10
Operation
Caution
Monitor furnace if percent time input is
set greater than 40% on and particu-
larly when the control is set on “9” or
above. The furnace may overheat and
burn out the elements or thermocouple
if not properly monitored under these
conditions.
Caution
Do not use in the presence of flamma-
ble or combustible chemicals. Fire or
explosion may result; this device con-
tains components which may ignite
such materials.
Hot Surface
“Caution: Hot Surface. Avoid Contact.”
To avoid burns, do not touch this fur-
nace on the exterior or interior sur-
faces during use or for a period of time
after use.
Operation of Manual and
Automatic Models
Observe These Warnings Before Operating
Your Furnace:
Manual Control Models (F21120-33,
F21125, F21120)
The control switch is a combination ON/OFF switch and
temperature control. The furnace is ON at any setting of
the control switch except in the OFF position. Turn the
control switch counterclockwise to set rate of heating.
Cycle Light: The amber cycle light will illuminate whenev-
er the power is being applied to the elements.
The marks on the control indicate the percent of time
power is applied to the heating elements. An increase in
percent time “On” results in a higher chamber temperature.
Adjust control switch to maintain desired temperature set-
ting. To turn the furnace off, turn control either fully clock-
wise or fully counterclockwise to the OFF position.
Pyrometer
The pyrometer with a thermocouple indicates the chamber
temperature. It does not control the furnace in any manner.
It is provided to enable the operator to observe the tem-
perature within the chamber.
