charger, and then connect inverter charger bypass to AC distribution panel input.

With an RCD (ELCI in NA) it would be nice if you could go through that before the inverter, then back to the panel. (This way, the inverter is also RCD protected.)

As far as load shedding goes, one should switch off all loads (not required) when leaving the boat. Typically, the charger and refrigerator are the only AC loads that should be left on. With an inverter / charger combo, the charger is ialways on when shore power is connected, and off should it be (event accidentally) disconnected.

If someone nicely (not) disconnects your shore power, the fridge will kill your batteries. Most inverter/chargers have a programmable low voltage cut-off that defaults at 10.5 Vdc. Check the battery voltage under load when at 50% state of charge with the fridge running, and set the low voltage cut-off to that amount (likely between 11.5 and 12.0 Vdc). That way, if you accidentally loose shorepower, the inverter will try to preserve the contents of your fridge, until the point where to do so would start hurting your batteries, which usually have a higher value than perishables.

Ramblin Rod
Marine Service Provider
About Sheen Marine

Victrons (and I bet other charger/inverters) can be set to either Invert, or Charge Only. On Charge Only, they merely pass through shore power and will disconnect AC loads in case shore power is interrupted. That's of course the way they should be set when you're off the boat.

They should not be left on "Invert" when you're off the boat. Don't ask me how I know

[ramblinrod]

Originally Posted by Dockhead

Victrons (and I bet other charger/inverters) can be set to either Invert, or Charge Only. On Charge Only, they merely pass through shore power and will disconnect AC loads in case shore power is interrupted. That's of course the way they should be set when you're off the boat.

They should not be left on "Invert" when you're off the boat. Don't ask me how I know

Well, I disagree with you. I believe all non-essential AC loads should be disconnected at the AC panel before leaving the boat, regardless how an inverter/charger is configured.

Rather than go through the hassle of defeating functionality, a better solution (IMHO) is to shut off undesirable AC loads, leave it in Inverter/Charger mode, and set (one-time) the low voltage cut-off as I recommended.

Unless slips are individually metered and charged, leaving AirCon running while away from the boat for extended periods:

1. Wastes electricity.
2. Costs everyone in increased slip fees.
3. Risks sinking the boat (if the seawater pump through hull is not closed.)
4. Risks burning up the seawater pump, if the strainer clogs.
5. Keeps others awake listening to your water discharge.

In other words, don't do it. Instead, incorporate some passive ventilation in the boat for when away, and only run the AirCon when aboard.

Ramblin Rod
Marine Service Provider
About Sheen Marine

[Dockhead]

Originally Posted by ramblinrod

Well, I disagree with you. I believe all non-essential AC loads should be disconnected at the AC panel before leaving the boat, regardless how an inverter/charger is configured.

Rather than go through the hassle of defeating functionality, a better solution (IMHO) is to shut off undesirable AC loads, leave it in Inverter/Charger mode, and set (one-time) the low voltage cut-off as I recommended.

Unless slips are individually metered and charged, leaving AirCon running while away from the boat for extended periods:

1. Wastes electricity.
2. Costs everyone in increased slip fees.
3. Risks sinking the boat (if the seawater pump through hull is not closed.)
4. Risks burning up the seawater pump, if the strainer clogs.
5. Keeps others awake listening to your water discharge.

In other words, don't do it. Instead, incorporate some passive ventilation in the boat for when away, and only run the AirCon when aboard.

Ramblin Rod
Marine Service Provider
About Sheen Marine

??? I don't even have air conditioning.

[mitiempo]

Originally Posted by carstenb

One issue that had us scratching was that all shore power went through the inverter. We installed a 1200W inverter - result? we could only draw 1200W shore power or else the inverter crashed.

Many inverter chargers - Victron Multiplus for one line - will pass through 30 amp or (50 amp depending on model) shorepower even though the inverter output is less.

[ramblinrod]

Originally Posted by Dockhead

??? I don't even have air conditioning.

You are correct, that if you leave the low voltage cut-off at the factory setting, the inverter will take the batteries down lower than they should be taken, if you accidentally lose shore power.

But I disagree that the inverter should be switched to charge only mode when leaving the boat, if one has an AC fridge. Instead, setting a more suitable low voltage cut-off is a better solution.

This way, the unit will automatically switch to charger only mode, if the batteries get too low, else, it will do the best it can to keep the fridge running.

I mentioned air con in the prior post, as I do see many, many boats in marinas with Air Con running and nobody aboard all week. Very bad idea, for all reasons stated. I'm glad you're not one of them.

[mitiempo]

Originally Posted by ramblinrod

Standard practice is to connect shore power directly to marine inverter charger, and then connect inverter charger bypass to AC distribution panel input.

Ramblin Rod
Marine Service Provider
About Sheen Marine

Most inverter manufacturers require a breaker on the AC feed to an inverter/charger. It is also common sense to have one.

[ramblinrod]

Originally Posted by carstenb

One issue that had us scratching was that all shore power went through the inverter. We installed a 1200W inverter - result? we could only draw 1200W shore power or else the inverter crashed.

hmmmm - we had to install an automatic switch so whenever the shore power was plugged it, it circumvented the inverter

another thing to be aware of is some inverter have a high power usage even when they are "turned off" drawing up to 1AH

Hi Carsten,

I wish I knew what type of inverter you have.

A proper marine inverter connected to the AC distribution panel, should be equipped with a shore power pass thru mode.

When shore power is applied, the shore power is automatically passed through the inverter to the AC distribution panel. This should not limit current below the shore power rating, which should be 30 A for a 1200W inverter.

Conversely, when shore power is disconnected, the inverter provides the AC voltage to the distribution panel to the limit of it's rating (1200 W in your case), and disconnects the shore power ground to the AC.

ABYC complaint inverters (for shore power connection) have an internal relay which breaks the inverter ground connection to neutral, when shore power is connected.

Can you advise make and model of your inverter?

And yes, when inverters are "on", there is some 12Vdc power consumption, even when there is no AC load. The smarts and displays have to run all the time, as it has no idea when someone is suddenly going to switch on a high AC load or disconnect shore power.

This is where an inverter/charger really shines. If it has shore power it is in charger mode, and fills batteries. When shore power is disconnected, it draws from batteries to make 120Vac still readily available. There is no external integration required between the inverter and charger, to ensure one stops running whne the other one starts.

[smac999]

Originally Posted by Dockhead

Victrons (and I bet other charger/inverters) can be set to either Invert, or Charge Only. On Charge Only, they merely pass through shore power and will disconnect AC loads in case shore power is interrupted. That's of course the way they should be set when you're off the boat.

They should not be left on "Invert" when you're off the boat. Don't ask me how I know

I was playing with a victron this week and was disappointed there is no charger off mode. if you turn the unit off you lose all AC on the boat. not good for servicing the DC system. the magnums have a charger off mode. where all AC still passes but unit doesn't charge. if I start installing victrons I'll have to put a manual AC bypass before it. so I can have AC on boat but unit not charging.


otherwise some other features look good. like the 2 outputs for inverter vs non inverter loads. normally I just split these loads before inverter. but then load sharing or boost doesn't work if the inverter / charger only has some of the current going through it.

[ramblinrod]

Originally Posted by mitiempo

Most inverter manufacturers require a breaker on the AC feed to an inverter/charger. It is also common sense to have one.

Absolutely!!!!!!

Per ABYC, within 10 feet of the vessel shore power inlet, there has to be a breaker (line and neutral) with reverse polarity indication, matching the current rating of the shore power inlet (and cable). There could also be an AC source switch, (e.g. shore power / generator) in circuit.

My unclear point was that all AC goes through the inverter/charger.

[mitiempo]

Originally Posted by Jimlad

Hi Folks

My existing shore power set up takes the feed into an RCD protected distibution box and then feeds individual MCB's to sockets, fridge, calorifier, battery charger and galley sockets. All works well.

I now want to install a combi inverter/charger.
I believe I will need to fit an RCD into the feed from the inverter. I will of course disconnect the existing charger feed as this will be redundant and I will need to ensure that the calorifier can never be run from the inverter power.

Someone told me that I will need some 'load-shedding' arrangement within the distribution box, but I'm not sure what is meant by that.

Any other issues that I need to know?
Some pointers from someone who has been down this route on how I should do the job would be much appreciated.

You are getting a lot of information, most of it good. But a lot of it is in my opinion too complicated for one whose knowledge on marine AC systems is limited. By your own admission you "dislike electricity because you cannot see it."

The best, most foolproof way of wiring an inverter is in the Pdf in post #4. It uses a sub-panel that only includes items you want to power with the inverter. It is a the same system I described to you on Sailnet last night. It is all laid out in the Pdf in an easy to follow manner.

It always scares me a bit when someone who doesn't understand electricity wants to install an item that can be deadly if done incorrectly is asking how on an internet forum. It is, in my opinion, best to know what each wire is there for rather than just copying a diagram

I do know what an F&C 44 ketch is. It would be a shame if it burned because of a bad installation. It is very important to know what you don't know.

If you do not understand the Pdf in post #4 or the installation manual for an inverter/charger it is best if you hire a qualified professional.

[mitiempo]

Originally Posted by smac999

I was playing with a Victron this week and was disappointed there is no charger off mode. If you turn the unit off you lose all AC on the boat. Not good for servicing the DC system. The magnums have a charger off mode. Where all AC still passes but unit doesn't charge. If I start installing victrons I'll have to put a manual AC bypass before it. So I can have AC on boat but unit not charging.

*All inverters should have an on/off switch in the DC positive to the inverter. While I have not tried it I wonder if it will still pass AC with a disconnected DC+ input.

*As well as a sticker on the main AC panel that the boat is inverter equipped. Prevents surprises of the unpleasant kind.

[smac999]

Originally Posted by mitiempo

*All inverters should have an on/off switch in the DC positive to the inverter. While I have not tried it I wonder if it will still pass AC with a disconnected DC+ input.

*As well as a sticker on the main AC panel that the boat is inverter equipped. Prevents surprises of the unpleasant kind.

maybe, the magnums will continue to pass if DC is lost. but will not start to pass if ac turned on with no DC, just gives low bat fault.

this boat didn't have an inverter switch. it had a few weird issues.