Water Heater Thermostat: How Does It Work?

Almost every water heater sold in India comes with a thermostat. Without that, it is impossible to control the water temperature in the water heater.

But do you know how a Water Heater Thermostat works? Where does it fit in the water heater? How many thermostats are used in a water heater?

I believe many of you do not know the answer to these questions. That is why, in this article, we will cover more about the Water Heater Thermostat and how it works.

What Is Water Heater Thermostat?

A water heater thermostat is a safety device that controls the temperature of the water inside the water heater. Thermostats are also found in other appliances like Refrigerators and ACs where we control the temperature.

When we set a temperature in a water heater, we instruct the thermostat to cut off the power when the desired temperature is reached.

water heater thermostat

The moment the set temperature goes down, the thermostat starts acting again and establishes the power connection. So in another way, it saves power too.

Small water heaters have only one thermostat whereas big-capacity water heaters have two. For small-capacity water heaters, the thermostat is usually fixed at the lower side of the tank whereas, for the big water heaters, you will get a thermostat at the top and bottom portion of the tank.

Both the thermostats may not work together. For example, if you want to use just about 1-2 liters of water from an 8-liter water heater tank, then probably the lower thermostat is sufficient.

In the case when you need more water than the tank capacity, both the thermostat has to work together to give you the desired water temperature.

How Does A Water Heater Thermostat Work?

A thermostat is a temperature-activated switch. It is a thermistor that responds to heat by producing an electric current. The intensity of current increases with the increase in water temperature and vice versa.

The change in electric current intensity sends a signal to the controller when to cut off the power or when to turn on the power.

For example, if the controller senses low-intensity current, it may continue supplying power to the water heater element. But the moment it senses a high-intensity current, it will cut off the power for safety reasons.

Every water heater has a reset button called an Emergency Cut-Off (ECO) switch. The ECO switch trips if the thermostat fails.

Does Water Heater Thermostat Save Power?

Water Heater Thermostat has nothing to do with the power saving. It is more of a safety device than a power-saving device.

Yes, controlling the power when the desired temperature is reached, saves some amount of power, but think about it in another way. If you keep your water heater always on thinking that the thermostat will do the power-saving job, it will keep on running throughout the day consuming more power than it can save.

So, don’t depend on the thermostat to save power. Turn off the geyser once done to save power.

FAQ | Water Heater Thermostat

How To Tell If Water Heater Thermostat Is Bad?

If the water heater is not heating the water at all or if it is heating too much, there are chances that the thermostat went bad.

Never use a water heater if the thermostat has gone bad as you may experience boiled water which may cause burn injuries.

Can You Replace A Thermostat On A Water Heater?

Yes, you can. But you need to call a trained technician to do the job for you.

What Is The Ideal Temperature For Water Heater?

The ideal temperature of water inside the water heater should be around 50°C because that’s what the human body can tolerate. Although in water heaters, the temperature range varies from 40°C to 70°C

What Happens When The Thermostats Fail?

Every water heater has a reset button called an Emergency Cut-Off (ECO) switch. The ECO switch trips if the thermostat fails.

How Many Thermostats Does A Water Heater Have?

Normally there is one thermostat in water heaters but if the capacity is big, then there could be two thermostats.

Rajib Is The Founder And The Key Brain Behind RiansDeal. A NIT 2004 Graduate In Mechanical Engineering With Close To Two Decades Of Experience In Designing Large Appliances And Consumer Electronics Products.


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