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a. Remote Alarm Contacts

Remote alarm connections are also included on the termi-

nal strip (Figure 2-2) providing Normally Open (N.O.) and
Normally Closed (N.C.) contacts. COM is the Common termi-
nal. The remote alarm will activate when either the incubator’s
temperature goes out of the set alarm limits.

2.4 Power Connection

See the serial tag on the side of the unit for electrical spec-

ifications, or refer to the electrical schematics at the end of this
manual.

Connect the incubator to a grounded, dedicated
circuit. The power cord connector is the mains
disconnect device for the incubator. Position the
incubator so the unit can be easily disconnected.

For Model 3920, plug the provided 10 ft. power cord with

the NEMA 5-20 plug into the power outlet connection on the
back of the cabinet, then into the grounded dedicated electrical
circuit.

2.5 Start-Up Procedure

Preset the controls as follows:

Overtemp Safety Thermostat  . . . . . . . . . . . .(Fully Clockwise)
Undertemp Safety Thermostat  . . . . .(Fully Counterclockwise)
Main Power Switch  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ON
Temperature Controller . . . . . . . . . . . . . . . . . .Desired Setpoint
Door Heater  . . . . . . . . . . . . . . . . . . . . . . . . . .40% (factory set)

Turn the Main Power switch on. The Power indicator and

Heat indicator will light. Turn the Refrigeration switch on and
the indicator will light.

The compressor and refrigeration lights will not
come on if the chamber temperature is within
±4°C of the temperature controller.

2.6 Setting the Overtemp Safety Thermostat

Allow the chamber temperature to stabilize, then set the

overtemp safety thermostat as follows:

1. Turn the overtemp control knob slowly counterclockwise

until the audible alarm sounds and the overtemp indica-
tor lights.

2. Turn the overtemp control knob clockwise approximately

two units on the scale. The alarm should be silenced and
the overtemp indicator light should go out.

The overtemp safety thermostat is now set a few degrees

above the control temperature setpoint. When the chamber tem-
perature rises to the overtemp control point, the alarm system
will activate, power to the heaters will shut off, and the cham-
ber temperature will be maintained at the overtemp control
point.

When an overtemp condition occurs, the cause must be

determined and corrected before normal operation under the
main temperature controller can be resumed.

Note:

When the chamber temperature control setpoint is

changed, the overtemp safety thermostat must be reset to
accommodate the change.

2.7 Setting the Undertemp Safety Thermostat

Allow the chamber temperature to stabilize, then set the

undertemp safety thermostat as follows:

1. Turn the undertemp control knob slowly clockwise until

the audible alarm sounds and the undertemp indicator
lights.

2. Turn the undertemp control knob counterclockwise

approximately two units on the scale. The alarm should
be silenced and the undertemp indicator light should go
out.

The undertemp safety thermostat is now set a few degrees

below the control temperature setpoint. When the chamber tem-
perature drops to the undertemp control point, the alarm system
will activate, power to the compressor will shut off, and the
chamber temperature will be maintained at the undertemp con-
trol point.

When an undertemp condition occurs, the cause must be

determined and corrected before normal operation under the
main temperature controller can be resumed.

Note:

When the chamber temperature control setpoint is

changed, the undertemp safety thermostat must be reset to
accommodate the change.

Model 3920__________________________________________________________________Installation and Start-Up

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