Troubleshooting a pleasure boat’s ice box conversion refrigeration
can be a difficult task as there are no too refrigeration
installations the same. This boat owner’s refrigeration complaint deals mainly with poor daily performance. Details reported on this thread posting
Refrigeration is powered by a single
¾ horse 110 volt compressor with two eutectic holding plates. One plate contains approximately five gallons of eutectic solution the smaller plate one and one half gallon of solutions.
Freezer is 7 cu ft and frig is 3 cu ft.
COMMENT, recommended frozen eutectic solution for a reasonable holding plate in tropical weather
one gallon for each cubic foot of freezer and ½ gallon of solution for each cubic ft of refrigerator
System manufacturer Technicold if it was assembled before 2008 Rich Beers Marine
it would have been by them after Jan 11, 2008 Northern Lights
acquired and produced the Technicold Brand.
Owner reports refrigerant seemed to operate way to hot -- 150 degrees by laser thermometer. The compressed gas line coming out of it was 200 degrees. The incoming gas line was 58 degrees.
Hermetically sealed compressors on any water cooled system will run much warmer without external air cooling
. In most cases a water cooled system’s compressor has only source of cooling
sub cooled returning gas vapor from evaporator.
Quality of insulation
is not known?
COMMENT, The best way to test resistance to heat conductance through insulation is by comparing exterior surface temperature of insulation against boat’s interior
ambient temperature when box interior
is at desired operating temperature. If the Delta
T is less than 4 degrees F insulation is good. If Delta
T is greater than 4 degrees but no exterior moist condensation
more energy a day will be required. If condensation
is present on exterior surface of insulation it is a good idea to consider improving present insulation.
Experience over time generally is a better source of information than published books
. I do not see where my books
or any other book will lead you quickly to the correct answers. Trouble shooting must be a process of elimination by non destructive methods. My experience with advising owners to call technicians is not good and most often turns a simple problem into a nightmare. There is more information on my web site and forum regarding pleasure boat size refrigeration performance than you will find anywhere else.
Your Holding plate system should not cycle off and on by thermostat until the plate is frozen solid. If compressor is cycling it will be because of high side pressure is dangerously high or low pressure is running in an extremely low vacuum.
COMMENT, An extended compressor off period of 3 to 5 minutes is required to reduce the next compressor starting load. Do not confuse this differential setting between what is referred to as hysteresis on more efficient small evaporator systems like those used with small Danfoss compressors.
Sight glass moisture indicators shows signs of moisture. The manual says green is dry, and yellow/green stripes is wet. The yellow is faded and has a green tint to it so I wonder if it's only somewhat wet.
COMMENT, Poor operating performance as owner describes is not related to a color change of the moisture detecting paper or paint
inside the refrigerant sight glass. Most of these ¾ HP systems are assembled with various off the shelf components that may or may not be perfectly compatible with sight glass moisture detector material.
Jumping to the conclusion to do destructive dehydration testing to an operating system based on sight glass color while cruising I consider a mistake.
When will there be bubbles in sight glass. COMMENT, It is also a mistake to pay too much attention to bubbles in sight glass as again all systems and sight glass installations are not the same. Regulating refrigerant flow with holding plate evaporators is always changing based on thermo expansion valve tonnage and stability of superheat within holding plates. In many systems bubbles in sight glass are clear only when holding plates are frozen solid. Sight glasses with larger window chambers allow refrigerant to phase change to a vapor as they enter glass area and may not fill glass with liquid even when system is correctly charged.
COMMENT, Dennis is correct do not add to the FREEZER box heat load with additional heat absorbing items. His Quote “Want to just warn about the adding water bottles to the freezer to add thermal mass. Although cold ice is good to have in the freezer, putting water bottles (containing liquid water) in the freezer takes quite a while to freeze, and in the mean while will warm up the food
items in the freezer, perhaps melting some critical foods. We simply don't do it as we find it makes a bigger problem than it solves.”