I'm an A/C convert

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Jimmyt
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Re: I'm an A/C convert

Post by Jimmyt » Sun Jul 15, 2018 5:35 pm

Roger that. The Billy box reference was for whgoffrn, who hadn't heard of it before. My apology for chasing squirrels and my response to you was a couple of posts earlier.

Crap - I guess I did it again... :?

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Re: I'm an A/C convert

Post by solarfry » Mon Jul 16, 2018 10:47 am

Jimmyt wrote: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....
Sounds like a good idea.

The ocean/lake water temp goes down as you go deeper. In summer the top 2 ft run 80 degrees. Going down 6'+ it is at 75 degrees. I you pump that water continuosly through a radiator with a fan it should lower cabin temp down to 84 -80 degrees when the temp outside is 95 degrees. To get any lower you have to go deeper and blow more air through radiator. You would not need any evaporation nor a tank. Only a pump, radiator, hose and a fan. You can tie the hose to the anchor rope to get it deep.

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Jimmyt
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Re: I'm an A/C convert

Post by Jimmyt » Mon Jul 16, 2018 3:20 pm

To be clear, I think it will be a waste of his time in central Florida. Maybe I should have been more concise. Current surface temps in central Florida are over 80. If he's anchored near a beach, or in an inlet, or even in a marina, he's not going to have access to deep water. Even if he could get 75 deg water, and pump it through a deep counter flow coil, he could only approach 77-80 deg leaving air temp. If it's 95 deg in central Florida at night, 77-80 deg air will be at saturation. Bottom line, it might be a bit cooler using this strategy, but it will be very damp; which is why I said he would need mechanical.cooling or a bunch of cold storage to achieve what I consider to be "comfort conditions". In all likelihood, he will have to deal with condensation on the coil at these conditions also, so I would suggest making some arrangement to deal with condensate.

A lot of folks like to tinker with ideas, and I don't want to discourage that. I do want to help him manage expectations though. This is a radically different situation than the guy in Ontario who has 54 deg water to work with. The idea could work well in Ontario with the right equipment - under the specific conditions described.

Tonight's low in Miami is 78 deg, which is cooler than the surface water temp by several degrees. Ambient temp is 88 deg now, but will be down to 82 by.10pm. It will crawl downward toward 78 until sunrise. So, if 80-85 deg is the best we can do with a rigged up coil and pump, I'm not sure it's worth the effort over a fan that ventilates the boat. If it stays at 95 all night long, 80-85 would be a definite improvement, but it's going to be very damp - my admiral would be preparing to mutiny...

Not trying to get crossed up, but since you quoted my post and basically said it was a good idea, I just wanted to go on record with a polite disagree.

It's all good. :wink:

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sailboatmike
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Re: I'm an A/C convert

Post by sailboatmike » Mon Jul 16, 2018 4:35 pm

I don't think there is a "one size fits all" approach to cabin cooling, some don't have access to shore power, some live in climates that make evaporative cooling (swamp boxes) pointless, some live in climates that heating is more an issue than cooling.

Its horses for courses, the only thing that is really universal is trying to keep the heat out in the first place, effective covers for the windows especially the X and M front windows which I find really heat the cabin up as they point toward the sky, a good long boom tent to keep the sun off the cabin roof, if the heat doesn't get in its much easier to cool

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Jimmyt
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Re: I'm an A/C convert

Post by Jimmyt » Mon Jul 16, 2018 4:37 pm

Amen!

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Re: I'm an A/C convert

Post by Catigale » Tue Jul 17, 2018 10:47 am

The ultimate solution is

Sail Northward.

Just don't go as fas a the Jeanette... "In the Kingdom of Ice" - good read.

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sailboatmike
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Re: I'm an A/C convert

Post by sailboatmike » Tue Jul 17, 2018 3:51 pm

Catigale wrote:The ultimate solution is

Sail Northward.

Just don't go as fas a the Jeanette... "In the Kingdom of Ice" - good read.
That makes it one LONG sail North from here and it would get a lot HOTTER before it got any cooler :D

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Re: I'm an A/C convert

Post by DaveC426913 » Thu Jul 19, 2018 10:07 pm

Went out and bought a 20" box fan for $25.

Either place it over the forward hatch (a bit noisy maybe), or make a frame for the main hatch.

Still gonna keep the comforter-soaked with water for unusually hot days.

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Re: I'm an A/C convert

Post by Catigale » Fri Jul 20, 2018 6:20 am

Jimmyt wrote:To be clear, I think it will be a waste of his time in central Florida. Maybe I should have been more concise. Current surface temps in central Florida are over 80. If he's anchored near a beach, or in an inlet, or even in a marina, he's not going to have access to deep water. Even if he could get 75 deg water, and pump it through a deep counter flow coil, he could only approach 77-80 deg leaving air temp. If it's 95 deg in central Florida at night, 77-80 deg air will be at saturation. Bottom line, it might be a bit cooler using this strategy, but it will be very damp; which is why I said he would need mechanical.cooling or a bunch of cold storage to achieve what I consider to be "comfort conditions". In all likelihood, he will have to deal with condensation on the coil at these conditions also, so I would suggest making some arrangement to deal with condensate.

A lot of folks like to tinker with ideas, and I don't want to discourage that. I do want to help him manage expectations though. This is a radically different situation than the guy in Ontario who has 54 deg water to work with. The idea could work well in Ontario with the right equipment - under the specific conditions described.

Tonight's low in Miami is 78 deg, which is cooler than the surface water temp by several degrees. Ambient temp is 88 deg now, but will be down to 82 by.10pm. It will crawl downward toward 78 until sunrise. So, if 80-85 deg is the best we can do with a rigged up coil and pump, I'm not sure it's worth the effort over a fan that ventilates the boat. If it stays at 95 all night long, 80-85 would be a definite improvement, but it's going to be very damp - my admiral would be preparing to mutiny...

Not trying to get crossed up, but since you quoted my post and basically said it was a good idea, I just wanted to go on record with a polite disagree.

It's all good. :wink:
You will find Chip did the math on this about 8 years ago and it doestwork. Remember the enthalpy ( heat) of melting ice is huge so water at 0 C has much less cooling capacity than ice at 0C ,water at 15c even less.

The rate of heat transfer is proportional to the temperature delta, so not only do you have not enough cooling capacity, you don’t have enough rate heat transfer without a huge exchange and fan.

Trying to make this work is the same as trying to make 2+2 = 10

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Jimmyt
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Re: I'm an A/C convert

Post by Jimmyt » Fri Jul 20, 2018 8:07 am

At 54 degree water temp, there is plenty of cooling capacity IF THE AMBIENT DEW POINT IS 48 deg F, such as was the case in Ontario the other day when we were originally kicking it around. Under these conditions, I can do sensible-only cooling (no latent cooling, ie no dehumidification), which reduces the capacity requirement considerably. This is the basis for chilled beam or radiant cooling systems which routinely use water temperatures at 60 deg F or higher to cool large buildings.

Comfort conditioning is an art based on science. In any humid area, or humid conditions other than the conditions described, you are correct; 15 deg C (59 deg F water temp) would not result in cooling to WHAT MOST PEOPLE consider to be comfort conditions - without additional measures. ASHRAE defines comfort conditions to be a much bigger target than my wife (and most of our friends) consider comfortable, so I’ll stick to a narrower definition of comfort. The general science included in your statement was virtually all correct. However, the particular climate described in the OP would allow comfort conditions to be achieved using 54 deg F water.

As several have mentioned, there ain’t no pantyhose solution - one size does not fit all. Also, the “artist” might choose to apply a system that might seem ill suited for certain reasons. For example, I could use radiant cooling in the south east, but only after reducing the space dew point low enough to prevent the radiant system from raining in the building. This is usually accomplished by a separate dedicated vent air conditioning system which would require mechanical refrigeration or colder water (basically to get the additional latent capacity as you indicate). These systems typically incorporate control interlocks, etc to keep condensation from happening; resulting in a level of complexity that would not be appropriate for a sailboat. That is, unless you are Highlander, who seems to revel in complexity... At any rate, you have to assess the risks/rewards for doing this sort of ART. I might choose to just cut off my ear instead.

And, if I missed your point and you were talking about using raw water cooling in Florida, please disregard the insane discussion above... :)

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Billy Box

Post by vkmaynard » Sat Jul 21, 2018 6:03 pm

We've had this unit for at least 6 years. Works AWESOME!

Had to turn down the AC last weekend, too cold with a 5000 BTU unit. Paid $60 on sale for the AC.

Picture with rear glass installed. Really adds to the experience looking outside and watching everyone else sweat :D

The Billy Box also makes a great bench and bar.

Worth every penny!! Ask my family and friends.

Theses pics were posted a long time ago but can't find them due to the broken search on this site.

Victor

Image
Image

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rsvpasap
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Re: I'm an A/C convert

Post by rsvpasap » Sat Jul 21, 2018 9:52 pm

Original Billy Box post which includes excellent details and photos:


viewtopic.php?t=8396

Image

Additional helpful photo:

Image

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Ponaldpe
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Re: I'm an A/C convert

Post by Ponaldpe » Sun Jul 22, 2018 6:25 am

Have any if the :macm: 26M owner's put a Billy Box on their boat/ If so how do you like it?

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Jimmyt
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Re: I'm an A/C convert

Post by Jimmyt » Sun Jul 22, 2018 8:48 am

This is one approach.
https://m.youtube.com/watch?v=2AGnbt-KHYA

Billy box is a great solution for X, but M requires something different - particularly if you or your crew has any physical challenges.

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Re: I'm an A/C convert

Post by whgoffrn » Sun Jul 22, 2018 11:36 pm

Is the billy box sturdy enough to sit on or a take a step onto to step over it.... I do have a small 5k btu ac and its annoying to constantly store it somewhere in the boat then at night put it back in the hatch and find the wood blocks I cut to prop it up and the extra hatches...etc etc ....I should be happy just to have ac but always looking for an easier way....wondering if the billy box will support weight to slide across it and if u can tow the boat with it in place

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