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I'm an A/C convert

A forum for discussing topics relating to MacGregor Powersailor Sailboats

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Re: I'm an A/C convert

Postby vizwhiz » Wed Jul 11, 2018 12:06 am

So my idea was to go to the auto junkyard and find a plastic tank radiator from a small car. Get a 12V computer type fan large enough to move a bit of air. Get a small bilge pump. Get some hose. Test the concept on seawater directly. This is a short term, intermittent use item. Once you drain it in the morning, no worries about growth. Copper tubing in the radiator should hold up to seawater well enough to last quite a while. When it fails, back to the junkyard! :wink:

I really really like the 1-gallon reservoir idea to keep the supply pump from running often. I can see this easily becoming an item that has potential in that form, a reservoir, radiator, thermostat-driven pump to mitigate the effects of too-cold water forming condensation, even a thermostat controlled fan to conserve power, if desired.

I was planning to add a thermostat to the fan on my redneck cooler a/c to (a) conserve power, and (b) conserve ice. No reason to keep cooling if the return air says the v-berth is cool.

I can even see all these concepts working together. Ice, reservoir, and radiator with fan using ice water for cooling instead of trying to use air-over-ice. Hmmmm... Hmmmm...
:idea:
:)
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Re: I'm an A/C convert

Postby Jimmyt » Wed Jul 11, 2018 7:17 am

Vizwhiz - if you have the parts lying around and have plenty of time on your hands, give it a shot.

I'll give you some pesky geek-speak to consider. A one gallon reservoir will give you about 60 seconds of meaningful cooling capacity in central Florida on a hot day, if the water is around 45 deg. You'll need a fan that will do 150-200 cubic feet per minute to cool the cabin on a hot day. If you only cool at night, and the night time low is 76 deg, you will need to dehumidify to achieve comfort. This will require reducing the air to around 55 deg as it goes through your radiator. Otherwise, ventilate the cabin and call it done. If it's 85-95 deg at night, you'll need mechanical refrigeration, or significant ice or cold water storage.

Ice storage cooling has been around for a long time. It was often used to lower power bills for commercial properties. You would make ice during periods where the power company needed load, then use the ice for cooling when the power company was low on capacity. It was also used on buildings like churches to reduce equipment sizes, and cut energy costs. You make ice all week to carry you through the brief weekend load.

For one 8 hour night in central Florida, with a crew of 2, let's assume you could handle it with 6,000 btu/hr capacity for rough proof of concept. 6,000 btu/hr x 8 hr = 48,000 btu. Melting the ice at 32 deg F, and then warming the water from 32 - 55 deg F will give us about 163 btu/lb of ice. So, for that one night of cooling, equivalent to your window unit, you'll need about 295 lbs of ice. 48,000 btu / 163 btu/lb = 294.48 lb. Ice storage jobs typically have swimming pool size insulated ice tanks for this reason. Your idea will work fine, but you'll need a lot of ice. I did not calculate the cooling load, because we didn't determine what ambient conditions we're shooting at, and what cabin conditions we're trying to achieve. My hunch is, the load may be a bit less on most days, and a bit more on peak days. Whether or not you shade the boat during the day would impact the load.

Unless you are sailing in spring fed waters, don't waste your money on raw water cooling in central Florida. The water is too hot in our neck of the woods, and the humidity is too high. The best you and I could do this month is about 85 deg F and around 70-75% rh. Night time lows over the water would probably allow us to beat that with pure ventilation.

Evaporative cooling gives a better yield per pound of water, but won't work for those of us who live in the swamps.

Now, if you,re going to use an ice tank for cooling while under sail; and make ice in the marina overnight, you have a concept that has merit. Although, you'll have to have TWO refrigeration systems on the boat if you sleep aboard. One to make ice, and the other to cool the cabin. Now, where do we put our 36-40 gallon ice storage tank....
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Re: I'm an A/C convert

Postby K9Kampers » Wed Jul 11, 2018 7:44 am

Image
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Re: I'm an A/C convert

Postby Jimmyt » Wed Jul 11, 2018 9:09 am

:D :D :D
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Re: I'm an A/C convert

Postby vkmaynard » Wed Jul 11, 2018 12:21 pm

Billy Box for the X 8)
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Re: I'm an A/C convert

Postby Jimmyt » Wed Jul 11, 2018 3:29 pm

I get it. It gives you the flexibility of using it like a travel trailer if the mood strikes you - works on the hard. Price and ease of install is pretty hard to beat.
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Re: I'm an A/C convert

Postby Catigale » Thu Jul 12, 2018 11:44 am

We rehash the swamp cooler and ice AC every summer, so there is a lot to search for. It was worth a try 50 years ago, but now the Borg Collective is wiser.

Short version

A 12500 BTU Hour AC is called a 'One Ton" AC unit, because it gives the same cooling capacity in one day as ONE TON of ice.
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Re: I'm an A/C convert

Postby SENCMac26x » Thu Jul 12, 2018 5:12 pm

+1 for the Billybox.

I've found myself getting out of bed in the middle of the night to turn the A/C down on more than 1 occasion.

Plus I like the extra step getting on and off the deck, stretching out and it's fairly popular for people to sit on facing forward too (for some reason).

In the winter, pull out the AC and enjoy extra storage.

Pair it with the fold up captain's seat to regain any lost cockpit space.

(I was very lucky the P/O of Private Island did both)
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Re: I'm an A/C convert

Postby SENCMac26x » Thu Jul 12, 2018 5:12 pm

+1 for the Billybox.

I've found myself getting out of bed in the middle of the night to turn the A/C down on more than 1 occasion.

Plus I like the extra step getting on and off the deck, stretching out and it's fairly popular for people to sit on facing forward too (for some reason).

In the winter, pull out the AC and enjoy extra storage.

Pair it with the fold up captain's seat to regain any lost cockpit space.

(I was very lucky the P/O of Private Island did both)
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Re: I'm an A/C convert

Postby DaveC426913 » Fri Jul 13, 2018 11:58 pm

I had to go look up Billy Box to be sure you guys were actually talking about A/C units.

Well, it's a no-go for me so, while I appreciate all the input, I'm really just hearing things I won't be doing.
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Re: I'm an A/C convert

Postby vizwhiz » Sat Jul 14, 2018 8:56 am

DaveC426913 wrote:I had to go look up Billy Box to be sure you guys were actually talking about A/C units.

Well, it's a no-go for me so, while I appreciate all the input, I'm really just hearing things I won't be doing.


Hey Dave, we did kinda take this thread on all sorts of rabbit trails! But it was fun... :wink:

So do you think you’ll stick to the portable unit plus generator?
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Re: I'm an A/C convert

Postby Jimmyt » Sat Jul 14, 2018 9:14 am

Sorry Dave. Got distracted.

Ran a few preliminary numbers and evaporative cooling could work for you. You could put the evaporative rig at the foredeck hatch and leave the companionway clear. The Toronto conditions I saw were 90 deg F, 48 deg F dew point, and 54 deg F water. A small pump to keep your evaporative media saturated with 54 deg water, a catch pan/ drain to capture the excess and run it off deck, a fan capable of 200-500 cfm, and enough power to run it for the time you want to sleep; and voila.

For ideas, the following video gives a few diy approaches. Please do not attach your evaporative media directly to your fan. This guy apparently hasn't heard about electricity and water not being a good mix... see the Option 4, super cooler version where he is dripping water through the media using a pump. You would want to rig something like this, but safer... you also need to limit the face velocity over your evaporative media to keep water entrainment down. You want cooling - not a shower.

https://m.youtube.com/watch?v=DJN3lwVLGxs

As you stated earlier, the portable ac unit would fit your needs - easily stashed out of the admiral's traffic pattern. I agree that the dual duct unit would be strongly preferred, otherwise, you will be drawing in a large quantity of 90 deg air to make up for the exhaust duct discharge. This will require shore power or a generator. More than a window unit, but no mortgage required. Installation fairly easy.

Hatch mounted ac unit. Pricey, but easy to install. Shore power or gen set required for power. Not sure if you can find a new one, but used ones available.

All can meet your no-crawl over requirement. None require extensive modifications or installation skills.

Jim
Last edited by Jimmyt on Sat Jul 14, 2018 7:33 pm, edited 1 time in total.
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Re: I'm an A/C convert

Postby whgoffrn » Sat Jul 14, 2018 2:49 pm

Does anyone have some good pics of what this billy box thing is......I just sit a 5k BTU ac in the hatch and have a couple of blocks of wood to keep it tilted at the right angle and new door hatches cut for when the ac is in.....so I'm just curious what the benefit of a billy box is unless just to look better cosmetically than some plywood with a cutout for the ac unit....just curious if anyone has any pics
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Re: I'm an A/C convert

Postby Jimmyt » Sat Jul 14, 2018 2:55 pm

viewtopic.php?t=8396#p93134

This may be the prototype...
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Re: I'm an A/C convert

Postby DaveC426913 » Sun Jul 15, 2018 11:40 am

Oh, I see you don't step over it so much as ... sit on it and rotate.
Image


Still a no-go tho. It's the Admiral's knees. They don't fold.

We're still leaning toward the Cabin Cooler. It's diminutive size and use of off-boat resources are a big plus.

Just trying to decide if $470 is worth the likelihood of us actually needing it again this season. That was an unusually hot weekend.
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