Tech Tip 3
Are new boat refrigerators better than the older ones?
Product improvements in small 12 volt refrigeration seem to be in reverse. Several years ago when a friend was planning an extended blue water cruise, I was asked to recommend tools and spare parts to support his refrigeration system. Because these small air cooled systems were so reliable, I recommended only standard tool kits and two spare refrigerator parts, a cooling fan and an electronic control module, for his Danfoss BD powered compressor system, . Fans back then were the only part of a system that was service life limited at 5 to 7 years of live-aboard use. Electronic control module failures were unpredictable mainly because of improper boat wiring or incorrect handling of the condenser air cooling medium’s heat disposal. When installed correctly these efficient systems were so reliable that Electric-Iceman, a company in Miami 18 years ago, offered a lifetime warranty for an additional one time $25 charge. This warranty policy today, with the current generation of pleasure boat refrigeration, might bankrupt a company.
There are still several companies assembling extended life refrigeration units with inexpensive DIY life time maintenance. Most of the old reliable systems avoided problems associated with water cooling and add on gadgets. Many of the old systems stood the test of time because they followed simple basic designs of refrigerant gas vapor and liquid flow with no extra electronic troublesome gadgets. There are new excellent 12/24 volt powered variable speed Danfoss compressor refrigeration systems without additional gadgets that do not leak refrigerant or have problems with refrigerant flow. with the correct applications the new variable speed compressors systems can be much more energy efficient, but, in most cases, any one of the following options added to a standard Danfoss compressor system can reduce overall performance and reduce reliability:
- Fan cooled evaporators like VD14,15,16, and 15- as they prevent low refrigerator box temperatures and require manual frequent evaporator fin defrosting.
- Pump circulating water used as a cooling medium creates a very unfriendly and unreliable system because of pump failures, water flow restrictions, air in water intake blockages when the boat is in rough water and total failures due to electrolysis. Also a disadvantage to live-aboard boaters, is that there is no refrigeration when the boat is on the hard for maintenance.
- Ice Box Conversion Refrigeration system that depends on O-rings to provide a permanent life time refrigerant seal is not a wise choice.
- Also, systems that have demonstrated more than a few serious problems, such as refrigerant flow problems is a poor choice when choosing a system.
- Electronic thermostats that are intended to control box temperature instead of a capillary tube evaporator’s temperature can and will unbalance a system’s efficiency by overpowering the evaporator and they are more likely to fail in marine environments than manual snap action thermostats.
- Being able to adjust the compressor speed to achieve the best System Coefficient Of Performance (SCOP) is a great improvement in balancing all of a system's components. The other advantage of the BD50 and BD35 variable speed compressor is the ability to reduce the compressor speed to its best energy efficient speed, COP, for the lowest daily energy consumed, while maintaining the desired box temperature. The fact is, if your refrigeration unit ,at its lowest speed, can maintain the desired thermostat set, box temperature at the least daily amperage then increasing the compressor speed in small heat load boxes is not necessary. Installation of troublesome automatic speed controls is also unnecessary in small heat load boxes.
A tooling list for repairing maintenance problems of the new generation of unfriendly systems consists of:
Refrigerant 134a servicing equipment adaptable to ¼ inch serving ports and a refrigerant deep vacuum pump that is required for some manufacturer's systems . In countries where the Clean Air Act defining Montreal protocols apply, a Refrigerant recovery pump and recovery tank are also required even for 134a refrigerant repairs.
The basic assumption that a new icebox conversion refrigeration unit is better and more efficient than earlier models is generally overrated by creative advertising. When it comes to reliability and mechanical break downs, the simpler leak proof, well designed systems are more reliable. How often is a refrigeration repairman needed for a home refrigerator or an older 12 volt Danfoss Powered systems?
In summary; select a simple system where problems are not difficult to identify or correct using technical knowledge on board assisted by a local mechanical mechanic. If one e-mail or phone call will not get the system back in service you may have purchased the wrong system.
