Twenty five years ago Adler Barbour to increased sales added a small
water cooled condenser and a larger BTU brush type
motor compressor, labeling it as the Super Cold Machine. Several years later the larger brush type
compressor was replaced with the same smaller standard Cold machine’s Danfoss brushless compressor. In warmer climates where the
water cooling option was to improve performance the added amperage to operate
water pump off set the savings projected for a Super Cold Machine. I believe
Isotherm was the first company using water cooled only on small Danfoss BD compressor. The
Isotherm unit was short lived I believe do to short
water pump life. Isotherm water cooled units did not supplement compressor
cooling with fan air but did circle compressor on three sides with 11 ft of water and condenser cooling coils. Once the creative water cooling was a great
marketing idea other companies and job shops came out with their version of water cooling Danfoss BD compressors. At first small ice box
refrigeration conversion companies designed units that circulated water through condenser with a 12 volt
pump and eliminated the air cooled fan and its condenser. Water circulating pumps performed poorly when boats were in motion. Any 12 volt
pump motor with
brushes that is expected to run fifty present of the time will be short lived. I once
sold four of these pumps to a boater planning an extended
cruise. Some companies used positive
displacement pumps that were an improvement when
boat was in motion but these pumps also had a short life span. Magnetic circulating small pumps are now available with extended life. Still the main problem with circulating water condenser is maintaining water flow. Circulating water cooling is not a
refrigeration system that can be left unattended for more than a day. When system with only a pumped circulating water condensers unit were not as dependable as air cooled condensers manufactures began adding a second fan cooled condenser. With both types of cooling medium condensers allowed
boat captain to select either or both condensers. One problem with the dual condenser systems is the air cooled condenser is not always designed to be installed where air is ducted in from one area and warm air exhausted to another area.
The next generation of water cooled small ice box conversion refrigeration units after experiences with pumped water condenser problems manufacturers tried
hull mounted submerged condensers. These
hull mounted units eliminate the cooling fan saving from 3 to 6 amp-hrs per day. Refrigeration companies pushing the believed improved performance from water cooled units actually got their major
marketing boost from the new variable speed Danfoss compressors and not water cooling. The problem without a condenser and compressor cooling fan exposes compressor to excessive temperatures in warm seawater. The loss of an air cooling fan has an affect on
service life of compressor and also
service life of the
electric control module. Hull mounted condensers whether
keel coolers or through hull coils suffer from two of the pumped water unit’s major troubles, loss of metal material if zinc protectors are not maintained and both of these hull condensers need frequent
cleaning to maintain their efficiency.
Yes, water cooled refrigeration systems larger than 800 Btu per hour do normally require water cooling with all the unfriendly problems that come with water cooling.. Considering all the risks involved with water cooling a refrigeration system smaller than 1/6 horse
power the question is, what motivated the interest and belief that an expensive water cooled system offered an improved benefit to the average boater. Not every boater operates their boat in water temperatures of 65 to 75 degrees F where water cooling could be more efficient than air cooling. Manufacturers when it comes to product risk and reward will sell what ever the buyer believes is an advanced product. One misinformed statement you hear frequently is water cooling is a better heat conductor in a
refrigerator than air. The problem here is none of these small water cooled systems
sold today control the temperature passing through condenser to control liquid refrigerant pressure as well as ambient air temperature inside boat.
Yesterday I answered an
email from a boater wanting to install two 12/24 volt refrigeration systems with BD50 compressors in a large
aluminum hull boat. Having seen and experienced the damage cased by low voltage discharge through condenser water I would never again recommend seawater refrigeration cooling on an
aluminum boat without adequate
electrical isolation and regular sacrificial zinc
maintenance. It is one thing to sell a water cooled system that destroys itself but I do not ever again want to be involved with a design that causes a boat hull skin to be reduced to ½ its original thickness in one year because of low voltage discharge.
The Following questions will help test your beliefs on small pleasure boat
marine refrigeration.
1. Air cooled refrigeration units of less than 800 Btu per hour are more efficient than water cooled when seawater temperature is above 80 degree F. or below 65 degrees? True or False
2. Danfoss recommends and approves the BD model compressor to be water cooled in application engineering data
sheets? True or False
3. Air cooled refrigeration is five times less expensive to maintain than water cooling? True or false
4. Water cooled refrigeration systems provide better controlled over refrigerant pressures True or False.
6. Water cooled systems cost more than Air cooled? True or False
7. Water mixed in refrigerant has caused total system replacement? True or False
8. Compressor life span is much shorter on water cooled units? True or False
9. Damage from low voltage discharge is greater from water cooled units? True or False
10. On water cooled units reliable dependable cooling is compromised? True or False
11. Average qualified refrigeration
mechanic understands and can
repair the different water cooled small refrigeration units? True or False
12. Air cooled units put out an average of 300 Btu of uncomfortable heat per hour inside a boat? True or False
13. Air cooled units can be relied on to
work efficiently for weeks or months without someone onboard as long as electricity is available? True or False
14. Variable speed water pumps can help to improve cooling mediums effect on refrigerant pressures? True or False
15. Using
fresh water tank to reduce performance risks of other types of water cooling heat disposal? Good idea or Bad idea
16. Low voltage discharge sacrificial zincs and their regular
maintenance are not required on air cooled units? True or False
17. When salesperson says it is a high end unit could this be just creative advertising? True or F
18. Is Water cooling small BD compressor refrigeration units an advantage or disadvantage?