Fridge on a small yacht?

[MABell]

What I did.

I have a H26. I'm going to assume it’s nearly the same as the H24.
I enclosed the space meant to hold a cooler to make an ice box out of it. I glued 4 inches of pink foam insulation underneath and on the sides of the ice box area. Made it a well insulated ice box itself. I can keep things cold in it for 5 days. If you look at my albums - you can see a pic. I’m not in the south, so that may make a difference, but certainly don’t have to worry about recharging the battery bank. Best if you can find solid block ice. Glacier ice works well also if you have the opportunity.

 

[Stu Jackson]

JK's right.

The All-Important Energy Budget:

http://c34.org/bbs/index.php/topic,3976.0.html

 

[Kings Gambit]

Let's look at some numbers.

My Nature Power 85-watt solar panel specs out at 3.7 amp/hr in best sunlight conditions (high incidence), averaging no more than 180 amp/week by the specs. The fridge, I figure, draws about 3 amp/hr when it is running. It runs maybe 20 to 30 min/hr for 24 hr every day I'm out; so average 0.4 amp/hour x 24 hr/day x 7 day/week = approx. 70 to 80 amp-hr/week. All other weekly power needs have to be supported by the remaining 100 solar amp-hr to keep the batteries "level." I can tell you it doesn't happen--the masthead [10-Watt halogen] anchor light alone takes more than half of the remaining [when I use it]. So, unless you're getting one of the efficient fridges mentioned by Chief RA, better count on a couple of solar panels totaling more than 100 watts. ALTHOUGH--theoretically---a 40-watt panel that specs out at 112 amp/week [the Nature Power of that model] should be able to support the fridge if is there is next to nothing else to support.

 

[Chief RA]

KG: A problem with your calculations. A 3a reefer with a 33% work time (20 min per hr) will be 1 amp per hr avg not .4. You will use 24a per 24hrs. Thats a good reefer. Since you indicate your panel makes about 37a a day you might be OK. I use the amp rating of a panel x .25 for the avg per hr production over 10 hrs. Im assuming a fixed panel concept. Of course there are various methods but measuring is best. I would add another 85w panel and you would be in fat city! Chief

 

[Kings Gambit]

KG: A problem with your calculations. A 3a reefer with a 33% work time (20 min per hr) will be 1 amp per hr avg not .4. You will use 24 a per 24 hrs. That's a good reefer. Since you indicate your panel makes about 3.7a a day you might be OK. I use the amp rating of a panel x .25 for the avg per hr production over 10 hrs. Im assuming a fixed panel concept. Of course there are various methods but measuring is best. I would add another 85w panel and you would be in fat city! Chief

Chief, Thanks--I knew that; that's why for some reason I was already using 1 amp instead of 3 in the multiplication by 0.4. So 1.2 amp/hr x 24 hr/day x 7 day/wk = 202 amp-hr/week estimate for the fridge. So, yeah-- a 40-watt panel would not make it. I stand revised!! [It was already a late night by the time I got around to doing the math!]

 

[Chief RA]

KG: No problem, as I am just trying to help when I can in my fields of expertise. I used to teach this stuff at Butte College. Chief

 

[Stu Jackson]

Chief & KG - good on you for correcting the math.

KG - could you help me understand amp hours per week? I don't get it at all. Energy budgets are usually done on a per DAY basis. In a week's time it could well be that some days get higher use than others in which case a given panel output may not be abler to keep up, while over the course of the week when the boat sits unused, it could. Thanks.

 

[Chief RA]

Stu: Check your emails as I sent you one. Yes, these figures are just rough estimates after all. Chief

 

[Kings Gambit]

Stu,

So, I don't know if you're referring to the units I used (amp-hr/week) as off base(?), or the fact that power usage was estimated on a weekly, rather than daily, basis (or both). I'm not the technical expert here as others may be; however, on the latter, we're talking about sustained use of refrigeration aboard the yacht in the face of other power requirements.

Daily output of the solar panel varies, of course, but the number of amps is based on minimally 7 hr of full sunlight per day to get the estimated weekly output. Daily power usage also varies, as you note. Some days I recharge my hand-held VHF or cell phone, others not; some days the fridge runs a few minutes more than others; some days I run the radar briefly while at anchor, others not. Sometimes I use the 10-watt halogens below at night; other nights not, etc. Weekly amp output is a specification on the sheet from Nature Power; so it has some evident relevance to some minds. It makes sense to estimate the average weekly power budget, even if monitored daily, although there are more variables. If the panel ultimately keeps the batteries level over the course of a few weeks on the hook, I don't care if there is always a daily balance; should I?

As for the units---the panel puts out 180 amps per week. I'm aware that the number of available amp-hr/wk depends on what you're running. However if we take it [that which is running] as the cumulative weekly power burden, then it works as expressed that way.

 

[Stu Jackson]

KG, yes, it's the weekly thing that has me confused. The explanation you have given makes sense, except that because of the very varying loads on a daily basis, the part that's missing is the storage capacity to assure the house bank doesn't go below 50%. I do understand the nature of the varying loads, and I think that your example is reasonable but not necessarily reflective of real world loads on larger boats like ours to try to explain to the OP about his issue. In all my years with our Link 2000 battery monitor, I have been keeping careful track of our energy use. Here is an example: Record of Daily Energy Use of 100 ah per day:

http://c34.org/bbs/index.php/topic,6353.msg41471.html#msg41471

That's what we use, and the fridge is 60 ah per day of that 100 ahs. It's an old fridge!!!

In any event, based on my energy budget spreadsheet in my previous link, there are three categories: daysailing, overnight anchor and night at sea. The differences in use are dramatic.

All I'm suggesting is that when doing energy budgets, DAILY use needs to factored, not weekly, because unless the house bank capacity is known, some daily uses could draw down the bank prior to "refill" over the course of a week.

Daily is also the most common ah usage that I've found in my reading about the subject.

That's all.

 

[Kings Gambit]

Yeah, it's a zero sum game--cut power demand or increase power generation & storage capacity. I'll be switching over to LED's soon, although I already routinely use an oil lantern at night to light the inside of the boat. I don't really wish to buy another panel and another storage battery to sop up the excess amps that two 85-watt solars will likely produce. And, as I said earlier, we're considering ways of cutting down on the running of the fridge at anchor.

 

[Stu Jackson]

KG, we use a trawler lamp, too. I rarely use the regular cabin lamps, except for an LED galley fixture and the LEDs in the V berth for reading in bed. I am led (pun intended!) to believe that many boaters put on all their interior lights at night. How else would you explain the move (stampede) to LEDs to cut energy use? I could go all LEDs and not cut out much, if anything.

We used to turn off our fridge at night, left a towel over the top, was still OK in the morning.

 

[Chief RA]

Stu: How big is your reefer? My space is even more limited so a 2.3cf was the largest the boat would accomodate. We are very pleased with its frugal amp performance and its amazing capacity! Chief

 

[Benny17441]

Stu, I think we all agree that on a cloudy day power production from a solar panel can be very inadequate. If we spread out the power production over a number of days we will get to a point where the figure stabilizes somewhat over similar periods of time. It seems that the average over a week's time produces a more significant figure than could be experienced by measurements in a single day. A week's time also brings some rhythm into a sailor's life. Our weekly activities tend to repeat themselves. Solar panels are best used in conjunction with a suitable battery bank and if we think of the produced power as a recharging source for the batteries we can see how we can also average out the power usage over a week's time. If we allow the batteries to discharge at peak usage and then catch up in idle times then the average weekly figures become more useful. As production figures and sunlight can frequently fall outside the predicted averages it would be wise to build in a performance cushion to cover those events.

 

[Stu Jackson]

Stu: How big is your reefer? My space is even more limited so a 2.3cf was the largest the boat would accomodate. We are very pleased with its frugal amp performance and its amazing capacity! Chief

I'd guess between 5 & 6 cu ft. The fridge is an Adler Barbour cold machine, vintage 1986. It predates the mandated Shrader valves. It's been working just fine, except for when I didn't check the electrical connections!!! Just like Richard Kollmann warns about. It runs at 4.9 A, 50% of the time. I do all the pre-cool stuff, too.

 

[Chief RA]

Benny: I already stated that my solar system sustained my reefer and total demands for 4 days with little to no sun! No, we won't all agree. I would hardly call that 4 day result "very inadequate"! In fact I was VERY IMPRESSED! Chief, EE

 

[kito]

I have been doing some research on these ac/dc units (not the cheap thermoelectric ones) and it seems that the ARB portable ones are getting high praise. They are basically built for 4x4 off-road use so are pretty tough. Pretty price tag too though. They have a Danfoss compressor and draws only .7 amps per hour. Anyone have one of these?. I am looking at the 50 quart version and goes for $875 on Amazon. When I finally get my boat into the marina I plan on spending weekends on it rain or shine. I really want a fridge/freezer that will actually keep things frozen plus not have to mess with ice.

 

[Chief RA]

Isotherm 2.3cf, .7ah avg, freezer, 750 dollars. They have chest models as well. Go to www.defender.com. Read all posts on this thread for more info. Chief

 

[Crazy Dave Condon]

Good morning gentlemen;

I have read the posts and only one seemed to look at reality of things. First, I sold many of the 240's and stayed many weekends/ weeks on them.

This is a trailerable boat but smaller than most with constraints to storage, space and so forth in the cabin and cockpit. As an example, solar panes to many get in the way when the boat is in use with wires all over the place depending on the installation. What I am getting at is the space constraints. Secondly, most use the 240 mostly for the weeknds and sometimes for a week. If for a week, most folks generally come in to resupply or usually stop somewhere to empty the porta poti for example. What I advocated is the more expensive will built cooler using ice as one respondent pointed out. Why make this boat so electronic but rather keep it simply. Basically, it is the old RDF (radio directional finder) theory.

I use to tell my folks to carry a simple battery operated am radio, VA state highway road map and compass as a backup and a list of the am radio stations in the Tidewater area. Should the battery/batteries die, loose the gps overboard and so on, a person could use the am radio finding the strongest signals from at least two stations and cross plot that on the insert of the Chesapeake Bay on that highway road map which would give them a good idea where they are at. It worked well for me twice at night on the Chesapeake Bay once in fog. Keep it simple and keep it stupid.

The 240 is a simple small boat, keep it simple and enjoy without all that darn high falootin stuff on board.

crazy dave

 

[Regular Guy]

I also bought an EdgeStar 43 Quart Portable Fridge/Freezer ($479). It's small 43 quarts box but a real fridge/freezer. It comes with all cables.
Keep your foods and drinks chilled or frozen. Runs on 110V AC or 12 and 24 V DC.
Has a full range digital thermostat, adjustable from -8 to 50 degrees F will hold a stable temperature under most conditions. The usage is 65 Watt when running or in Amps 5.4A @ 12V DC / 2.7A @ 24 DC.
It has a nice digital display outside showing the inside temperature and allows from there to adjust the temperature. But it cannot freeze or refrigerate to the same time.

I bought it recently, have no experiences at the time. The rating was 4.5/5. I think it will work for me in Florida. My electrical cooler was not working well. First I do not believe it cooled realy 40 F under room temperature. But even if it wood, by 95 F in galley the food wood be in 55 F.

Energy Balance:
I have two 12V batteries, group 24 and 27, 80 and 90 Ah =170Ah. When assuming the fridge runs about half of the time that would be 5.4A x 12h = 64.8Ah the day. Full batteries would last about 170Ah/64.8Ah=2.6 days.
To make it work over 5 days it needs some additional energy. Total need 5x64.8Ah=324Ah. Additional need at least (324-170)Ah=154Ah.
Assumed solar elements deliver 10h the day, 50h in 5 days. They had to add at daytime constantly 154Ah/50h=3.08A or real 12Vx3.08A=36.96Watt

I do not have solar elements on my boat yet. My outboarder delivers 12A and with that and hopping on longer trips all three days in a hookup marina I hope it will do it.