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  5. Service Handbook

A.O. Smith dre-120 Service Handbook

Manual is about: commercial electric Water Heaters 100 SERIES

Summary of dre-120

  • Page 1

    1 service handbook printed in the u.S.A 0908 315014-000 servicing should only be performed by a qualified service agent. Commercial electric water heaters models dre-52/80/120 series 100 & dve-52/80/120 series 100 installation considerations - pre service checks - water heater construction - operati...

  • Page 3: Table of Contents

    Commercial electric water heater service manual table of contents introduction ....................................................................... 2 qualifications ...................................................................... 2 service warning ..............................................

  • Page 4: Introduction

    Introduction servicing should only be performed by a qualified service agent 2 introduction this service manual is designed to be an aid in servicing and troubleshooting the commercial electric water heater models listed on the cover.The instructions, illustrations and procedures contained in this m...

  • Page 5

    Servicing should only be performed by a qualified service agent 3 introduction instruction manual have a copy of the instruction manual that came with the water heater on hand for the correct model water heater you are working with before servicing. Installation information given in this service man...

  • Page 6: Installation Considerations

    Installation considerations servicing should only be performed by a qualified service agent 4 installation considerations installation information given in this service manual is not a complete installation instruction. Installation information covered in this service manual has a limited focus as i...

  • Page 7

    Servicing should only be performed by a qualified service agent 5 installation considerations electrical requirements grounding review the electrical ground requirements given in the instruction manual that came with the water heater and ensure the water heater has been properly grounded. The water ...

  • Page 8: Pre Service Checks

    Pre service checks servicing should only be performed by a qualified service agent 6 pre service checks wiring connections with the power supply to the water heater turned off ensure the wiring connections are properly tightened to all components including: high voltage terminal blocks, fuse blocks,...

  • Page 9: Water Heater Construction

    Servicing should only be performed by a qualified service agent 7 water heater construction water heater construction there are two types of commercial electric water heaters covered in this manual. See figure 1 on page 8 and figure 2 on page 9. Surface mount control models the first type of water h...

  • Page 10

    Water heater construction servicing should only be performed by a qualified service agent 8 surface mount control models figure 1.

  • Page 11

    Servicing should only be performed by a qualified service agent 9 water heater construction electronic control models figure 2.

  • Page 12: Operation & Service

    Operation & service servicing should only be performed by a qualified service agent 10 operation & service this section of the manual will cover the principles of electricity, single and three phase power, fuses, surface mount thermostat/eco combination controls, heating element construction & opera...

  • Page 13

    Servicing should only be performed by a qualified service agent 11 operation & service ohms law a law that explains the relationship between voltage, current and resistance. The law states that the electric current flowing through a conductor is equal to the voltage divided by the resistance. The fo...

  • Page 14

    Operation & service servicing should only be performed by a qualified service agent 12 single and three phase power the water heaters covered in this manual can be field converted for a single or three phase power supply - see pages 15 and 16. These water heaters can be factory ordered for standard ...

  • Page 15

    Servicing should only be performed by a qualified service agent 13 operation & service checking single phase (1Ø) power a single phase power supply consists of two wires connected to the l1 and l2 terminals of the power distribution block, the l3 terminal is not used. On a single phase (1Ø) 277 volt...

  • Page 16

    Operation & service servicing should only be performed by a qualified service agent 14 checking three phase (3Ø) power a three phase power supply consists of three wires connected to the l1, l2 and l3 terminals of the power distribution block. All three wires are “hot” with voltage present. Voltage ...

  • Page 17

    Servicing should only be performed by a qualified service agent 15 operation & service phase conversions - surface mount control models internal wiring connections between the power distribution block and the heating elements are different on surface mount control (see figure 1 page 8) and electroni...

  • Page 18

    Operation & service servicing should only be performed by a qualified service agent 16 phase conversions - electronic control models internal wiring connections between the power distribution block and the heating elements is different on surface mount control (see figure 1 page 8) and electronic co...

  • Page 19

    Servicing should only be performed by a qualified service agent 17 operation & service fuses the water heaters covered in this manual have power circuit fuses to protect the heating element circuits. Electronic control models will have two additional fuses to protect the primary winding of the 120 v...

  • Page 20

    Operation & service servicing should only be performed by a qualified service agent 18 surface mount thermostats the surface mount control model water heaters covered in this manual have “separate” thermostat/eco (energy cut out) combination controls mounted to the surface of the storage tank direct...

  • Page 21

    Servicing should only be performed by a qualified service agent 19 operation & service thermostat & eco test 1 secure power to the water heater at the main breaker or disconnect switch. 2 ensure tank temperature is less than 100°f/38°c - dump water to lower tank temperature if necessary. 3 press the...

  • Page 22

    Operation & service servicing should only be performed by a qualified service agent 20 heating elements this section of the manual provides information on how to determine the actual voltage and wattage rating of a heating element along with tables showing heating element configurations, heating ele...

  • Page 23

    Servicing should only be performed by a qualified service agent 21 operation & service heating element ratings heating elements are labeled with their voltage and kw rating - see image below. The element shown here is a 6000 watt (6 kw) 240 volt element. Heating element configurations the table belo...

  • Page 24

    Operation & service servicing should only be performed by a qualified service agent 22 heating element amperage this table shows the approximate amp draw for the various heating elements used. First determine the actual rated wattage and voltage of the element being tested - see heating element rati...

  • Page 25

    Servicing should only be performed by a qualified service agent 23 operation & service heating element amperage test this test should be considered as a first diagnostic procedure for the common service complaints of no hot water or not enough hot water. The heating element amperage test shown on th...

  • Page 26

    Operation & service servicing should only be performed by a qualified service agent 24 heating element voltage test this test is typically performed after an amperage test (see page 23) has determined one or more heating elements is not drawing correct amperage. 1 secure power to the water heater at...

  • Page 27

    Servicing should only be performed by a qualified service agent 25 operation & service heating element resistance & ground tests this is a two part test. In the first part of this test the actual resistance (ohms) of each heating element is measured. In the second part of this test each heating elem...

  • Page 28

    Operation & service servicing should only be performed by a qualified service agent 26 heating element ground test 1 secure power to the water heater at the main breaker or disconnect switch. 2 verify with an ac volt meter that there is not any voltage present at the power distribution block (see fi...

  • Page 29

    Servicing should only be performed by a qualified service agent 27 operation & service element sensors electronic control models covered in this manual monitor all heating elements using element sensors. Each element sensor monitors 3 heating elements. There will be one element sensor for each bank ...

  • Page 30

    Operation & service servicing should only be performed by a qualified service agent 28 element sensor operation when current (amperage) flows through a wire in an electrical circuit a magnetic field is developed that radiates out from the wire. The individual current sensors detect this magnetic fie...

  • Page 31

    Servicing should only be performed by a qualified service agent 29 operation & service contactors this section of the manual provides information on how contactors used on electronic control models are constructed, how they work and how to test contactor operation - see figure 2 on page 9 for locati...

  • Page 32

    Operation & service servicing should only be performed by a qualified service agent 30 contactor configurations this illustration shows how contactors are configured and how they provide power to the heating elements on electronic control model water heaters, this is a redundant contactor configurat...

  • Page 33

    Servicing should only be performed by a qualified service agent 31 operation & service contactor inspection a thorough visual inspection of the contactors used on electronic control models should be performed as part of any regular maintenance program and whenever the water heater is being serviced....

  • Page 34

    Operation & service servicing should only be performed by a qualified service agent 32 contactor coil voltage - at contactor this test procedure will measure contactor coil voltage at the contactor. 1 ensure tank temperature is less than 100°f/38°c - dump water to lower tank temperature if necessary...

  • Page 35

    Servicing should only be performed by a qualified service agent 33 operation & service contactor coil voltage - at ccb this test procedure will measure contactor coil voltage where it originates at the j4 wiring terminals on the ccb. See page 42 for the ccb’s j4 wiring terminal location. 1 ensure ta...

  • Page 36: 120 Vac

    Operation & service servicing should only be performed by a qualified service agent 34 transformers this section of the manual provides information on how to test and ensure the multiple tap 120 vac control circuit transformer is wired properly on electronic control models. This section will also pr...

  • Page 37

    Servicing should only be performed by a qualified service agent 35 operation & service 120 vac control circuit transformer test 1 ensure the main breaker or disconnect switch is turned on. 2 verify with an ac volt meter that proper voltage is present at the power distribution block (see figure 2 on ...

  • Page 38

    Operation & service servicing should only be performed by a qualified service agent 36 24 vac transformer test 1 ensure the main breaker or disconnect switch is turned on. 2 verify with an ac volt meter that proper voltage is present at the power distribution block (see figure 2 on page 9 and pages ...

  • Page 39

    Servicing should only be performed by a qualified service agent 37 operation & service immersion temperature probe this section of the manual provides information on how test the immersion temperature probe on electronic control models - see figure 2 on page 9 for location. The immersion temperature...

  • Page 40

    Operation & service servicing should only be performed by a qualified service agent 38 temperature sensor resistance test 1 secure power to the water heater at the main breaker or disconnect switch. 2 unplug the j5 plug from the ccb circuit board - see page 42 for location. 3 using an ohm meter: set...

  • Page 41

    Servicing should only be performed by a qualified service agent 39 operation & service temperature sensor dc voltage test 1 ensure the main breaker or disconnect switch is turned on. 2 verify the ccb circuit board has the correct input voltage at the j2 socket and is properly grounded - perform the ...

  • Page 42

    Operation & service servicing should only be performed by a qualified service agent 40 eco voltage test 1 ensure the main breaker or disconnect switch is turned on. 2 verify the ccb has the correct input voltage at the j2 socket and is properly grounded - perform the checking power and ground to the...

  • Page 43: Electronic Controls

    Servicing should only be performed by a qualified service agent 41 electronic controls electronic controls this section covers the electronic control system used on electronic control models - see figure 1 on page 9. The control system includes a ccb (central control board) and a uim (user interface...

  • Page 44

    Electronic controls servicing should only be performed by a qualified service agent 42 ccb - central control board all wiring connections and sockets will be identified in the following pages. The troubleshooting section of this manual will refer to this illustration and information..

  • Page 45

    Servicing should only be performed by a qualified service agent 43 electronic controls ccb socket & wiring terminal identification refer to the illustration on page 42 for physical location of the sockets and wiring terminals. J1 socket - transformer j2 socket - 120 vac power supply j3 wiring termin...

  • Page 46

    Electronic controls servicing should only be performed by a qualified service agent 44 j7 socket - enable / disable circuits 1 & 2 (see pages 45 & 54) j8 socket - not used j9 socket - not used j10 socket - not used j11 port - communication port - uim display (user interface module) j12 socket - heat...

  • Page 47

    Servicing should only be performed by a qualified service agent 45 electronic controls ccb enable/disable circuit(s) test the electronic control system includes two enable/disable circuits (see page 54) for use with field installed supervisory controls such as building ems (energy management system)...

  • Page 48

    Electronic controls servicing should only be performed by a qualified service agent 46 checking power and ground to the ccb the ccb circuit board is powered by the120 vac control circuit transformer (see pages 34-35) at the j2 socket, pins 1 & 3 (see page 42). This procedure is performed to ensure t...

  • Page 49

    Servicing should only be performed by a qualified service agent 47 electronic controls uim - user interface module uim components the uim’s major components include a circuit board with lcd display and a button pad overlay which contains the five user input buttons. Service notes - button pad ribbon...

  • Page 50: Electronic Control System

    Electronic control system servicing should only be performed by a qualified service agent 48 electronic control system control system features advanced diagnostics: plain english text and animated icons display detailed operational and diagnostic information. Lcd screen on the front of the water hea...

  • Page 51

    Servicing should only be performed by a qualified service agent 49 electronic control system the desktop screen the illustration below shows the control system “desktop screen.” this is the default screen. If there are no active fault or alert conditions and no user input for approximately 10 minute...

  • Page 52

    Electronic control system servicing should only be performed by a qualified service agent 50 table 1 status icons icon description water temperature in the tank has fallen. Shaded area of the animated thermometer icon will rise and fall in response to water temperature in the storage tank as sensed ...

  • Page 53

    Servicing should only be performed by a qualified service agent 51 electronic control system table 2 - operating states table 3 - control system menus state description standby the water heater is not in an active heating cycle. This usually indicates the temperature in the tank has reached the oper...

  • Page 54

    Electronic control system servicing should only be performed by a qualified service agent 52 temperatures menu operating set point user adjustable setting 90°f to 190°f range; factory default is 120°f. When the water temperature sensed by the control system from the immersion temperature probe reach...

  • Page 55

    Servicing should only be performed by a qualified service agent 53 electronic control system temperature settings the operating set point and the differential settings are adjusted in the temperatures menu. The following instructions explain how to adjust these user settings and navigate the control...

  • Page 56

    Electronic control system servicing should only be performed by a qualified service agent 54 heater status menu this menu displays non adjustable operational information. This menu contains more information that can be displayed on one screen of the lcd display. Use the up & down buttons to navigate...

  • Page 57

    Servicing should only be performed by a qualified service agent 55 electronic control system economy mode setup menu this menu contains settings used to establish an “economy set point” and “economy mode” operating periods. This control system feature can help reduce operating costs during unoccupie...

  • Page 58

    Electronic control system servicing should only be performed by a qualified service agent 56 economy mode settings setpoint adjustment value action display from the desktop screen, press the operational button underneath “menu” to enter the main menu. (see uim navigation on page 48) notice how the t...

  • Page 59

    Servicing should only be performed by a qualified service agent 57 electronic control system economy mode settings time clock settings action display from the desktop screen navigate to the economy mode setup menu - see page 56 for instructions. Use the up/down buttons to select (highlight in black)...

  • Page 60

    Electronic control system servicing should only be performed by a qualified service agent 58 economy mode settings daily operating mode settings action display economy mode all day: from the economy mode setup menu use the up/down buttons to select (highlight in black) the daily sub menu for “sun.” ...

  • Page 61

    Servicing should only be performed by a qualified service agent 59 electronic control system alarm output setup menu permits user to set the condition (from a list of options) for when the ccb’s integral alarm output relay will be energized. Alarm relay connections (common, normally open, normally c...

  • Page 62

    Electronic control system servicing should only be performed by a qualified service agent 60 display settings menu permits user to set display options for viewing information on the uim’s lcd screen. Temperature units adjustable user setting that changes temperature units display to celsius °c or fa...

  • Page 63

    Servicing should only be performed by a qualified service agent 61 electronic control system heater information menu this menu displays non adjustable operational information. Elapsed time total accumulated time the control system (water heater) has been energized. Total heating time total accumulat...

  • Page 64

    Electronic control system servicing should only be performed by a qualified service agent 62 current fault / alert menu this menu displays non adjustable operational information. With the fault history sub menu selected in main menu; press the operational button underneath “select” to display the cu...

  • Page 65

    Servicing should only be performed by a qualified service agent 63 restore factory defaults menu this control system menu allows the user to restore most of the control system’s user settings to their factory default settings. User settings in the alarm output setup and display settings menus are un...

  • Page 66: Troubleshooting

    Troubleshooting servicing should only be performed by a qualified service agent 64 troubleshooting common service problems no hot water 1 hot water supply valve turned off. 2 check power to the water heater - see pages 12 - 14. 3 check thermostat/eco controls on surface mount control models - see pa...

  • Page 67

    Servicing should only be performed by a qualified service agent 65 troubleshooting electronic control models the remainder of the troubleshooting section covers electronic control models only. Fault conditions when the control system declares a fault condition it will display a fault message on the ...

  • Page 68

    Troubleshooting servicing should only be performed by a qualified service agent 66 control system unresponsive (cont) displayed message condition/indicates check/repair uim is inoperable uim does not respond to any user input using the operational and/or up and down buttons. • ensure ribbon cable fr...

  • Page 69

    Servicing should only be performed by a qualified service agent 67 troubleshooting fault and alert messages troubleshooting procedures for the most common fault and alert messages are covered in this section. In the tables that follow the first column shows the fault or alert message as displayed by...

  • Page 70

    Troubleshooting servicing should only be performed by a qualified service agent 68 fault & alert messages displayed message condition/indicates check/repair “temp probe open” (fault condition) the control system has detected an open circuit in the temperature sensor. The control system will declare ...

  • Page 71

    Servicing should only be performed by a qualified service agent 69 troubleshooting fault & alert messages displayed message condition/indicates check/repair “energy cut out (eco)” (fault condition) the control system has detected excessive water temperature inside the water heater. The eco high temp...

  • Page 72

    Notes.

  • Page 73

    Notes.

  • Page 74

    Notes.

  • Page 76

    2 500 tennessee waltz parkway, ashland city, tn 37015 technical support: 800-527-1953 • parts: 800-433-2545 • fax: 800-644-9306 www.Hotwater.Com.