Thermometers are the only tool for monitoring and controlling a wood stove. Finding the ideal location for a thermometer is a critical part of the heating and safety process of a wood stove. Heating my home with wood for over 40 years with multiple stoves has given me many helpful and practical insights into how wood stoves work and heat a home. This article and my other blog articles will hopefully help people that would like to start saving money with a wood stove or just enjoy the heat that a wood stove provides.
What is the best place for a thermometer on a wood stove? A thermometer needs to be placed where the stove gets the hottest and ideally where the stove changes temperature (up and down) the most. Finding this location on the stove is generally easy but may take a little experimentation. The rest of this article will look at the best way to do this and then how to monitor your wood stove for efficient and safe operation.
The Hot Spot
A wood stove is a simple piece of equipment, so it is not rocket science to find the hot spot. Even in the new wood stoves that have a catalytic converter or some other form of conversion to burn up the particles that pollute the air when burning wood. The science for finding the hot spot is…, heat rises. Pretty simple! Somewhere on the top of the stove will generally be the hottest spot on the stove.
That spot will vary depending on the conversion equipment inside the stove and needs to be verified. There may even be a spot that will stay hot as the fire decreases because the converter is continuing to produce heat. That would not be the best place for the thermometer to be located.
The ideal spot on a stove is where the temperature rises with the increase of temperature of the flames in the firebox or falls with the decrease of the flames in the stove. The key is to find this spot and consistently monitor the same spot on the stove.
How to Find the Hot Spot
Watching one of the round magnetic thermometers stuck to the stove and moving it around on the stove will work. It will take some time but is one way to find the spot. A faster way to find the hot spot is to use a hand held infrared thermometer to locate the best spot as the stove is heating up. As the stove heats up, the thermometer can be aimed quickly from area to area to locate the spot that is heating up quickly, as the fire increases in temperature.
The same can be done as the stove cools. This will take a little longer as a stove cools much slower than it heats up. This would be something you do not want to do with a spring type thermometer. They do not adjust quickly as the stove cools and the readings are not accurate.
Chimney Temperature
Reading the temperature of the chimney is important if you are concerned with chimney fires. The temperature of the chimney typically does not correlate to the temperature of the firebox, especially in a stove with a catalytic system. It will be closer if you have an older stove or a home built stove that does not have a catalytic converter or a newer non-catalytic stove.
A quickly increasing temperature in the chimney is the sign of creosote burning in the chimney. If you have ever experienced a chimney fire, it can be a nerve racking situation, depending on the type of chimney you have. If you monitor the chimney for this reason, it is understandable. But, typical temperature monitoring, on the stove surface, can also detect the possibility of a chimney fire.
A fast increase in the firebox temperature could be an indication of an issue. If the wind increases outside and the fire heats up too fast, this could cause a fire in the chimney. Monitoring the stove temperature accurately and all the time could prevent unwanted overheating of the stove and therefore a burnout in the chimney.
Monitoring a Wood Stove
Once you know the location of the stove that heats and cools as the firebox of the stove changes temperature, a more permanent thermometer should be placed at the location you have chosen. A coil type, magnetic thermometer will display the temperature plus or minus 10 degrees. The other issue of a standard magnetic thermometer (and there is not much difference from the $9 version and the $39 version) is the slow response of the coil. The reading could take as long as three to five minutes to register on the face of the device.
Let me make a suggestion of a new device that will change the way you monitor your stove. Use a constant digital display. There are several versions available depending on how you would like to view the readings. All, however, should use a magnetic thermocouple that is placed on the stove in the location chosen to be the hot spot on the stove. The magnetic thermocouple, which also should be designed to operate to 2400 degrees fahrenheit, is then connected to a digital display which reads out instantaneous readings of the wood stove surface temperature.
The best digital thermometer will not only show the temperature on the digital display, but will also send this information to your smartphone using a WiFi connection. This connection also allows the unit to send alarms if the temperature reaches a pre-set value. This gives you the advantage of knowing when the wood stove reaches a temperature that you determine is too high.
The ability to have high alarms is game changing when it comes to wood stove operation. In the past you would have to be in the same room as the wood stove to know what the temperature was and is. You would always be tied to the room where your wood burner is located and your home to keep the stove burning evenly and make your home safe.
With the introduction of a WiFi enabled temperature sensor, you can be anywhere and know what the temperature of your stove is. You will be notified if the stove is out of temperature range and can act accordingly.
In addition to being notified when the stove is too hot (or tending too hot) you can set a low alarm and know when the stove is too cool. This could happen if the wood you are burning (which may not be a dense enough wood) burns up too fast and the stove needs re-stoking. You may just forget to fill the stove and it runs out of wood. Whatever the reason, the thermometer will alert you.
The Best Wood Stove Thermometers
These thermometers are available at TempSure.net. They have been developed specifically for wood stoves by TempSure.net. The 2400 degree magnetic thermocouple was designed and built only for TempSure.net and tested to survive and work to that temperature.
The Basic digital display is just that. A temperature display only. It uses the same thermocouple but will display an accurate temperature and give an instantaneous digital reading so you can know accurately the temperature of your wood stove.
The TempSure.net is the WiFi version described above that will provide all the features mentioned above and give you the ability to view your stove’s temperature anytime, anywhere.
Wood Heat and Safety
The heat from a wood stove is a comfortable form of heat. The temperature of the stove can be increased to quickly raise the temperature of a room or whole house. Changing the temperature of a wood stove can be a safety issue if the stove is not monitored properly. Few stoves have a thermostat that is just turned up to adjust the room temperature.
On a typical wood burning stove, an air vent that increases air flow to the fire is used to increase the fire temperature. Opening this air vent will increase the temperature quickly but must be monitored to prevent the stove from overheating. Having a thermometer that provides instantaneous temperature feedback is the best way to know if the stove temperature is increasing, decreasing or stabilizing.
A thermometer with a digital display that reads to the tenth of a degree fahrenheit is the best tool to complete this task. This level of monitoring is necessary to fully take control of your wood stove. In the past, the best way to set the temperature was to turn the vent control by X number of turns or adjust the sliding vent cover to mark Y on the scale. That worked fine until the wind picked up by 10-15 mph and increased the temperature by 50 or 150 degrees.
Now with several versions of digital stove thermometers, you can take control of your stove and set the temperature quickly and accurately. The new digital stove thermometers available now are the best innovation for wood stoves since the air tight stove was designed and built. Digital thermometers give you full control of your stove as long as you understand the principles that wood stoves are built from.
The Chemistry of Fire
There must be three elements present for a fire to burn. The three elements are Fuel, in this case wood, Heat, and Oxygen. If you take away one of the elements the fire will go out. Once the fire is started (heat applied), a wood stove is controlled by the amount of air that is introduced into the firebox. More air, hotter fire! Less air, less fire! Again, burning wood is not rocket science, it’s fire science.
Wood stoves have a device that controls the amount of air that is introduced into the firebox. Most have a manual lever, sliding vent, or valve that is used to open or close the air flow. The newer stoves have an automated valve that is controlled by a thermostat. Either way, monitoring the temperature of the firebox will assist in controlling the fire better and keeping your home safer.
The outdoor wind speed has a definite effect on the amount of air drawn into a wood stove. The exhaust of a stove is through a chimney. This chimney must exhaust directly to the outdoors. When the wind speed increases, which is typical of a cold winter day, the effect on a stove can be dramatic. The wind across the chimney will draw more air out of the stove (up the chimney) thus creating a vacuum in the firebox and then drawing more air into the stove. This quickly raises the temperature of the fire.
With a stove that has manual control for air, the effect of increased wind could raise the temperature in minutes. With no automated control of the input air, the stove could burn out of control quickly. With a digital stove thermometer (especially one with a high temperature alarm) this problem could be eliminated before it becomes an issue. The alarm would alert the owner of the need to reduce the air flow to the firebox and thus reduce the temperature of the fire.
Low Temperature
The other end of the scale is a wood stove that has burnt up all its fuel (second part of the fire triangle) and is losing temperature fast due to the lack of fuel. This could happen overnight or after a brief wind event burns up additional fuel (wood) and is out of wood before expected. A low temperature alarm that is sent to a smartphone would save having to restart the stove and having the home reach a much colder temperature than desired.
Keeping the stove at a consistent burning heat is key to keeping a home at a comfortable temperature. If a wood stove swings from too cold to too hot, this makes the output of the stove also swing too high and too low. An inconsistent stove temperature makes the objects in a home, the floors, walls, furniture, etc. also cool and heat. Once these objects have cooled down the requirement for additional heat to warm not only the air but also the objects increases the demand for heat from the stove.
This creates an overworked and inefficient system for heating. Keeping the stove consistent is the key to a comfortable home heating system. A consistent temperature in the wood stove creates a consistent temperature in the home and an efficient home heating system.
The Best Type of Thermometer
A thermometer should have the following characteristics. First it should be digital and read to the tenth of a degree. This assures that a minute change in temperature is noticeable. A tenth of a degree in temperature rise is very obvious when an air vent on a stove is opened or there is an increase in the wind speed.
The second attribute of a quality thermometer is a thermocouple that is capable of at least 1000 degrees Fahrenheit and ideally will work to 2400 degrees Fahrenheit. The thermocouple is the device that is placed in contact with the stove and connects to the digital readout device. The thermocouple detects the temperature, transmits the signal through a cable to the digital readout device where it is displayed.
Ideally this thermocouple is magnetic so it can be placed anywhere on a metal stove. This allows the movement of the thermocouple to find the consistent hot spot on the exterior of the stove.
The need to read up to and survive over 1000 degrees Fahrenheit is critical because a stove can easily and quickly exceed this temperature if a creosote burn out of the stove occurs. This is when the creosote builds up in the firebox or chimney reaches a temperature that ignites the creosote and it flash burns.
This is another time when an immediate notice from a digital thermometer could prevent a chimney or even home fire. Closing the doors or air vents quickly is the best way to squelch the flames and drop the temperature quickly.
The analog, round, metal thermometers that are on almost every wood stove manufactured for the past 50 years will no longer be the standard found on stoves around North America. The new normal will be a digital thermometer that is connected to your smartphone.
Conclusion
Monitoring a wood stove temperature is extremely important for several reasons. Using a digital thermometer is the best option when it comes to accurately monitoring your wood stove.
- The first step when monitoring your wood stove is to find the external spot on the stove that heats and cools as the firebox heats and cools.
- A digital display allows the owner of the stove the ability to quickly and accurately react to the output of the stove.
- The ability to view the temperature from a smartphone and receive alerts is the most important development in wood stove accessories since they started manufacturing them 50 years ago.
- A stove will heat more efficiently when the temperature of the stove is kept consistent.
Additional Questions
Should I draw outside air to feed my wood burning stove? Drawing outside air should make your stove and your home more efficient. Before doing this make sure you check with the manufacturers’ recommendations on installation and maintenance.
Are wood burning stoves safe today? When operated safely a wood stove is as safe as a furnace based on statistics from the fire safety institute.