Isotherm Air Cooled Refrigeration System Sizing

[Ward H]

I'm ready to replace the non working Adler Barbor refrigeration system in the ice box of my Catalina 30.
The spec for the ice box 3.2 Cubic Feet. They are known to be poorly insulated so I will do what I can to improve the insulation as part of the installation.

I'm looking at the Isotherm 2301 which is spec'd for 5.3 Cu Ft fridge.

My question for the group is this:
Any advantage to upsizing to the 2501 which is spec'd for 7.1 Cu Ft. Fridge? Do the manufacturers under spec their units or are they pretty much right on?

The main purpose of the fridge/ice box is to keep beverages cold and ready for sailing. Most food will still be housed in the ice chest used to transport it between home and boat.

 

[bawlmer]

Ward. I did this to the icebox on my 270 a few years ago. I used the Isotherm SX2010. Its cheaper and does a great job on my icebox. I think it is about your size or a little larger. You can use the spray foam from Home Depot if you have room. I caulked around all the edges and open cracks . That made a real difference. It takes my box down to 24 degrees if I let it. Also Defender puts these things on sale toward the end of the summer. I don't know if oversizing your unit is that effective. I remember from my tower building days that over spec-ing an HVAC unit has no benefit to the room you are cooling. But that is AC and I will let others smarter than me chime in. Also that fridge was one of the best things I added to the boat. It makes life way easier.

 

[Stu Jackson]

Any advantage to upsizing to the 2501 which is spec'd for 7.1 Cu Ft. Fridge? Do the manufacturers under spec their units or are they pretty much right on?

Ward,

I agree with @bawlmer about oversizing, 'cuz I was an HVAC engineer. However, I think the other thing beyond the size of the box is the amount of insulation that the manufacturers have assumed is installed in sizing their equipment. So, Ward, it's BOTH that you need to consider. I'm sure this is discussed on Richard Kollmann's website, although when I just went there I couldn't connect - http://www.kollmann-marine.com/Refrigeration/

A friend of mine recently added refrigeration to his late 80s C34, and he insulated the heck out of the box. He then tracked his ah use and it was half of what most of us would expect! He selected the unit based on box size.

Insulation reduces run time, reducing the energy necessary to keep the box cool. Oversizing, OTOH, potentially reduces run time but at the expense of the unit not running long enough at all to cool the entire box; it will cycler on and then stay off for a longer time.

Size the unit based on the vendor's cubic footage balanced with their anticipated amount of insulation. It's a little bit of a tough balancing act. Kollmann's website, IIRC, had information on unit sizing and insulation. Hope you can get into it.

Good luck, great addition.

 

[Hello Below]

although when I just went there I couldn't connect - http://www.kollmann-marine.com/Refrigeration/

Lose the hyphen.

Kollmann Marine - Index

Kollmann Marine - Index

www.kollmannmarine.com

 

[markwbird]

I did the isotherm as well. My ice box was right on the border between two sizes plus it is well insulated and I live in a cooler climate. I went with the larger size anyway. Now I have the option of having a freezer if I choose. I have to keep it at very nearly the lowest setting or my drinks freeze. The cool thing is that the compressor rarely comes on. Works really well. You will not regret going bigger. Just make sure the evaporator will fit.

 

[dLj]

Insulation has been key in my mind.

Really important to design the open/close "system" really tight/well insulated.

Musing a bit, I've been looking for some time what cryogenic cylinders use for insulation. In addition to a vacuum, the insulation is like nothing I've ever seen. Anybody know? They have the highest R factor I know of. I'd really like to know how they do it, I do know is highly specialized.

dj