Last month my water heater suddenly stopped working. I was absolutely clueless as to why this is happening out of nowhere. While it has been working great for years, it just stopped working suddenly. While I was trying to fix things out, I noticed my pilot light wasn’t on and the status code was saying “Thermopile Voltage Low”.
I was quite confused and honestly very annoyed because I just couldn’t figure it out. However, I kept my self calm and tried to found the culprit as to why my thermopile voltage is low?
After doing some research, I understood that thermopile is an essential component of a water heater that keeps the water heater functioning. Without sufficient voltage in thermopile, the pilot light won’t turn on.
In my case, the the thermopile voltage was lower than the expected which made my water heater stopped working. So, I decided to first fix it myself, then call a technician if required. Luckily, I was able to fix the “low voltage” error in my thermopile without needing a technician.
In this post, I am going to walk you through the steps I took to fix low thermopile voltage problem. We will first start with what the thermopile is and how does it work, various causes of low voltage in a thermopile. Lastly, I will tell you my proven fixes that actually solved the problem.
What is thermopile and how does it work?
Very first thing – what is thermopile and how does it work?
Well, to be straight forward – a thermopile is an important component of heating appliances that convert heat into electricity. And when it generates electricity, it gets the power to control the gas flow in the appliances.
This device functions by using several tiny units of thermocouples and once exposed to heat, they connect in a series to generate electricity.
You can easily find these thermocouples placed near a pilot light. When the pilot light burns, it heats the thermopile which then generates enough electricity to keep the gas valve open and keep the appliance working.
When the thermopile voltage is lower than expected, it means not enough heat is converted which causes the appliance to not work properly. When the thermopile senses the change in temperature, it shuts off the gas supply to prevent any leaks or accidents from happening.
What does the “thermopile voltage low” mean?
The status code “Thermopile voltage low” means your thermopile is not creating enough electricity needed to run the appliances, so when the voltage is low, it’s an indication that there’s not enough heat.
A thermopile is made from multiple small units called “thermocouples”, these units are connected in a series, forming a chain, to produce electricity.
These thermocouples then send electricity to the gas control valves to heat up the appliances but if the electricity is not enough, the appliances will not be able to function properly.
Just for an example, in water heaters, if the pilot light goes out, the thermopile will not be able to produce voltage which will make the gas valves close to prevent the gas from leaking.
So for a thermopile to work, it needs enough temperature difference to create electricity for the heater to work.
Cause of low voltage thermopile
Once I figured out the core functionality of a thermopile and the how it works, my next task was to find the various reason as why my thermopile could have a low voltage.
I did some research and I got to know that there could be several reasons for a low thermopile voltage. For example – it could be a wiring problem, dirt accumulation in the thermopile or thermo couple, or it could be a weak pilot flame.
I’m going to list some core reasons that you can use to identify the cause:
Issue With Cold Junction
There are two types of junction – hot junction and cold junction.
A hot junction is a point in the thermopile where the thermocouple connects to the instrument, and it is considered the reference junction for temperature measurement, while the hot junction is exposed to the heat source.
A cold junction plays a very important role in helping thermopile to generate enough electricity. The electricity would only be generated when there is a temperature difference between cold junction and hot junction.
But if there’s no temperature difference between these two junctions, the voltage will be reduced and hence, no electricity would be generated.
Loose Wiring
There are many wires inside the thermopile and if they are damaged or loose, can cause low voltage or malfunction in appliances.
There are three important wiring connected with the thermopile, one is connected to gas control valves, the second is connected to the pilot light assembly, and the third is connected to the control circuit wiring.
The wires that connect the thermopile to the gas control valves maintains the flow of gas into the appliance. If this wiring is loose or damaged, the gas valve will not be able to receive enough voltage, which will then result in the appliance not working or shut down.
The wires that connect the thermopile to the pilot assembly allow the heat from the pilot light to keep working and generate electricity. If this wiring is damaged or loose, then the thermopile won’t be able to generate enough heat, resulting in reduced voltage.
The wire that connects the thermopile to the main control circuit, ensures the appliance is working with safety by sending voltage readings to the control board.
Dirty Thermopile
With time, dirt can easily accumulate on the thermopile. Not to mention, but, this was the case with me as well.
The build of dirt, debris, or soot can cause the thermopile to not function properly. Sometimes there’s a carbon build-up on the outer layer of the thermopile, it happens from burning all the time. This build-up can limit the effectiveness of the thermopile, causing it to not function properly.
When I checked under my water heater, there was surely some dust collected under it. So, I straight away started cleaning my thermopile and it’s internal parts.
After cleaning it, I did see a bit of improvement in the performance of my thermopile. So, you can try cleaning the area around your thermopile first.
Weak Pilot Flame
The weak pilot flame can also be the reason why the thermopile is not working properly and heating up the appliance.
In my case, the pilot light won’t stay turned on, i tried again and again, only for it to go off again after a short time.
Since the thermopile needs heat to generate electricity, if the pilot light doesn’t work properly, the thermopile will not be able to work too.
If the thermopile doesn’t have a proper heat source, it will not be able to work.
So, make sure to check if your pilot light has a clogged orifice or maybe the gas pressure is low. If there’s such an issue with the pilot flame then first try to resolve that, then you can be able to solve the thermopile low voltage problem.
Worn out Thermopile
When was the last time you replaced your thermopile? Well, if it’s been quite long since you can’t remember when it happened, then I guess, it’s time to replace it with a new one.
A thermopile can also wear out over time from overuse. As it degrades its ability to function properly also goes down.
If you have tried cleaning the pilot flame and checking for wire damage, but there’s no change in the production of voltage, then it’s likely because your thermopile is worn out and needs to be changed.
If you notice that your pilot flame is low or goes out frequently, a layer of sooting, and if you notice a strong gas odor then shut the gas supply and ventilate the area, it’s probably a case of worn out thermopile.
How to fix thermopile voltage low?
I remember how frustrated and clueless I was when I didn’t know what was wrong with my water heater but after doing some digging, I finally found the cause and it was none other than low thermopile voltage.
If you are dealing with a similar situation then these fixes can help you save your thermopile.
In this section, I will tell you how I fixed the low thermopile voltage problem and help you out with the same. I will share what exactly I did to deal with this and hopefully what worked for me, will help you out too!
1. Start by cleaning your thermopile
The first thing I did was to cleaning thermopile and the area around it.
In most cases, dirty thermopiles can cause low voltage as the build of dust and debris reduces its efficiency. I used a wire brush to clean the thermopile, you can also use fine sandpaper to clean the soot and debris accumulated on it.
However, don’t use too much pressure or you will end up damaging the surface, just use your soft hand to remove any dirt or grime that may be insulating the thermopile.
This cleaning may get your thermopile back to working normally once the dirt and debris are removed from it. It will be able to absorb the heat properly and restore voltage to normal levels again.
2. Test the thermopile voltage
After I was done cleaning the thermopile, the next thing I did was to measure its voltage. I wanted to check if it was generating enough power or not since my pilot flame was still not fully lit.
Since my pilot flame still not liting up after cleaning, I knew there was still a problem. I grabbed a multimeter and set it in millivolts, then placed it on the thermopile’s terminals to measure it’s voltage.
For the thermopile to work properly, the voltage should be around 500 to 750 millivolts, when the pilot flame is fully on.
To test the thermopile voltage, follow the steps below:
Step 1: Remove the thermocouple cover and set the multimeter to the Volts DC option.
Step 2: Now, disconnect the 2 wires that leads into the control valve.
Step 3: Now, connect these wires with the multimeter and turn on the ignition of thermocouple. Note down the readings.
When I checked, the reading was way below the minimum which is 300 millivolts. If this is the same with you, you should be following my next fixes I did to make things work out.
Overall, if the voltage around thermopile is too low, it’s a clear sign that your thermopile needs more attention or even a replacement.
3. Inspect cold Junction
Another thing I learned while figuring out this problem is to check the cold junction where the thermopile connects to the gas valve.
In some cases, this area can corrode or loosen, which then affects the voltage. I checked and did find a loose connection which was responsible for low low-voltage. I tightened the screw and make sure everything was fine, after that I did notice a slight improvement.
If you are having a cold junction problem, using a standard amplifier can really make a huge difference. This deice helps amplify the voltage difference between the thermocouple junctions and boosts the power that your thermopile produces.
In my case, I used the ammplifier with INA series from the Texas Instruments, and here’s how you can amplify the voltage difference across the junctions:
Wiring: Connect the hot junction positive input of the amplifier(non-inverting input) and cold junction to the negative input of the amplifier(inverting input).
Powering the amplifier: Next, make sure to provide the right amount of power to the amplifier. And, note down the voltage gain.
Getting the right voltage gain: Now, you won’t be able to get the right voltage gain in the first attempt. Instead, you will have to keep adjusting the register to get the right amount of voltage.
For example, my thermopile needed 2000mV to work properly. After inserting the amplifier, I saw 20mV voltage across the thermopile which is obviously low and won’t let my water heater work. So, I calculated the gain voltage and adjusted the resistor to 100. This helped me created the required voltage difference across the junctions.
Now, you can calculate gain using formula:
Gain = Output Volate/Input Voltage, which is in my case was, 2000mV/20mV = 100 Gain.
Also, another thing to keep in mind, is a cold environment, wind, and high moisture area can mess with your thermopile’s junction and affect the voltage.
So make sure to install it in a dry and normal temperature environment.
4. Inspect the pilot flame
Another important thing to check is the pilot flame – which is significant element for generating heat to keep the thermopile working. The first thing I checked was the pilot flame if it was strong and steady, reaching the thermopile properly.
If you notice a weak or flickering pilot flame, there might be a problem with the gas supply, it might be clogged, leading to low-voltage production.
In my case, the pilot flame was a bit small and weak, so I cleaned the pilot assembly and adjusted the gas valve by making sure the gas valve is fully open to the appliance, to ensure a strong and steady blue flame.
Next, I also checked if there is any gas leakage by applying soap solution on the valve. And, there I got the problem. I noticed my gas valve had leakage problem confirmed with the soap solution.
I changed the gas valve with the new one and was just crossing my fingers to work properly. And, thankfully it worked just like before!
5. Inspect thermocouple wire settings
While, I was able to fix my problem by changing the gas valve that connects the thermopile to the appliance, I want to talk about other fixes that could be helpful for my readers.
Sometimes there’s a problem with the wiring which can cause low voltage, so make sure to check the wiring thoroughly between the thermopile and the gas valve.
If there’s damage to the wiring or they are corroded, then replace them and clean if there’s just some dust. I made sure that the wires were tightly connected and secure, which improved the performance.
So make sure to not overlook this step as it can make a big difference.
6. Replace the thermopile (only if necessary)
If all of these steps fail to make any improvement and you’re still getting thermopile voltage low error code then replacing it might be the best option.
While in my case the problem was the leaking gas, however, you could have to replace the thermopile if none of the above mentioned fixes works for you.
To remove the thermopile, just make sure to shut off the gas supply and power. After removing the old one, install the new thermopile, ensuring the connections were secure and connected securely to the control valve.
This was the last resort fix, I tried and luckily the voltage returned to normal and the water heater was working fine without any problem.
Last but not least! Choose the correct thermopile for your appliance, ask which goes best with the water heater or fireplace.
Conclusion
A thermopile is a crucial component in home heating appliances and its function is to convert heat into electricity. If your appliance is not working properly and showing signs of weak pilot flame or the burner keeps turning off, then it might be due to low thermopile voltage.
To fix the low thermopile voltage issue, I first cleaned the dirt and debris on the thermopile as it can act as an insulator and keep it from absorbing the heat.
After that, I tested the voltage with the help of a multimeter, to check the voltage range, it should be between 500mV to 750mV but if it is below 300 then there’s an issue with the thermopile.
I also checked for loose or damaged wiring and made sure all connections were tight and secure. Make sure to check the cold junction and the pilot flame too, as they can also contribute to affecting the voltage.
Lastly, if none of these solutions work, I highly recommend you call a professional electrician for further assistance.
It can be quite frustrating and tiring while dealing with the thermopile low voltage issue. But as I also learned from my experience, with a little patience and some right tools, you can definitely fix this issue yourself!
