# No A/C when motoring?



## NickPapagiorgio (Jan 21, 2009)

Hi everyone, 

I don't own a boat (yet), but we've done a fair amount of chartering on the Nothern Chesapeake Bay. Our last trip was July 6-8 during the extreme heat. The high temperature was well over 100 degrees and the wind was constantly at our back (when there was wind). 

Usually, it's fairly comfortable down below when under way becuase the air temps are usually lower on the water and there's generally a pretty good breeze. On this trip however, it was just unbearable. 

We had my 2-year-old son with us and it was way too hot for him to take a nap down below, so he ended up being pretty miserable for most of the trip. 

Anyway, I was wondering why you can't use the engine to power the A/C like in a car. The boat we had out was a Catalina 350, but as far as I know, most, if not all, sailboats are set up so that the A/C is only operational if plugged into shore power or if you have an onboard generator. Anyone know why? Also, how hard would it be, or is it even possible, to rig something up to allow the A/C to run while the engine is on?

Thanks, 

Kevin


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## deniseO30 (Nov 27, 2006)

The HP required to power AC is fairly high even in very efficient systems. It is possible with a boat that has on-board generation. The propulsion engine can do it HP wise yet it would be running nearly all the time.


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## PorFin (Sep 10, 2007)

The comparison of a car to a boat is not a good one, for several reasons:

As Denise noted, your typical auxiliary engine in a sailboat is way smaller than the one found in your average minivan -- think about 1/4 or less of the output. 

Compounding the issue is that the volume to be cooled inside a boat is probably at least double of that in the minivan.

Certainy not an insurmountable problem, but really expensive to solve. 

If you want to run an engine driven system, then you've got to drop in a new larger one that probably won't fit in the space designed for it by the designer. This could also throw off your wieght/balance and cause trim issues. You also would almost never get the engine anywhere near its optimum power curve, unless you're running the a/c constantly. This is not a great thing for a diesel engine.

The more typical solution is to install a genset that can handle the load needed to run the a/c. Only runs when you need it, can also be used on the hook, etc, etc. However, they don't come cheap, and also pose a challenge trying to carve out space for it as well as the weight issues noted above.

Most people find that 12v fans are a good enough alternative.


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## Tim R. (Mar 23, 2003)

Our boat has an engine driven 5kw generator that can run the Mermaid marine reverse cycle AC when motoring.


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## night0wl (Mar 20, 2006)

On extremely nasty days, I've been known to run the Honda EU2000 Generator to run the A/C below while underway.


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## travlin-easy (Dec 24, 2010)

I have an emergency, 8,000-watt generator at home. It's powered by a 5-HP, air cooled engine. When we were without power last summer I was able to run a 10,000 BTU air conditioner, lights and a TV with no problem at all. That 10,000 AC unit cooled 1,450 square feet in no time at all. There, I believe it is quite feasible to utilize an automotive air conditioning system on a sailboat and not consume very much HP from the engine while running. I believe the only reason it has not been done at this point is no one would want to pay for the installation of this type of system that would not likely be used very often.

Now, if the boat only has a 10 to 15 HP diesel engine, 5-HP could constitute a loss of 33 to 50 percent of the boat's available power. Keep in mind, though, that the HP rating of the boat's engine is usually at 2/3 to 3/4 of the engine's maximum RPM (sometimes higher), therefore a 5-HP drop at lower RPM would really be significant.

Boats with larger engines, such as the 55-HP Perkins, 30-HP Atomic-4, etc..., could easily handle a relatively large, automotive air conditioning system and suffer very little power loss. At one time in my life I owned a VW Micro-Bus that had a air conditioner. The van had a 4-cylinder, 36-HP engine. When there were 4 adults in the van, the air conditioner had to be shut down in order to maintain speed when pulling up fairly steep hills. On flat roadways it ran just fine with the AC running full blast. When my 33-Morgan O.I. is underway, the A4 runs at just 1,800 RPM to push it along comfortably at 6-knots. I sincerely believe that the engine would easily handle an automotive AC unit, but I'm too old to undertake the project.

Good Luck,

Gary


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## Allen-deckard (Jul 26, 2011)

http://www.ebay.com/itm/1950s-Thermador-Car-Cooler-VINTAGE-Swamp-Cooler-/180919989487?pt=Vintage_Car_Truck_Parts_Accessories&vxp=mtr&hash=item2a1fabf4ef#ht_2027wt_689

Not saying this would fit the bill at all but used this in the 50s on VW beetles that were running 20hp motors.

Big downside is that it will add humidity to the cabin up side is that it will drop temp an average of 20 deg and only has a fan to run. Anyway old school thought.


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## JimsCAL (May 23, 2007)

I think the answer to the original question is that most people are much more concerned about A/C when in the slip and thus AC shore power is the way to go. Don't want to have to run the diesel all the time in the slip. A generator is the solution for A/C when away from shore power.


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## deniseO30 (Nov 27, 2006)

travlineasy said:


> I have an emergency, 8,000-watt generator at home. It's powered by a 5-HP, air cooled engine. When we were without power last summer I was able to run a 10,000 BTU air conditioner, lights and a TV with no problem at all. That 10,000 AC unit cooled 1,450 square feet in no time at all. There, I believe it is quite feasible to utilize an automotive air conditioning system on a sailboat and not consume very much HP from the engine while running. I believe the only reason it has not been done at this point is no one would want to pay for the installation of this type of system that would not likely be used very often.
> 
> Now, if the boat only has a 10 to 15 HP diesel engine, 5-HP could constitute a loss of 33 to 50 percent of the boat's available power. Keep in mind, though, that the HP rating of the boat's engine is usually at 2/3 to 3/4 of the engine's maximum RPM (sometimes higher), therefore a 5-HP drop at lower RPM would really be significant.
> 
> ...


Gary the easiest way would be to get a window box. remove the gas, run the comp lines to a engine mounted comp. (with tubing and hoses) and use the condenser or a water cooled condenser. A few tricks with 12 volt relays and a inverter for the blower. it would work.. would look "cobbled" however


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## travlin-easy (Dec 24, 2010)

I thought about that, too, Denise. Also watch the video at 




Gary


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## deniseO30 (Nov 27, 2006)

Not in production and he's really not saying anything about the machine itself.

"Published on Apr 3, 2012 by Manzar Qayyum

kabin Kool has devolved in 6 different model hot & cool air conditioners suitable to install in all kind of semi truck sleepers ,Boats and ambulances,Roof top and duel evaporator unit is for RVs,we also have 3 models in 9000 ,12000 and 18000 BTU for domestic,office and commercial use with solar power or DC batteries(to mitigate the load shading)"

He's not telling something, and that something is the load requirements Unless it missed it on the Vid.

No matter how you power it.. AC in those BTUH ranges need 3/4 to 1=1/2 HP this just is a fact.. it can of course be reduced and managed with scroll or rotary compressors that have very low starting torque.

Here's the specs on a typical 1 HP 12 volt motor;

Grainger Industrial Supply
Description: Permanent Magnet DC Totally Enclosed Fan-Cooled Motor, HP 1, RPM 1800, Armature DC Voltage 12 VDC, NEMA Frame 56C, Mounting Face/Base, Service Factor 1.00, Bearings Ball, Full Load Amps at Nameplate Volts 80.0, Thermal Protection None

80 amps! how long would that last on batteries? LOL

This guy at least is honest. says it runs 35- 50 amps


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## travlin-easy (Dec 24, 2010)

I was hoping to see specs on the system as well, and the video indicated that he was running the unit on a couple solar panels that he showed on the top of the RV. Can't punch 80 amps from any solar panel that I know of. 

I'll try to call the telephone numbers on the video and see if I can get that information.

Gary


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## night0wl (Mar 20, 2006)

How about this kind of solution:






If worried about humidity, then you'll can run some kind of metal ductwork/tubing through the ice to keep it isolated from the ice.

To make/keep ice for the cooler, have one of these running *IN THE COCKPIT UNDER SHADE*
Amazon.com: NewAir AI100SS Portable Ice Maker: [email protected]@[email protected]@http://ecx.images-amazon.com/images/I/[email protected]@[email protected]@41f3fc53xKL

I think the 12v icemaker debate has been had, and what resulted was crap. So best to run this badboy on an inverter. Someone measured that these portable icemakers take about 4-6 amps through an inverter. So, in the peak of your day, if you have solar panels, you should be generating more than enough amperage to run the icemaker to hopefully fill the ice chest/swamp chest with ice.

Then you can run with "A/C" enough to cool a decent size room with just a 12v fan 

This seems like an interesting "dump load" project for those days your panels and windgen are cranking out amps with nowhere to go!


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## night0wl (Mar 20, 2006)

Then there's this option:






Looks pricey


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## night0wl (Mar 20, 2006)

aaaaaand finally, this option which would factor the humidity aspect of things:






Still need a way to generate ice/icewater for this system to work...and you have added amp draw of a water pump now.


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## travlin-easy (Dec 24, 2010)

Well, I called the telephone numbers on the video, the first one was some young girl who left a message saying she was not available. The second, (916)712-1314 was a guy that apparently invented the air conditioner, who sounded like he was from India, said to send him a text message to the telephone number, which I cannot do from my PC, or at least I don't know of a way to do it. I asked him if the unit was commercially available and he said yes, and please send him a text message.

Cheers,

Gary


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## -OvO- (Dec 31, 2011)

There were a couple of things about that "cabincool" video that looked sketchy. The big one was the use of a remote thermometer to make claims about exterior / interior temps. It's not like a real, analog thermometer is expensive or difficult to operate. It seemed clear to me that the huckster was taking the temperature of a dark-colored bit of metal on the side of the RV and claiming that was ambient air temperature. Note that the cameraman didn't even show you what the thermometer was pointing at, just the display. Then he pointed it at the guts of his gizmo and, oh look, there's some tiny thing down in there that is *really* cold (probably the evaporator itself), and finally points it into the maw of the conventional AC air vent and doesn't find any object in there that is more than ordinarily cool... Too fishy for me.


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## deniseO30 (Nov 27, 2006)

There was a time when a 36,000 btu central air unit would draw nearly all of the 40 amps at 230 volts it was hooked up for. Now.. they run on about 9 -12 amps for the same capacity.. while they have made great strides in HP vs capacity. They still need a good share of HP to handle any kind of capacity.


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## NickPapagiorgio (Jan 21, 2009)

Thanks for all the replies... I didn't think about the power output or cooling size requirements of the boat v. a car, but I guess that answers my question. I know a generator can be used but I just figured it would be simpler to just use the boat's engine. I guess I was wrong. I'm sure there's a way to do it on certain boats, depending on the size of their engine, but I don't think a one-size-fits-all approach is feasible. 

Thanks, 

Kevin


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## Brewgyver (Dec 31, 2011)

travlineasy said:


> I have an emergency, 8,000-watt generator at home. It's powered by a 5-HP, air cooled engine. When we were without power last summer I was able to run a 10,000 BTU air conditioner, lights and a TV with no problem at all. That 10,000 AC unit cooled 1,450 square feet in no time at all. (snipped)


Hi Gary,

Think you missed a digit when reading the data on you 8 kw genny at home. It's physically impossible to generate 8 kw with 5 hp. 1 hp = ~746 watts, or just shy of 11 hp for 8,000 watts. And that conversion is at 100% efficiency, which is also impossible, as there are always losses in any conversion of energy. Typical 8 kw gensets have 15 hp engines.

That said, most moderate sized boat A/C systems are only 6 to 8kbtu, or 1/2 - 1/3 ton, and shouldn't be any problem to run on a 2 kw or larger genset.


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## Brewgyver (Dec 31, 2011)

deniseO30 said:


> There was a time when a 36,000 btu central air unit would draw nearly all of the 40 amps at 230 volts it was hooked up for. Now.. they run on about 9 -12 amps for the same capacity.. while they have made great strides in HP vs capacity. They still need a good share of HP to handle any kind of capacity.


This is getting a bit off topic. The current draw of any refrigeration circuit is dependent on the cooling load. The factors that determine the load include the temperature and humidity both in the area being cooled and the outside air, where the heat is being rejected. A typical 3 ton condenser (the exterior component on a typical central A/C) has a 30 amp MAXIMUM overcurrent protection requirement. Yours may be on a 40 amp breaker, but shouldn't be, and if you look in the disconnect you'll probably find 30 amp fuses. My house's 3 ton (36,000 btu/hr) condenser runs about 18-20 amps fully loaded (measured last week, with outdoor temp >100 F) , and it's 19 years old.


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## Brewgyver (Dec 31, 2011)

night0wl said:


> Then there's this option:
> 
> Solar Air Conditioner ***** 10,000 BTU Window Unit - YouTube
> 
> Looks pricey


It's also highly deceptive. While the base A/C unit might be rated at 10kbtu, and would deliver that while "on the grid", it's not possible to run at that load on three 180 watt solar panels. It MIGHT just be possible to run a 5 or 6kbtu unit on that supply... but even then not at full load. The 10k would require six panels, or about $3,000 for JUST the panels.


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## Armchair Sailor (Jul 30, 2012)

NickPapagiorgio said:


> Hi everyone,
> 
> We had my 2-year-old son with us and it was way too hot for him to take a nap down below, so he ended up being pretty miserable for most of the trip.
> 
> ...


Slightly offtopic. You could use towed generator also, and do "space cooling", i.e. just cool the space near the baby with a small, modern, highly energy efficient air conditioner.


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## deniseO30 (Nov 27, 2006)

Brewgyver said:


> This is getting a bit off topic. The current draw of any refrigeration circuit is dependent on the cooling load. The factors that determine the load include the temperature and humidity both in the area being cooled and the outside air, where the heat is being rejected. A typical 3 ton condenser (the exterior component on a typical central A/C) has a 30 amp MAXIMUM overcurrent protection requirement. Yours may be on a 40 amp breaker, but shouldn't be, and if you look in the disconnect you'll probably find 30 amp fuses. My house's 3 ton (36,000 btu/hr) condenser runs about 18-20 amps fully loaded (measured last week, with outdoor temp >100 F) , and it's 19 years old.


Eh? I'm talking in general about how much has changed since the hundreds of systems I've designed and installed, serviced, repaired, replaced, since the late 70s Not "mine" Many new machines are using 2 speed scroll comps, variable speed blowers, piston comps are slowly disappearing from air conditioning equipment.

a 19 year old machine is old from an energy use comparison even though it may be still be in good running condition. You may want to ck into a new 16 SEER 2 speed scroll comp condenser and variable speed air handler... just saying.. but it is very $$$


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## deniseO30 (Nov 27, 2006)

NickPapagiorgio, sea frost makes a engine driven Air conditioning system BTW


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## travlin-easy (Dec 24, 2010)

Back on topic - I've spent much of the evening looking at videos on YouTube of Swamp Coolers, some of which are very ingenious. Essentially, they are all nothing more than mid-size cooler chests filled with ice with a small fan motor mounted mounted at one end on the lid, and an exhaust port at the other end. Some baffle plates inside would make them far more efficient by making the air travel over greater distances before exiting the cooler chest, but overall, they seem to work quite well and consume very little power in the process--especially those utilizing compute fans. Before heading to the sunny south for winter I intend to construct one, maybe as soon as next week. Should be fun, and if it works in Maryland's oppressive heat and humidity, it will work anywhere on the planet. 

Here's one you may wish to look at: 




Cheers,

Gary


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## LinekinBayCD (Oct 19, 2009)

NickPapagiorgio said:


> Hi everyone,
> 
> I don't own a boat (yet), but we've done a fair amount of chartering on the Nothern Chesapeake Bay. Our last trip was July 6-8 during the extreme heat. The high temperature was well over 100 degrees and the wind was constantly at our back (when there was wind).
> 
> ...


Like you we did a lot of chartering on the Chesapeake when the kids were little. My fix wasn't the AC. I started chartering in Maine.


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## mikel1 (Oct 19, 2008)

"Cooler" air conditioner video is interesting . . . like the concept, wonder how long the ice lasts . . .


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## Armchair Sailor (Jul 30, 2012)

"Swamp coolers" work best in hot but arid climates. I am afraid that Maryland in the summer won't qualify...

If the humidity of the air is already 100%, the water won't evaporate in the cooler, so no cooling effect.


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## deniseO30 (Nov 27, 2006)

Legionnaire's Disease became infamous in Phila PA in that type of equipment. "swamp cooling" coolers are essentially a "water tower" with wooden slats that water is recirculated over. as air by fan or gravity moves over them. The wood and reservoir will get nasty.. real nasty.


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## Brewgyver (Dec 31, 2011)

Cooling by ice is a dead end. Mechanical cooling capacity is measured in tons, from the days when ice was used for large cold storage, etc, and the "ton" is the btu equivalent of the cooling provided by a ton of ice melting over a 23 hour period. 12,000 btus/hr = 1 ton of cooling. A typical window A/C unit runs from 0.5 to 1.5 tons. So, to provide the equivalent of a smallish window unit, you would go through just shy of 42 pounds per hour.


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## travlin-easy (Dec 24, 2010)

One of the many videos I watched said two bags of ice in a well insulated cooler chest will last about 5 hours. The cooling effect, obviously, will depend upon the cubic feet of space you intend to cool, humidity level, etc.. Lots of factors to contend with. I'll begin working on my cooler-chest air conditioner next week and provide you with the results. My office is about the same size as the interior of my Morgan 33 Out Island. If it makes a big difference here, it will likely have a positive impact on the boat's cabin temperature.

Cheers,

Gary


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## Brewgyver (Dec 31, 2011)

Well, 40 pounds of ice (two bags), 144 btu/lb, over five hours, 1,152 btus/hr, or about one fifth the cooling provided by a small window unit or portable A/C. Cheap to build, yes, certainly. Operating cost? Another story.


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## Armchair Sailor (Jul 30, 2012)

deniseO30 said:


> Legionnaire's Disease became infamous in Phila PA in that type of equipment. "swamp cooling" coolers are essentially a "water tower" with wooden slats that water is recirculated over. as air by fan or gravity moves over them. The wood and reservoir will get nasty.. real nasty.


Interesting. Maybe drop a silver coin in the water reservoir then. And be sure to never let the water be stale. For example always run the cooler to exhaustion of water. I think that should be sufficient to drastically reduce the chance of the disease.


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## deniseO30 (Nov 27, 2006)

Armchair Sailor said:


> Interesting. Maybe drop a silver coin in the water reservoir then. And be sure to never let the water be stale. For example always run the cooler to exhaustion of water. I think that should be sufficient to drastically reduce the chance of the disease.


AS, good but the media, (usually wood) will still get nasty. hvac suppliers sell tablets to treat the water.


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