A/C that runs off a battery...

[NiceAft]

I am not anywhere near knowledgeable about air conditioners, and their installation. Do all of the suggestions posted so far also need a through the hull for water ingress, and one for water egress? This one did.

[Tomfoolery]

Standard DC-powered marine A/C systems do. I've never seen one that was air-to-air, though I suppose they might exist (just 'cause I didn't see it . . . ).

Not talking about window units in a Billy Box, of course. That's a cost effective way to add air conditioning. Not so cost effective is how to store enough energy and then put it back, all while not being connected to shore power.

[Be Free]

I am not anywhere near knowledgeable about air conditioners, and their installation. Do all of the suggestions posted so far also need a through the hull for water ingress, and one for water egress? This one did.

Most (all that I know of) marine AC units have an underwater through-hull to pick up water. It is usually well below the waterline so it never becomes exposed. That works for a boat with five or more feet of permanent keel to protect it. No so much for a boat that may be beached on purpose. Some have another through-hull (above water) for the "used" water to exit. Some put it in the bilge and allow the bilge pump(s) to remove it.

[Be Free]

... That's a cost effective way to add air conditioning. Not so cost effective is how to store enough energy and then put it back, all while not being connected to shore power.

Hence the 2Kw (or so) inverter generator. We just don't have enough "real estate" to install enough solar to keep up with enough batteries to run an AC off batteries. I really wish it were possible but I can't make the numbers work and I don't know of anyone who has succeeded. We can carry enough battery power to do the job (it's expensive but it can be done); we just can't recharge them with the amount of solar that will fit on the boat. It's going to take a generator and a good battery charger.

[Russ]

Most (all that I know of) marine AC units have an underwater through-hull to pick up water. It is usually well below the waterline so it never becomes exposed. That works for a boat with five or more feet of permanent keel to protect it. No so much for a boat that may be beached on purpose. Some have another through-hull (above water) for the "used" water to exit. Some put it in the bilge and allow the bilge pump(s) to remove it.

My marina in NJ had mostly powerboats and almost ALL had A/C. At night all you could hear through the marina was water from their A/C being pumped over.

Makes sense to use water to cool A/C as it's much more efficient.

[NiceAft]

That seems to be more like a heat pump.

I had a cousin in upstate N.Y. that used the same system in his house. He tapped an underground well.

[Jimmyt]

That seems to be more like a heat pump.

I had a cousin in upstate N.Y. that used the same system in his house. He tapped an underground well.

You are correct. The cooling-only marine system is an air conditioner with a water-cooled condenser. If it heats and cools, it's often called a water source heat pump.

All air conditioners are "heat pumps" (moving heat from a source to a sink). A reversing valve allows switching the source and sink so that you can either heat or cool the occupied space with one system. The term "heat pump" is commonly used when referring to a system with a reversing valve; although I would argue that a more accurate term would be a reversible heat pump. Although, nobody gives a rats backside...

The heat source and the heat sink can each be a variety of media; water, air, earth, etc. There are heat pump water heaters that take heat out of the air and reject it into the water in the tank, simultaneously providing space cooling and domestic hot water. This is an air source, water sink, heat pump.

Your cousin's system is typically called a water source heat pump (although that's only true when in the heating mode). It can be done with well water, although some areas don't like you pulling out of aquifers and running it through equipment, then dumping it back in. Another common installation involves boreholes with a u-tube inserted and grouted in place. The heat exchange liquid is piped from the surface, down the borehole, and back up. Very small chance of contaminating the ground water with this approach. You also see trenched systems with tubing placed in the trench. Both of these are often referred to as ground-coupled heat pumps (they are water source, ground coupled).

You will see numerous companies use the term "geothermal" referring to ground-coupled systems. Not really the correct use of the term.

Lots of terminology. Lots of different configurations. All are designed to move heat from where you don't want it to where you do want it (or where you don't care if it winds up there...).

[NiceAft]

Excellent explanation. Thank you.

Now get in your Mac, go to Glasgow, and convince that group to stop just talking at the COP 26, and do something constructive before COP27.

[Tomfoolery]

That seems to be more like a heat pump.

I had a cousin in upstate N.Y. that used the same system in his house. He tapped an underground well.

You are correct. The cooling-only marine system is an air conditioner with a water-cooled condenser.

And then there are water-cooled condensers that use city water. I’ve seen this in NYC, in my first so-called engineering job many many moons ago. Some bodega had air conditioning running, but being on the ground floor of a glass curtain wall building with no window to put an air conditioner (usually over a door in such places), the condenser used city water, which then just flowed into a sink drain.

While cooling towers lose a bit of water through evaporation, this water was single use. It was allowed long ago, and grandfathered, but even back then, if you replaced it, use of direct city water instead of a cooling tower or air cooling was out of the question.

Just thought it was interesting. Like a marine system, but using city water instead of sea or lake water.

[Russ]

And then there are water-cooled condensers that use city water. I’ve seen this in NYC, in my first so-called engineering job many many moons ago. Some bodega had air conditioning running, but being on the ground floor of a glass curtain wall building with no window to put an air conditioner (usually over a door in such places), the condenser used city water, which then just flowed into a sink drain.

While cooling towers lose a bit of water through evaporation, this water was single use. It was allowed long ago, and grandfathered, but even back then, if you replaced it, use of direct city water instead of a cooling tower or air cooling was out of the question.

Just thought it was interesting. Like a marine system, but using city water instead of sea or lake water.

Yup.

My dad's office on 666 5th ave in NYC used city water for cooling. I guess they just dumped the used water into the sewer. I recall one year during a severe drought they couldn't use the water for A/C and had to shut the building. Crazy way to cool.

[Jimmyt]

Never seen one-pass city water before; but did troubleshoot a system that was one-pass well water that discharged into the bayou. Building had about 10 water-source reversible heat pumps in it. Used a good bit of well water (though insignificant compared to an office building in NYC). Asked them how they got it permitted and they got this silly look on their faces.

For yucks, the problem with the two units that weren't working was no waterflow. The original installer used flex hose to make the connection at the equipment. He twisted/kinked the flex hose... To be fair, the hose was insulated, making the problem a bit difficult to find (for the 5 or 6 techs that came before me).

We designed bore hole systems almost exclusively. Did one small unit in a powerhouse that I used a keel-cooler on to prevent running raw water through the heat pump. Easier to do maintenance on the outside of a keel cooler than the interstitial space between concentric tubes.

Did a lot of cooling tower systems, but used in conjunction with chillers on big chilled water systems.

[Tomfoolery]

And then there are water-cooled condensers that use city water. I’ve seen this in NYC, in my first so-called engineering job many many moons ago. Some bodega had air conditioning running, but being on the ground floor of a glass curtain wall building with no window to put an air conditioner (usually over a door in such places), the condenser used city water, which then just flowed into a sink drain.

While cooling towers lose a bit of water through evaporation, this water was single use. It was allowed long ago, and grandfathered, but even back then, if you replaced it, use of direct city water instead of a cooling tower or air cooling was out of the question.

Just thought it was interesting. Like a marine system, but using city water instead of sea or lake water.

Yup.

My dad's office on 666 5th ave in NYC used city water for cooling. I guess they just dumped the used water into the sewer. I recall one year during a severe drought they couldn't use the water for A/C and had to shut the building. Crazy way to cool.

Small world - the admiral worked at 666 5th Ave when we were dating, back in the 80’s. She worked for Wang Laboratories (the word processing pioneers) when I met her, then Citibank/Citicorp. I actually encouraged her to apply to Citi, but she didn’t want to because the office was in Westchester County instead of the city, but after a couple of years she was back in Manhattan, at 666, then eventually at 399 Park Ave. Best move she ever made (you’re welcome, dear).

[Be Free]

Small world - the admiral worked at 666 5th Ave when we were dating, back in the 80’s. She worked for Wang Laboratories (the word processing pioneers) when I met her, then Citibank/Citicorp. I actually encouraged her to apply to Citi, but she didn’t want to because the office was in Westchester County instead of the city, but after a couple of years she was back in Manhattan, at 666, then eventually at 399 Park Ave. Best move she ever made (you’re welcome, dear).

Getting smaller. I wrote my first program on a Wang 720A in the early 70's. Cutting edge, 1K of memory, about the size of a microwave, no monitor. It belonged to the engineering program but I wrote several multi-person games that would run on it with the help of an IBM Selectric.

[OverEasy]

For what it’s worth saw a post/article a while back for a sailboat at anchor “single use” cooling system that used a deep intake line and a shallow depth discharge line with a simple 12vdc powered circulator pump and a 12vdc fan automotive radiator.

Cooler water up from the bottom through the radiator and then returned to sea. Deeper the intake the cooler the water. Screen filter on intake line.

Note: That boat also used sun shades over the decks and cabin to reduce solar thermal loads.

I suspect one would want to replace the auto radiator fan with a more efficient marine type fan to reduce the amperage draw further but it does look like an interesting concept to knock down the ambient cabin temperature a few degrees….

Somethings better than nothing.

[OverEasy]

Hi All

Recently found something of actual interest on this topic yesterday while surfing YouTube!
(It’s not the single use system I was looking for but is something that might be of interest to those desiring a true battery powered air conditioning system.)

The O’Kellys
Oct 28, 2021
FINALLY! The Holy Grail - Air Conditioning off Batteries on our Sailboat



System is entirely 12VDC powered.
Not a 115VAC system powered via an inverter so that cuts a chunk of the power requirements right there.
This is a commercial unit that can be DIY installed.
Not cheap but could actually provide air conditioning all night long without a generator running.
Getting enough solar panel area to recharge the batteries during the day would require some doing but I believe that if one wanted to it might be accomplished (at least while anchored).

The BTU of cooling vs wattage consumed is remarkably low.
The kicker is that this same unit is also a heat pump and is capable of warming up the cabin if desired!

The system does require a pair of through hull penetrations for the exchanger to work.
The system shown in the video is cooling a master stateroom that is equivalent to the interior of a Mac26X or Mac26M.








While the upfront costs are something to consider, this might be of interest to those desiring a commercial off the shelf system that runs directly on 12VDC that has the capability of providing operational battery powered heat pump air conditioning cooling (and heating).

Best Regards,
Over Easy