Wood stoves are an excellent source of heat in a home or garage and can radiate a dry warmth in a large area if needed. The primary means of regulating a manually operated wood stove is watching a thermometer attached directly to the surface of the stove or chimney pipe. I have heated my home for over 40 years with a wood stove and understand the details of how a stove works. Creating a comfortable atmosphere in a living or working space is the goal of everyone that owns and operates a wood burner.
How do you choose a thermometer to monitor your wood stove? A thermometer should be accurate, have a fast response when the stove temperature changes, transmit a signal to you wherever you are and be capable of alerting you when the stove deviates from high and low temperature settings. All four of these requirements should be met when choosing a thermometer for a wood stove. The remainder of this article will explain why each of these requirements are critical to the safe and efficient use and operation of a wood stove.
A thermometer placed correctly and monitored can make all the difference between a “comfortable” atmosphere or a family room that is closer to the arctic tundra. That is a pretty wide range of outcomes for a home but those of you who have come home to a burnt out wood stove in January know exactly what I am describing. Warming up a cold house from 36 degrees F to 70 degrees F with a 20 MPH wind wailing outside can take 12 to 24 hours depending on the size of the house and type of stove you use.
Let’s look at each of the four requirements for a stove thermometer one at a time to gain a better understanding of how each is important.
Why is an Accurate Thermometer Important?
I used (just like most of you) a magnetic thermometer stuck to the top of my stove for over 30 years. It was all we had as the wood burning public and gave a picture of how hot the stove was when I was within 10 feet of the stove “looking at it”. The magnetic spring steel thermometer would display “350” give or take 10 degrees F and I knew it was fine. At that moment in time.
Plus or minus 10 degrees F is not accurate. It is a ballpark reading but we put up with that since it was the only option there was. It was fairly consistent since the same thermometer was used year after year in the same spot on the stove. We all knew by watching the little white arrow approximately what the temperature was on the stove.
Then, many of us found a handheld infrared digital thermometer at Sears that gave us a quick but very accurate reading. We would point and pull the trigger until we found the hottest (and coldest) spot on our stove. It was a great tool (and kind of fun) but still only worked when we were in the room and pulling the trigger.
The “accuracy” became very helpful. An exact plus or minus 1 degree F could be determined on a wood stove. This was great to know but was not really helpful unless you could stand next to the stove and pull the trigger all the time. The next item ties into the first item as a must have requirement for a wood stove thermometer.
Fast Response Time, Critical in a Stove Monitor
The fast response of a wood stove thermometer is critical because of the changing dynamics involved in wood stove heat. When something changes, the stove needs to be adjusted either by an automated system or by a manual correction to the stove to compensate. What can change on a wood stove? Air flow that feeds the fire or the fuel which is the wood.
A change in one of these two inputs to the wood stove will quickly alter the temperature output of the stove. To clarify this I will spend a few minutes describing the basic operation of a wood stove and just how a fire burns.
How Fire Burns
Fire is based on a triangle of three items. Fuel, heat and oxygen. A fire needs all three to burn. Take away any one of these and the fire goes out. Add one or more and the fire burns hotter.
Wood stoves that became popular in the 1980’s were called “Air Tight” because unlike an open fireplace, the firebox was encased in a steel box. That “box” was and is the fire box where the wood actually burns. The doors of the stove are designed and constructed to seal when closed and reduce the air through those seals. The air is introduced through a very controlled “valve”. This valve is adjusted to control the amount of air allowed into the fire. Opening the valve increases the fire and makes the stove hotter. Closing the valve reduces the air into the fire and cools the stove.
Other factors have a huge effect on the fire temperature and the time it takes to burn the wood in the fire box. This includes the type of wood used to stoke the fire, the dryness of the wood or “cure” of the wood, and the wind speed and direction. Those factors are discussed in length in other articles I have written.
Wind speed can change the temperature of a wood stove faster than any other factor especially since you have no control of the wind. When the wind increases, (as it can quickly in a North American winter) the air flow over a chimney will draw more air through a stove. Even with an “air tight” stove, the chimney must be open to allow the smoke to exhaust out of the stove. This allows for air to be drawn out of the stove which will happen when the wind speed increases.
If your stove is manually operated, you need to be aware of these outside factors that can affect the operation and temperature of your stove. This is when a fast response to change in temperature along with accurate temperature reading will allow you to operate your stove more efficiently.
When the wind increases, the air introduced to the fire increases almost instantly. This in turn increases the burn in the firebox and will turn up the output of the stove. A 10 MPH increase in wind can increase the stove output by 50-100 degrees F in a matter of minutes. As a homeowner and wood stove user, this change can make a significant increase in heat inside the house. This also means that the wood supply inside the stove will be depleted faster meaning a shorter time before re-stoking the stove.
The same can happen in reverse. A strong wind can diminish and the draw on the stove decreases. This will lower the temperature in the firebox and decrease the output of the stove. Cooling happens slower as a stove will hold its heat and cool much slower than when it heats up.
How a Fast Response Thermometer Will Help?
Having a monitor on your wood stove will provide the information you need when changes occur. A 5 degree F increase in temperature over a 5 minute period is a significant change. An accurate thermometer that detects these changes will allow stove owners to adapt to the changes and make the appropriate adjustment to a manual stove.
The key to effective and efficient heat is consistency. A wood stove should be kept at a consistent temperature to maintain an even heat in a home. Being able to monitor and adjust to external changes are crucial to operating a wood stove efficiently.
Monitoring a Wood Stove from Anywhere
Most of us do not want to or cannot be at home 24/7 to “watch” the wood stove burn. That is about as exciting as watching paint dry or grass grow. In reality, a wood stove is a heat source like any furnace with one difference. We need to feed the fire and adjust the airflow.
I was always just a little concerned when I would fill the stove in the morning and leave for work. 9 to 10 hours without knowing what the stove was doing…
Then I built my first WiFi enabled temperature monitor. It was revolutionary. I could know the temperature of my stove all day wherever I was. At work, at Home Depot, at church, at the grocery store or even just out in the yard or while working in the garage. I could view the temperature anytime/anywhere on that wonderful device, my smartphone.
That first device allowed me to view the temperature no matter where I was and that was a huge relief. The freedom it provided was revolutionary. I could tell when the wind picked up or slowed down. I knew if I was running low on wood in the firebox even when I was out to dinner. This was great but there was one more feature that was needed to automate the simplicity of a perfect wood stove monitor.
High and Low Temperature Alerts
No one wants to look at their smartphone constantly (except to watch cat videos), especially to monitor the temperature of a wood stove. As mentioned earlier, a wood stove is a heat source meant to replace a furnace. We never monitored our furnaces except with a smart thermostat to view the temperature or turn it up or down while we are gone.
What a wood stove monitor needs to be complete is temperature alerts when the stove becomes too hot or when it is too cool. The monitor should send an alert to my smartphone when the threshold is crossed for a temperature that is too high or if the temperature drops below a preset level.
Now I do not have to interrupt my Boneheaded boater of the week YouTube video to know that my wood stove is maintaining a constant temperature. The monitor I use will notify me if my stove becomes too hot or too cool. This makes the operation of my wood stove easier and less stressful.
High temperature alerts can alleviate several situations that occur with a manually operated wood stove. First, they can warn you of a change in wind event that was mentioned earlier in this article. Depending on the temperature window you set on your stove, a fast increase in temperature can be detected and allow you to reduce the air input and bring the temperature down to within range.
Described here is another safety issue that many wood stove owners have had occur after refueling. You leave the door or air vent open to quickly bring the stove up to temperature. After walking away you are distracted by another project and forget that the door is open. The good news is, instead of finding a roaring fire and black smoke billowing out of the chimney, a text message that the stove is too hot alerts you to the impending danger.
On the other end of the spectrum, a low temperature alert can warn of the lack of fuel in a stove. A common mistake is just forgetting to fill the stove when it is time. It could be that the wood used is too dry and burns faster than expected. It could also be that the stove was burning a little hotter than normal but did not set off an alert and used up the fuel faster than expected. Whatever the reason, a stove that is burning too low either needs fuel or requires the air to be opened to increase the heat. A low temperature alarm will alert you to all of these issues.
Where Do I Get One of These?
I searched for years for a wood stove thermometer that had all of these features. There was no such thing available. The only option was to assemble one myself. I did just that and in 2017, TempSure.net was started. To this day it is still the only wood stove monitor that has all of the features mentioned above and more.
Not only can the TempSure monitor measure temperature to a tenth of a degree, it will instantly display the current temperature of any wood stove. It also transmits the temperature by WiFi to a local access point or wireless router. This information is then sent via the internet to an App installed on any smartphone. The free App (Apple iPhone or Android) allows any user to view the temperature on the monitor and set high and low alerts on your phone.
Additionally, the data is stored and can be displayed on a graph showing the temperature of a stove over time. This data can aid in the operation and maintenance of a wood burning stove.
All the settings that can be monitored can also be updated and revised from a smartphone. This makes viewing and updating information easy and convenient.
All events are also recorded and stored such as lost WiFi, change in settings, alarm status and battery status. Any of these alerts can be sent as an email or just viewed in the event log if you do not want alerts sent. This gives a clear picture of what has happened at the monitor and when it happens.
As far as battery life, in typical transmit mode, the batteries will last 2 months between charges. For those that prefer the fastest transmit time (transmissions from the monitor to the local WiFi), the battery will last about 30 days. If you prefer to never have to charge the monitor, it can be connected to power with the included USB cable permanently.
How Long Will it Last?
A good question. The monitor is designed to operate 24/7/365 in a commercial environment. The TempSure WiFi monitor kit with the magnetic sensor (thermocouple) is designed and built to last as long as your wood stove. It is rugged, accurate and built to last.
Conclusion
The four features that a wood stove thermometer should have are: accurate readings, a fast response time for readings, have the ability to transmit a signal to you wherever you are and be capable of alerting you when the stove deviates from high and low temperature settings.
At this time there is only one wood stove temperature sensor system available and it is the TempSure system available at TempSure.net.
Additional Related Articles
If you are looking for a wood stove and not sure which one is for you, check out this article.
The 25 Best Wood Burning Stoves. It describes the features and pitfalls of 25 of the best stoves on the market today.
As mentioned above, here is the article on What are the Best Types of Wood to Burn? Wood types and other information on burning wood are included.
Another question you may be interested in is Can I Operate a Wood Burning Stove More Efficiently? There are many ways to improve your efficiency that are explained in the article including:
- Type of stove you use.
- Fuel.
- Type of wood.
- Preparing your wood (Drying properly).
- The actual operation of the stove.