Categories
Maintenance Thermostat

How to test electric water heater thermostat with digital multimeter

Disclaimer: This post contains affiliate links for which I earn a commission.

Note: Before starting, click here to open a new tab in Amazon to search for any tools or equipment that you might need.

A faulty water heater thermostat is an inconvenience to you, your family, or your business. Although there are different types of failures, a malfunctioning electrical system is a common problem. The point of failure may vary and could be faulty wiring or loose connections, a bad heating element, or a water heater thermostat.

A failure in the thermostat, heating element, or both could lead to completely cold water. Or partly warm water that does not reach the set temperature.

If your water heater stops providing you with hot water according to your settings and requirements, you can test the element and thermostat to ensure they are functioning properly. 

Thermostat role in water heaters

The main work of a thermostat in a heater is to regulate and maintain the water temperature, hence ensure safety and optimize energy use. When it starts malfunctioning, it cannot control the water temperature to suit your requirements. 

In practice, the thermostat controls the heating elements to maintain the water at the set temperature. When the water is cold, the thermostat automatically powers the elements to heat the water to the desired temperature. Upon reaching the set temperature, the thermostat shuts off the element, until the water gets colder again. As such, its work is to ensure the water temperature remains constant at a certain set level. Consequently, it reduces the risks of heating the water to very high and unnecessary temperatures, hence reducing the energy use without compromising comfort.

water heater thermostat

Types of water heater thermostat failures and impact

A faulty thermostat may not provide any control, or may only function partially and could result in your water not reaching the usual hotness levels.

Potential faults include;

  • A completely open thermostat that does not power the element at all.
  • A partial open thermostat – heats the water partially such that the temperature does not reach the desired level.
  • A short circuit- In this case, the thermostat does not provide any control and will continuously heat the water. Most often, a shorted thermostat results in the tripping of the heater reset button or high limit switch. 

Most standard water heaters have two thermostats, an upper one and a lower one. If one of these fails, it impacts the water heating process differently. For example, when the upper thermostat goes bad, you will notice that cold water will run out of the heater when you turn on the hot water tap. On the other hand, with a faulty lower thermostat, the water is initially hot, but it becomes cold after some time.

How to test the thermostat with a digital multimeter

Once you suspect that a thermostat is faulty, it is best practice to test and confirm that it requires a replacement.

Before testing the thermostat, confirm that the heating element is in working condition. Otherwise, an open-circuited heating element or one with a short circuit to the ground will result in some misleading measurements.

Please check here on how to test a heating element with a multimeter.

Unless physically broken, the common problems with the thermostats are due to failure in electrical continuity, which usually gets faulty due to wear and tear, unstable or poor quality power, etc. To identify the problem, you can use an analog or digital multimeter to test for continuity. 

Tools for testing water heater thermostat

Although the tools may vary according to the model, below is the list of the items you require.

  • A flat screwdriver 
  • Philips screwdriver
  • Nut driver 
  • Digital multimeter
  • Non-contact voltage tester
  • Basic technical skills

Let us now look at the steps you need to test the thermostat with a multimeter.

Step 1: Disconnect electrical supply to the heater

For safety reasons and accurate measurements, disconnect the power from the electrical panel. You can do this by turning off the breaker. To confirm that there is no power; use a meter or non-contact voltage tester at the terminals

Step 2: Remove the water heater’s access panels

Use a flat screwdriver or nut driver to remove the lower and upper thermostat access covers. Roll the insulation that covers the thermostat back and also remove the internal plastic covers. You can tape the insulating material in a place and put it out of the way as you work on the thermostat.

Step 3: Confirm that there is no power to the water heater

To avoid short circuits or electric shocks, ensure that the electrical supply is off. You can use a digital meter to measure the voltage across the thermostat terminals, which should give zero volts if off. Alternatively, use a non-contact voltage tester to confirm. 

Step 4: Confirm Reset button has not tripped

The reset button may trip when there is a problem with eth thermostat. For example, it may trip the reset switch if the thermostat has short-circuited contacts or out of calibration. Also, the reset button may trip due to a faulty heating element. 

Step 5: Disconnect the thermostat wiring

Before removing the cables, draw the wiring diagram to avoid making mistakes when reconnecting. Alternatively, take a picture using a camera or even a mobile phone. 

To physically remove the wires, use the Phillips #2 screwdriver to loosen the screw and pull each cable out. Repeat this for each of the terminals.

Step 6: Check the thermostat continuity with a digital meter

Set the digital multimeter to the lowest resistance range. Most meters have a typical low range of 200ohms and may include a tone.

Place one of the meter probes on the screw terminal on the left side of the thermostat. Place the second probe on the other terminal, still on the left side. The digital meter should display a low resistance reading, hence confirming continuity. If the meter reading is very high or open, the thermostat is faulty and will require a replacement. 

Testing water heater thermostat

Repeat the test on the terminals on the right side and also for the other thermostat.

If the thermostats are functional and the water heater still does not function properly, test the wiring and heating elements. 

Please see our guide on how to test a heating element with a digital meter.

Conclusion

An electric water heater uses a thermostat to maintain the water temperature at the desired level. A failure in the thermostat makes it hard to control the heating elements and the water temperature. 

Most often, the water does not get hot as per the set temperature. Fortunately, you can test a thermostat with only a few tools and basic skills. However, you need to be careful and ensure that you have disconnected the electrical power before checking the thermostat for continuity. Once you identify a faulty device, remove and replace it with a similar model.

Categories
Bath Maintenance Tankless Water Heaters

Can I Install a Water Heater Myself?

Disclaimer: This post contains affiliate links for which I earn a commission.

Note: Before starting, click here to open a new tab in Amazon to search for any tools or equipment that you might need.

Today, there are many offline and online tutorials and videos that provide step-by-step guides on how to install water heaters. While the information makes it look like it is easy to do the installation, it might not be a good idea to do it yourself, especially if you have never done it before. 

Most often, the tutorials will give you step-by-step instructions based on an ideal situation. However, your environment and skills are also vital and will determine how you do the work. Moreover, it is not just the physical placement; there are various issues such as the electrical system, gas piping system, venting, access, and other factors that determine performance, reliability, and safety. 

Ideally, it is advisable to seek professional help, especially if you do not have the necessary technical skills. However, if you have these, you can do the installation as long as you ensure that you adhere to all the codes, regulations, and safety precautions. 

Generally, the installation process of a hot water system is a multi-disciplinary exercise that requires knowledge in plumbing, electrical, safety, and others. Additionally, in some countries, you need to comply with relevant codes and obtain permits to perform the work. That said, while you can install the small point-of-use tankless water heaters and especially the plug-in types, you need to consider engaging a professional installer when you have large multi-user water heaters.

Risks of installing a water heater incorrectly

While proper installation and regular maintenance ensure safe and reliable operations, the system will fail when it reaches its end of service life. However, a wrong installation is risky and more dangerous than a normal failure.

Hot water systems are dangerous

Usually, problems with the electrical or gas systems are dangerous and can lead to short circuits, explosions, fires, and other situations. If you are replacing an older system, you need to safely remove it and prepare the space for the new water heater. The heaters use an energy source. This could be gas, electricity, or both, and you must ensure the safe and reliable infrastructure to safely deliver these to the heater system. Incorrect wiring could cause electric shocks or fires. Also, if your heater is propane or natural gas-powered, you need proper piping and connections, otherwise, a minor leak from poor installation may lead to fire risks and explosions. 

Also, failure to install the water heater properly could lead to pressure build-up and tank explosion. 

Voiding warranty

Most manufacturers and even insurance policies will only honor claims for systems installed according to set requirements. In most cases, they require a professional and licensed plumber or installer. Failure to do this will void the warranty or insurance cover.

Time factor

Even when you have technical skills in other fields, installing some water heater models is quite involving and may take you longer than what you save by avoiding a professional. 

Generally, installing your water heater improperly and failing to comply with relevant plumbing, building, and electrical codes could expose yourself and your family to financial, safety, and legal risks. For the above and other reasons, you may need to think twice about installing a water heater by yourself. While you will save some money, the benefits may not warrant taking the risk.

To determine if you can install your water heater by yourself, below is a typical guide on how to perform the replacement or a new installation of an electric-powered model.

How to install a water heater 

If you decide to install the water heater, below are some of the basic steps. Please note that these may vary from one type and model of a water heater to another. Other factors that affect the installation procedure include the type of fuel, whether gas or electric, tank or tankless, capacity, outdoor or indoor, and other issues. While you can install some small models such as the point of use (POUs) and other low-demand models, the procedures may be complex for larger models.

Tools to install a water heater

Below is a list of tools to do the installation.

  • A set of screwdrivers
  • Wrench
  • Flexible hoses
  • Pipe cutter
  • Plumbers tape
  • Voltage detector
  • Soldering iron or torch
  • Solder wire
  • Solder flux
  • Sandpaper cloth, dielectric connectors, etc. (optional)

Step by step instructions on how to install an electric water heater

In our guide, we are assuming that you are replacing a defective system. You will, therefore, first remove the old one and then install the new heater.

Switch off the electrical supply to the water heater

Before working on the water heater, disconnect the power at the panel. Ideally, switch off the water heater’s circuit breaker. Use a voltage detector to ensure that the wires at the heater do not have any power. 

electric circuit breaker

Empty the tank 

If you are replacing a storage-based water heater, empty the tank by

  • Open one of the hot water outlets and letting the water run until it is cold.
  • Afterward, turn off the water heater cold water supply.
  • Use the drain valve to remove all the water from the tank. You may use a hosepipe to pour the water outside or into a sink.
  • To drain the tank faster and allow air to move in, open the hot water faucet and the T&P valve.

Physically disconnect the electrical wires

To avoid confusion, sketch the wiring diagram before removing the wires. If possible, take a photo of the wiring before disconnecting. 

Remove the electrical wires supplying the water heater. Before touching the cables, confirm again that the circuit breaker is off and that they are not carrying any current. As you remove each wire, ensure that you label or mark them appropriately.

Detach the water pipes 

Remove both the water input and output pipes. If the pipe is damaged, you may cut the pipe, but leave as much of the good part as possible. However, if the pipe is still in a good position, you can use it with the new unit, and you need to remove it carefully.

Replace the water heater

Remove the old empty water heater and move it out of the way.

Place the new heater and align it well so that electrical and plumbing connections will fit properly

Prepare the pipes

You need to prepare the old pipes by thoroughly cleaning them with sandpaper. Clean the ends that will connect to the new heater until they are shiny and free of rust and other debris.

Connect the electrical wires

Use the wiring diagram provided by the manufacturer to connect the electrical wires. Ensure that you have grounded the tank by connecting the green wire appropriately. Once done, cover the junction box securely.

install a water heater

Attach the water supply lines

  • With the unit aligned correctly, attach the cold and hot water pipes in their respective positions. 
  • If not already in place, a good practice is to use flexible hoses to attach the heater inlet and outlet and the cold and hot water copper pipes, respectively. The flexibility enhances safety and especially in case of an earthquake. When making connections use the plumber’s tape to line the threads and ensure tight bonding.
  • Open the nearest hot water faucet and turn on the cold water supply to the water heater.
  • Check for leakages, and if none, continue and fill the tank with water. 

Connect the temperature and pressure discharge pipe

  • Use the appropriate fitting to attach the discharge pipe to the T&P valve.
  • Ensure that the pipes’ ends and fittings are clean before attaching them.
  • You may use the solder to make the connections. 

Reconnect the electrical power supply 

Once you fill the tank with cold water, switch on the circuit breaker at the service. If all is well and the connections are correct, the power should reach the water heater. If there is no electrical power on the water heater, turn off the breaker before checking the wiring.

NB: Do not apply the power when the tank does not have enough water since this will cause the heating elements to dry fire and burn if not fully submerged. 

Supply all the hot water lines

Open each hot water outlet and let the water run for some time until it stops sputtering. Doing this removes the air from the tank and pipes.

Set the temperature at about 120 degrees Fahrenheit let the water heat for some time. The process may take a few hours to heat and reach the set temperature. While in the process, monitor the discharge pipe. If it starts dripping, know that the pressure could be too high and make the necessary adjustments.

While this guide assumes that you are replacing an old water heater, it is also applicable if you have a new unit. If installing the new system, skip the first five steps and start at step 6.

Common mistakes to avoid when installing a water heater

While the installation may vary depending on the type of water heater, energy source, environment, and other factors, there are some common mistakes that you should avoid. These include;

Incorrect water heater sizing

It is vital to ensure that the water heating system is the right size. Otherwise, a small unit will need to run for a much longer time, hence wear out much faster. 

install water heater

Similarly, a much larger system will cost more in terms of purchase and running costs. Additionally, it will take up more space and more costly accessories.

Placing the gas or electrical power shut-offs out of site

These controls must be in easy to access and visible locations for normal operations and handling emergencies. They allow you to cut off the electrical supply or flow of the gas into the tanks.  

In practice, you should never heat an empty tank. However, if the shut-off is inaccessible, it means that you must leave it on, even before you complete the installation and added water to the tanks. Consequently, immersion heating elements, which must work when in water, will overheat and burn out. Similarly, if you apply a flame to an empty tank, it will overheat and crack the tank.

Installing the water heater in a difficult location

A difficult-to-access location can be a challenge when installing and maintaining the water heater. Additionally, it may be risky to work in such as place and could also pose other hazards. Usually, the building codes recommend the minimum dimensions you require to access the water heater. They also specify the minimum floor space required to install the heater. Failure to adhere to the building codes results in difficulty installation and challenges in putting the units and tank in and out of the tight spaces.

Loose gas supply pipes and electrical wires

Ideally, you need to secure the electrical power and gas supply lines to the walls and floors to minimize vibrations, loose connections, movements, and associated risks. Also, ensure that they are out of the way from other objects to prevent damage. Where necessary, protect the lines, such as using the appropriate conduit or trunking for the electrical wires.

Other errors include

  • Mixing different metals: – increases the risk of galvanic corrosion. In case there is a need to use two types of metals. Separate them with a dielectric connector to avoid direct contact.
  • Ineffective venting of the exhaust gases in gas-powered based water heaters
  • Replacing a good and serviceable water heater
  • Poor soldering
  • Installing the wrongly sized water heater, etc

Conclusion

While, in most cases, nothing prevents you from installing your water heater, you need to understand what is involved, the risks and impact of your actions. What you need to know is that installing the water heater is not an average DIY project, and could lead to serious performance and safety issues. The installation requires a broad set of skills, including plumbing, electrical, ventilation, carpentry, and more, depending on the environment and where you are installing the system.