Bunn FMD-5 User Manual

26

FIG. 14 CONTROL THERMOSTAT

Location:
 

The control thermostat (mechanical or electronic) 

is located inside the dispenser on the upper left side 

of the housing.

Test Procedure:
Mechanical Thermostat:

1.  Disconnect the dispenser from the power source.

2.  Disconnect the black wire of the control thermostat 

from the black lead from the limit thermostat.

3.  Remove bulb from the tank.

4.  With a voltmeter, check the voltage across black 

wire on the control thermostat and the white or red 

wire on the tank heater with the tank heater switch 

in the “ON” (lower) position. Connect the dispenser 

to the power source. The indication must be:

 

a) 120 volts ac for two wire 120 volt models.

  b) 208 volts ac for three wire 120/208 volt mod-

els.

  c) 240 volts ac for two wire 240 volt models and 

three wire 120/240 volt models.

 

d) 230 volts ac for two wire 230 volt models.

5.  Disconnect the dispenser from the power source.

If voltage is present as described the control thermostat 

is operating properly. Reinstall bulb into the tank.

If voltage is not present as described, replace the 

thermostat.

P1445

Electronic Thermostat (Optional):

1.  Disconnect the dispenser from the power source.

2.  Disconnect the black wire of the control thermostat 

from the black wire from the limit thermostat.

3.  Remove temperature probe from the tank.

4.  With a voltmeter, check the voltage across the black 

wire from the control thermostat and the white  wire 

on the tank heater with the tank heater switch in 

the “ON” (lower) position. Connect the dispenser 

to the power source. The indication must be120 

volts ac for two wire 120 volt models.

If voltage is present as described the control thermostat 

is operating properly. Reinstall temperature probe into 

the tank.

If voltage is not present as described, replace the control 

thermostat.

Removal and Replacement:

1.  Disconnect the wires from the thermostat.

2.  Remove the thermostat capillary bulb/temperature 

probe by firmly pulling up on the capillary  grommet 

at the tank lid. 

3.  Loosen the two #8-32 screws securing the thermo-

stat bracket to the upper left rear of the dispenser 

housing.

4.   Remove thermostat bracket and thermostat as an 

assembly.

5.  Install the new thermostat and bracket inside the 

dispenser housing on the upper left rear side and 

tighten the two #8-32 screws.

6.  Slide the grommet to the line 4.5" above the bulb 

on the new capillary tube (mechanical thermostat 

only).

7.  Insert the capillary bulb/temperature probe  through 

the hole in the tank lid and press the grommet firmly 

and evenly so that the groove in the grommet fits 

into the tank lid.

8.  Carefully bend the capillary tube so that the tube and 

bulb inside the tank are in the vertical position and 

away from any electrical connections (mechanical 

thermostat only).

9.  Refer to Fig. 15 and reconnect the wires.

NOTE - The capillary tube must be clear of any electrical 

termination and not kinked.

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