shelolab SRI21D, Руководство по установке и эксплуатации

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USER MAINTENANCE
Factors in Ice Build Up
Incubators and diurnal chambers used for biologic oxygen demand studies and other closed-
container applications will generally require infrequent and very short defrost runtimes. However,
runtimes may be prolonged and occur more frequently if the incubator is used in a high humidity
environment with the door opened several times a day or left open for prolonged periods. Units with
open media containers, water pans, and other sources of evaporating water in the incubation
chamber may also experience significant ice buildup. This will necessitate long runs of the auto
defrost cycle twice a day. If the humidity is high enough and the temperature is set toward the low
end of the unit performance range, humidity can overwhelm the defrosting cycle, and significant ice
accumulation may occur on the coil.
Figure 12: Ice on the Cooling Coil
Loss of Efficiency
As ice accumulates, it insulates the heat-transporting coolant fluid within the coil, driving an
increasing loss of chilling efficiency. This may even cause false high temperature readings on the
defrost thermostat and prevent the system from recognizing that a defrost run is needed. When this
occurs, the first sign of trouble is often a rise in the chamber temperature, even though the main
control temperature set point has not been changed.
Units with heavy accumulations of ice on the cooling coil must be manually defrosted by shutting
down the unit for a 24-hour period. This provides sufficient time for the ice to melt. See the next
page for manually defrosting the chamber.
Forcing the Defrost Cycle
For units that are icing up from high humidity and low temperature settings, Sheldon Manufacturing
offers a defrosting system retrofit kit that replaces the defrost thermostat installed at the factory. The
retrofit kit automatically turns off the compressor for ten minutes every twelve hours, regardless of
the temperature on the coil surface. Please see the SHEL LAB website for pricing or contact Sheldon
Technical Support if you have any questions. Part Number 9900577.