Supplemental Cooling

[FourPoints]

I am considering adding some supplemental cooling to my ice chest to extend the life of the ice and maybe even allow me to still chill things if I'm out of ice all together. I just picked up a Dometic soft sided thermoelectric cooler on clearance for $20, and the cooling unit comes off as a stand alone piece. It would be a simple matter to fashion a new lid to the ice chest that the cooling unit fits into to suck heat out of the top of the ice chest and blow cooled air down. Has anyone tried rigging one of these thermoelectric coolers up to the lid for additional cooling?

I know they are not the most efficieant means of cooling, but as I mentioned, I'm only looking for supplemental cooling to the ice, and to extend the life of the ice so it doesn't melt as quick. This unit draws 3A, and installed in the soft side cooler is rated for a 27 deg cooling below the ambieant air temp, but I think most TEC's are good for 40deg, so I think it's a function of the poorly insulated soft side cooler.

Thoughts?

 

[Ross]

I have 4 inches of foam insulation that will keep cold with 40 pounds of ice for a week. Insulation is more effective and less costly than electricity.

 

[Steve Dion]

How much battery power do you plan to have to keep one of these unit cooling? You probably need 200-300 amps for a 2 day weekend in the middle of the summer.

Purchase a high quality cooler and pack it with ice. You will be better off.

 

[Allan12210]

I buy a slab of dry ice at the grocery store and stick it in the ice. It gives an extra day or so to the rest of the ice. Also, we cover the ice and food not to be used for a couple of days with bubble wrap.

 

[capejt]

Don't waste your time and money!

I tried one of those units a couple years ago. What a disappointment! A couple of things you should remember:
1. These things work by removing heat more than generating cold. What that means is that no matter how much voltage you give it, it will only cool as well as it can dissipate the heat it generates (and picks up from the cooler), and it DOES put off some serious heat.
2. They're just not designed to cool an entire ice box efficiently.

Stick to ice! It's easier and cheaper!

 

[RAD]

Go to Camping World and get a Fridge Airator.....been using this for years and it works well in addition to more insulation around the box also I keep a piece of hard foam on top of my lid and that helps too or a wet towel.
I get 5 days or more out of a block of ice

http://www.campingworld.com/shopping/item/fridge-airator/21016

 

[BobM]

I second the bubble wrap.

I buy a slab of dry ice at the grocery store and stick it in the ice. It gives an extra day or so to the rest of the ice. Also, we cover the ice and food not to be used for a couple of days with bubble wrap.

It makes a difference.

 

[Tim R.]

I have 4 inches of foam insulation that will keep cold with 40 pounds of ice for a week. Insulation is more effective and less costly than electricity.

Good point Ross, but insulation has a very high space cost which can be a limiting factor on many boats.

We also have a lot of insulation but in very hot humid weather I will get some condensation on the hull where my freezer is.

We live aboard so ice box room is very important to us. Luckily the power consumption is handled by the 2 - 130W solar panels.

 

[FourPoints]

I like the dry ice suggestion, but I dont know of anywhere around here close to get it, and a 30min trip is more costly than an extra bag or two of ice in a second cooler.

As for enough power, I wouldn't plan to run it 24x7, just during the heat of the day, when we are preparing food (aka in and out of the ice chest more frequently) and when we first get to the boat to pre cool the ice chest before packing the food, drinks, and ice in it. I have enough power that I could easily run it for 24 hours straight if needed, factoring in no rechargeing from the small solar system, which extends that some, and then there is the engine to recharge as well.

The way my ice chest is built I cannot get to the outside of it without cutting an access hatch, as it is part of the molded cabin pan (gotta love production boats). So adding extra insulation would not be easy at all. It does seem to be pretty well insulated already though as once the ice chest and its contents are fully cold (usually about the time the first 5# bag of cube ice is melted), it will stay cold and 10# of cube ice will last another 24-36 hours as long as we are not going into and out of the ice chest.

My thought is, and tell me if this sounds wrong, that I could use the TEC to pre cool the chest before loading it up, and leave it running for an hour or so after loading the food and ice as that is the time that the most ice gets used, just getting the system and contents down to temp, then the TEC cooler would remain off until lunch/dinner time, when lots of warm/hot air is let back into the chest, and let the TEC run for another half hour to hour to cool the air instead of relying on the ice alone. I figure using it like this would cost me on average between 5 and 10 ah a day net loss over my current power consumption, as the pre cooling would be negated by running the engine on the way out of the harbor.

 

[rbietry]

TEC Coolers

I had the same idea, and every time I worked the numbers it did not pay. Additionally I have a TEC cooler chest that I keep on the boat and run when i am at the dock. It only keeps water and other liquid refreshments cool, not cold.

 

[Peggie Hall HeadMistress]

Frozen foods..

Meat, sauces, soups, stews, juice, water...just about everything but fresh produce, eggs and carbonated beverages can be frozen. So freeze as much as possible at home so that your food becomes supplemental cooling.

Keep beverages in a separate cooler...save the fridge/ice box for food. 'Cuz people are after drinks a lot more often than food...and the less the door is opened, the longer the ice lasts.

Finally, drinks can stay cold in cold water--some of us are old enough to remember the old fashioned chest soda bottle machines...the bottles hung by their necks in icy water, put your nickel in to release the latch to remove one---so don't dump it to replace it with ice. Instead, add only enough ice to keep the water cold...you'll need less ice in the drinks cooler. Unfortunately this doesn't work for foods except for those in waterproof containers.

 

[FourPoints]

I had the same idea, and every time I worked the numbers it did not pay.

Can you expand on this some?

 

[Freedom77]

When we used to go cruising for a week at a time Penny would make up packets of food in Seal A Meal boiling bags and freeze. We had a seperate cooler just for frozen stuff. We would pack it with dry ice and it would last for days if we didn't keep opening the cooler. Dry ice in a regular cooler would give the food a funny taste. WE would freeze milk jugs and use the melt for drinking water. The more a cooler is packed the longer it will stay cool. Fair winds and Full Sails...

 

[Freedom77]

Meat, sauces, soups, stews, juice, water...just about everything but fresh produce, eggs and carbonated beverages can be frozen. So freeze as much as possible at home so that your food becomes supplemental cooling.

Keep beverages in a separate cooler...save the fridge/ice box for food. 'Cuz people are after drinks a lot more often than food...and the less the door is opened, the longer the ice lasts.

Finally, drinks can stay cold in cold water--some of us are old enough to remember the old fashioned chest soda bottle machines...the bottles hung by their necks in icy water, put your nickel in to release the latch to remove one---so don't dump it to replace it with ice. Instead, add only enough ice to keep the water cold...you'll need less ice in the drinks cooler. Unfortunately this doesn't work for foods except for those in waterproof containers.

Peggy, you have brought back some fond memories. Those old water filled soda machines were great. I can still taste it. Yum!! Fair Winds and Full Sails....

 

[FourPoints]

Keep beverages in a separate cooler...save the fridge/ice box for food. 'Cuz people are after drinks a lot more often than food...and the less the door is opened, the longer the ice lasts.

I have been doing that, but for the ice chest, when provisioning for a 2.5 day trip ,I am stuck being able to fit enough food, or enough ice, not both, hence my desire to get a little more life out of the ice by additional cooling some other way.

Finally, drinks can stay cold in cold water--some of us are old enough to remember the old fashioned chest soda bottle machines...the bottles hung by their necks in icy water, put your nickel in to release the latch to remove one---so don't dump it to replace it with ice. Instead, add only enough ice to keep the water cold...you'll need less ice in the drinks cooler. Unfortunately this doesn't work for foods except for those in waterproof containers.

My drink cooler (igloo 28qt marine cooler on wheels, and worth every penny I paid for it) , it keeps ice in there for about 48-60hrs, but has no drain so it fills up with cold water and does a really good job keeping drinks chilled for a long time. The ice chest on the other hand has a permenant drain to the bilge so as soon as the ice melts, I'm out of cooling.

This does give me an idea on how to trap some cold water though. There is a removable grate at the bottom, and a small well below it that could hold about half a gallon of water, with the drain in the middle. If I install a extension tube on the drain that comes up 2/3 of the way to the grate, then the well will fill with ice cold melt water and only drain to the bilge when it fills over the extension tube height, giving me some extra volume of cooling power.

 

[Stu Jackson]

If I understand what you're describing, you are really saying you have a hole at the bottom of your box. Most everything I've read has said close that opening. Also, we found on our C25 that block ice lasts way longer than cubes.

 

[FourPoints]

I do have a drain hole at the bottom of the ice chest. I will see how well it does with a few inches of ice water in the bottom, and also try just plugging the hole to see how it does.

Only one of of the places nearby carries block ice, and only for part of the season, when they aren't out (which is often). On the other side of the harbor there is another marina that carries block ice all season, but that's a 15 min drive with normal traffic, or a 20+ min boat trip to get there, so I'm often stuck with cube ice.

 

[Tim R.]

If I understand what you're describing, you are really saying you have a hole at the bottom of your box. Most everything I've read has said close that opening. Also, we found on our C25 that block ice lasts way longer than cubes.

I will expand on this a little Stu. Home-made block ice lasts longer than air injected ice that is usually sold in stores and marinas.

 

[SycloneDriver]

pre-cooling use only

A thermoelectric unit is just basically two heatsinks with a semiconductor in the middle and a fan unit. When switched off it is effectivly one heatsink. While turned off they are a large thermal leak. I would not mount one in a cooler that holds ice. Mounted in the lid for pre-cooling and then changing out the lid should be helpful.

I have two TECs, they work well at room tempatures but not on a hot boat. That's why I added a ac/dc fridge to my SJ77. I have cold drinks as soon as I step on the boat

 

[FourPoints]

A thermoelectric unit is just basically two heatsinks with a semiconductor in the middle and a fan unit. When switched off it is effectivly one heatsink. While turned off they are a large thermal leak.

I had wondered about that, That was one of the concerns I had, if I would loose more when it was off than I would gain when it was on, and it would have to be off a large percentage of time as I don't have the power budget to run the TEC non stop every trip I plan to go on, day trip yes, but longer 2-3 day trips no.

If I do anything with the TEC now, I think it would just be a temporary lid for the cooler for the precooling...