ITB Training Manual
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Step 4: Set voltmeter to DC voltage and connect the voltmeter leads to the coil terminals (wires still attached to ter-
minals). Approximate voltage reading will be around 155VDC. Go to Brew Valve test in the Test Outputs screen. Turn
on the brew valve and the 155VDC should drop to 1.5VDC or 0VDC.
Test Switches
There are two methods of testing the membrane switch. The easiest method is to enter the Test Switches menu by
selecting “Yes”. Depress the corresponding switch to be tested and the display will show the switch name on the
display. The name displayed indicates the membrane switch is working and if no switch name appears on the display,
indicates a defective membrane switch.
The second method can be used by referring to the schematic and tracing the appropriate pin terminals from the
CBA to the switch. Use an ohmmeter to test the switch for continuity when the switch is depressed. It is not uncom-
mon if you have a small amount of resistance when checking a membrane switch for continuity.
Refill
This function allows the operator to adjust the sensitivity of the refill circuit and to view the condition of water and
refill probe of lime scale build-up. This is mainly a troubleshooting feature. Water in different geographical locations
can have different conductivities. By adjusting, (range of 20 - 230), the sensitivity of the refill circuit, this will allow the
brewer to operate under various water conditions.
The level probe senses the water level in the tank by the conductive minerals in the water grounding out the very low
AC voltage applied to the probes. A high reading (approximately 255) indicates water is not touching, or not conduc-
tive enough to ground the circuit. A low reading (0-2) indicates the probe is grounded. Left side is the actual reading
and the right side is the adjustable refill threshold. BUNN constant refill threshold is set at 155 from the factory.
Procedure for resetting a new refill threshold number if the water is less conductive or low TDS. The highest known
number is 255 for open circuit. You take the actual water reading number and subtract it from 255. You then take
the difference and divide it by two = xx. You add the divided number onto the actual reading number and now this
becomes your new Refill Threshold setting number. See example below.
Water reads 80 and factory refill threshold is set at 155.
255 - 80 = 175
175 / 2 = 87.5
87 + 80 = 167 (This now becomes the new Refill Threshold number)
Note:
Always make sure that the # on the right is larger than the # on the left when water is contacting the tank refill
probe.
Service Fault Messages
The brewer features several error messages for problems occurring within the machine. These error messages will
show up on the display.
This message will be shown if the control board does not see the programmed water
temperature with 60 minutes.
TEST SWITCHES?
NO
YES
HEATING TIME
TOO LONG
HALF
FULL
ENABLE
ON / OFF
BREW
BREW
A
BREW
B
BREW
C
®
XX REFILL XXX
(-)
(+)
DONE
