Thermo Scientific MaxQ SHKA4000 Operating Manual page 31

Section 5
Operation
Optional
Refrigeration System
5-10 Incubated and Refrigerated Shakers
This section applies only to units supplied with this option. The
refrigeration system on the A and E series shakers are identical in
operation. Refer to Replacement Parts for refrigeration replacement parts.
When the unit power is on, refrigeration can be initiated by turning ON
the refrigeration switch which is located to the left of the defrost timer on
the lower right side panel of the shaker cabinet. This should be initiated
(turned on) only when a temperature set point of approximately 32°C or
less is required (based on your ambient temperatures). Both the main
power switch and the refrigeration switch need to be ON for the
refrigeration system to work. When the refrigeration switch is activated,
the compressor system will run continuously and the system will go
through the following routine:
Upon every activation of the refrigeration switch to the ON position, there
is an approximate 2-minute delay until the compressor becomes activated.
This is a safety feature, to prevent damage to the compressor in the case of
quickly switching the refrigeration switch off and on again. Because the
compressor does not turn on immediately after switching the refrigeration
switch to on, please note, THIS IS NORMAL. The defrost timer will
begin initiation. This may turn the fans off for several minutes until it
completes a normal defrost cycle.
During operation, the defrost timer will automatically "engage" every 4
hours, switching cold gas through the evaporator (inside) coils to hot gas in
order to defrost the coils. There is a dedicated sensor inside the coils which
will terminate the defrost when the temperature reaches a point where it is
assured that there is no ice or frost on the coil. At low set point
temperatures (i.e. 5°C), this defrost time will be longer than higher set
point temperatures (i.e. 25°C), which may initiate and terminate
immediately because the coils will be much warmer at higher set point
temperatures.
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