Bunn Coffee Maker OT15 Service Manual
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HIGH HEAT WARMER
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FAILURE TO COMPLY RISKS
GLASS FAILURE/HOT LIQUID
BURNS AND FIRE H
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AZARD
OPERATING & SERVICE MANUAL
BUNN-O-MATIC CORPORATION
POST OFFICE BOX 3227
SPRINGFIELD, ILLINOIS 62708-3227
PHONE: (217) 529-6601 FAX: (217) 529-6644
10021.0000G 7/00 © 1989 BUNN-O-MATIC CORPORATION
CONTENTS
Introduction ............................................................... 2
User Notices .............................................................. 3
Electrical Requirements ............................................. 4
Plumbing Requirements ............................................ 4
Initial Set-Up.............................................................. 5
Adjusting Brew Volumes............................................ 6
Operating Controls..................................................... 6
Coffee Brewing .......................................................... 7
Cleaning..................................................................... 7
Troubleshooting ......................................................... 8
Service....................................................................... 12
Wiring Diagrams........................................................ 26
INTRODUCTION
This equipment will brew a half-gallon batch of coffee into an awaiting decanter at the press of a button. The
OT has two and the RT has five warmers to keep the beverage at the right temperature, on the RT one of which is
capable of heating water to boiling. The brewer is only for indoor use on a sturdy counter or shelf.
WARRANTY
Bunn-O-Matic Corp. (“Bunn”) warrants the equipment manufactured by it to be commercially free from defects
in material and workmanship existing at the time of manufacture and appearing within one year from the date of
installation. In addition:
1.) Bunn warrants electronic circuit and/or control boards to be commercially free from defects in material and
workmanship for two years from the date of installation.
2.) Bunn warrants the compressor on refrigeration equipment to be commercially free from defects in material
and workmanship for two years from the date of installation.
3.) Bunn warrants that the grinding burrs on coffee grinding equipment will grind coffee to meet original factory
screen sieve analysis for three years from date of installation or for 30,000 pounds of coffee, whichever comes first.
This warranty does not apply to any equipment, component or part that was not manufactured by Bunn or that,
in Bunn’s judgement, has been affected by misuse, neglect, alteration, improper installation or operation, improper
maintenance or repair, damage or casualty.
THE FOREGOING WARRANTY IS EXCLUSIVE AND IS IN LIEU OF ANY OTHER WARRANTY, WRITTEN OR
ORAL, EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF EITHER
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. The agents, dealers or employees of Bunn are
not authorized to make modifications to this warranty or to make additional warranties that are binding on Bunn.
Accordingly, statements by such individuals, whether oral or written, do not constitute warranties and should not
be relied upon.
The Buyer shall give Bunn prompt notice of any claim to be made under this warranty by telephone at (217)
529-6601 or by writing to Post Office Box 3227, Springfield, Illinois, 62708-3227. If requested by Bunn, the Buyer
shall ship the defective equipment prepaid to an authorized Bunn service location. If Bunn determines, in its sole
discretion, that the equipment does not conform to the warranty, Bunn shall repair the equipment with no charge
for parts during the warranty period and no charge for labor by a Bunn Authorized Service Representative during
the warranty period. If Bunn determines that repair is not feasible, Bunn shall, at its sole option, replace the
equipment or refund the purchase price for the equipment.
THE BUYER’S REMEDY AGAINST BUNN FOR THE BREACH OF ANY OBLIGATION ARISING OUT OF THE SALE
OF THIS EQUIPMENT, WHETHER DERIVED FROM WARRANTY OR OTHERWISE, SHALL BE LIMITED, AS
SPECIFIED HEREIN, TO REPAIR OR, AT BUNN’S SOLE OPTION, REPLACEMENT OR REFUND.
In no event shall Bunn be liable for any other damage or loss, including, but not limited to, lost profits, lost sales,
loss of use of equipment, claims of Buyer’s customers, cost of capital, cost of down time, cost of substitute
equipment, facilities or services, or any other special, incidental or consequential damages.
Page 2
10021 071700
USER NOTICES
Carefully read and follow all notices on the equipment and in this manual. They were written for your protection.
All notices on the equipment should be kept in good condition. Replace any unreadable or damaged labels.
00831.0000
00658.0000
00656.0000
Page 3
WARNING
!
HIGH HEAT WARMER
DO NOT BOIL DECANTER DRY
KEEP COMBUSTIBLES AWAY
FAILURE TO COMPLY RISKS
GLASS FAILURE/HOT LIQUID
BURNS AND FIRE HAZARD
00688.0000
10021 101598
200 OR 240V.A.C.
L1 BLACK
L2 RED
ELECTRICAL REQUIREMENTS
CAUTION - Do not connect the brewer to the power source until specified in Initial Set-Up.
WHITE
NEUTRAL
L1 BLACK
120V.A.C.
MODELS OT15 & 20 require 2wire, grounded service rated
120 volts ac, 15 or 20 amp respectively, single phase, 60 Hz.
L2 RED
WHITE
NEUTRAL
L1 BLACK
120V.A.C.
208 or 240V.A.C.
120V.A.C.
MODELS OT35 & RT35 require
3-wire, grounded service rated
120/208 or 120/240 volts ac, 20
amp, single phase, 60 Hz.
Model 15 has an attached
cordset.
Electrical Hook-Up
Model OT15 has an attached cordset.
Models OT20, OT35, & RT35, proceed as follows:
CAUTION – Improper electrical installation will dam-
age electronic components.
1. An electrician must provide electrical service as
specified.
2. Using a voltmeter, check the voltage and color
coding of each conductor at the electrical source.
3. Remove the front panel beneath the sprayhead
and rotate the control thermostat knob fully
counterclockwise to the "OFF" position and replace the panel.
4. Remove the rear panel, feed the cord through
the strain relief, and connect it to the terminal
block.
5. Connect the brewer to the power source and
verify the voltage at the terminal block before
proceeding. Replace the rear panel.
6. If plumbing is to be hooked-up later be sure the
brewer is disconnected from the power source.
If Plumbing has been hooked-up, the brewer is
ready for Initial Set-Up.
PLUMBING REQUIREMENTS
This brewer must be connected to a cold water
system with operating pressure between 20 and 90
psi from a 1/2" or larger supply line. A shut-off valve
should be installed in the line before the brewer. Install a regulator in the line when pressure is greater
than 90 psi to reduce it to 50 psi. The water inlet
fitting is 1/4" flare.
RED
NEUTRAL
L1 BLACK
MODELS OTA, RTA & RT35B
require 2-wire, grounded service rated 240 volts ac or 200
volts ac, 20 amp single phase,
MODEL RT25B requires 2wire, grounded service
rated 100 volts ac, 20 amp
single phase, 50 Hz.
50 Hz.
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NOTE - Bunn-O-Matic recommends 1/4" copper tubing for installations of less than 25 feet and 3/8" for
more than 25 feet from the 1/2" water supply line. A
tight coil of copper tubing in the water line will facilitate moving the brewer to clean the counter top. BunnO-Matic does not recommend the use of a saddle valve
to install the brewer. The size and shape of the hole
made in the supply line by this type of device may
restrict water flow.
This equipment must be installed to comply
with the Basic Plumbing Code of the Building Officials and Code Administrators International, Inc. (BOCA) and the Food Service
Sanitation Manual of the Food and Drug Administration (FDA).
Page 4
100V.A.C.
P1709
10021 101598
PLUMBING REQUIREMENTS (Cont.)
Plumbing Hook-Up
Model OT15 has an attached water strainer, proceed to step 2.
Models OT20, OT35, & RT35, proceed as follows:
1. Remove the rear panel and bottom pan. Run the long piece of tubing from the strainer (supplied) under the
brewer and attach it to the water inlet fitting on the solenoid. Reinstall the bottom pan and rear panel.
2. Flush the water line and securely attach it to the 1/4" flare fitting on the strainer.
3. Turn on the water supply.
INITIAL SETUP
CAUTION - The brewer must be disconnected from the power source throughout the initial set-up, except when
specified in the instructions.
1. Remove the front panel.
2. Rotate the control thermostat knob fully counterclockwise to the "OFF" position and replace the
panel.
3. Insert an empty funnel into the funnel rails.
4. Place a decanter containing a small amount of
water on the warmer beneath the funnel.
5. Connect the brewer to the power source, place
the On/Off brew station warmer switch the upper position, and momentarily press the
start switch. Water will begin flowing into
the tank. When water stops flowing into the tank,
initiate a second and a third brew cycle. During
this third brew cycle the tank will fill to its capacity and the excess will flow from the
sprayhead, out of the funnel, and into the decanter.
NOTE - The On/Off brew station warmer switch must
be in the upper position to initiate and complete a
brew cycle.
6. Place the On/Off brew station warmer switch in
the lower position.
7. Disconnect the brewer from the power source.
8. Remove the front panel.
9. Rotate the control thermostat knob fully clockwise to the "ON" position and replace the front
panel.
10. Connect the brewer to the power source and wait
approximately twenty minutes for the water in
the tank to heat to the proper temperature. Some
water will drip from the funnel during this time;
this is due to expansion and should not occur
thereafter.
11. Place an empty decanter under the funnel.
12. Place the On/Off brew station warmer switch in
the upper position and momentarily press the
start switch. Empty the decanter after water has
stopped flowing from the funnel.
13. Allow the water in the tank to reheat to the proper
temperature.
14. Place an empty decanter on the warmer and press
the start switch. Check the water volume in the
decanter after water has stopped flowing from
the funnel. It should be 64 ounces.
15. If not, adjust the Timer as described in Adjusting
Brew Volumes (Page 6).
16. Repeat steps 13-15 until 64 oz. water volume is
achieved.
J1
J2
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Page 5
TL4
TL3
TL2
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P1690
10021 071700
ADJUSTING BREW VOLUMES
CAUTION - Disconnect the power source from the brewer prior to the removal of any panel for the replacement
or adjustment of any component.
NOTE: Prior to setting or modifying batch sizes, check that the brewer is connected to water supply, the tank is
properly filled, and a funnel and server are in place.
1. Modifying batch sizes. To modify a batch volume, first check that the SET/LOCK switch is in the “SET”
position on the circuit board.
To increase a batch size. Press and hold the START or BREW switch until three clicks are heard. Release the
switch (Failure to release the switch within two seconds after the third click causes the volume setting to be
aborted and previous volume setting will remain in memory) and press it again one or more times. Each time
the switch is pressed, two seconds are added to the brew time period. Allow the brew cycle to finish in order
to verify that the desired volume has been achieved.
To decrease a batch size. Press and release the START or BREW switch once for every two-second interval
to be removed from the total brew time period; then immediately press and hold down the START or BREW
switch until three clicks are heard. Release the switch. (Failure to release the switch within two seconds after
the third click causes the volume setting to be aborted and previous volume setting will remain in memory).
Allow the brew cycle to finish in order to verify that the desired volume has been achieved.
2. Setting batch sizes. To set a batch volume, first check that the SET/LOCK switch is in the “SET” position on
the circuit board. Press and hold the START or BREW switch until three distinct clicks are heard, and then
release the switch. (Failure to release the switch within two seconds after the third click causes the volume
setting to be aborted and previous volume setting will remain in memory). View the level of the liquid being
dispensed. When the desired level is reached, turn the ON/OFF switch to “OFF” (lower). The brewer remembers this volume and will continue to brew batches of this size until the volume setting procedure is repeated.
NOTE: When brewing coffee, batch volumes will decrease due to absorption by the coffee grounds.
3. Setting programming disable feature. If it becomes necessary to prevent anyone from changing brew times
once programmed, you can set the SET/LOCK switch to the “LOCK” position. This will prevent any programming to be done until switch is once again placed in the “SET” position.
OPERATING CONTROLS
MODEL OT
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MODEL RT
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Page 6
10021 071700
MODELS OT & RT
A. On/Off Brew Station Warmer Switch
Placing the switch in the upper position supplies
power to the brew station warmer and enables brewing. Placing the switch in the lower position cuts
power to the brew station warmer and stops brewing.
Stopping a brew cycle after it has been started will
not stop the flow of water into the funnel until the
tank syphons down to its proper level.
E. Upper Warmer Indicator Lamp
Glows whenever the upper warmer switch is in
the upper position showing that the warmer is on.
F. Left Rear Warmer Rotary Switch
Rotating the knob to the "ON" position supplies
power to the left rear warmer. Rotating the knob to
the "OFF" position cuts power to the left rear warmer.
NOTE - The On/Off brew station warmer switch must
G. Left Front Warmer Rotary Switch
be in the upper position to initiate and complete a brew
cycle.
B. On/Off Brew Station Warmer Indicator Lamp
power to the left front warmer. Rotating the knob to
the "OFF" position cuts power to the left front warmer.
Glows whenever the On/Off brew station warmer
switch is in the upper position showing that the
H. Right Front Warmer Rotary Switch
warmer is on and that the automatic brew cycle can
be started.
C. Start Switch
power to the right front warmer. Rotating the knob to
the "OFF" position cuts power to the right front warmer.
Starts a brew cycle when the On/Off brew station
warmer switch is in the upper position.
D. Upper Warmer Switch
Placing the switch in the upper position supplies
power to the upper warmer. Placing the switch in the
lower position cuts power to the upper warmer.
I. Right Rear Warmer Three Heat Rotary Switch
positions supply power to the right rear warmer. Rotating the knob to the "OFF" position cuts power to the
right rear warmer. The “HIGH” position of this switch
makes the warmer capable of boiling water.
COFFEE BREWING
Start each brew cycle with an empty, clean, half-gallon decanter.
Rotating the knob to the "ON" position supplies
Rotating the knob to the "ON" position supplies
Rotating the knob to the "LO", "MED", or "HIGH"
1. Insert a BUNN® filter into the funnel.
2. Pour the fresh coffee into the filter and level the bed of grounds by gently shaking.
3. Slide the funnel into the funnel rails.
4. Place the On/Off brew station warmer switch in the upper position.
5. Momentarily press the start switch.
6. When brewing is completed, simply discard the grounds and filter.
CLEANING
1. The use of a damp cloth rinsed in any mild, non-abrasive, liquid detergent is recommended for cleaning all
surfaces on Bunn-O-Matic equipment.
2. Check and clean the sprayhead. The sprayhead holes must always remain open.
3. With the sprayhead removed, insert the deliming spring (provided) all the way into the sprayhead tube.
When inserted properly, no more than two inches of spring should be visible. Saw back and forth five or six
times. Then, repeat this step for the air vent tube.
NOTE - In hard water areas, this may need to be done daily. It will help prevent liming problems in the brewer and
takes less than a minute.
Page 7
10021 071700
TROUBLESHOOTING
A troubleshooting guide is provided to suggest probable causes and remedies for the most likely problems
encountered. If the problem remains after exhausting the troubleshooting steps, contact the Bunn-O-Matic
Technical Service Department.
• Inspection, testing, and repair of electrical equipment should be performed only by qualified service personnel.
• All electric components have 120 volt ac voltage on their terminals. Shorting of terminals or the application
of external voltages may result in equipment failure.
• Intermittent operation of electronic equipment is unlikely. Component failure will normally be permanent. If
an intermittent condition is encountered, the cause will likely be a switch contact or a loose connection at a
terminal or crimp.
• Solenoid removal requires interrupting the water supply to the valve. Damage may result if solenoids are
energized for more than ten minutes without a supply of water.
• The use of two wrenches is recommended whenever plumbing fittings are tightened or loosened. This will
help to avoid twists and kinks in the tubing.
• Make certain that all plumbing connections are sealed and electrical connections tight and isolated.
• This brewer is heated at all times unless disconnected from the power source. Keep away from combustibles.
WARNING
• Exercise extreme caution when servicing electrical equipment.
• Disconnect the brewer from the power source when servicing, except when electrical tests are specified.
• Follow recommended service procedures
• Replace all protective shields or safety notices
Problem
Equipment will not operate.
Brew cycle will not start.
Probable Cause
1. No power or incorrect voltage
1. No water
2. Water Strainer
3. Flow Control
Remedy
(A) Connect the brewer to the power
source.
(B) Check the terminal block for the
proper voltages.
(C) Check circuit breaker/fuse.
Check plumbing and shut-off valves.
(A) Direction of flow arrow must be
pointing towards brewer.
(B) Remove the strainer and check
for obstructions. Clear or replace.
(A) Direction of flow arrow must be
pointing away from the solenoid.
Page 8
(B) Remove the control and check
for obstructions. Clear or replace.
10021 101598
TROUBLESHOOTING (cont.)
Problem
Brew cycle will not start. (cont.)
Water flows into tank continuously
(On/Off brew station warmer switch
"OFF").
Water flows into tank continuously
(On/Off brew station warmer switch
"ON").
Probable Cause
4. On/Off Brew Station Warmer
Switch
5. Start Switch
6. Brew Timer
7. Solenoid Valve
1. Solenoid Valve
1. Brew Timer
Remedy
Refer to Service - On/Off Brew Station Warmer Switch for testing procedures. See page 19.
Refer to Service - Start Switch for
testing procedures. See page 25.
Refer to Service - Brew Timer for
testing procedures. See page 13 or
14.
Refer to Service - Solenoid Valve for
testing procedures. See page 24.
Refer to Service - Solenoid Valve for
testing procedures. See page 24.
Refer to Service - Brew Timer for
testing procedures. See page 13 or
14.
Water is not hot.
Decanter warmer is not hot.
1. Limit Thermostat
CAUTION: Do not eliminate or bypass limit thermostat. Use only
B.O.M. part #29329.1000
2. Control Thermostat
3. Tank Heater
1. Warmer Switches
2. Decanter Warmers
Refer to Service - Limit Thermostat
for testing procedures. See page 23.
Refer to Service - Control Thermostat for testing procedures. See
page 16.
Refer to Service - Tank Heater for
testing procedures. See page 26.
(A) The Warmer Switch(es) must be
in the "ON" position for the warmer
to operate.
(B) Refer to Service - Warmer
Switch(es) for testing procedures.
See pages 19,20, & 21.
Refer to Service - Warmers for testing procedures. See pages 17 & 18.
Page 9
10021 071700
TROUBLESHOOTING (cont.)
Problem
Spitting or unusual steaming from
sprayhead.
Inconsistent beverage level in decanter.
Probable Cause
1. Control Thermostat
2. Lime build-up
CAUTION: Tank and tank components should be delimed regularly
depending on local water conditions.
Excessive mineral build-up on stainless steel surfaces can initiate corrosive reactions resulting in serious
leaks.
1. Flow control
Remedy
Refer to Service - Control Thermostat for testing procedures. See
page 16.
Inspect the tank assembly for excessive lime deposits. Delime as required.
(A) Direction of flow arrow must be
pointing away from the solenoid.
(B) Remove the control and check
for obstructions. Clear or replace.
Consistently high or low beverage
level in decanter.
Dripping from sprayhead.
2. Improper water pressure
3. Syphon system
1. Brew Timer adjustment
1. Syphon system
Check the operating water pressure
to the brewer. It must be between
20 and 90 psi (138 and 620 kPa).
Water should flow freely from the
sprayhead for approximately twenty
seconds after the brew solenoid has
shut-off and then stop flowing
abruptly. The brewer must be level
from front-to-back to syphon properly.
Adjust the brew timer as required to
achieve the recommended 64 oz for
each brew cycle.
Water should flow freely from the
sprayhead for approximately twenty
seconds after the brew solenoid has
shut-off and then stop flowing
abruptly. The brewer must be level
from front-to-back to syphon properly.
2. Solenoid Valve
Page 10
Refer to Service - Solenoid Valve for
testing procedures. See page 24.
10021 071700
TROUBLESHOOTING (cont.)
Problem
Beverage overflows decanter.
Weak beverage.
Probable Cause
1. Beverage left in decanter
1. Type of paper filters
2. Coffee
3. Sprayhead
4. Funnel loading
Remedy
The brew cycle should be started
only with an empty decanter under
the funnel.
BUNN® paper filters should be used
for proper extraction.
A sufficient quantity of fine or drip
grind coffee should be used for
proper extraction.
B.O.M. sprayhead #01082.0000
should be used to properly wet the
bed of ground coffee in the funnel.
The BUNN® paper filter should be
centered in the funnel and the bed
of coffee leveled by gentle shaking.
Brewer is making unusual noises.
5. Water temperature
1. Solenoid Valve
2. Plumbing lines
3. Water supply
Place a funnel over an empty decanter on the warmer beneath the
sprayhead. Place the On/Off brew
station warmer switch in the upper
position, press the start switch, and
check the water temperature immediately below the sprayhead with an
accurate thermometer. The reading
should not be less than 195° F. Ad-
just the control thermostat slightly
clockwise to increase the water temperature.
The nut on top of the solenoid valve
must be tight or it will vibrate during operation.
Plumbing lines should not rest on
the counter top.
(A) The brewer must be connected
to a cold water line.
Page 11
(B) Water pressure to the brewer
must not be higher than 90 psi (620
kPa). Install a regulator if necessary
to lower the working pressure to approximately 50 psi (345 kPa).
10021 071700
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