Read the manual thoroughly and understand all of the instructions, cautions, and warnings before using this equipment. If any section of the manual is not understood, contact your nearest authorized dealer, or contact Generac Customer Service at 1-888-436-3722 (1-888-GENERAC), or www.generac.com with any questions or concerns.
Underspeed: Error Codes 1600-1603
Environment
This article applies to error codes 1600-1603, UNDERSPEED, for Generac air-cooled home standby generators.
Note: The term "error code" is used interchangeably with 'alarm code,' 'fault code,' 'fault alarm' and similar terminology. Error code applies to all such terminology.
Overview
Error codes: 1600-1603
Alarm: UNDERSPEED
Issue: Engine speed is too slow.
Cause: The unit is overloaded or has fuel supply issues.
Contents:
- Your options are limited beyond performing basic troubleshooting checks on components and verifying that everything appears normal.
- After performing basic troubleshooting checks, you can attempt to clear the alarm and manually restart the unit.
- Sometimes, clearing the alarm and attempting to restart the unit is all that is needed, as the alarm may be a one-time occurrence that does not indicate a persistent issue.
Troubleshooting steps are designed to help rule out simple, user-resolvable issues that may trigger an error. They are not intended to diagnose or fix underlying problems that require professional attention.
While following these steps can help avoid unnecessary service calls, errors that persist or occur intermittently should always be addressed by a Generac IASD. If you are ever uncertain or confused about any troubleshooting step, do not proceed—your safety is the top priority.
- Overload condition/ Sudden change in load
- Fuel supply
- Airflow (intake and exhaust)
- Scheduled maintenance tasks
By systematically reviewing these areas, you can identify and resolve potential issues or help verify that a Generac IASD diagnosis is required.
Overload condition
An overload happens when power demand exceeds the generator's capacity. While running wattage of house appliances may be within limits, startup wattage - the surge when appliances turn on - can be 3-4 times higher. During an outage, if multiple large appliances start at once, this surge can overload or bog down the generator.
How do I know if the issue may be related to overload?
Signs of overload: Audible fluctuations in generator speed. Load managers typically prevent this by staggering appliance startups.
-
- If an overload condition is suspected, you may be able to verify by running the generator with no loads connected.
- If the issue persists, proceed to other troubleshooting checks.
- If the generator runs fine with no load, proceed to troubleshoot the overload condition below.
Troubleshooting an overload condition:
1. Identify non-essential loads.
- Review the loads connected to the unit.
- Identify loads that are not critical during an outage.
2. Remove non-essential loads.
-
Disconnect or deactivate non-essential loads.
-
This can be done by unplugging non-essential loads or switching off non-essential breakers at your main electrical panel.
-
Ensure that the remaining load is within the unit's recommended operating capacity.
3. Verify load management device functionality.
- Check any Generac Load Managers for functionality and correct configuration for lockouts.
Note: If the engine speed issues continue without a load, continue with additional troubleshooting checks below or contact a Generac IASD for further diagnosis.
Sudden Changes in load
A sudden sizeable electric load change occurs when the amount of electricity used in your home shifts dramatically quickly. This can occur when a large appliance, such as an air conditioner, heater, or pump, suddenly turns on or off.
How does this impact your generator?
Your unit relies on stable and consistent operation to produce electricity properly. A sudden increase or decrease in a large electrical demand can interfere with the unit's function and lead to unexpected errors and shutdowns.
Troubleshooting sudden changes in load:
If there is a sudden change in load, it may not be able to maintain the required speed. (i.e., large air conditioning unit powered on)
-
- If you utilize any load management systems, verify they work as expected. (Generac Load Manager, Smart AC Module)
- If the generator's speed fluctuates audibly, try running it without a load to determine if something in the house is pulling irregularly or too much power.
- Remove non-essential loads
- If the engine speed issues continue without a load, consider the maintenance steps below or contact a Generac IASD for further diagnosis.
The generator requires the right mix of fuel and air to run correctly. Issues like low fuel levels, incorrect fuel settings, or improper fuel pressure can disrupt fuel delivery, affecting engine speed and performance. Verifying these components can help identify possible causes of the underspeed error.
Fuel shutoff valve:
Verify that the fuel shutoff valve is open (ON).
If the valve is closed (OFF) or partially closed, the correct amount of fuel cannot reach the unit and may cause issues.
Verify correct fuel selection:
The unit is capable of operating on Natural Gas (NG) or Liquid Propane (LP) and is set manually during installation in two places:
-
-
- Controller menu setting: The controller should be set to match the fuel source being used.
- Fuel jet orientation: The fuel jets must be physically oriented to the correct fuel type.
- The controller fuel selection and the fuel jet orientation must match the fuel source used.
- Important: If your unit was not recently installed, these settings are unlikely to be incorrect. However, verifying them is still considered best practice to rule out a potentially user-resolvable issue.
Verify fuel levels
For units operating on Liquid Propane (LP)
-
-
- When LP levels drop below 30%, fuel pressure may be affected, which can cause operational issues. Check your LP fuel levels to verify you are above 30%.
For units operating on Natural Gas (NG)
-
-
- Natural gas grids can be impacted during major outage events or construction. Contact your natural gas supplier to verify any known issues in your area.
- Note: Most natural gas suppliers post outage or supply disruption alerts on their websites.
Fuel Pressure
Proper fuel pressure is critical to engine performance. If it's too high or too low, fuel delivery may be affected, leading to engine issues. Checking fuel pressure requires specialized equipment and expertise, so ONLY qualified professionals should perform this inspection.
What to know about checking fuel pressure:
- Improper fuel pressure can lead to operational alarms. However, due to the specialized equipment and safety considerations involved, fuel pressure checks must be performed by a professional.
- Before considering fuel pressure, it's important to follow a systematic diagnostic process with a Generac IASD. Think of this like checking a low tire—before replacing it, you would first check the air pressure and see if it holds air. Similarly, fuel pressure should only be evaluated after ruling out other common causes like the fuel shutoff valve, fuel levels, and air intake.
- If all other troubleshooting checks do not resolve the issue, work with your dealer to determine whether contacting your gas supplier to verify fuel pressure is the next logical step in the troubleshooting process.
Proper airflow is critical for engine performance. Blocked air intake or exhaust can disrupt the air-fuel ratio and cause starting issues.
Inspect clearance around the unit (Intake and exhaust):
-
- Maintain a clear 3-foot area around the unit.
- Remove any debris, vegetation, or snow that could block airflow.
Air filter check
Dirty/blocked air filter
- Inspect the air filters for dirt, damage, or blockage. Air filters can prevent airflow to the engine, affecting the fuel-to-air mixture ratio and engine performance.
Cold weather conditions
- In freezing temperatures, moisture in the air filter can freeze, blocking airflow to the engine.
- If temperatures are low, check the air filter for ice buildup and clear any obstructions.
Why would this be something to check?
Required maintenance:
Sometimes, checking user-serviceable components and performing recommended maintenance can temporarily or permanently resolve engine speed errors.
Like any engine, proper maintenance and adherence to the recommended maintenance schedule are essential for reliable operation and unit longevity. Neglecting routine maintenance can lead to performance issues and potential errors.
Note: The above list includes some of the more common causes of an underspeed alarm and related component troubleshooting. It is not intended to be exhaustive; other factors may also contribute to these issues.
Step 1. Perform the checks above to identify any user-resolvable issues.
Step 2: Clear the alarm at the generator's control panel.
Step 3: Attempt to start the unit manually by pressing the blue MANUAL button on the controller.
Note: Never start a generator while under load.
The error tells you what is wrong, but the scenario in which it occurs may provide important context as to why you are getting this error. This error is often linked to certain common causes when it appears in a specific situation.
Review the scenarios below and find the one that best matches your situation. The information provided for each scenario can help you understand why the error is occurring in that context.
Scenarios:
A. In an outage/utility power failure
In an outage scenario, overload conditions and fuel supply issues should be key troubleshooting considerations for underspeed errors:
Overload Conditions:
- If the home has bone an extended time without an outage, changes in demand may have occurred since the generator was first installed. Additions like a home expansion, pool heater, or second AC unit can increase the load beyond the generator's capacity, especially if load managers aren't functioning correctly.
Fuel supply issues:
- Liquid Propane (LP): Levels below 35% can affect performance.
- Natural Gas (NG): grids may be stained or damaged during widespread outages. Check with your NG supplier for outage or grid status updates.
Important Note: Anytime power transfer has occurred and the generator is under load, all loads must be disconnected before restarting. The generator must be allowed to reach full speed and "warm up" before reconnecting loads.
B. When attempting to exercise
Units do not exercise under load, so troubleshooting should not focus on overload conditions or sudden changes in load.
When an underspeed alarm occurs during a generator's exercise cycle, consider the following:
1. Is it a recurring issue?
- If the generator was installed within the past year, the problem is commonly related to the installation. Contact the installer to confirm the installation meets specifications.
- Underspeed alarms during exercise are typically related to fuel delivery issues or routine maintenance, not electrical problems. The installer responsible for the fuel system should investigate, focusing on fuel pressure and regulator distance.
- Improper installation can lead to competition for fuel supply between household appliances and the generator and inadequate fuel supply.
- Improper regulator placement can impact fuel pressure, resulting in starting issues.
- Improper pipe sizing can impact fuel pressure, resulting in starting issues.
2. Seasonal weather changes:
- Fuel pressure that was barely adequate in summer may cause issues in winter due to colder temperatures.
3. If the generator has been installed for over a year:
- Overspeed alarms are more likely linked to maintenance.
- However, if your home's fuel system has been modified recently, these changes could be contributing factors.
Troubleshooting Steps
- Start with general troubleshooting as outlined above.
- If unresolved:
- For generators installed within the last year, contact the installer.
- For generators older than one year, contact a Generac IASD.
C. During installation
- This may be due to air pockets in the fuel system. When the fuel system is installed, if the air is not correctly bled from the fuel lines, it may contribute to starting issues temporarily due to air pockets in the fuel line. .
- Confirm that the correct fuel was selected during setup at the controller.
- Home Standby units are factory-set to Natural Gas. If you are using LP, you must select LP at the controller and adjust the fuel jet nozzles to the LP position.
- For more information on the field conversation of the fuel jets, see the following article:
- There may be an issue with your fuel pressure or fuel system. For this type of issue, we recommend contacting your installer to verify the unit has been installed according to the specifications outlined in the installation manual.
Note: A minimum 250-gallon LP tank is required for all home standby generators that utilize LP fuel.
D. Intermittently
Resolving intermittent underspeed issues can be challenging because they are difficult to replicate. While we recommend contacting a Generac IASD for diagnosis, you can help by noting the conditions when the issue occurs. Consider patterns such as:
Providing detailed observations can help identify the root cause, as the ability to replicate the issue is key to an accurate diagnosis.
Additional considerations:
1. If the generator was installed within the past year, the problem is commonly related to the installation. Contact the installer to confirm the installation meets specifications.
- Underspeed alarms are typically related to fuel delivery issues or lack of routine maintenance, not electrical problems.
- The installer responsible for the fuel system should investigate, focusing on fuel pressure and regulator distance.
- Improper installation can lead to competition for fuel supply between household appliances and the generator and inadequate fuel supply.
- Improper regulator placement can impact fuel pressure, resulting in starting issues.
- Improper pipe sizing can impact fuel pressure, resulting in starting issues.
- Verify that the routine maintenance schedule has been followed.
2. Seasonal weather changes:
- Fuel pressure that was barely adequate in summer may cause issues in winter due to colder temperatures.
3. If the generator has been installed for over a year:
- Underspeed alarms are more likely linked to maintenance.
- However, if your home's fuel system has been modified recently, these changes could be contributing factors.
Troubleshooting Steps
- Start with general troubleshooting as outlined above.
If unresolved:
- For generators installed within the last year, contact the installer.
- For generators older than one year, contact a Generac IASD.
For additional general troubleshooting, see the following article: Troubleshooting intermittent or difficult to replicate alarms, faults, and error codes
E. Winter conditions
It is common for extreme weather conditions to be an important factor to consider when an underspeed alarm occurs. While Generac Home Standby generators have an operating range between -29°C (-20°F) to 40°C (104°F), extreme cold and snow can impact the generator in otherways.
First step: Clear any snow and ice from around the generator to allow for airflow, especially near the intake and exhaust.
Second step: Check the air filter for freezing. Moisture trapped in the air filter can freeze and block airflow.
Regulator issues:
Extreme cold can impact fuel external fuel regulators, especially in regions not accustomed to freezing temperatures. Regulators are temperature-rated, and those not designed for cold climates may experience issues.
For more information on preparing your generator for snowstorms, see the following article:
F. Units installed within the last year
- If the unit has been installed within the last year, this may point to an issue with the installation that has only become apparent due to seasonal changes.
G. Units installed for longer than a year
If troubleshooting worked:
- If troubleshooting was successful, take note of the potential factors that may have contributed to the fault alarm.
- Taking note of the weather, time, and situational factors surrounding the occurrence may help identify external factors if the issue arises in the future.
If troubleshooting failed:
- If the unit still has not started, it is recommended that a local Generac Independent Authorized Service Dealer (IASD) be contacted for diagnosis.
What to know when working with a Generac IASD for diagnosis and repair:
- Only a Generac IASD can submit warranty claims and perform warranty repairs.
- Leave the error code present on the unit so it can be properly diagnosed.
- Keep records of all maintenance performed.
- Note any situational factors or details related to the alarm occurrence; this information may help the technician diagnose the issue more effectively.
- How Can I Find a Generac Service Dealer in My Area?
