Absorption refrigeration is a relatively infrequent alternative to compression refrigeration. However, the technology behind absorption refrigerators is almost 100 years old. Absorption refrigerators cool a space by boiling a liquid into a rapidly expanding gas. As the gas expands, it conducts heat away from the refrigerated space. Absorption refrigerators are used in many different situations. Small refrigerators that can run on a propane tank are often installed in campers, cabins, and houseboats. These refrigerators use a mixture of ammonia and water. Large refrigerators are used for industrial applications. These chillers generally use a solution of lithium bromide. There are several ways an absorption refrigerator can malfunction. An improperly calibrated heat source will reduce the efficiency of the unit. Corrosion or crystallization can block tubes and valves. The unit may also leak air, water, refrigerant, or steam.
Check Power Sources
The first step to take when troubleshooting any appliance is to check the power sources. Inspect the outlet and plug if they exist, or the disconnect and circuit breaker if the machine is hard-wired. Check the wiring at the thermostat as well. Look for loose connections or corrosion. Test the on-off switch to verify that it works. Use a voltage detector to inspect the power lines. Even if the hot power line is working, there may be a problem with the neutral or ground line.
Check for Leaks
A large industrial chiller will have numerous pipe joints and seals. In some factories steam may be used as a power source. Check the fittings on any steam pipes. If the chiller is powered by gas, check the gas fittings. Check the pipes which carry both chilled and hot water. Check for refrigerant leaks. Leaks can happen in both directions. Air leaking into a sealed chamber can be just as disruptive as refrigerant fluid leaking out of the chiller.
Beware of Crystallization and Corrosion
Crystallization is a common problem that was pervasive in older absorption chillers. Several adverse conditions can cause the lithium bromide to permanently separate from the water and form salt deposits on the boiler walls. Causes include low temperature cooling water, pressure reduction valve failure, and air leaks. The lithium bromide solution also contains heavy metals which act as corrosion inhibitors. The solution must be flushed and recharged periodically to keep rust protection strong. Corrosion or crystallization deposits can block pumps, pipes, and refrigerant lines. This will cause the boiler to fail. It is difficult to check for signs of this damage without opening the system.
If there are no obvious problems with the chiller, take a minute to review your expectations. Relative to compression refrigeration, absorption refrigeration is a more costly and less efficient technology. The chilled water used in some systems is no cooler than 46 degrees F. These types of chillers can be used for space cooling but are unsuitable for low-temperature refrigeration and freezing of perishable foods. Most industrial chillers also require a cooling tower; air cooling alone is often insufficient.