Hayward Universal H-Series Low NOx Service/Installation: H150FDN H200FDN H25 - Page 57

57 Figure 53: Troubleshooting Code LO LO IF AC AO Fault Diagnosis Step Remedy Temperature limit switch fault Temperature limit switch fault (cont'd) Ignition Failure Blower vacuum switch closed. Blower vacuum switch open. 1. Check for faulty wiring or Inspect temperature limit switch wiring. Ensure wire harness teminals connection. are securely fastened to spade terminals on temperature limit switches. If OK, proceed to step 2. 2. Verify state of temperature Remove wire leads from limit switch and jumper leads. Operate heater. limits' contacts Measure continity across limit switches. If closed, LO code is not caused by temperature limit switch fault. If open, proceed to step 3. Remove jumper from leads and reconnect leads to temperature limits. 3. Verify that water flow is adequate Verify that water flow rate to heater is above the minimum required (20 GPM for H150FD and H200FD, 25 GPM for H250FD and H300FD, 30 GPM for H350FD and H400FD). If OK, proceed to step 4. 4. Temperature limit switch Replace temperature limit switch. is defective. 1. Ensure gas supply shutoff Ensure that main gas shutoff installed adjacent to heater is open. Ensure valves are open. that knob on gas valve inside unit is in ''on'' position. If OK, proceed to step 2. 2. Check for low gas supply Ensure inlet gas supply pressure is between the minimum and maximum pressure values indicated on rating plate. If OK, proceed to step 3. 3. Check for faulty flame Inspect flame sense wiring. Ensure wire harness terminals are securely sense wiring or connection. fastened to flame sense and to control module. If OK, proceed to step 4. 4. Check for faulty gas valve Inspect gas valve wiring. Ensure wire harness terminals are securely wiring or connection fastened to spade terminals on gas valve. If OK, proceed to step 5. 5. Check for gas valve failure or gas valve relay failure. 1. Measure voltage across gas valve during trial for igintion. If 24VAC is present and gas valve does not open, gas valve is defective. Replace gas valve. 2. If 24VAC is not present, gas valve relay on control module is defective. Replace control module. 6. Check for blockages in gas orifices and burners Inspect gas orifices for blockages which could prevent gas flow. Remove and inspect burners for blockages. 1. Check for defective blower on relay or control module. Disconnect Blower plug fron Control Module. With heater off, measure continuity across pins 1 and 2 of receptacle on Control Module. If closed, control module relay is defective. Replace control module. If OK, proceed to step 2. 2. Vacuum switch is defective. Replace blower vacuum switch. 1. Check for faulty vacuum Check tubing and replace if necessary. If OK, proceed to step 2. switch tubing 2. Check for faulty vacuum Inspect vacuum switch wiring. Ensure wire harness terminals are switch wiring or connection. securely fastened to spade terminals on vacuum switch. If OK, proceed to step 3. 3. Check for faulty blower Inspect blower wiring. Ensure plug on blower is securely fastened to wiring or connection control module. If OK, proceed to step 4. 4. Check for defective vacuum switch Disconnect Blower plug from Control Module. Measure resistance across Blower windings. Winding resistance across lead should be in the following range; Red-to-White: 8 to 9 ohms. If measured values vary substantially from these values, Blower is defective. Replace. If OK, proceed to step 5. 5. Check for defective blower relay. Disconnect Blower plug from 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. If 120VAC is not present, control module relay is defective. Replace control module. If OK, proceed to step 6 6. Vacuum switch is defective Replace blower vacuum switch.