Thermo Scientific 815 Operating And Maintenance Manual page 28

Possible Solutions
(continued)
Thermo Scientific
Note Software version 2.00 and later has a 30 minute delay for the lowe
and high alarm to avoid nuisance alarms caused by door openings.
8. Ice buildup on evaporator coils:
Excessive frost buildup is the result of the introduction of outside
moisture. This may be caused by the evaporation of liquids placed in
the chamber, or it may be the result of excessive opening of the door
during high humidity conditions. The door gasket should also be
examined for proper seal. If repairs are necessary, contact Technical
Services.
9. Excessive line voltage variation:
Incubator will operate satisfactorily over full temperature range (-10°C
to 50°C) when line voltages vary from nominal voltage by -5% or
+10%. Larger voltage variations may impair the Temperature Control.
Correct as required.
10. Excessive ambient temperature variation:
If the incubator is placed close to the air-conditioning outlet, hot
radiators, or direct sunlight, or if the ambient temperature changes
drastically, the chamber temperature will be affected. Correct as
necessary.
Caution The incubator should not be operated in an environment where
the ambient temperature exceeds 90°F, as the compressor thermo-overload
will be tripped and will result in a wide band control cycle of
approximately ±4°C. Such cycling should not be misinterpreted as a
malfunction of the electronic controls.
11. Overcharged compressor:
This would happen only if compressor was overcharged after installation.
For correct charge, see nameplate located behind lower portion of
door. If unit has more charge than shown, it will not reach 50°C.
Compressor must be discharged and recharged correctly.
12. The circuit design calls for continuous compressor operation. If
compressor cycles "On-Off", it is an indication that the starting relay is
overriding the control circuit. This may be the result of excessive
(90°F) ambient temperature adjacent to the compressor, excess dirt on
the compressor, or a relay malfunction. Provide additional wall
clearance and/or circulation around the unit, clean compressor, or
contact Technical Services.
Section 4
Service
s
Refrigerated Incubator 4-7