To Replace Solid State Relay; To Replace Door Switch (Microswitch) - Barnstead 30400 Operation Manual

M S
AINTENANCE AND
46
ERVICING

To Replace Solid State Relay:

a. Disconnect furnace from power supply.
b. Remove the screws on the front dial and the
screws on the lower back cover.
c. Remove the upper back cover.
d. Disconnect the element lead wires and one
ground wire from back of furnace. Also, discon-
nect T/C lead wire from terminal block. (Note
placement and connection of wires).
e. Slide control section forward and disconnect two
wires from door switch. (Note placement and
connection of wires).
f. Control section can now be removed from fur-
nace housing.
g. Disconnect the wires from the relay and remove
relay. (Note placement and connection of wires).
h. Install new relay.
i. Reverse steps a - e to reassemble furnace.
j. Test operation of furnace.
To Replace Door Switch
(Microswitch)
a. Disconnect furnace from power supply.
b. Remove the screws on the front dial and the
screws on the lower back cover.
c. Remove the upper back cover.
d. Disconnect the element lead wires and one
ground wire from back of furnace. Also, discon-
nect the lead wire from terminal block (note
placement and location of wires).