Refrigerator on a boat

If that figure is accurate you will need to install a towing winch to handle the battery barge.

Hi,

Marmot - He says it's full size so it must run at full power 24/7.

As Marmot says you will need some pretty hefty batteries to support that sort of load,.

As for your supply question it is not a complicated setup to have a couple of contactors, one for each supply controlled by Aux contacts that only allow one to be closed at any time.

Any Marine Electrician should be able to build you one in a box that just needs to be connected to the two supplies.

Many inverters incorporate a transfer switch that automatically connects the load to shorepower when it is available.

There is no need to mess around with expensive homebuilt devices that when they fail can create more electrical excitation than you planned on.

Hate to point out the obvious, but there is a reason you have a genny. That being so you could have the comforts of a/c, TV and a full size fridge. If you're sleeping on the hook and don't want the genny on for a/c, then shut it.
The fridge will maintain its temp for several hours if the door isn't opened. Otherwise, enjoy the comforts of a bigger boat and accept there is a cost, but it's only a few gph.

Refrigerators don't run all the time. How did you come up with 1800 watts?
That sounds like a startup load. They are usually more like 2-3 amps @ 120V running (300 watts). Maybe run 8 hours out of 24. A typical 21 cu ft would be energy star rated at 500-600 KWh per year.

600 KWh / year / 365 days = 1644 W / day
1644 w/day / 8 hour run time = 206 w/hour

This link might be helpful.

http://www.batteryweb.com/pdf/inverter_battery_sizing_faq.pdf

There are many inverters out there that can automatically switch over as soon as the A/C power fails. No user input required. You would wire this after your Gen/Shore switch.

Something like a Xantrex XM1000 or XM1800 Pro Series should work for you.

Seems like you are going to need to add battery capacity and that will add some weight not to mention having to find a place for them.

I have the same setup with a full size fridge. I run the genny whenever I am running my engines (going somewhere). If I am on the hook, I shut it down and the fridge stays cold for several hours with no problem. We have over-nighted for several days by running the genny for a few hours in the morning and evening and leaving it off overnight. A few frozen soda bottles of water helps as well as a well stocked fridge and freezer.

AC/DC fridges by Tundra and Norcold (some say Nevercold) are apartment sized. I've never seen anything bigger.

Hi,

What????

No outsourced call centre where the staff speak something they purport to be English but no one else can understand?

You certainly struck it lucky with that one.

not to forget Mastervolt - world class products and we always had a faultless service from their network

Pascal:

Can you really run air conditioning off your inverter? I have a client who says he's heard of this, but I thought he was nuts...compressor start-up amperage draw and all that...

Yes. Mermaid 16,000 BTU, Xantrex 3000 Watt continuous / 5000 W Peak.

However you are not going to do it long off of a battery bank. Running amp draw is about 110 Amps at 12V DC. You'll need at least 200 amps of alternator(s) on your engine(s) to keep up. Plus at least an 8D just to carry the startup load. Single 8D will probably give you about 45-50 minutes of run time.

So it's possible but only practical on a boat where you expect the mains to be running whenever you need A/C and you have high capacity alternators with a high capacity combiner.

I had the setup but my primary purpose was not to run A/C. The A/C did work fine on the few occasions I used it that way though. I also know of someone running a 7,000 BTU A/C off of an 1800W inverter.

If you really wanted to go DC, you'd be better off using a small DC genset feeding into a battery bank and then an inverter. Or perhaps better yet DC air conditioning with a DC genset and battery bank.

DC gensets are small and efficient compared to most AC sets.

If you decide to install the inverter careful about one particular aspect of the installation. Most of the smaller units come with built-in overcurrent protection for the installed AC outlets but not for a circuit that is hard wired through them. I have come across several installations that missed on this point owner and professionally installed. The diagrams that come with them usually show all the other details but this aspect is covered in the small print and seems to get overlooked.

And I guess that would be a Panda?