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A.O. Smith 500 Service handbook

Manual is about: COMMERCIAL GAS WATER HEATERS

Summary of 500

  • Page 1

    Commercial gas high efficiency water heaters service handbook printed in the u.S.A. 0914 329297-000 500 tennessee waltz parkway ashland city, tn 37015 for models: bth 120 thru 500 series 200/201 installation considerations - pre service checks - construction - operation & service - troubleshooting s...

  • Page 2: Table of Contents

    1 table of contents introduction .......................................................................................2 qualifications ........................................................................................2 service warning ............................................................

  • Page 3: Introduction

    2 servicing should only be performed by a qualified service technician introduction this service handbook covers the water heater model and series numbers listed on the front cover only. The instructions and illustrations contained in this service handbook will provide you with troubleshooting proce...

  • Page 4: Installation Considerations

    3 servicing should only be performed by a qualified service technician installation considerations this section of the service handbook covers some of the critical installation requirements that, when overlooked, often result in operational problems, down time and needless parts replacement. Costs t...

  • Page 5: Features And Components

    4 servicing should only be performed by a qualified service technician features and components combustion blower & burner assembly air intake assembly low gas pressure switch combustion blower gas control valve/ venturi assembly spark igniter ground wire blower gasket spark igniter flame sensor spar...

  • Page 6

    5 servicing should only be performed by a qualified service technician top view: bth 120 - 250 models blocked exhaust switch powered anode (short, bth 150-250 models only) powered anode (long) blower prover switch upper temperature probe blocked air intake switch ccb assembly burner/ blower assembly...

  • Page 7

    6 servicing should only be performed by a qualified service technician sequence of operation flow chart yes no water is heated to set point 24 volt gas valve de-energized inter-purge cycle 24 volt gas valve de-energized retries up to two more times post-purge cycle control system locks out “ignition...

  • Page 8: Fault And Warning Codes

    7 servicing should only be performed by a qualified service technician fault and warning codes 1. Low gas pressure change back advanced low gas pressure fault occurred 2 mins ago gas pressure is below minimum required to operate this unit. Check gas pressure and switch. Call a service professional: ...

  • Page 9

    8 servicing should only be performed by a qualified service technician gas supply systems low pressure building gas supply systems are defined as those systems that cannot under any circumstances exceed 14” w.C. (1/2 psi gauge). These systems do not require additional pressure regulation. Measuremen...

  • Page 10

    9 servicing should only be performed by a qualified service technician 5. When installing multiple water heaters in the same gas supply system it is recommended that individual positive lock-up gas pressure regulators be installed at each unit from the supply gas connection on the water heater. Serv...

  • Page 11

    10 servicing should only be performed by a qualified service technician 7. Record the supply gas pressure. 8. Use the enable/disable switch located on the front of the water heater and put the unit in enabled mode. The settings on the water heater may need to be changed to cause the water heater to ...

  • Page 12

    11 servicing should only be performed by a qualified service technician 2. Blower operation error change back advanced blower operation error fault occurred 2 mins ago blower prover pressure switch may have failed closed. Check/replace pressure switch. Call a service professional: your company name ...

  • Page 13

    12 servicing should only be performed by a qualified service technician pressure switch tests complete pressure switch testing involves three procedures: • "continuity test during standby" below. • "continuity test during operation" on page 13. • "pressure test during operation" on page 13 thru page...

  • Page 14

    13 servicing should only be performed by a qualified service technician continuity test during operation this test is performed while the combustion blower is running at high speed during the pre-purge operating state. The test is performed on all three pressure switches. Disconnect the two wires to...

  • Page 15

    14 servicing should only be performed by a qualified service technician as follows: • blower prover switch - normally open contacts, close on a rise in pressure. • blocked air intake switch - normally closed contacts, open on a fall in pressure. • blocked exhaust switch - normally closed contacts, o...

  • Page 16

    15 servicing should only be performed by a qualified service technician the water heater's rating label) for the water heater being serviced on hand before calling. Blocked air intake: note these are negative pressures; in a vacuum. If the pressure reading taken at the blocked air intake switch sens...

  • Page 17

    16 servicing should only be performed by a qualified service technician 3. Blower prover open change back advanced blower prover open fault occurred 2 mins ago the blower prover switch remains open after the blower has been energized. Call a service professional: your company name here (press [down]...

  • Page 18

    17 servicing should only be performed by a qualified service technician 4. Ignition failure check/ repair • determine whether or not the burner is igniting by looking through sight glass. Because the control system will shut off the gas control valve if 2-3 seconds if ignition is not detected, you m...

  • Page 19

    18 servicing should only be performed by a qualified service technician • reinsert connector on flame sensor and make sure the electrical connection is clean and tight. • recycle unit again to start another ignition cycle. If the burner ignites but the flame sense rod still fails to detect flame, co...

  • Page 20

    19 servicing should only be performed by a qualified service technician • remove and reinsert the circuit board end of the gas control valve connector. Make sure it is connected tightly and that the pins are clean. • recycle unit again to start another ignition cycle. If you still do not see a brief...

  • Page 21

    20 servicing should only be performed by a qualified service technician 5. Blocked air intake change back advanced blocked air intake fault occurred 2 mins ago restriction in air intake. Check intake pipe and termination for blockage. Call a service professional: your company name here (press [down]...

  • Page 22

    21 servicing should only be performed by a qualified service technician 6. Blocked exhaust change back advanced blocked exhaust fault occurred 2 mins ago restriction in exhaust pipe. Check exhaust pipe and termination for blockage. Call a service professional: your company name here (press [down] fo...

  • Page 23

    22 servicing should only be performed by a qualified service technician 7. Flame sensor error change back advanced flame sensor (error) fault occurred 1 mins ago flame sensor rod detected flame when gas valve should be off. Shut off gas until repaired. Press the advanced button for (press [down] for...

  • Page 24

    23 servicing should only be performed by a qualified service technician gas control valve voltage tests 1. The animated gas control valve status icon is displayed on the control system uim during these operating states. See "(uim) user interface module screen" figure on page 54. Check for 24 vac sup...

  • Page 25

    24 servicing should only be performed by a qualified service technician flame sensor ignition of the burner is controlled electronically. The principle of operation for electronic ignition relies on flame sensing current to prove the fuel gas flowing to the burner has been ignited. Flame sensing req...

  • Page 26

    25 servicing should only be performed by a qualified service technician flame sensing current test during the heating cycle the flame sensing current is normally greater than 8.0 μa with a clean flame sensor. Over time the flame sensor can degrade and this will reduce flame sensing current. With hea...

  • Page 27

    26 servicing should only be performed by a qualified service technician 8. No water change back advanced no water alert: alert occurred 2 mins ago no water detected by powered anode. Call a service professional: your company name here (press [down] for more....) causes: • the controller has not dete...

  • Page 28

    27 servicing should only be performed by a qualified service technician cleaning method: if corrosion is present on the air side of the anode, use a wire brush to clean the outer nut and brass wire terminal tab. To clean the inner nut, remove the outer nut and the brass wire terminal tab. Do not rem...

  • Page 29

    28 servicing should only be performed by a qualified service technician 9. Anode shorted change back advanced anode shorted alert: alert occurred 0 mins ago the powered anode is shorted to earth ground or the tank. Note: this is an alert. The unit will continue to heat water in (press [down] for mor...

  • Page 30

    29 servicing should only be performed by a qualified service technician 10. Temperature probe short (upper or lower) change back advanced upper temp probe (short) fault occurred 0 mins ago upper temperature probe may be shorted. Check connector and resistance of probe. Press the advanced button for ...

  • Page 31

    30 servicing should only be performed by a qualified service technician if the resistance of the temperature sensor is below 390 ohms the control system will lock out and display temp probe short on the uim. If the resistance of the temperature sensor is above 56,000 ohms the control system will loc...

  • Page 32

    31 servicing should only be performed by a qualified service technician results/actions • if the ohm meter shows continuity (closed circuit) between the two outside pins (red wires) the eco switch has reset properly. If the control system continues to lock out displaying energy cut out (eco) on the ...

  • Page 33

    32 servicing should only be performed by a qualified service technician 11. Temperature probe open (upper or lower) change back advanced lower temp probe (open) fault occurred 0 mins ago lower temperature probe may be open. Check connector and resistance of probe. Press the advanced button for (pres...

  • Page 34: Venting

    33 servicing should only be performed by a qualified service technician venting this section of the service handbook is not a complete venting installation instruction. Refer to the instruction manual that came with the water heater; ensure the venting has been installed per all instruction manual r...

  • Page 35: Intake Air Connection

    34 servicing should only be performed by a qualified service technician intake air connection the intake air connection has a screen and a hose barb installed at the factory, see figure below. The intake air connection screen is installed to prevent debris from entering the combustion blower and/or ...

  • Page 36

    35 servicing should only be performed by a qualified service technician electrical connections – all models the water heaters covered in this service handbook require a 120 vac, 1Ø (single phase), 60hz, 15 amp power supply and must also be electrically grounded in accordance with local codes or, in ...

  • Page 37

    36 servicing should only be performed by a qualified service technician 5. Connect the ground wire from the power supply to the grounding lug inside the junction box. See junction box assembly figure below and "wiring diagrams" on page 52 & page 53. 6. Replace junction box cover when connections are...

  • Page 38: Installation Check List

    37 servicing should only be performed by a qualified service technician installation check list the list below represents some of the most critical installation requirements that, when overlooked, often result in operational problems, down time and needless parts replacement. Before performing any t...

  • Page 39: Operation And Service

    38 servicing should only be performed by a qualified service technician operation and service how it works this section of the service handbook will cover operation, common service procedures and water heater construction. The water heater covered in this service handbook has a helical shaped coil h...

  • Page 40

    39 servicing should only be performed by a qualified service technician service note: the 5 pin pwm signal plug must remain plugged in to the 5 pin socket on the blower assembly at all times (bth 120-250 models only). Disconnecting this plug will cause the combustion blower to stop. If the electroni...

  • Page 41

    40 servicing should only be performed by a qualified service technician blower speed control – bth 300 thru 500 the ccb monitors a feedback signal from a sensor that is installed on the blower. The ccb interprets the pulse signal from the sensor and then sends a signal to the variable frequency driv...

  • Page 42

    41 servicing should only be performed by a qualified service technician variable frequency drive – bth 300 thru 500 the bth 300 - 500 models have a variable frequency drive (vfd) that controls the rpm of the blower motor. The vfd receives a signal from the central control board that instructs the vf...

  • Page 43: Burner Assembly

    42 servicing should only be performed by a qualified service technician burner assembly the burner is a radial design burner with a steel fiber jacket on the outer surface and is part of a larger burner assembly. Figures below show side views of the complete burner assembly removed from the water he...

  • Page 44: Instructions

    43 servicing should only be performed by a qualified service technician combustion blower and burner removal/ installation instructions refer to the combustion blower & burner assembly, heater top view images in this service handbook and the instruction manual supplied with the heater for heater com...

  • Page 45: Spark Igniter

    44 servicing should only be performed by a qualified service technician spark igniter the water heaters covered in this service handbook use a spark igniter. The spark igniter has two rods: the sparking rod that has ceramic insulation and the grounding rod, see figure below. During trial for ignitio...

  • Page 46

    45 servicing should only be performed by a qualified service technician the control system is programmed to start sparking a few seconds before the gas control valve opens. See the "sequence of operation flow chart" on page 6. Service notes: • the animated lighting bolt status icon is visible on the...

  • Page 47

    46 servicing should only be performed by a qualified service technician gas orifice - bth 300 thru 500 models refer to orifice chart below for correct gas orifice size. Bth 120 thru 250 models and all natural gas models do not use a gas orifice. Orifice chart - bth 300 thru 500 models model/series 3...

  • Page 48

    47 servicing should only be performed by a qualified service technician ccb (central control board) the ccb is a printed circuit board mounted inside a protective plastic enclosure, see figures below and on next page. The ccb circuit board is the main control. All instructions for ignition and tempe...

  • Page 49

    48 servicing should only be performed by a qualified service technician ccb cover removal and replacement the cover on the ccb enclosure must be removed for various service procedures outlined in this service handbook. Refer to the instructions below when removing and replacing the ccb cover. Wiring...

  • Page 50

    49 servicing should only be performed by a qualified service technician ccb circuit board layout 11 12 1 j1 6 j5 j3 j1 3 j4 j1 7 j1 0 j9 j1 4 j1 5 j1 j6 j1 2 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 5 6 6 6 6 6 6 7 7 8 8 8 9 9 7 10 8 ccb (...

  • Page 51

    50 servicing should only be performed by a qualified service technician ccb connection identification j1 socket - high voltage in pin # description 1 ground 2 aux nc 3 aux no 4 aux common 5 not used 6 aux no 7 aux common 8 line voltage 9 neutral j5 socket - blower logic (vfd/ blower) pin # descripti...

  • Page 52

    51 servicing should only be performed by a qualified service technician j14 socket - limit string pin # description 1 anode 2 grounding 3 flame sensor 4 condensate 5 not used 6 condensate 7 gas pressure switch 8 gas pressure switch 9 gas control valve 10 gas control valve 11 24v 12 24v return j15 so...

  • Page 53

    52 servicing should only be performed by a qualified service technician wiring diagram – bth 120 thru 250

  • Page 54

    53 servicing should only be performed by a qualified service technician wiring diagram – bth 300 thru 500

  • Page 55: Control Overview

    54 servicing should only be performed by a qualified service technician control overview interaction with the water heater controller is through an uim display called the user interface module (uim). This screen is also referred to as the “desktop” or “desktop menu”. Up and down buttons and three op...

  • Page 56

    Commercial gas high efficiency water heaters for additional information contact: a. O. Smith corporation 500 tennessee waltz parkway ashland city, tn 37015 tech support: 800-527-1953 parts: 800-433-2545 www.Hotwater.Com copyright © 2014 a. O. Smith water heater company, all rights reserved..