A thermocouple is a tiny device found towards the bottom of gas water heaters.It measures temperature.These devices regulate the amount of gas that should pass through them in order for them to function properly.It then makes use of this process to heat up enough hot water to meet the demands of your home.
What is a thermocouple on a gas heater?
The thermocouple on gas fired heating appliances is mounted to sense the presence of a gas flame or gas pilot flame. The other end of the thermocouple's tubing connects to a port on the gas regulator or gas valve.
How to service a thermocouple for a water heater?
The first step for servicing a thermocouple for a water heater is the disconnecting gas control valve. You should turn off the gas control valve on the system and close the shutoff section on the gas source piping of the water heater.
How do thermocouples work?
Working Principles Of Thermocouples When two wires composed of dissimilar metals are joined at both ends and one of the ends is heated, there is a continuous current which flows in the thermoelectric circuit.
How do you replace a thermocouple on a gas-fired furnace?
On a gas-fired furnace you may need to remove first the furnace cover and then a flame shield. Keep any mounting screws for re-use. Remove the old thermocouple at the gas valve by unscrewing its mounting bolt from the gas valve. Typically a thermocouple connects to the bottom of a gas valve using "right-hand" threads.
What does a thermocouple do in a gas heater?
Thermocouples are sensors used to measure temperature. It is a device used inside a gas furnace in Kansas, to assist the pilot light in keeping your furnace running and safe. It works rather like a fail-safe to keep unburned gas from accumulating and burning, exploding or causing another type of health risk.
How does a thermocouple activate the gas valve?
The thermocouple responds to changes in temperature by producing an electrical current that causes the gas valve that supplies the pilot light to open when the temperature is high or to close when there is no direct heat source.
What happens when a thermocouple goes out?
Normally when the thermocouple malfunctions or isn't working, it simply shuts off the gas to your heater. This is important, particularly if the pilot light is out, because it prevents harmful gas from leaking into your home.
How do you test a thermocouple on a gas heater?
0:373:10How to test a thermocouple with meter - YouTubeYouTubeStart of suggested clipEnd of suggested clipIt should study out at zero. You're going to take the common ground the black lead hook it to theMoreIt should study out at zero. You're going to take the common ground the black lead hook it to the copper of the thermocoupler.
How do I know if my thermocouple is bad?
After about a minute, when you're sure the probe has gotten hot, place one lead on the shaft of the thermocouple and the other lead on the connector. If the reading is less than 25 millivolts, the thermocouple is bad and needs to be replaced.
Can I bypass a thermocouple?
Realistically, you have just disabled the thermocouple, but you can also reach in and unclip it from its holding bracket where it meets the pilot light. In most cases it will be held on with a gravity clip, but some are held on with a screw that must be removed with a small screwdriver.
How often should thermocouple be replaced?
Thermocouples can last up to 10 years if properly installed and maintained, while furnaces can last 15-20 years, although either may wear out sooner in multifamily units.
Can thermocouples be cleaned?
Yes, you can clean a thermocouple, but the task must be done with a light touch. Remove the thermocouple from the process assembly, using a steel wool or emery cloth, lightly clean the tip removing any build up. Cleaning a thermocouple is not a fix for an issue, such as inaccurate readings.
Can you replace a thermocouple yourself?
It's easy to replace and a new one costs $5 to $10. Rather than trying to unfasten the thermocouple inside the water heater's burning chamber, it's easier to remove the whole burner and thermocouple assembly.
What causes a thermocouple to fail?
After enough time, metal fatigue can cause a thermocouple to break. Thermocouples that are regularly exposed to extreme heat stress or extreme conditions are more likely to go through metal fatigue. If thermocouples start to give out unusual readings, it may be suffering from metal fatigue.
Should thermocouple be in pilot flame?
The pilot flame should touch the thermocouple at a specific level. If the flame is blue and weak, and barely reaches the thermocouple, it needs to be stronger. If it extends well above the thermocouple, it's too strong.
How many millivolts should a thermocouple put out?
25 to 35 millivoltsThe normal millivolt output is 25 to 35 millivolts; on some, you may even get up to 35. The other part of this safety pilot system is the electromagnet (power unit). It is if you will the LOAD and we can say the thermocouple is the SOURCE.
Does gas go through a thermocouple?
Because the thermocouple shuts off the gas supply when it doesn't sense a flame, it prevents your furnace from receiving any gas when the pilot light is out.
How does the gas valve work?
The furnace gas valve operates by electromagnets. The primary valve -- also known as the safety valve -- supplies gas to the pilot light. The second valve -- also known as the main valve -- allows gas to flow to the burner trays. The thermocouple (or thermopile) generates the power holds the safety valve open.
How does a thermocouple safety valve work?
0:311:42How Does a Thermocouple Work in a Water Heater? | Repair and ReplaceYouTubeStart of suggested clipEnd of suggested clipBut enough to power the gas valve. The thermocouple also acts as a safety switch if the pilot lightMoreBut enough to power the gas valve. The thermocouple also acts as a safety switch if the pilot light goes out then the thermocouple will cool down the voltage will drop and the gas valve will shut off
How does a gas valve work without electricity?
Without millivolts of electricity being generated, the gas valve cannot open and will remain in the closed position. A pilot light has two primary functions. One is to generate millivolts in order to open and close the gas valve.
How does a thermocouple work?
It is made of nickel and copper and when heat is applied to it, it produces a very small voltage. These two dissimilar metals create a tiny voltage when they are heated.
What happens when the temperature inside the heat exchanger reaches a certain set point?
When the temperature inside the exchanger reaches a certain set point, contacts open and the blower disengages stopping all airflow until the next call for heat the furnace sequence of operation begins anew.
What is a blower motor?
The blower motor introduces warm air throughout the ductwork and the dwelling. The thermostat satisfies as the heat reaches the setpoint. The main valve closes and the main burners cease burner with the lack of gas. The blower continues to run to dissipate the heat.
What happens if the pilot valve is closed?
If the pilot valve is closed then gas will not be provided to the burners on a call for heat. The pilot valve will remain open as long as there is a pilot flame and the thermocouple/thermophile is in good working order.
What is a pilot gas valve made of?
It is made of nickel and copper and when heat is applied to it, it produces a very small voltage. These two dissimilar metals create a tiny voltage when they are heated. In a standing pilot gas system, the gas valve utilizes the pilot valve.
When the heat in the heat exchanger reaches a designated set point, the fan limit control closes a?
When the heat in the heat exchanger reaches a designated set point, the fan limit control closes a switch that engages the blower motor.
What is a flame proof system?
It is a basic and time-tested system that provides a reliable way of proving a flame. It employs a thermocouple (some systems can use a thermophile which is a lot of thermocouples embedded in one piece) and a gas valve that has two separate valves inside of it.
What is the time constant of a thermocouple?
A time constant has been defined as the time required by a sensor to reach 63.2% of a step change in temperature under a specified set of conditions. Five time constants are required for the sensor to approach 100% of the step change value. An exposed junction thermocouple offers the fastest response. Also, the smaller the probe sheath diameter, the faster the response, but the maximum temperature may be lower. Be aware, however, that sometimes the probe sheath cannot withstand the full temperature range of the thermocouple type. Learn more about thermocouple response times.
What is the difference: thermocouples, RTDs, thermistors and infrared devices?
In addition, Thermocouples generally can measure temperatures over wide temperature ranges, inexpensively, and are very rugged, but they are not as accurate or stable as RTD’s and thermistors. RTD’s are stable and have a fairly wide temperature range, but are not as rugged and inexpensive as thermocouples. Since they require the use of electric current to make measurements, RTD’s are subject to inaccuracies from self-heating. Thermistors tend to be more accurate than RTD’s or thermo couples, but they have a much more limited temperature range. They are also subject to selfheating. Infrared Sensors can be used to measure temperatures higher than any of the other devices and do so without direct contact with the surfaces being measured. However, they are generally not as accurate and are sensitive to surface radiation efficiency (or more precisely, surface emissivity). Using fiber optic cables, they can measure surfaces that are not within a direct line of sight.
What happens when two wires are joined at both ends?
When two wires composed of dissimilar metals are joined at both ends and one of the ends is heated , there is a continuous current which flows in the thermoelectric circuit. If this circuit is broken at the center, the net open circuit voltage (the Seebeck voltage) is a function of the junction temperature and the composition of the two metals. Which means that when the junction of the two metals is heated, or cooled, a voltage is produced that can be correlated back to the temperature.
What is an infrared sensor?
Infrared Sensors can be used to measure temperatures higher than any of the other devices and do so without direct contact with the surfaces being measured. However, they are generally not as accurate and are sensitive to surface radiation efficiency (or more precisely, surface emissivity).
Is a RTD a thermocouple?
RTD’s are stable and have a fairly wide temperature range, but are not as rugged and inexpensive as thermocouples. Since they require the use of electric current to make measurements, RTD’s are subject to inaccuracies from self-heating.
Where are Thermocouples Used on Heating Equipment?
Thermocouples are used as safety devices that will shut off equipment by shutting down the LP or natural gas fuel supply on some gas-fired heating equipment such as gas fired furnaces, gas fired heating boilers, and gas fired water heaters.
Why do you have to replace a thermocouple?
It would be unusual to get a batch of bad thermocouples such that you have to keep replacing them because of an inherent defect in the thermocouple itself. Not unless they were all made by the same company in the same batch.
What is a thermopile?
A thermopile looks like a thermocouple, and does a similar job - sensing temperature, such as a gas flame to function as a safety device. But thermopiles sense temperature without having to contact the object being monitored. Watch out: thermopiles and thermocouples are not interchangeable.
Why won't my gas burner light?
Common causes for the refusal of a gas burner to light when the pilot is on include a bad gas valve or most likely a defective thermocouple or thermocouple connection.
What size wrench to use for thermocouple sensor?
The wrench size is typically 7/16". Pull down gently to pull the thermocouple's end out of the mounting well on the gas valve. Remove the other end of old thermocouple sensor at its mount at the burner or pilot flame. Typically there is a clip that holds the thermocouple to the pilot flame tube.
What is the device that responds to temperature change by a change in voltage output?
A thermocouple is an electrical device that responds to temperature change by a change in voltage output.
What do the red arrows on a Holland furnace mean?
Photo at left: red arrows indicate the thermocouple tubing and assembly; blue arrows indicate the pilot light tubing & assembly on a horribly rusted Holland brand gas furnace.
Why do water heaters use thermocouples?
The thermocouple for the water heater operates as a safety instrument to identify the burning condition for gas-powered systems. This means that if the thermocouple works improperly, there is no solution for identifying if the pilot is burning or not, and you will not have hot water resources in your pumping circuit. You can try to relight the system if you want to test the thermocouple’s problem.
When the new thermocouple is set up for both electronic model and standing pilot styles of water heaters, should the?
When the new thermocouple is set up for both electronic model and standing pilot styles of water heaters, the burner, pilot, and thermocouple should be reconnected to the gas control valve.
How to Check if You Have a Dirty Thermocouple for Water Heater?
It cannot also give correct outputs. It will sometimes cut the gas link to the furnace when the pilot light is operating. In this condition, the soot has covered the thermocouple.
What tube must be reconnected to the gas control section?
The pilot source tube, burner tube, and thermocouple must be reconnected properly to the gas control section.
What type of ignition is used in a water heater?
The kind of ignition style you have in your thermocouple for a water heater will specify how you fix it. With both a standing pilot or electronic type, the thermocouple is a part of the burner setup. However, with a standing style, there is only a pilot and thermocouple combined with the burner, while with an electronic model, there is both the thermocouple and pilot and the electronic igniter combined with them.
What happens if you remove the manifold assembly from the burner source?
If you remove the manifold assembly from the burner source accurately, the internal components will not be damaged. If the burner does not remove simply, check around the main surface because there may be extra connections.
How much does it cost to replace a thermocouple?
When your thermocouple doesn’t operate properly, you should replace it by employing a professional plumber to apply it with a total cost of about $200.
How do thermocouples work?
Thermocouples work based on the thermoelectric effect. This process involves thermal energy being converted to electrical energy. As two different metal wire conductors are connected, a voltage occurs which varies with temperature changes. As a change in temperature is detected at the measuring point, a voltage is created (variation is electron density of each metal). The voltage is then measured and calculated as temperature.
How to remove a thermocouple from a heater?
The thermocouple can also collect dirt and bugs. Remove the flame screen from the heater and remove the thermocouple by unscrewing the bolts.
How to connect a thermocouple to a tilt switch?
Connect the other end to the gas valve. Use an 8mm wrench to tighten this connection. Run the thermocouple and wires back through the box housing.
What happens if the thermocouple is not getting heat?
If the thermocouple is not getting any heat, the pilot light for your heater will not stay lit. There are ways to bypass if this need be until you can get the thermocouple replaced.
Why is my patio heater not working?
You bought the patio heater to keep you nice and toasty when you are sitting outside. But it is no good if it is not working. Bad weather as well as wear and tear can be the reasons the heater is not working.
How to loosen a thermocouple?
Unscrew the box housing at the back of the thermocouple and slide it back. Loosen the nut that holds the thermocouple in place with a pair of pliers. Then you can pull the wire connectors loose with your hand.
How to put a thermocouple back in?
Essentially putting it back in the reverse way as the old thermocouple was removed. Insert it through the hole at the front, reconnect the housing, and tighten the bolt around the new thermocouple.
How much current does a thermopile have?
Thermopile with 750mV output and ~3ohm resistance would make 250mA short-circuit current or 125mA @ 375mV @3ohm load so you have about 45mW max available for the valve. Suprisingly little for electromechanical valve!
How many millivolts does a thermopile generate?
A thermopile is a bunch of series connected thermocouples that generates maybe 800 millivolts and this is also in the pilot flame. The thermopile controls another valve that is in series with a switch type thermostat to turn the main burner on and off to control the temperature output of the device.
How does a washer water valve work?
The main valve is actuated by the pressure of the fluid itself and the electric signal controls a very small pilot valve. Water valves for washers work on the same principle. Thermocouples might give some voltage in open circuit but that falls when in-circuit. I see them more as current sources than voltage sources.
How to open a valve?
You open the valve by pushing with your finger. Then the solenoid only has to hold the valve open.
What is the open circuit voltage of a thermostat?
The open circuit voltage is 750 mV across this thermostat.
Is a thermocouple a solenoid?
It seems the thermocouple is more likely a thermopile and the current it generates operates a solenoid coil.
Can a thermocouple control a thermostat?
I have never seen a thermocouple singlehandedly control a thermostat. Thermostats either were bimetallic or have electronics.
