Aerco Benchmark BMK 750

Questions and Answers

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anthony10Nov 27, 2025
How to resolve an Airflow Fault during Run on my Aerco Benchmark BMK 750?
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  Lawrence SmithNov 27, 2025
  If the Aerco Boiler experiences an Airflow Fault during Run, several factors could be at play. The blower might have stopped running due to thermal or current overload; check the combustion blower for signs of excessive heat or high current draw. A blocked blower inlet or inlet ductwork is another possibility; inspect the inlet to the combustion blower, including any ductwork leading up to it, for signs of blockage. A blockage in the air filter or Blocked Inlet switch could also be the cause; remove the air filter and Blocked Inlet switch and inspect for signs of blockage, cleaning or replacing as necessary. A defective Blocked Inlet switch may also be the problem; verify that 24 VAC is present between each side of the switch and ground. If 24 VAC is not present at both sides, replace swit...
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tracywhiteAug 25, 2025
What causes a Delayed Interlock Open error on my Aerco Boiler?
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  Gary MillerAug 25, 2025
  If the Aerco Boiler shows a Delayed Interlock Open error, the following could be the reasons: the Delayed Interlock Jumper might not be properly installed or is missing; check to ensure the jumper is properly installed across the delayed interlock terminals in the I/O Box. If there are 2 external wires on these terminals, check to see if an end switch for a proving device (such as a pump, louver, etc.) is tied these interlocks. Ensure that the device and/or its end switch is functional. A jumper may be temporarily installed to test the interlock.
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tjuarezAug 29, 2025
How do I troubleshoot an Interlock Open error on my Aerco Boiler?
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  deleonjenniferAug 29, 2025
  If the Aerco Boiler displays an Interlock Open error, verify that a jumper is properly installed across the interlock terminals in the I/O box. If there are two external wires on these terminals check any Energy Management system to see if they have the units disabled (a jumper may be temporarily installed to see if the interlock circuit is functioning). Check that proving switch for any device hooked to the interlock circuit is closing and that the device is operational.
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Lauren EscobarAug 31, 2025
How do I fix a Stepper Motor Failure on my Aerco Benchmark BMK 750 Boiler?
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  Dr. Jessica Moore MDAug 31, 2025
  If the Aerco Boiler reports a Stepper Motor Failure, consider these potential causes: the Air/Fuel Valve might be out of calibration, requiring you to perform the Stepper Feedback Calibration procedure in Section 6, section 6.2.1. Check that the Air/Fuel Valve is connected to the C-More Controller. Loose wiring connections to the stepper motor could be the issue; inspect for loose connections between the Air/Fuel Valve motor and the wiring harness. A defective Air/Fuel Valve stepper motor would need replacement. Check DS1 & DS2 LEDs on Power Supply Board. If they are not steady ON, replace Power Supply Board. Check “Heartbeat” LED DS1 and verify it is blinking ON & OFF every second. If not, replace IGST Board.
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David WaltersDec 1, 2025
Why does the High Water Temp Switch keep opening on my Aerco Benchmark BMK 750 Boiler?
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  Lauren ChapmanDec 1, 2025
  If the High Water Temp Switch opens in the Aerco Boiler, several factors could be responsible: a faulty water temperature switch, which needs testing to ensure it trips at its set temperature. Incorrect PID settings can also cause this; check the settings and reset them to default values if they've been changed. A faulty shell temperature sensor might be the problem; measure the resistance of the Shell sensor and BTU sensor at a known water temperature using the resistance charts in Appendix C. Ensure that the unit is not in MANUAL mode; if it is, switch to AUTO mode. Also, verify that the unit setpoint is not greater than the Over Temperature switch setpoint; the temperature switch should be set higher than the unit’s setpoint. Finally, system flow rate changes occurring faster than the u...
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David SparksSep 22, 2025
What to do if my Aerco Benchmark BMK 750 reports a Recirc Pump Failure?
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  Travis ArmstrongSep 22, 2025
  If the Aerco Boiler indicates a Recirc Pump Failure, the internal recirculation pump has likely failed and needs replacement.
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Stephanie ConwaySep 18, 2025
What does it mean when my Aerco Benchmark BMK 750 shows an SSOV Switch Open error?
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  eric26Sep 18, 2025
  If the Aerco Boiler displays an SSOV Switch Open error, the actuator may not be allowing for full closure of the gas valve; observe the operation of the Safety Shut-Off Valve (SSOV) through the indicator on the Valve actuator and ensure that the valve is fully and not partially closing. The SSOV may be powered when it should not be. Remove the electrical cover from the SSOV and check switch continuity. If the switch does not show continuity with the gas valve closed, either adjust or replace the switch or actuator.
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Tara WillisSep 18, 2025
How do I troubleshoot an Outdoor Temp Sensor Fault on my Aerco Benchmark BMK 750?
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  christopherjohnsonSep 18, 2025
  If the Aerco Boiler displays an Outdoor Temp Sensor Fault, inspect the Outdoor Temperature sensor for loose or broken wiring. Check resistance of sensor to determine if it is within specification. Ensure that the correct sensor is installed.
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Steven SextonSep 12, 2025
Why is my Aerco Benchmark BMK 750 showing a High Exhaust Temperature?
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  Amy ShannonSep 12, 2025
  If the Aerco Boiler shows a High Exhaust Temperature, poor combustion calibration could be the cause. Check combustion calibration. If exhaust temperature is greater than 200o F (93.3oC), check combustion calibration. Calibrate or repair as necessary.
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Ryan PooleSep 8, 2025
What causes a Remote Setpoint Signal Fault on my Aerco Boiler?
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  Christine JamesSep 8, 2025
  If the Aerco Boiler displays a Remote Setpt Signal Fault, the potential causes include the remote setpoint signal not being present due to it not being installed, wrong polarity, a defective signal at the source, or broken or loose wiring. Check the I/O Box to ensure the signal is hooked up, and if not, hook it up. If installed, check the polarity. Measure the signal level and check the continuity of wiring between the source and the unit. If using a 4 to 20 mA signal, ensure the signal is isolated at the source. Check the DIP switch on the PMC board to ensure it is set correctly for the type of signal being sent. Check control signal type set in item 6 of the Configuration menu.