Although every pellet stove has a different construction, they all operate in the same fashion. On this page, we’ll provide a basic rundown of what's happening behind the scenes, provide signs to look for when your pellet stove isn’t working, and provide guidance on how to fix common pellet stove issues.
How A Pellet Stove Starts Up
No matter which pellet stove you’re trying to troubleshoot, they all follow the same startup procedures. Below is an overview of these procedures:
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The Pellet Stove Powers On
Shutdown timer commencing. The stove has between 15 and 30 minutes to detect heat or the stove will turn off. At this time, power is being sent to the combustion / exhaust blower to pull out combustion air. Once the air has started flowing through the stove, a pressure switch commonly called a vacuum switch either senses this pressure and closes the circuit to the feed motor and igniter, or senses back pressure and opens the circuit to the feed motor and igniter. If your stove has a hopper lid safety switch, this switch will be in line with the feed circuit.
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Feeding And Ignition
If the feed circuit is not open (pressure switch closed), pellets will begin to dispense into the burnpot. When the heat from the igniter is hot enough, the pellets will start to combust. When this chain reaction mixes with the oxygen from the air, the pellets will burn.
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Proof Of Fire
Every pellet stove has a sensor to detect “proof of fire”. The type of sensor used is unique across manufacturers. Harman uses an exhaust mounted RTD probe, Quadrafire uses a burnpot mounted thermocouple, Lennox Whitfields use an optical sensor, most box store brands use a thermal heat resistor, and everybody else uses a thermal snap disc. Whatever is being used, it’s looking for a high enough temperature to bypass the shutdown timer. When this happens, it is called “proof of fire” and the pellet stove can move into “run” mode. After proof of fire, this is when you can make changes and see the changes happen. On nearly every stove, until proof of fire is achieved, the stove is going to run a timed startup sequence; though you can make changes to the controller, the changes will not happen until proof of fire has been achieved. If the stove never detects a temperature high enough for “proof of fire”, the stove will shut off when the shutdown timer expires. The shutdown timer is going to be between 15-30 minutes. If your stove starts up normally but shuts down with a fire burning within 30 minutes every time, the proof of fire sensor is either dirty or needs to be replaced. Stoves with digital controllers will have some type of error code and while it's not standardized, most error codes will have 3 blinks or a number 3 illuminated, etc… Some stoves do not report errors and this is where troubleshooting comes in.
Common Pellet Stove Problems And How To Troubleshoot Them
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Pellet Stove Will Not Turn On
The stove hasn’t started yet and we’re experiencing a problem...it doesn’t have power. Here’s what to look for. Did you leave the stove plugged in all summer? You may have had a power surge event and never knew it. Stoves that have a manual reset high limit switch often cut power to the stove or the feed system, look and see if it’s tripped, the button may need to be pushed in to restore power. Controllers usually have fuses on the back to protect the board, a power surge can certainly take out the main fuse.
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Pellet Stove Not Feeding At Startup
If your stove will power on but will not feed pellets at startup, or the stove will not enter into the startup procedure from the get-go, here are some things to check.
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High-Limit Sensors
With the exception of Whitfield stoves and analog controlled stoves, If the room blower is on at the start-up, something is wrong with the overheat control sensors, most commonly referred to as manual reset “high-limit” sensors or switches. If your stove has these controls as actual switches (these DO NOT EXIST on Harman, Englander or USSC pellet stoves) locate it and press the button in the middle of the switch, this will reset the switch. On a Quadrafire stove, the high-limit will actually kill all the power to the stove altogether. If this was the problem, we need to figure out why. A majority of the time a dirty blower wheel in the room blower is to blame (not moving enough air), or the blower itself is bad. IF you cannot freely spin the blower wheel, replace the blower. If you left your stove plugged in during the offseason, or if it has been plugged in since the last time you used it, and you had a power surge, these switches can sometimes roll out and need to be reset. Error codes for this are usually #4 or #4 and #5.
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Pressure Switch (Vacuum)
If you go to start the stove and the stove turns on and then shuts off within 30 seconds of powering it up, the vacuum pressure switch in the stove may not be closing its circuit. Most of the time, this has to do with a clogged hose, blocked vent, or dirty stove. Most stoves that are suffering from this error and have error reporting will display this as a #2 error. If the exhaust blower fails (stops spinning), the stove will display a vacuum switch error. Always make sure the exhaust blower is spinning. Many stoves have a hopper lid switch in-line with the feed or the pressure switch, make sure the hopper lid is closed when troubleshooting. Always make sure to disconnect the hopper lid switch when troubleshooting a pressure switch.
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Hopper Lid Switch
Most stoves that have a hopper lid switch will wire the switch inline with the pressure switch or inline with the feed system. Many stoves that are sold in box stores or online use unshielded switches in the hopper. When people overfill the hopper, sometimes the pellets being crammed into a confined space can break or dislodge a wire from the underside of the exposed wire connections in the switch. Bypass the wires going to this switch. Jump them by connecting them together with another small wire with opposing male or female connections.
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Auger Jam
The pellet stove may be fine, but the auger itself may be jammed with something foreign. Look for signs of the feed motor struggling to turn.
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Pellet Stove Starts Up But Randomly Shuts Down
If your pellet stove starts up as normal and builds a nice fire, only to then shut down (either abruptly or slowly), it's due to either a mechanical or sensor issue. There are three symptoms to look for: 1. The burnpot is empty after shutdown, 2. The burnpot is full of unburned pellets, or 3. The burnpot is full of partially burned pellets.
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The Burnpot Is Empty After Shutdown
If all pellets in the burnpot have burned up and there’s no residual fuel in the burnpot, one of three things is happening; 1. The feed motor is slowing down as the stove heats up, 2. The power to the feed motor is being interrupted, 3. Fuel is having a hard time feeding into the burnpot. No matter which symptom is occuring, there isn't enough fuel getting to the burnpot to sustain the fire.
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The Feed Motor Is Slowing Down As The Stove Heats Up
When an auger motor becomes old and tired, it spins slower. Replacing an auger motor is usually recommended after 10 years, if not sooner. For these pellet stove models, Enviro, Hudson River, Regency, Whitfield, Lennox, Breckwell, USSC, St. Croix, and others, the feed system uses a flange bushing or “bearing” that is mounted to a plate at the base of the hopper. When this bearing starts to wear out, dust from the hopper will get between the bearing and the auger shaft and cause the rotation of the shaft to slow down. This will also wear out the motor. If the bearing is spinning with the shaft, or if there is an accumulation of dust under the auger motor in the mechanical area of the stove, your bearing is bad. Replace the bearing, plate and feed motor.
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Slow Feeding Issues With Quadrafire And Heatilator Pellet Stoves
There is no auger bearing on these stoves. The feed motor has a capacitor in-line with the motor that can “flip” the polarity of the power to the motor. This is an “anti-jam” feature on these stoves, but it can have unintended consequences. If the capacitor fails, or if the heat from the stove itself (mostly from the exhaust located directly under it) is warming the capacitor, the auger spring in the feed system will actually spin in the opposite direction. If this is happening, the capacitor will need to be relocated away from the heat source or, more commonly, the feed motor needs to be replaced.
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Slow feeding on Harman Pellet Stoves
If the feeding system slows down on your Harman pellet stove, here are 3 things to check. 1. Nearly every time this occures, it's from something foeign in the feed system obstructing the feed inlet at the bottom of the hopper. This is usually a piece of plastic from a pellet bag. 2. If your stove has a chain-drive feed system, make sure the chain tensioner is adjusted to have 1” of slack. 3. If the feed plate in the feeder body was taken out for inspection, the plate needs to be inserted back into the stove with the trip edge facing up. If the plate is upside down, the stove will not feed pellets correctly.
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The Power To The Feed Motor Is being Interrupted
When the stove is running, the combustion motor is moving air through the stove. Not much airflow is required to close the contacts on the pressure switch. Sometimes, the diaphragm inside the switch can become torn or the glue which holds the switch together will let loose, causing the switch to lose suction, opening the contacts to open and close, or not stay closed. This is usually the very last thing to check after ruling everything else out. Usually pressure switches do not fail.
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Fuel Is Having A Hard Time Feeding Into The Burnpot
If there is too much dust, the small number of pellets needed to sustain the fire may not be enough fuel. Usually, if this is the case, the stove will start-up and run fine if it's set to the high heat setting, but at lower heat settings the fire will die out. A simple cleaning will fix this issue.
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The Burnpot Is Full Of Unburned Pellets After Shutdown
When the stove shuts down and there are unburned pellets in the burnpot, one of two things has occurred; 1. The feed was interrupted for an extended period of time, 2. The fire consumed the pellets in the burnpot, meaning by the time more fuel was fed into the firebox, there were not enough embers to reignite the fuel, causing the new fuel to extinguish the flames.
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Foreign Objects
Make sure that your hopper and feed chutes are free and clear or anything that is not a wood pellet, this includes excessive dust in the hopper.
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Pellets Bridging In The Hopper
Make sure that you do not have an abundance of pellets longer than 1 ¼” long. Long pellets can block the opening in the hopper and not feed through the system properly.
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Check Your Draft
If your stove has a draft restriction or damper rod, make sure that the draft is set accordingly. Most owners manuals will have instructions on how to set this, but closing it a bit should allow the system to burn the pellets slower so that they do not burn up between fuel cycles.
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Automatic Reset High-Limit Switches
Some stoves have high-limit safety sensor switches which turn off the fuel feed when an overheating situation occurs. As the stove cools back down, the feed cycle will reset, unfortunately, there will be no embers to re-ignite the fire. What you see is the unburnt fuel.
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Windward venting connections
If your stove's venting is a straight shot out of your house, a gust of wind can sometimes create a "puff" in the stove, blowing the fire out.
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The Burnpot Is Full Of Partially Burned Pellets
The power was cut to the stove while it was running. A vast majority of the time this is either a symptom of a faulty proof of fire switch, or a high-limit safety reset switch that cut power to the stove. An extended power loss event can do this too, if the power does not come back on before the stove has cooled to a point lower than the proof of fire threshold.
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Pellet Stove Starts And Runs, But It Is Feeding Too Much Fuel And It Is Not Completely Burning
99.9% of the time this problem occurs because the stove, vent, or both are very dirty. They can be so dirty that air isn't able to flow through the vent system fast enough. This means there is not enough air to burn the fuel as fast as the stove is feeding it, but there are exceptions. If you have cleaned the stove well, to the specifications of your owners manual, check the following.
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Damper
If you have a damper control, make sure that it is not closed. If you can open the damper, this may solve the problem. Luckily, when the stove is running, setting a damper is easy. When your stove has a high flame, close the damper fully, if you see an orange lazy flame, open the damper until the fire is bright and there is subtle movement on the burnpot of the smallest pellets. This is the correct setting.
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Burnpot
Make sure that your burnpot is clean and the holes are free and clear.
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Ashpan, Doors, and Other Openings
The firebox on a pellet stove needs to be airtight. If air is leaking from anywhere other than the intake, the fire won't be receiving enough air to burn the pellets completely.
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Stack Effect
If you suspect that your house may be too air-tight, and your stove does not use outside air for combustion, open a window slightly in the room where the stove is installed. This may help restore the pressure in the house so the stove can exhaust properly.
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Leeward OAK Connection
If your stove uses outside air for combustion, but is installed on a side of the house opposite of the prevailing wind (leeward), then the air pressure from the wind passing over the house may pull air away from the leeward side as it passes. Generally, this would only happen on a very windy day.
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Pellet Stove Will Not Shut Off
Shutting down a stove by letting it run out of fuel, or simply by pulling the power cord is not only improper, it can also be dangerous. If the stove will not shut off on it's own, here's what to look for.
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Low Limit Sensor (Proof Of Fire)
If the low-limit switch is broken it usually will not make a connection, but in some rare cases, the switch may be stuck in the closed position. Remove one wire from the low limit switch and see if your stove powers off, if so, replace the low-limit switch.
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Controller Decal Skin
Sometimes, stoves which use a digital controller with a plastic decal on the front can develop cracks on the decal. These cracks can form around the heads of the buttons under the decal. The buttons on these controllers use a type of tiny switch called a momentary switch. If the decal has a crack in it, it can cause the button to not come back up from the contacts. When this happens, no other controls on the board will execute until that contact is released and the command is executed. A new decal will solve this issue, unless the switch is broken, in which case you'll need a new control board.
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Thermostat Bridged Connection
Quadrafire and Heatilator pellet stoves ONLY run with a thermostat, but many other stoves allow for thermostats to be used. Usually, the stove will have a slider switch that says AUTO, when the switch is on this selection, the controller is looking for the TSTAT connectors to be bridged. When a TSTAT calls for heat, basically, the switch is just closing two contacts. When the TSTAT is not calling for heat, the circuit is open or NOT bridged. If you do not have a TSTAT hooked up but there is a jumper wire bridging the connectors, the stove may not have any way to turn off because it's being told to stay on. Remove the jumper or TSTAT wires and see if the stove powers off.
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Harman Pellet Stoves ESP Sensor
The ESP probe in the exhaust is looking for 95°F to cut power to the stove. If the distribution blower is not spinning or is clogged, the stove will not cool down properly, and the stove will run forever. Likewise, a dirty vent or stove may restrict airflow, causing the stove to run for a very long time as it tries to cool down. Usually, if a pellet stove is using a thermocouple or RTD probe to measure the stove temperature, and it's looking for the lowest heat value to turn off, it’s not going to be a faulty sensor. When these fail, the stove usually shuts off. Lastly, with Harman, the pressure switch has to be in the closed position for the stove to turn off. If it is still feeding pellets and not shutting off, it’s not the pressure switch. If that is open, pellets will not feed.
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Bad Control Board
If all else has failed, and you cannot get the stove to shut down, there may be something wrong with the controller. It doesn’t happen very often, but it does happen. Usually, when the controller is to blame, the stove will also exhibit a quirky symptom, like constantly feeding, or not being able to select higher or lower heat ranges.
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