Control Thermostat - Bunn U3 Operating & Service Manual

SERVICE (cont.)

CONTROL THERMOSTAT

FIG. 6 CONTROL THERMOSTAT
Location:
The control thermostat is mounted on the right
front of the component bracket.
Test Procedures:
1. Disconnect the brewer from the power source.
2. Locate the thermostat and the voltage check
points.
3. Connect the brewer to the power source.
Check Voltage Across
Model
Black wire on thermostat
120/208V & 120
from main harness to white
240V - 3 wire w/
wire in terminal block.
ground single phase
Red wire on thermostat
230V - 2 wire w/
from main harness to black
ground single
wire in terminal block.
phase
Black wire on thermostat
208V or 240V - 2
from main harness to red
wire w/ground
wire in the terminal block.
single phase
Black wire on thermostat
280V or 440V - 4
from main harness to white
wire w/ground 3
wire in terminal block.
phase
Black wire on thermostat
380V - 3 wire w/
from main harness to white
ground 3 phase
wire on step down trans-
w/ stepdown
former.
transformer
4. Disconnect the brewer from the power source.
If voltage is present as described, proceed to #5.
If voltage is not present as described, refer to the Wiring
Diagrams and check the brewer wiring harness.
5. Disconnect the black wires from the control ther-
mostat.
6. Check for continuity across the terminals on the
control thermostat with the control thermostat in
the "ON" position (fully clockwise), continuity must
not be present when the thermostat is in the "OFF"
position (fully counterclockwise).
If continuity is present as described, the control ther-
mostat is operating properly.
If continuity is not present as described, replace the
control thermostat.
Removal and Replacement:
1. Disconnect the wires from the control thermo-
stat.
2. Remove the thermostat capillary bulb by firmly
pulling up on the capillary at the component
bracket. This will disengage the grommet from
P2209.60 the component bracket.
3. Remove the #8-32 screw securing the control
thermostat and mounting bracket to the component
bracket. Remove control thermostat and bracket
as an assembly.
4. Remove knob from control thermostat.
5. Remove the two #6-32 screws securing the control
thermostat to the thermostat mounting bracket.
Remove and discard thermostat.
6. Install new control thermostat on thermostat
mounting bracket and secure with two #6-32
Voltage
screw.
120V
7. Install knob on thermostat.
8. Install thermostat and mounting bracket on the
component bracket and secure with one #8-32
230V
screw.
9. Carefully bend the capillary tube so that the tube
and bulb inside the brewer are in the vertical posi-
tion.
208V or
NOTE: The capillary tube must be clear of any electrical
240V
termination and not kinked.
10. Refer to Fig. 7 and reconnect the wires.
220V or
11. Adjust the control thermostat as required.
254V
120V
FIG. 7 CONTROL THERMOSTAT TERMINALS
Page 17
BLK from Main Har-
ness (All Models Ex-
cept 230V CE Models
RED from Main
Harness (230V CE
Models)
BLK to Limit Thermostat
(All Models Except 230V CE
Models
RED to Limit Thermostat
(230V CE Models)
P1730.80
10060 080900