BLOWER VACUUM SWITCH FAILED OPEN

F1 F1

AC BLOWER VACUUM SWITCH FAILED CLOSED AC BLOWER VACUUM SWITCH FAILED CLOSED UHS If the blower vacuum switch is closed before blower start-up, the control module will not start the blower. Pre-check is executed by the control module. A. Disconnect the blower plug from the control module. IDL2 IDL F2 With the heater off, measure the control module receptacle s continuity across pins 1 and 2 (UHS, IDL2 & IDL) and pins 3 & 4 (IDL2 & IDL only). If either is closed, replace the control module. B. If the relay is open, check the vacuum switch. If it is closed, the blower vacuum switch failed and must be replaced. AC Blower Vacuum Switch Failed Closed Blower Vacuum Switch Control Module. F2

AO BLOWER VACUUM SWITCH FAILED OPEN AO BLOWER VACUUM SWITCH FAILED OPEN UHS If the blower vacuum switch opens unexpectedly during operation, the heater will shut down and attempt to re-light if there is still a call for heat. If the blower vacuum switch does not close after the blower starts, the control will stop the ignition trial & go into lockout. The blower will continue to run for post-purge. Automatic reset is immediate after the switch closes. Blower Blower Vacuum Switch Control Module/Ignition Board Gray Vacuum Tubing A. Check for faulty vacuum switch tubing and replace if necessary. B. Check for faulty vacuum switch wiring or connection. Wire harness terminals must be securely fastened to spade terminals on vacuum switch. IDL2 D. Check for defective vacuum switch by disconnecting blower plug from control module. Measure resistance across blower windings. Winding resistance across lead should be in the following range: IDL: Black to White 30-45 ohms Red to White 90-130 ohms IDL2: Black to White 10-14 ohms Red to White 18-22 ohms UHS: Red to White 8-9 ohms AO If measured values vary substantially from these values, the blower is defective and should be replaced. E. Check for a defective blower relay by disconnecting blower plug from the control module. Place heater in Pool or Spa mode. Lower set point temperature to generate call for heat. During pre-purge period, measure for 120VAC across pins 1 and 2 (UHS & IDL2) or L1 & IND low (IDL). IDL If 120VAC is not present, the control module relay is defective, which means the control module must be replaced. F. If the above steps do not resolve the problem (the error still exists), the vacuum switch is defective and must be replaced. F3 C. Check for faulty blower wiring or connection. Plug on blower must be securely fastened to control module. Blower Vacuum Switch Failed Open F3

BD BAD BOARD OR SECONDARY HIGH VOLTAGE FAULT Bad Board or Secondary High Voltage Fault BD BAD BOARD OR SECONDARY HIGH VOLTAGE FAULT UHS Control Module / Ignition Board Extra Fuses Fuse Board Wiring Harness Transformer A. Verify that FC4 fuse on fuse board is not open. Remove FC from fuseholder. Measure continuity across fuse. If OK, reinstall fuse and proceed to step 2. If fuse is open, proceed to section titled Open FC4 Fuse. IDL2 B. Verify high voltage output from fuse board. Disconnect plug from P6 connector of fuse board. Measure for 120VAC across pins 3 and 5 of P6 receptacle on fuse board. If OK, reconnect plug and proceed to step 3. If not OK, go to step 4. C. Check for defective wiring harness. Disconnect plug from E10 connector of contol module. Measure for 120VAC across pins 1 and 3 of plug on wiring harness. If OK, replace control module. If not OK, replace wiring harness. D. Check for defective transformer. Disconnect plug from P4 connector of fuse board. Measure for 120VAC between pins 4 and 6 of plug from transformer. If OK, proceed to step 5. If not OK, replace transformer. E. If the above steps have not resolved the error condition, the fuse board is defective and must be replaced. NOTE: Red letters above correspond with adjacent illustrations. F4 BD F4

BO BYPASS OPERATION (FOR EXTERNAL CONTROLS) F 5 BO Bypass Operation (for external controls) BO BYPASS OPERATION (FOR EXTERNAL CONTROLS) UHS, IDL2, IDL, ED2 The bo code is more of an information code than a fault code, with the bo standing for Bypass Operation. A bo code indicates the heater s internal thermistor is disabled, allowing the external thermostat control to operate. This prevents any confusion between the two temperature-sensing devices during heater operation though the heater s thermistor will still prevent the heater for exceeding 104 o F. F 5

CE COMMUNICATION ERROR F6 COMMUNICATION ERROR UHS Control Module/Ignition Board. Display Board Membrane Switch/Keypad. ERROR DETAIL: COMMUNICATION ERROR BETWEEN CONTROL MODULE & DISPLAY INTERFACE ASSEMBLY A. Power down heater and re-power. This is similar to rebooting a computer. IDL2 B. If rebooting does not solve the problem, inspect the display interface wiring. Ensure the display interface plug is securely attached to the control module. C. If steps A & B do not resolve the CE error, the control module and/or display interface assembly are defective and must be replaced. F6 CE Communication Error If communication between the ignition board and the display board is not established within 3 seconds of power-up, an error will be displayed. After communication is established, if it is lost for 30 seconds, the error will be displayed. The error code will be cleared upon a valid data exchange between boards.. CE

F 7 EE ELECTRICAL ERROR EE ELECTRICAL ERROR Control Module / Ignition Board Replace the Control Module / Ignition Board. UHS IDL2 EE Electrical Error F 7

FLAME PRESENT WITH GAS VALVE CLOSED / HEATER FLAME SENSING FAULT BELOW: HF INDICATES A GAS VALVE FAULT ON NEWER MODELS (UHS, IDL2) RIGHT: HF INDICATES A FLAME SENSING FAULT ON OLDER MODELS (IDL, ED2) HF HEATER FLAME SENSING FAULT HF IDL, ED2 FLAME PRESENT WITH GAS VALVE CLOSED UHS, IDL2 Ignitor / Flame Sensor Control Module / Ignition Board Gas Valve If flame is sensed without the gas valve energized, the control will go into lockout. A. Check all wiring and connections for Flame sensor. B. Replace flame sensor (IDL) or ignitor (ED2). C. Replace control module/ignition board if problem still exists. SHUT OFF GAS TO HEATER IMMEDIATELY. The gas valve is defective and needs to be replaced. UHS ED2 F8 IDL2 IDL HF NEW: Gas Valve Fault or OLD: Heater Flame Sensing Fault HF F8

HS MAXIMUM RETURN WATER TEMP EXCEEDED F 9 HS Maximum Return Water Temp Exceeded HS MAXIMUM RETURN WATER TEMPERATURE EXCEEDED UHS, IDL2, IDL, ED2 If water temperature exceeds 105 F, the heater will shut down and go into lock-out. Automatic restart is 2 minutes after water temp drops below 105 F. Control Module External Thermostat (if system uses one) NOTE: In most cases, no replacement part will be needed. A. Verify water flow is adequate. Low water flow will cause high temperature. (Generally, 25 gpm is needed by smaller heaters, while 300,000 btu/h heaters may require 40 gpm or more. See heater s operating manual.) B. Verify set point setting of remote thermostat us below 108 F. If external control is used, verify that external thermostat is set below 104 o F. (External thermostat may be faulty and need to be replaced.) C. Verify integrity of exchanger. D. Check for possible bad ignition/control module. F 9

IF IGNITION FAILURE (INSUFFICIENT FUEL) F 10 IGNITION FAILURE (INSUFFICIENT FUEL) UHS, IDL2, IDL, ED2 REQUIRED DIAGNOSTIC TOOLS Manometer Multimeter Flame Sensor Ignitor Ignition Board / Control Module Gas Valve IF B. Check for low gas supply pressure by ensuring inlet gas supply pressure is between the minimum and maximum values indicated on rating plate. If OK, proceed to next step. C. Inspect flame sense wiring, and ensure wire harness terminals are securely fastened to flame sense and to control module. If OK, proceed to next step. IF occurs when the heater passes all safety checks but the heater fails to ignite. Without the proper gas/air mixture, the heater will not light. Since the heater has gone through most of the steps within the Sequence of Operation, the problem is most likely gas supply or a faulty ignition board, flame sensor, ignitor or gas valve. Investigate and ensure that the gas train is correct. The source of an IF code is found in the gas train 90% of the time. E. Check for gas valve failure or gas valve relay failure.1. Measure voltage across gas valve during trial for igintion. I. If 24VAC is present and gas valve does not open, gas valve is defective and must be replaced.2. II. If 24VAC is not present, gas valve relay on control module is defective, which means the control module must be replaced. F. Inspect gas orifices for blockages that could prevent gas flow. Also remove and inspect burners for blockages. Ignition Failure While IF actually stands for Ignition Failure, this code is often referred to as the Insufficient Fuel code since the most common reason for an IF code is inadequate gas supply to the heater. F 10 A. Ensure that main gas shutoff adjacent to heater is open. Ensure that knob on gas valve inside unit is in on position. If OK, proceed to next step. D. Inspect gas valve wiring, and ensure wire harness terminals are securely fastened to spade terminals on gas valve. If OK, proceed to next step. IF

IO IGNITOR FAILURE F 11 IO Ignitor Failure UHS IO IGNITOR FAILURE Ignitor Control Module / Ignition Board A. Check for faulty wiring or connection. B. Replace ignitor. C. Replace Control Module/Ignition Board NOTE: Red letters above correspond with adjacent illustrations. C B IDL2 C B F 11

F 12 UHS (SEE SWITCH OPEN WITHIN SAFETY LIMIT STRING SWITCH OPEN WITHIN SAFETY LIMIT STRING F13) F14) IDL2 (SEE ED2 F13) (SEE F15) F 12 LO (SEE Switch Open within Safety Limit String IDL LO LO

LO SWITCH OPEN WITHIN SAFETY LIMIT STRING (UHS, IDL2) F 13 LO Switch Open within Safety Limit String (UHS, IDL2) LO SWITCH OPEN WITHIN SAFETY LIMIT STRING High Limit Switches (Water) Pressure Switch Vent Pressure Switch UHS, IDL2 Control Module Wiring Harness NOTE: lo is normal when pump is off. Otherwise, lo means a control loop switch is open. Therefore, check for the following: Possibility 1: Water Pressure Switch Fault A. To verify that the pump is running, turn the pump OFF and watch to see that the LO code clears. If LO does not clear, proceed to next step. B. Verify that water flow rate to heater is above minimum required: 20 GPM for H150--- and H200---, 25 GPM for H250--- and H300---, 30 GPM for H350--- and H400---. If OK, proceed to next step. C. Check the water pressure switch for faulty wiring and connections: Ensure wire harness terminals are securely fastened to spade terminals on water pressure switch. If OK, proceed to next step. D. Verify the state of water pressure switch contacts: Remove wire leads from water pressure switch and jumper leads. Then attempt to operate the heater, measuring continuity across water pressure switch. If closed, LO code is not caused by water pressure switch fault. If open, proceed to next step (after removing jumper from wire leads and reconnecting wire leads to water pressure switch). E. Ensure that low pump pressure does not exist. Clean filter or clear blockages. Check position of valves in plumbing system. If OK proceed to next step. F. Adjust water pressure switch setting as shown on page 33 of UHS Installation Manual (only if heater is above or below water level). If LO does not clear, the water pressure switch is defective and must be replaced. (CONTINUED) Possibility 2: Vent Pressure Switch Fault (For UHS indoor installations only) G. Check the vent pressure switch for faulty wiring and connections: Ensure wire harness terminals are securely fastened to spade terminals on vent pressure switch. If OK, proceed to next step. H. Verify the state of vent pressure switch contacts: Remove wire leads from vent pressure switch and jumper leads. Then attempt to operate the heater, measuring continuity across vent pressure switch. If closed, LO code is not caused by vent pressure switch fault. If open, proceed to next step (after removing jumper from wire leads and reconnecting wire leads to vent pressure switch). I. Ensure that flue is not blocked or restricted: See indoor vent sizing requirements in installation manual. If OK, the vent pressure switch is defective and must be replaced. Possibility 3: High Limit Switch Fault J. Check the high limit switch for faulty wiring and connections: Ensure wire harness terminals are securely fastened to spade terminals on high limit switch. If OK, proceed to next step. K. Verify the state of high limit switch contacts: Remove wire leads from high limit switch and jumper leads. Then attempt to operate the heater, measuring continuity across the high limit switch. If closed, LO code is not caused by a high limit switch fault. If open, proceed to next step (after removing jumper from wire leads and reconnecting wire leads to high limit switch). L. Verify that water flow rate to heater is above minimum required: 20 GPM for H150--- and H200---, 25 GPM for H250--- and H300---, 30 GPM for H350--- and H400---. If OK, the high limit switch is defective and must be replaced. Finally, remember that the problem could exist in the wiring harness and also the control module. F 13

F 14 LO SWITCH OPEN WITHIN SAFETY LIMIT STRING IDL High Limit Switches (Water) Pressure Switch Vent Pressure Switch Control Module Wiring Harness LO Possibility 1: Water Pressure Switch Fault A. To verify that the pump is running, turn the pump OFF and watch to see that the LO code clears. If LO does not clear, proceed to next step. B. Verify that water flow rate to heater is above minimum required: 20 GPM for H150--- and H200---, 25 GPM for H250--- and H300---, 30 GPM for H350--- and H400---. If OK, proceed to next step. C. Check the water pressure switch for faulty wiring and connections: Ensure wire harness terminals are securely fastened to spade terminals on water pressure switch. If OK, proceed to next step. D. Verify the state of water pressure switch contacts: Remove wire leads from water pressure switch and jumper leads. Then attempt to operate the heater, measuring continuity across water pressure switch. If closed, LO code is not caused by water pressure switch fault. If open, proceed to next step (after removing jumper from wire leads and reconnecting wire leads to water pressure switch). E. Ensure that low pump pressure does not exist. Clean filter or clear blockages. Check position of valves in plumbing system. If OK proceed to next step. F. Adjust water pressure switch setting per instructions in IDL Installation Manual (only if heater is above or below water level). If LO does not clear, the water pressure switch is defective and must be replaced. (CONTINUED) Possibility 2: Terminal Block Fault G. Check if a remote on/off device connected to terminal block is open: Turn remote device on, and watch for LO code to clear. If LO does not clear, go to step I. If a remote on/off device is not connected to heater, go to step H. H. Verify that jumper has been removed: If remote on/off control is not used, the two far-right terminals of terminal block should be jumpered. If jumper is not present. add jumper. Then, if LO code does not clear, proceed to next step. I. Inspect terminal block wiring. Ensure wire harness terminals are securely fastened to terminal block. If OK, terminal block is defective and should be replaced. Possibility 3: Vent Pressure Switch Fault J. Check the vent pressure switch for faulty wiring and connections: Ensure wire harness terminals are securely fastened to spade terminals on vent pressure switch. If OK, proceed to next step. K. Verify the state of vent pressure switch contacts: Remove wire leads from vent pressure switch and jumper leads. Then attempt to operate the heater, measuring continuity across vent pressure switch. If closed, LO code is not caused by vent pressure switch fault. If open, proceed to next step (after removing jumper from wire leads and reconnecting wire leads to vent pressure switch). L. Ensure that flue is not blocked or restricted: See indoor vent sizing requirements in installation manual. If OK, the vent pressure switch is defective and must be replaced. Possibility 4: Temperature Limit Switch Fault M. Check the high limit switch for faulty wiring and connections: Ensure wire harness terminals are securely fastened to spade terminals on high limit switch. If OK, proceed to next step. N. Verify the state of high limit switch contacts: Remove wire leads from high limit switch and jumper leads. Then attempt to operate the heater, measuring continuity across the high limit switch. If closed, LO code is not caused by a high limit switch fault. If open, proceed to next step (after removing jumper from wire leads and reconnecting wire leads to high limit switch). O. Verify that water flow rate to heater is above minimum required: 20 GPM for H150--- and H200---, 25 GPM for H250--- and H300---, 30 GPM for H350--- and H400---. If OK, the high limit switch is defective and must be replaced. Finally, remember that the problem could exist in the wiring harness and also the control module. F 14 (IDL) Switch Open within Safety Limit String (IDL) NOTE: lo is normal when pump is off. Otherwise, lo means a control loop switch is open. Therefore, check for the following: SWITCH OPEN WITHIN SAFETY LIMIT STRING LO

LO SWITCH OPEN WITHIN SAFETY LIMIT STRING (ED2) F 15 LO Switch Open within Safety Limit String (ED2) LO SWITCH OPEN WITHIN SAFETY LIMIT STRING High Limit Switches (Water) Pressure Switch Vent Pressure Switch ED2 Control Module Wiring Harness NOTE: lo is normal when pump is off. Otherwise, lo means a control loop switch is open. Therefore, check for the following: Possibility 1: Water Pressure Switch Fault A. To verify that the pump is running, turn the pump OFF and watch to see that the LO code clears. If LO does not clear, proceed to next step. B. Check the water pressure switch for faulty wiring and connections: Ensure wire harness terminals are securely fastened to spade terminals on water pressure switch. If OK, proceed to next step. C. Verify the state of water pressure switch contacts: Remove wire leads from water pressure switch and jumper leads. Then attempt to operate the heater, measuring continuity across water pressure switch. If closed, LO code is not caused by water pressure switch fault. If open, proceed to next step (after removing jumper from wire leads and reconnecting wire leads to water pressure switch). D. Ensure that low pump pressure does not exist. Clean filter or clear blockages. Check position of valves in plumbing system. If OK proceed to next step. E. Adjust water pressure switch setting per instructions in IDL Installation Manual (only if heater is above or below water level). If LO does not clear, the water pressure switch is defective and must be replaced. (CONTINUED) Possibility 2: Automatic Temperature Limit Switch Fault F. Check the (automatic) temperature limit switch for faulty wiring and connections: Ensure wire harness terminals are securely fastened to spade terminals on the temp limit switch. If OK, proceed to next step. G. Verify the state of (automatic) temperature limit switch contacts: Remove wire leads from (automatic) temp limit switch and jumper the leads. Then attempt to operate the heater, measuring continuity across (automatic) temp limit switch. If closed, LO code is not caused by (automatic) temperature limit switch fault. If open, proceed to next step. H. OUTDOOR UNITS ONLY: Check for high winds or severe downdrafting and, if necessary, install High Wind Stack. (For indoor units, skip ahead to next step.) I. Ensure that flue is not blocked or restricted: Refer to vent sizing requirements. J. Check for sooted or damaged exchanger. If sooted or damaged, the exchanger should be cleaned (and may need to be replaced). Possibility 3: Manual Temperature Limit Switch Fault K. Repeat steps F through J for manual temperature limit switch. L. Reset manual temperature limit switch. If switch continues to trip, replace the manual temperature limit switch. Possibility 4: High Limit Switch Fault M. Check the high limit switch for faulty wiring or connections. Ensure wire harness terminals are securely fastened to spade terminals. N. Verify state of high limit contacts. Remove wire leads from high limit switches and jumper leads. Operate heater, and measure continuity across high limit switches. If closed, LO code is not caused by high limit switch fault. If open, remove jumper from leads, reconnect leads to high limit switches, and proceed to next step. Possibility 5: Inadequater Water Flow Fault Q. Verify that water flow rate to heater is above minimum required: 25 GPM. R. At this point, it must be assumed that a high limit switch is faulty and must be replaced. F 15

SB KEYPAD FAILURE F 16 SB Keypad/Membrane Switch A. Replace keypad/membrane switch. UHS IDL2 F 16 KEYPAD FAILURE Keypad Failure SB

SF TEMPERATURE SENSOR INPUT FAILURE F 17 TEMPERATURE SENSOR INPUT FAILURE Thermistor Control Module UHS A. Check where the thermistor connects to the board to see if it has become disconnected or damaged. B. Replace thermistor if wire or connection is damaged. C. Replace control module if connection on board is damaged IDL ED2 F 17 SF IDL2 Temperature Sensor Input Failure D. Replace control module if new thermistor does not correct fault. SF

FAULT CONDITIONS WITH NO CODE FAULT CONDITIONS WITH NO CODE UHS, IDL2 Fuses (FC1, FC2, FC3, FC4) Fuse Board Wiring Transformer Control Module Wiring Harness K. Remove FC3 fuse from fuseholder. Measure continuity across fuse. If fuse is open, proceed to fault condition Open Fuse: FC3 or F1. If OK, reinstall fuse and proceed to step L. L. Disconnect P4 connector from fuse board plug. Measure for 24VAC between pins 1 & 2 of plug from transformer. If 24VAC is not present, replace the transformer. Otherwise, replace fuse board. A. Verify that low & high voltage is being output from fuse board: Open Fuse: FC2 or FC1 If OK, reconnect P6 plug and proceed to next fault condition, Low Voltage Circuit Fault. Otherwise, reconnect P6 plug and proceed to step B. B. Verify heater is getting field power by measuring for field supply voltage across terminals of TB1 terminal block on fuse board. C. Inspect fuse board wiring, and ensure all plugs are securely fastened to fuse board. D. Remove FC1 and FC2 fuses from fuseholder. Measure continuity across fuse. If fuses are open, proceed to fault condition Open Fuse: FC2 or F1. If fuses are OK, reinstall them and proceed to step E. M. Check that proper voltage selector plug is installed. N. If 120VAC plug is installed but field supply voltage is 240VAC, FC1 and FC2 fuses will have opened. Install the correct voltage selector plug (240VAC) and new FC1 and FC2 fuses. O. Inspect transformer wiring. Ensure insulation on wiring is not worn. If OK, replace the transformer. Open Fuse: FC3 or FC1 P. Inspect gas valve wiring. Ensure insulation on wiring is not worn. Q. Measure for resistance across gas valve terminals and between each terminal and ground. If short exists, replace gas valve. R. Inspect control module wiring. Ensure insulation on wiring is not worn. If OK, replace the control module. Open Fuse: FC4 E. Check that the proper voltage selector plug is installed in fuse board. S. Inspect ignitor wiring. Ensure insulation on wiring is not worn. F. Disconnect P4 connector from fuse board plug. Measure for 24VAC between pins 1 & 2 of plug of transformer and for 120VAC between pins 4 & 6. If 24VAC or 120VAC is not present, replace transformer. Otherwise, replace fuse board. T. Inspect blower wiring. Ensure insulation on wiring is not worn. Low Voltage Circuit Fault G. Disconnect P5 connector from fuse board plug. Measure for 24VAC across pins. Reconnect plug. If OK, proceed to step H. Otherwise proceed to step K. V. Disconnect blower plug from control module. Measure resistance across blower windings. Winding resistance across lead should be in the following range: IDL2: Black to White 10-14 ohms UHS: Red to White 18-22 ohms Red to White 8-9 ohms If measured values vary substantially from these values, blower is defective and must be replaced. Otherwise, replace the control module. F 18 H. Inspect control module wiring. Ensure all plugs are securely fastened to control module. U. Disconnect ignitor plug from control module. Measure resistance across Igniter. If shorted, replace ignitor. Fault Conditions with NO CODE J. Remove F1 fuse from fuseholder. Measure continuity across fuse. If OK, replace control module. If fuse is open, proceed to fault condition Open Fuse: FC3 or F1. Heater Will Not Power Up Disconnect the P5 connector from fuse board plug, and measure for 24vac between pins on fuse board receptacle. Reconnect the P5 plug, and disconnect P6 connector plug on the fuse board. Measure for 120VAC between pin 3 and 6 of receptacle on fuse board. I. Verify 24VAC across R and C terminals on control module. If not OK, replace harness. F 18