Servicing Commercial Machines
For example, a slab of ice that is lopsided - heavy on one end and light on the other - usually indicates a shortage of refrigerant entering the evaporator. This can be the result of a low refrigerant charge or a defective metering device.
One way to determine if the evaporator is being fed the proper amount of refrigerant is to look at the suction line leaving the evaporator midway through the freeze cycle. At that point there should be a coating of frost on the line. If no frost is present, it could indicate a shortage of refrigerant being fed into the evaporator.
This usually can be verified by measuring the superheat at this location. A superheat reading higher than what is recommended by the manufacturer will confirm that the evaporator is starved for refrigerant.
Loss Of Water
Another common service problem with ice machines is loss of water during the freeze cycle. If the water in the sump is lost either down a drain or into the ice bin during the freeze cycle, the evaporator will be starved for water.Depending on the design of the machine, one of two things can happen: either the machine will produce very thin ice shells or no ice at all, or the freeze cycle will be much longer than normal.
Loss of water can be the result of several problems.
One common cause of this problem is a cracked sump pan. This normally will require the sump pan to be replaced. Occasionally it can be repaired using some type of approved sealant. Always verify that any sealant used in an ice machine is approved for that usage.
Another common cause of losing water during the freeze cycle is water flowing down a drain. This can cause several different problems with an ice machine, depending on its design.
Some ice machine manufacturers incorporate a dump valve to purge the remaining water in the sump during the harvest cycle. If the dump valve is stuck open or leaking, it can cause water to continually drain during both the freeze and harvest cycles.
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Some ice machine designs in-corporate an inlet water float to fill the sump with water during the harvest and freeze cycles. If the water valve sticks open or leaks, it will cause the sump to overfill with water, causing water to flow down an overflow drain. Depending on the severity of the water loss, this situation will cause either a longer-than-normal freeze cycle or no ice to be produced.
Another possible cause of water loss is an ice machine that is not level. This could cause water to be lost into the ice bin or down a drain.
No matter the cause, a technician should be able to examine the evaporator and water flow during the freeze cycle and look for signs of water loss from the sump. Once he identifies this problem, he can investigate the cause and resolve it.
Marchese is owner of Coldtronics of Pittsburgh. He can be reached at 412-734-4433, joe@coldtronics.com, or www.coldtronics.com.
Publication date: 02/07/2005
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