Allmand MAXI-HEAT MH500iQ

Questions and Answers

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Benjamin OliverAug 18, 2025
Why is my Allmand MAXI-HEAT MH500iQ smoking and building up soot?
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  Sara SandersAug 18, 2025
  If your Allmand Heater is smoking upon firing or soot is rapidly building up in the chamber and on the flame detector, several issues could be the cause. It might be due to an incorrect nozzle size or burners not adjusted for your operating altitude, in which case you should replace the nozzle with the correct size or adjust the burners. A faulty nozzle can also cause this, so consider replacing it. Check the alignment of the electrodes and adjust if needed. Ensure the air band assembly is properly set and tightened. Finally, if you're using No. 2 Diesel fuel, use it up or blend it with No. 1 diesel, and remember to clean the cad cell flame detector before reuse.
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Chris HowardAug 20, 2025
What to do if the main fan will not come on, and the Allmand MAXI-HEAT MH500iQ shuts down on high limit?
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  Brett DodsonAug 20, 2025
  If the main fan of your Allmand Heater won't turn on and the unit shuts down due to a high limit, first, check the air flow to make sure both ducts are in place and clear of obstructions. Next, verify the pump pressure, as the unit might be over-firing, and adjust the pressure if required. Also, ensure that the correct nozzle is installed by checking the manufacturer’s specifications. Finally, inspect the high limit switch, and change it if necessary.
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Kayla NguyenAug 23, 2025
What to do if the Allmand MAXI-HEAT MH500iQ Heater starts then locks out?
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  Hayley SmithAug 23, 2025
  If your Allmand Heater burner starts briefly and then locks out, requiring a manual reset at the oil primary control, the issue may be a faulty or fouled cad cell flame detector. Try removing and cleaning the cad cell. If the problem persists, replace the cad cell element.
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Anna MaddoxAug 26, 2025
What to do if Allmand Heater burner starts then locks out at the relay?
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  Kristin RamseyAug 26, 2025
  If your Allmand Heater burner starts up then locks out at the relay, try checking and cleaning the sensor. If the problem reoccurs, replace it. Also, check the yellow wires between the sensor and relay, and replace the sensor if issues continue. Inspect the fan switch, replacing it if necessary. Finally, check if power is reaching the motor; if not, replace the motor if the problem persists.
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Jennifer YatesAug 28, 2025
Why does my Allmand MAXI-HEAT MH500iQ Heater fail to start?
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  Janet WhiteAug 28, 2025
  If your Allmand Heater fails to start, first ensure the ON-OFF switch is in the ON position and that the unit is receiving adequate power (120V 60 HZ). Turn the switch on and check the electrical circuit capacity, noting that the OHV 600 requires a 30 AMP circuit. Also, check the fuel level and replace the fuel filter if it's clogged, and replace or clean the fuel hoses. Verify the nozzle assembly alignment according to the operating instructions. Replace the burner fuse if it has failed. Lastly, replace the high limit switch if it has failed in the open position.
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Emily AlvarezAug 30, 2025
What to do if Allmand Heater burner will not start?
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  stacy37Aug 30, 2025
  If your Allmand Heater burner will not start, check the fuse and replace it if necessary. Inspect the high limit switch and replace it if needed. Check the manual reset button on the oil burner motor and reset it if tripped by pressing and holding for 30 seconds. Ensure no light is reflected to the sensor, and clean the cad cell. Finally, check the sensor itself and replace it if necessary.
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Alicia LivingstonSep 2, 2025
Why won't the fan motor operate on my Allmand MAXI-HEAT MH500iQ?
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  ldiazSep 2, 2025
  If the fan motor on your Allmand Heater fails to operate, the cause may be a failed fan motor, in which case you should replace it. Alternatively, the fan cycling thermostat might have failed in the open position, requiring you to replace the thermostat.
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George StoneSep 4, 2025
How to fix delayed ignition on Allmand MAXI-HEAT MH500iQ Heater?
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  Ruth WashingtonSep 4, 2025
  If you're experiencing delayed ignition with your Allmand Heater, check for proper electrode setting, referring to the previous page for guidance. Inspect the isolators for cracks or soot/oil buildup, and clean or replace them. Ensure the air shutter isn't open too far and close it slightly. Verify that the pump pressure is correctly set, adjusting it to 140 psi if needed. Check and replace the fuel filter if it's dirty, and consider replacing the nozzle.
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Brittany MorrowSep 7, 2025
Why is the fire smoky in my Allmand Heater?
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  isabel20Sep 7, 2025
  If your Allmand Heater has a smoky fire, start by checking the burner fan blade and cleaning it if it's dirty. Inspect the combustion chamber for cracks or burnout and replace the chamber if necessary. Check the nozzle; if it's clogged, clean it to prevent an off-center fire. Ensure the center leg on the nozzle assembly centers the nozzle in the 4” tube, adjusting if required. Finally, check for a loose nozzle and tighten it.
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Christine ClaytonSep 9, 2025
What causes oil accumulation in the combustion chamber of Allmand Heater?
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  jamesvasquezSep 9, 2025
  If there's an accumulation of oil in the combustion chamber of your Allmand Heater, it's likely because the unit has been reset multiple times without ignition. To resolve this, tilt the unit up at the burner end to drain excess oil from the secondary chamber, allowing it to drain for 15-20 minutes or until all oil is removed. Open the electrical box and use a jumper on the fan switch to start the burner and fan together. Expect a smoky fire for a few minutes until the excess oil on the chamber walls burns off. Once stabilized, turn off the switch, let the fan cool the chamber, and then remove the jumper and close the electrical panel. If issues persist, refer to the DELAYED IGNITION section of the troubleshooting guide.