Table of Contents
Advertisement
Section 6 Maintenance
Parts Replacement
6-2
Freas Safety Oven
There are five major electrical parts or assemblies on each oven:
1. Blower Motor
2. Heater Assembly
3. Microprocessor Controller
4. RTD Temperature Sensor
5. High Limit Thermostat
Test and/or Replace
1. Blower Motor - With line switch "On", blower motor should be operating.
Open the oven door and air current moving from right to left can be felt
within the chamber.
The blower motor is equipped with a built-in thermal overload device to
prevent it from overheating.
Warning Disconnect oven from its electrical power source before proceeding. The
motor windings can be given a continuity test by placing an ohmmeter across
motor terminals 1 and 2.
To replace the motor, it is first necessary to remove the heater.
a. To gain access to heater, remove left inner diffuser wall. Remove heater
mounting screws. Tag and remove wire leads to bus bar terminals,
(located in the control compartment on table models) and remove heater.
b. Loosen set screw that locks blower wheel to shaft or motor and remove
blower wheel.
c. Remove motor mounting bolts and carefully withdraw motor and shaft
extension, if supplied, from unit.
d. Replace motor in reverse order. The blower must be positioned 1/4" from
blower intake plate which is adjacent to the heater. Check motor rotation
before installation. (Should be counterclockwise viewing shaft).
Warning Disconnect oven from its electrical power source.
2. Heater Assembly - If heater replacement is necessary, follow Step "a" in
motor replacement when installing heater.
The cold heater resistance should be approximately 16 ohms for 230V model.
s
s
Thermo Scientific
Advertisement
Table of Contents
