What Generator Alarms Mean

And

What to do About Them

Based on NFPA 110, 2010 edition

Chapter 5.6.5.2

Generator control panels can display a wide variety of alarms. Most alarms are required by code. However, some alarms can be confusing. A confused or hesitant operator is likely to call the service provider resulting in an expensive and totally unnecessary invoice.

Read this before you invest in an unnecessary service call.

If your generator is down, check the alarms listed below and also follow my Generator Recovery Flowchart.

Building codes specify the following alarms and are included on your generator’s control panel:

– Low Oil Pressure

-If the oil pressure falls low enough that engine damage could result, it will shut down the engine.
Check the oil level and fill if necessary. (Reset and try again)

(How to reset the control? go to Find Your Generator Control Panel)

– High engine temperature
When the engine temperature reaches a high enough level that damage could result, it will shut down.
Let the engine cool before you attempt a correction. Never check the coolant level until the engine is cool. See your operator’s manual for safety instruction.
After the engine has cooled, remove any restrictions to the cooling air flow. Check fan belts. Check to see if the coolant pump is leaking—look to see if coolant is dripping from it. Have a qualified engine mechanic check it out and clean the radiator core.

After the engine has cooled, remove any restrictions to the cooling air flow. Check fan belts. Check to see if the coolant pump is leaking—look to see if coolant is dripping from it. Have a qualified engine mechanic check it out and clean the radiator core.

– Overspeed

Generators are designed to shut down if the engine speed exceeds 10% of its rated speed. Not much you can do here except reset the alarm and restart.

We have found that the computerized controls used since 2000 react poorly and often send false signals when the battery cranking voltage drops below a preset level. Check your battery. (Battery Specific Gravity and Conductance Test) Make sure the coolant heater and battery charger are working properly. Check the battery voltage using a reliable multimeter.(How to Use a Multimeter to Check Your Battery)  Then replace the battery or charge the battery and reset the control. In our experience this sometimes clears the fault. (See Find Your Generator Control Panel on my Generator Recovery Flowchart)

– Overcrank

The generator will go into Overcrank if it runs through its cranking cycle without starting or if the cranking voltage drops below its preset level.

Check your battery age and voltage (See my video on how to check batteries)

– Remote Stop Station

The building code requires a remote manual stop station. This should have an alarm contact that signals a fault light on the generator control panel. If this alarm is on, just check to make sure your emergency stop switch has not been operated. (See: Find Your Generator Control Panel on my Generator Recovery Flowchart to find how to reset it, also see my video How to Set Up a Generator Stop Station)

Building codes (NFPA 110) specify the following additional alarms be present and separate from shutdown alarms.

The following alarms are warnings and do not necessarily shut the engine down. They are code required.

  1. Low oil pressure pre-alarm (Pre-alarms are only warnings. They do not shut you down. Check the oil)
  2. High engine temperature pre-alarm

 Let the engine cool before you attempt a correction. Never check the coolant level until the engine is cool. See your operator’s manual for safety instruction.

After the engine has cooled, remove any restrictions to the cooling air flow. Check fan belts. Check to see if the coolant pump is leaking—look to see if coolant is dripping from it. Have a qualified engine mechanic check it out and clean the radiator core.

Low coolant level (may also shut down. Let the engine cool before you attempt a correction. Never check the coolant level until the engine is cool. See your operator’s manual for safety instruction. On some models, the radiator needs to be filled all the way up.)

  1. Low fuel level (or pressure if LPG on NG. Check your fuel supply.)
  2. Generator supplies load (This means the transfer switch has switch the load from the utility to the generator)
  3. Control switch not in auto (includes generator and automatic transfer switch. Check the generator control switch and the automatic transfer control switch. Make sure they are both in automatic mode. See my Generator Recovery Flowchart)
  4. High battery voltage (The charger may have failed. See: How to use a Multi Meter
  5. Low battery voltage (The charger may have failed. See: How to use a Multi Meter
  6. Low cranking voltage (Measures the lowest battery voltage during cranking cycle. See: How to use a Multi Meter
  7. Battery charger AC fail (Make sure the charger is plugged in. Check the breaker)
  8. Lamp test (Just checks to see if the indicator lamps work, it may also reset the alarms on some models)
  9. Air damper shutdown, if appropriate (Shutdown)
    • Some engines, like Detroit Diesel, have an air damper on the intake manifold. This may need to be rest. It will prevent a start.

Additional alarms may also be present as follows. Some may be code requirements.

  • Low coolant level (Required by NFPA 110)
    • If your system has a coolant leak, this alarm will prevent a start when the coolant drops below the level sensor.
  • Low engine temperature (Required by NFPA 110)
    • This alarm will not lock the engine out; however, the generator may be hard to start due to cold temperatures. If you get it running, the light should go out after the coolant exceeds 600 F. Check and repair your coolant heater. Check your coolant heater weekly. See: Weekly Generator Operational Inspection and Testing )

Note: The alarms I have listed are NFPA required. Other alarms may be present like “RPM Sensor Loss”. This is not a required alarm, but it will shut the machine down. The primary reason for this alarm is to create an expensive service call.

“Auxiliary Fault” is also not a required alarm, but it may shut the machine down.

 One manufacturer connects six different faults to “Auxiliary Fault” They are:

  1. Over AC voltage
  2. Under AC voltage
  3. Over DC voltage
  4. Under DC voltage
  5. RPM sensor fault
  6. Low coolant level

Remember to clear an alarm on most generators, turn the control switch to “Off” before pushing the “Reset” button. Otherwise, it won’t clear.

Note: Some manufactures require you must be able to pat your head and rub your stomach while standing on one foot in order to clear an alarm. If you cannot clear an alarm send me an email: paul@generatorhelponline.com

Digital displays, alarm codes, and additional unnecessary alarms:

With the advent of digital displays, manufacturers developed an additional way to scare the bejesus out of operators and owners, and as a result create expensive service calls. Alarms other than NFPA required alarms are essentially video games. Their purpose is marketing. They create confusion, expensive service calls, and improve a vendor’s profits.

  • A log of alarm codes will be present in your operator’s manual—if you can find the manual. You are expected to lose it and call for help. The list of alarm codes is often incomplete to keep you guessing.
  • If by some slim chance they gave you a set of manuals and you find them, the language will be so obscure you will still not understand the meaning of the code. (The generator supplier is required by NFPA 110 to provide you with two complete sets of manuals)
  • Some codes displayed may not be in your manual. You will have to call your manufacturer’s representative to get an answer. This gives them an opportunity to sell you a service call.

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