Fitting an inverter into an existing AC system

[Jimlad]

[QUOTE=mitiempo;2029992]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."

I quite agree Mitiempo! Lots of opinions and ideas from the forum. The PDF in post 4 has indeed given me food for thought, and a diagram always makes for easier understanding IMHO.

A lot of replies presume the aircon is a requirement - not so as this was one of the first things consigned to the dumpster at the start of the re-fit.
Far better to use natural ventilation and a few small fans if required. Cold beer on the other hand........

[Dockhead]

Originally Posted by ramblinrod

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.

I always shut down refrigeration and all other systems when I'm off the boat for more than 24 hours. I isolate my batteries from the DC system, and leave only one AC circuit on -- the AC outlets, so that tube heaters can work. I close my sea cocks, too.

If I DID leave refrigeration working, I would never leave the inverter on, because in case of a shore power failure that would only delay spoiling of your food, and kill your batts in the process. What's the point?

Same thing with air conditioning. If I did have air conditioning, I might leave it on in the "dehumidify" mode while off the boat, which I think would be very useful. But I would absolutely keep the inverter switch on "charge only".

[Dockhead]

Originally Posted by mitiempo

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.

Correct. They don't invert all the AC power -- they pass it through via a transfer switch. Mine does 30 amps * 230v = about 7kW, which is a lot more than my 3kW inverter capacity.

One thing to take care with is that the wiring and other elements of the AC system is up to all this.

On a 230/70/3000 Multiplus (as an example), you can have, theoretically:

1. 30 amps of shore power (about 7kW)
2. 13 amps of inverted power (about 3kW)
3. Another 13 amps of momentary inverted power (about 3kW)

For a total of 56 amps.

I designed my system for 20 amps of shore power (16 amps nominal plus a bit -- sometimes I push it) but that is still 46 amps, which required heavier wiring to the electrical panel, different RCD, and some other components.

It's a good idea to have these professionally installed, considering the consequences of a mistake.

[ramblinrod]

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.

Yes, they will. The failsafe mode is AC pass thru.

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

Absolutely! I rarely see these on inverter installations but they should be on all. Else, anyone, (including owner, subsequent owner, or service provider, may open the main breaker, assuming all AC power is disconnected, only to find that the entire AC electrical system is live, due to an inverter mounted in some obscure location.

Ramblin Rod
Marine Service Provider
About Sheen Marine

[ramblinrod]

[QUOTE=Jimlad;2030066]

Originally Posted by mitiempo

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."

I quite agree Mitiempo! Lots of opinions and ideas from the forum. The PDF in post 4 has indeed given me food for thought, and a diagram always makes for easier understanding IMHO.

A lot of replies presume the aircon is a requirement - not so as this was one of the first things consigned to the dumpster at the start of the re-fit.
Far better to use natural ventilation and a few small fans if required. Cold beer on the other hand........

Yeah, I didn't post my usual warning for fear people are getting tired of seeing it, but here goes...

This kinda feels like the time I had kids pull up alongside in a run-about and ask for directions to a destination out in Georgian Bay.

After considering that I could be sending them to their peril if they didn't get my instructions right, I told them how to get to the nearest marina to buy charts.

So, the best advice I can give is to read ABYC E10 and E11 (Electrical Standards) cover to cover, and if there is anything you're not sure about, ask. If you have to ask more than 3 things, you need to read it again.

While Calder's and Casey's books are pretty good about certain systems, they really don't cover good general wiring practices well enough. (It's also a, "Just because you saw it on the internet (or read it in a book), doesn't mean you can do it", kind of a thing.

Next, my best advise is don't go cheap on the products. Use Ancor wiring and connectors, Marinco shore power cables and connectors, and Blue Sea panels and breakers.

Equipped with this, please don't burn your boat to the waterline (which is all too easy, even if your think you have it all figured out.)

There are things one just can't learn from an evening of reading or an hour of YouTube video viewing.

Just because 12Vdc won't electrocute you, doesn't mean it doesn't deserve your full respect and attention.

Before I knew what I know now, I was guilty of all kinds of electrical safety issues, and I was an Electronic Engineering Technician with 30 years experience.

As part of my current marine electrical seminar for boating groups, I start out asking...

"Who does their own electrical repairs and improvements?"

(About 50% of hands go up.)

Then I ask, "Of those, who believes it was done properly?"

(All the hands stay up.)

Then I ask, "Who is so sure of that, they will invite me aboard to perform an electrical inspection, free if it's safe, $200 if I find one electrical safety issue?"

(All the hands go down.)

After the seminar, when I've shown several images of tragic boat fires, and gone through many of the electrical safety issues I encounter, 2 or 3 come up and ask me to do a $200 inspection. They know (now) that they have (and I am going to find) electrical safety issues.

The reason I can do this, and stay in business, is because in my experience to date, about 90% of all boats on the water today have unsafe electrical issues, and about 50% of owner DIY work, is absolutely atrocious. If asked, nobody will say, "The wiring I performed is all wrong". They simply don't know just how unsafe it is.

I'm not saying, "Don't do your own electrical work." I'm just saying, "If you are going to do it, for everyone's sake (yourself, your crew, the next owner, and the boat), ensure you do it right, 100% right."

When you need it, a bilge pump must work, to the best of its potential performance, or a maritime tragedy could occur. When you need it a VHF must work, to the best of its potential performance, or a maritime tragedy could occur. When you need it, the engine starter must turn, to the best of its potential performance, or a maritime tragedy could occur. You get my drift.

There are few electrical / electronic devices aboard that could not become a critical piece of safety equipment some day. Even a Marguerite blender with a botched plug replacement. (A line/neutral short, with a secondary boat wiring or current limiting fault, could result in a catastrophic fire.)

Sailing gives one all kinds of freedom, to move without the sound of infernal combustion engines, to move without roads or guard rails dictating where, to move without adherence to strict schedule, and so on.

It also gives one the freedom to mess up electrical stuff if they don't know what they are doing, and the results could be horrific and life altering.

Ramblin Rod
Marine Service Provider
About Sheen Marine

[ramblinrod]

Originally Posted by Dockhead

I always shut down refrigeration and all other systems when I'm off the boat for more than 24 hours. I isolate my batteries from the DC system, and leave only one AC circuit on -- the AC outlets, so that tube heaters can work. I close my sea cocks, too.

IMHO, shutting down the refrigerator every time one wishes to leave the boat is impractical. All perishables would be lost. Why have refrigeration if not to preserve perishables. Oh yeah, we wouldn't want to let the beer get warm either.

If I DID leave refrigeration working, I would never leave the inverter on, because in case of a shore power failure that would only delay spoiling of your food, and kill your batts in the process. What's the point?

A well insulated fridge can have power unplugged for nearly 24 hours before temperatures rise to point of losing food. In most cases, one should have sufficient battery capacity from full charge to maintain the fridge for about 5 days before hitting 50% charge. Therefore, if one leaves the vessel Monday morning and accidentally switches off shore power, the batteries should maintain the fridge until the following Friday night. On return, the boat owner finds a cold beer and batteries in need of charge, instead of full batteries and a fridge full of warm beer and spoiled food.

Same thing with air conditioning. If I did have air conditioning, I might leave it on in the "dehumidify" mode while off the boat, which I think would be very useful. But I would absolutely keep the inverter switch on "charge only".

I think we simply disagree about the air con system. IMHO, rather than leaving the air con system on, one should seal the leaks in the boat, and install passive ventilation or solar vents, so the air con system can be shut off when the vessel is left unattended.

[Dockhead]

Originally Posted by ramblinrod

I think we simply disagree about the air con system. IMHO, rather than leaving the air con system on, one should seal the leaks in the boat, and install passive ventilation or solar vents, so the air con system can be shut off when the vessel is left unattended.

Well, there's nothing to agree or disagree about -- this is all personal preference and personal approach to operating boat systems.

I have excellent passive ventilation on my present boat, with six massive dorade vents, but the UK is a mildewy environment, and dehumidification is really valuable. I don't have air conditioning, but probably would use it for this if I were on shore power and left the boat for a while. I used to have a portable dehumidifier, but it stopped working last year, and it was a PITA to store on board anyway. I don't condemn or disapprove of people's either using or not using their air conditioning for this purpose -- their decision. But for those who have never tried it -- central air conditioning is a magic dehumidifier -- nothing like it in the world. Wish I had it.


Likewise with refrigeration -- if you have a small reefer which your batts can run for 5 days, then that's great. I don't. I have large front-loading reefer, and large separate freezer with separate compressor, and my batts can't run them for long. So I either leave a crewman on board, or clean out the fridges, when I leave the boat for more than 24 hours. Failed refrigeration, reefers full of rotten food, and dead batts, is a combination just too horrible to ever want to repeat (don't ask . . . ). I also close my sea cocks in this case. That's just the way I operate my boat, which is not to say that someone else, operating differently, is wrong.

[ramblinrod]

Originally Posted by Dockhead

Well, there's nothing to agree or disagree about -- this is all personal preference and personal approach to operating boat systems.

I have excellent passive ventilation on my present boat, with six massive dorade vents, but the UK is a mildewy environment, and dehumidification is really valuable. I don't have air conditioning, but probably would use it for this if I were on shore power and left the boat for a while. I used to have a portable dehumidifier, but it stopped working last year, and it was a PITA to store on board anyway. I don't condemn or disapprove of people's either using or not using their air conditioning for this purpose -- their decision. But for those who have never tried it -- central air conditioning is a magic dehumidifier -- nothing like it in the world. Wish I had it.


Likewise with refrigeration -- if you have a small reefer which your batts can run for 5 days, then that's great. I don't. I have large front-loading reefer, and large separate freezer with separate compressor, and my batts can't run them for long. So I either leave a crewman on board, or clean out the fridges, when I leave the boat for more than 24 hours. Failed refrigeration, reefers full of rotten food, and dead batts, is a combination just too horrible to ever want to repeat (don't ask . . . ). I also close my sea cocks in this case. That's just the way I operate my boat, which is not to say that someone else, operating differently, is wrong.

Don't understand. Mutually exclusive conditions. One cannot close all sea cocks AND leave air con running.

Again, if you set your inverter low voltage cut-off properly, you will not have dead batteries, should your shore power be accidentally disconnected. This will allow your inverter, to do exactly what it is intended to do (run AC loads when shore power is not available), in an attempt to avoid food spoilage. If it simply can't do it (period without shore power is too long) it will shut-down the inverter BEFORE the batteries are killed.

Notwithstanding, you are absolutely correct, anyone can do whatever suits them on their own boat.

Presently, we live on the boat on weekends, and I live it on it a few days through the week, when closer to customer boats I'm working on. To empty the fridge and shut it down every time I left the boat, would really negate the value of having the fridge in the first place.

[Dockhead]

Originally Posted by ramblinrod

Don't understand. Mutually exclusive conditions. One cannot close all sea cocks AND leave air con running.. . .

I guess you missed the part about how I don't have air conditioning at all

[ramblinrod]

Originally Posted by Dockhead

I guess you missed the part about how I don't have air conditioning at all

No, I didn't miss that.

I read where you close all seacocks when leaving the boat AND suggested that air con could be left running for dehumidification.

As most air con systems use pumped seawater, ya can't do both (close all seacocks and leave air con running).

Again, there are a number of very good reasons NOT to leave air con running, as I previously posted, and you seemed to disagree with by posting a contrary point of view.

[Stu Jackson]

OK, rod, chill. We hear you, and also hear DH, who noted that he carefully explained it is his way of managing his systems.

Back to the OP: Good material here. You really have to do some homework, research and hands-on to get experience with designing systems, selecting the equipment and doing an installation.

For example, both "sides" are right about automatic transfer switches and chargers.

Victron, for instance, makes two different kinds of inverter/chargers, one with and one without ATS.

Like this from their online manual for the one without the ATS:

To transfer the load to another AC source: the automatic transfer switch
If an automatic transfer switch is required, we recommend to using the MultiPlus or Quattro instead. The switch is included in these products and the charger function of the MultiPlus/Quattro can be disabled. Computers and other electronic equipment will continue to operate without disruption because the MultiPlus/Quattro features a very short switchover time (less than 20 milliseconds).

From here: https://www.victronenergy.com/invert...ompact#manuals


One thing to note is that the wiring information is online from all vendors, who many times show optional wiring arrangements for how you want manage your system.

[mitiempo]

Originally Posted by Stu Jackson

For example, both "sides" are right about automatic transfer switches and chargers.

Victron, for instance, makes two different kinds of inverter/chargers, one with and one without ATS.

Like this from their online manual for the one without the ATS:

To transfer the load to another AC source: the automatic transfer switch
If an automatic transfer switch is required, we recommend to using the MultiPlus or Quattro instead. The switch is included in these products and the charger function of the MultiPlus/Quattro can be disabled. Computers and other electronic equipment will continue to operate without disruption because the MultiPlus/Quattro features a very short switchover time (less than 20 milliseconds).

From here: https://www.victronenergy.com/invert...ompact#manuals

Stu

As far as I know all Victron inverter/chargers have a built-in transfer switch. Actually I don't believe I have seen an inverter/charger from any manufacturer without a transfer switch.

The Phoenix you linked to is an inverter, but not a charger.

[ramblinrod]

Originally Posted by Stu Jackson

OK, rod, chill. We hear you, and also hear DH, who noted that he carefully explained it is his way of managing his systems.

Back to the OP: Good material here. You really have to do some homework, research and hands-on to get experience with designing systems, selecting the equipment and doing an installation.

For example, both "sides" are right about automatic transfer switches and chargers.

Victron, for instance, makes two different kinds of inverter/chargers, one with and one without ATS.

Like this from their online manual for the one without the ATS:

To transfer the load to another AC source: the automatic transfer switch
If an automatic transfer switch is required, we recommend to using the MultiPlus or Quattro instead. The switch is included in these products and the charger function of the MultiPlus/Quattro can be disabled. Computers and other electronic equipment will continue to operate without disruption because the MultiPlus/Quattro features a very short switchover time (less than 20 milliseconds).

From here: https://www.victronenergy.com/invert...ompact#manuals


One thing to note is that the wiring information is online from all vendors, who many times show optional wiring arrangements for how you want manage your system.

Can't chill. My air con is off because I am away from the boat!