Immersion Thermostats

Heatraq stocks precision-engineered immersion thermostats designed to regulate water temperature safely and efficiently. Our range includes standard, adjustable and high-limit thermostats compatible with Heatrae Sadia and Baxi immersion heaters, helping prevent overheating while optimising energy use.

Each thermostat is tested for accuracy, durability and compliance, making them suitable for both domestic and commercial hot water systems. Whether you’re replacing a faulty control or carrying out preventative maintenance, our genuine immersion thermostats ensure dependable temperature control and system protection.

Related components:
If your thermostat has failed due to age, scale or overheating, you may also need a replacement Immersion Heater. For faster maintenance and guaranteed fitment, consider an Immersion Heater Plate Assembly.

Immersion Heater Thermostats - FAQs

What does an immersion heater thermostat do?

An immersion heater thermostat controls the temperature of the water inside your cylinder. It switches the heating element on and off to maintain the set temperature and includes a safety cut-out to prevent overheating.

Why does my immersion heater keep tripping the reset button?

If your immersion heater thermostat keeps tripping, it may be due to overheating, a faulty thermostat or a failing heating element. Repeated tripping is a common sign that the thermostat needs replacing.

How do I reset an immersion heater thermostat?

Most immersion heater thermostats have a reset button located behind the cover. If the safety cut-out has tripped, pressing the reset button can restore operation. If it continues to trip, the thermostat may be faulty and need replacing.

How do I know if my immersion heater thermostat is faulty?

Common signs include no hot water, water that is too hot, or the heater constantly switching on and off. A faulty thermostat can also cause the system to trip or fail to maintain a consistent temperature.

Can a faulty thermostat stop an immersion heater from working?

Yes — if the thermostat fails, it may prevent power from reaching the heating element, resulting in no hot water even if the element itself is still working.

What temperature should an immersion heater thermostat be set to?

Most immersion heater thermostats are typically set between 55°C and 65°C. This provides efficient heating while helping to prevent overheating and reduce the risk of scalding.

Are immersion heater thermostats universal?

No — immersion heater thermostats vary in length, compatibility and design. It’s important to choose a thermostat that matches your immersion heater and cylinder specification.

Can I replace an immersion heater thermostat myself?


Replacing an immersion heater thermostat is a straightforward task for a qualified professional. For safety, always ensure the power supply is isolated before attempting any work.

Do you supply immersion heater thermostats for different cylinder types?

Yes — we supply a wide range of immersion heater thermostats suitable for various cylinder types, including domestic and commercial hot water systems.

Do you offer next day delivery on immersion heater thermostats?

Yes — we offer next working day delivery on immersion heater thermostats for orders placed before 2pm, helping you restore hot water quickly.