A/C for Venture 23.

[thataway]

[srbaum]

As Bob stated there are units more suitable for saltwater use. After retiring for the USCG and taking care of at least 2200 small boats (boats less that 65'), I went to work for the Corps of Engineers and took care of their boats. I purchased and had many AC roof tops put on survey boats and had almost zero problems with them. They were all Coleman SeaMach/MarineMach 13500 BTU Air Conditioner, or similar in BTU ratings.

[Full Circle]

I wanted to add AC to Full Circle for our Great Loop trip and did lots of research. We never got it done and suffered a little as a result. A rooftop unit was the easiest way to go, but our roof was completely occupied by the Roofnest roof tent with solar panels on top.

Nevertheless, I came across a couple of solutions that I liked which haven’t been mentioned here yet.

1: Dometic RTX 1000/2000 12V rooftop units. These are real AC units with efficient 12V compressors. Compared to 120V units, they are substantially lighter, quieter, and lower-profile. You’ll want 400-ish amp-hours (at 12v) of battery capacity and 400+ watts of solar if you don’t have a generator.

2: There are a few relatively new portable AC units that tick a lot of boxes for C-Dory cooling. My favorite is the new ZeroBreeze Mark 3. Think sewing machine-sized box with flexible ducts for intake/output air. 5280 BTUs, 22 lbs, 46 dbs, condensation drain pump. It’s 48v, so you either buy the battery packs that attach to the unit and charge them using 110v current when available, or you use your house bank and convert to 48v. Similar units are made by Bouge RV and Ecoflow. My measurements suggested that it would sit on top of the dash above the V-berth opening with the exhaust hose sticking out the center window and the cool air blowing into the cabin via the built-in vent or ducted into the V-berth at night through the duct hose. We fabricated a curtain for the V-berth opening. Poking the hose through the corner should allow the unit to maintain pleasant sleeeping temps using very little power. (The Mark 3 has a thermostat; the Mark 2 did not.)

Regarding rooftop units, I’m surprised any of them can withstand regular salt water baths. They are engineered to sit on top of RVs, after all.

[Donald Tyson]

Dan, I'm new to this and I ask how do you plan get 400Amps to supply a roof unit without shore power? Can a standard battery bank supply this? I don't mean any disrespect, please forgive me if I stumble over this but a used medium age C-Dory 25 will be the most expensive thing (other than my house) that I'll ever buy. So the I don't want to muck up the looks of it by adding pipes, hoses and wiring all over the darn thing and I won't add something to a windows that bespeaks a 1950's Brooklyn garden flat. These Dometic 12V units that you refer to looks more factory built and clean and lean looking. But how to power it?

[Full Circle]

I’m no expert on this stuff, so you’ll want to find a qualified resource to help you put this all together. But here’s how I think about it. Some of my assumptions may be way off.

The unit “amp-hour” represents an amount of current (amps) consumed in one hour. (Voltage is assumed to be 12V in this example.) The Dometic unit draws 20 amps in “Eco” mode, which would probably be adequate at night but not during the day. Its max draw is close to 60 amps. Let’s assume that its average draw during a normal day is 30 amps. An AC unit, like a refrigerator, cycles to maintain the set temperature, so it’s not always on; the “duty cycle” is less than 100%. Let’s say the compressor is running 50% of the time and you leave the unit switched on all day.

In 24 hours, the unit will consume 30amps x 24 hours x .5 = 360 amp-hours from the battery bank. That’s probably not feasible with solar power only. Another more likely scenario is that you only run it at night so you can sleep. 20 amps x 8 hours x .5 = 80 amp-hours. Your actual usage would likely be somewhere in between — maybe 150 amp-hours per day?

A larger battery bank allows you to go longer before the batteries are depleted, which is why I mentioned 400ah. That’s 2 - 200ah lithiums, which would fit easily in a C-Dory. But you DO have to replenish that lost energy with some combination of solar, the engine alternator, a generator, or shore power. In a 12 volt system, that 150 amp-hours translates to approx 2000 watt-hours of energy consumed (150ah*12.6v=1890wh). A nominal 400-watt solar array is about all you have room for on a C-Dory, and it might produce 300 watts for 7 hours on a summer day, putting 2100 watt-hours back into the battery. This barely replaces what the AC used, and you still need to power all the other systems on the boat. So you’d either need to curb your AC use or find some more charging power.

This all begs a couple of questions: How often will you really need cooling when you’re NOT connected to shore power, and how do you feel about generator noise? Running air conditioning off-grid is still challenging — and expensive. In the end, it may make more sense to install a cheaper 120V rooftop unit and power it with either shore power or a generator.

Again - I haven’t done this yet, so some of my calculations could be off.

[Donald Tyson]

I'm not holding you to any exact statement, this is a discussion at this point and a discussion that I did not see coming until others assured me of how much I will need AC. I'm not a systems guy. I hate all the distractions of things electric. In a perfect world I'd prefer the peace of quietness.
I had figured battery powered fans would do. But I'm told no, that I'll need AC as the humidity and heat is too hard on old folks like me in so many areas. Dewalt and Ryobi fans that we use when camping are impressive but they only circulate air and they do not cool it.
I like solar. I use solar fans in my 800 cu ft wood kiln. The fans run for days as the wood dries with no juice past what their small solar panels provide. Liking solar and knowing how to discuss it and design systems with it is a whole other discussion.
What is an inverter?

[thataway]

See my answer about inverters in your other thread.

I never used air conditioning at Lake Powell even in the summer hottest days. I spent a year total time in the Caribbean (East and Western In Florida--at night I just opened the hatches of our sailboats and put up a wind scoop, and that was enough to sleep most of the time. There was almost always enough breeze to keep us comfortable.

When I got to Florida--there was no breeze in the marinas--and we felt the need for air conditioning--but we still did not get it in our sailboats. Fast forward to our first "trawler"--A Symbol 42 foot motor yacht, and we had 45,000 BTU of air conditioning...including the Flying Bridge.

Full Circle:

[Donald Tyson]

Well Gentlemen Its nice to see what is ahead of me, with a lot of forewarning. I do want to be as free of the shore power as reasonably possible. I'm not terribly against it but don't want to be dependent on it for daily use.
Thanks for all the comments. I hope to see how you all progress. I guess the smaller boats are easier to cool when there is no shore power available.

[thataway]

Actually I believe that the smaller boats are more difficult to aircondition since the larger (26/26&255) have more storage space, and a higher cabin top and headroom. I have used the same size window unit through the opening front window for both the 22 and 25. I have run them off shore power or a Honda EU 2200 generator,

[Donald Tyson]

Kevin,
So looking forward to your final solution. have fun with it and please share the outcome.
Don