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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 drive (VFD) which in turn

transmits the proper frequency to the blower to produce the proper blower speed and input. Refer to the

Variable Frequency Drive on next page for its operation.
Below is a chart for the blower rpms and corresponding VFD Hertz Readings for those rpms displayed on

the VFD.

Note:

These models are capable of modulating their input rate. Therefore, the RPM readings can be in

between the Heating Speed and Minimum Modulation Speed RPMs. The input rate should be verified

with the water heater operating at full input rate.

Model

Heating

Speed RPM

Heating Speed

VFD Hertz

Reading

Minimum

Modulation

RPM

Minimum

Modulation

VFD Hertz

Reading

Ignition

Speed

RPM

Ignition

Speed

VFD Hertz

Reading

BTH 300 Nat

3450

117.4

2350

79.7

4500

153.8

BTH 300 LP

3200

108.8

2310

78.5

5770

198.2

BTH 400 Nat

4625

158.3

2350

79.7

4500

153.8

BTH 400 LP

4200

143.2

2310

78.5

5770

198.2

BTH 500 Nat

5750

198.2

2350

79.7

4500

153.8

BTH 500 LP

5225

179.8

2310

78.6

5770

198.2

Содержание BTH 120

Страница 1: ...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 TROUBLE...

Страница 2: ...rol Valve Voltage Tests 23 Flame Sensor 24 Flame Sensing Operation 24 Flame Sensing Current Test 25 8 No Water 26 Powered Anodes 26 Power anode cleaning and removal 26 9 Anode Shorted 28 10 Temperatur...

Страница 3: ...o not attempt to perform any of the procedures described in this service handbook If you do not understand the instructions given in this service handbook do not attempt to perform any procedures outl...

Страница 4: ...ief Valve operation water discharged from the valve due to excessive pressure build up This condition is not covered under the limited warranty The Temperature Pressure Relief Valve is not intended fo...

Страница 5: ...er Gasket Blower Adapter Burner Gasket Burner Ignition Cable Sight Glass Sight Glass Gasket Burner Plate Burner Plate Gasket 150 250 Models Only SS Heat Shield 150 250 Models Only Flue Ring Gasket Ign...

Страница 6: ...bly Exhaust Condensate Elbow Ignition Control Junction Box Assembly UIM Label Color Green Label Color Blue Label Color Red Water Outlet 1 1 2 NPT TOP VIEW BTH 300 500 MODELS Water Outlet 1 1 2 NPT CCB...

Страница 7: ...ated Blower Prover switch contacts confirmed closed by control system Spark Ignition Control is energized 24 Volt Gas Valve is energized gas flows to Main Burner Is flame sensed at the Main Burner con...

Страница 8: ...lication or supply regulator may be operating improperly See Gas Pressure section below HIGH ALTITUDE The water heaters covered in this Service Handbook are certified for elevations up to 10 100 feet...

Страница 9: ...exceeding 14 W C under any upstream supply pressure or condition For Natural Gas BTH 120 250 models require a minimum gas supply pressure of 4 4 W C BTH 300 500 models require 4 8 W C and all models...

Страница 10: ...he water heater is experiencing a sustained drop in supply gas pressure of 1 5 W C or more and the water heater is experiencing repeated Ignition Failure fault conditions intermittent loss of flame or...

Страница 11: ...oint to end the heating cycle Use the Enable Disable Switch located on the front of the water heater and put the unit in disabled mode 11 Close the main gas shutoff valve serving the water heater 12 D...

Страница 12: ...is energized the Control System enters the Input Verification operating state During Input Verification the Control System monitors all three pressure switches to ensure their contacts are in the cor...

Страница 13: ...ween the two wiring terminals at each pressure switch see Figure below 5 After completing the tests confirm that all of the pressure switch wires are reconnected including the replacement part if nece...

Страница 14: ...eset the Operating Temperature Set Point if it was adjusted Run the water heater through a complete heating cycle before leaving to ensure it is operating properly Draw water from the nearest faucet t...

Страница 15: ...he tee with another piece of sensing tube 4 Restore power to the water heater if the water heater does not begin a heating cycle raise the Operating Set Point to activate a heating cycle 5 When the Co...

Страница 16: ...r any restrictions or debris at the intake air termination outdoors Check for condensate water in the sensing tube switch if the sensing tube has water in it replace the Blocked Air Intake Switch and...

Страница 17: ...ES The control has detected an open Blower Prover Pressure Switch during operation Blower Prover Pressure Switch sensing tube disconnected or kinked Loose or open wiring connections to Blower Prover P...

Страница 18: ...the burner ignites briefly then shuts off with an Ignition Failure error message follow these steps Remove the connector from flame sense rod picture of connector showing location on unit Inspect the...

Страница 19: ...lve problem If you do not see a brief blue flame through the sight glass during the ignition cycle at the moment the Gas Control Valve icon appears on the display follow these steps Remove and reinser...

Страница 20: ...r meter This electrical signal will only last for 2 3 seconds if the burner does not ignite or the flame sensor does not detect ignition 24 VDC PRESENT If 24 VDC is present on the Gas Control Valve co...

Страница 21: ...ional Your Company Name Here press DOWN for more CAUSES The Blocked Air Intake Switch has detected a possible restriction in the air intake pipe CHECK REPAIR Check pipe for restriction or excessive eq...

Страница 22: ...sional Your Company Name Here press DOWN for more CAUSES The Blocked Exhaust Switch has detected a possible restriction in the exhaust pipe CHECK REPAIR Check pipe for restriction or excessive equival...

Страница 23: ...roper operation If flame is not present cycle the unit Off by turning the Enable Disable switch to Disable wait for 5 seconds and cycle the unit On by turning the Enable Disable switch to Enable to se...

Страница 24: ...ification or Heating operating states see Figure below 24 VAC should be present Note that the Gas Control Valve Voltage is only present for a short period of time during the ignition period 2 Check fo...

Страница 25: ...n Page 2 SPARK IGNITER BURNER FLAME BURNER MUST BE GROUNDED CERAMIC INSULATOR FLAME SENSOR METAL CONDUCTOR CONTROL SYSTEM APPLIES AC CURRENT TO FLAME SENSOR AC CURRENT FLOWS FROM THE FLAME SENSOR TO T...

Страница 26: ...ethod shown in Figure below Enable water heating and ensure a call for heat is active when the Control System energizes the 24 Volt Gas Control Valve the meter will measure flame sensing current durin...

Страница 27: ...shown below CHECK REPAIR POWERED ANODES The water heaters covered by this Service Handbook are equipped with powered anodes BTH 120 models only use 1 powered anode all others will have two These anod...

Страница 28: ...to allow for socket tool to fit properly REAR ANODE REPLACEMENT METHOD 1 Remove the two blower connectors from the blower remove gas valve power plug and the two wires from the low gas pressure switch...

Страница 29: ...nk Note This is an alert The unit will continue to heat water in press DOWN for more CAUSES The controller has detected a low resistance or short to earth ground or the tank CHECK REPAIR Bent anode sh...

Страница 30: ...y monitors the state of the ECO switch contacts If the ECO activates contacts open due to abnormally high water temperature the Control System will lock out and display Energy Cut Out ECO on the UIM S...

Страница 31: ...rom the Temperature Probe see Figures on next page Compare the measured resistance to the values given in Temperatures Table below Temperature Probes are very reliable and should only be replaced when...

Страница 32: ...d the tank temperature is known to be at or below 100 F 38 C replace the Temperature Probe Follow the draining and filling instructions in the maintenance section of the Instruction Manual that came w...

Страница 33: ...Advanced button for press DOWN for more CAUSES The Upper or Lower Temperature Probe appears to be open very high resistance This fault code often means the connector has been corroded by cleaning che...

Страница 34: ...tion Power Vent configurations derive all combustion air from the room where they are installed and discharge all flue gases to the outdoor atmosphere through a sealed vent exhaust pipe Power vent con...

Страница 35: ...n collect inside and clog the Burner which can cause poor combustion sooting rough starting rough operation and Ignition Failure fault conditions and Control System lock outs The Burner is a radial de...

Страница 36: ...the absence of local codes with the National Electrical Code ANSI NFPA 70 or the Canadian Electrical Code CSA C22 1 If any of the original wire as supplied on the water heater must be replaced it mus...

Страница 37: ...eating is disabled The display CCB and other electrical components will still be energized and the display will read Water Heating Disabled The Enable Disable Switch can be used to disable operation a...

Страница 38: ...nt piping are within the maximum equivalent lengths required in the Instruction Manual that came with the water heater Exceeding the maximum length or number of elbows allowed will also lead to Blocke...

Страница 39: ...C from the Junction Box The CCB sends a signal from the J5 socket to a 5 pin wiring socket on the BTH 120 250 blower and VFD on the BTH 300 500 top cover control assembly The signal is an electronic i...

Страница 40: ...n operating state If blower speed reduction does not occur during the Trial For Ignition operating state ensure the 5 pin plug from the CCB is securely plugged into the matching 5 pin socket on the bl...

Страница 41: ...g VFD Hertz Readings for those rpms displayed on the VFD Note These models are capable of modulating their input rate Therefore the RPM readings can be in between the Heating Speed and Minimum Modulat...

Страница 42: ...l control board that instructs the VFD to transmit the proper frequency to the blower to produce the proper blower speed and proper input Three conditions must be met for the frequency drive to start...

Страница 43: ...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 heater with key components ident...

Страница 44: ...ires at the three spade connectors connecting the blower to the VFD and unplug the blower speed feedback connector from the wiring harness 9 Disconnect the 24 Volt power wires to the Gas Control Valve...

Страница 45: ...ounding rod see Figure below During trial for ignition the Control System powers a high voltage transformer Ignition Control from J6 and the Ignition Control supplies high voltage to the sparking rod...

Страница 46: ...Socket on the CCB and the Burner Adapter are not broken pinched or disconnected Ensure there is approximately 120 VAC at the J6 Socket on the CCB It is a good practice to check for any crack or damag...

Страница 47: ...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 300 200 201 400 200 201 500 200 201 Natural N A N A N A Prop...

Страница 48: ...uit board Diagnostic and operational messages are generated by the CCB and sent to the UIM see UIM User Interface Module Screen on Page 54 Most of the water heater s components such as the Spark Ignit...

Страница 49: ...lly unplugged Cover Removal Procedure Refer to CCB section on Page 47 for these instructions 1 Ensure power to the water heater is turned off 2 Remove the upper and lower temperature probe connectors...

Страница 50: ...cian CCB CIRCUIT BOARD LAYOUT 11 12 1 J16 J5 J3 J13 J4 J17 J10 J9 J14 J15 J1 J6 J12 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...

Страница 51: ...ommon 5 Not Used 6 AUX NO 7 AUX Common 8 Line Voltage 9 Neutral J5 Socket Blower Logic VFD Blower PIN DESCRIPTION 1 24V 2 PWM Signal 3 Not used 4 Blower Speed Feedback 5 Grounding J6 Socket 120V Out P...

Страница 52: ...re Switch 9 Gas Control Valve 10 Gas Control Valve 11 24V 12 24V Return J15 Socket Pressure Switches PIN DESCRIPTION 1 Blower Prover Pressure Switch Blocked Air Intake Pressure Switch 2 Blocked Air In...

Страница 53: ...52 Servicing should only be performed by a Qualified Service Technician WIRING DIAGRAM BTH 120 THRU 250...

Страница 54: ...53 Servicing should only be performed by a Qualified Service Technician WIRING DIAGRAM BTH 300 THRU 500...

Страница 55: ...inside the tank The second temperature on this screen is the Operating Set Point The Operating Set Point is the temperature at which the water heater will maintain the water inside the tank The third...

Страница 56: ...TERS 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 W...

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