Boiler Does Not Respond to Thermostat. What Should I Do?

Modern boilers rely on a variety of components to function properly. One of those components is the thermostat. There should be two thermostats – one for the house and one for the boiler. All the three components should work harmoniously to make sure you get hot water and heat when you need it.

If there’s a breakdown in communication whether it’s from the boiler or the thermostat, the boiler will get confused and won’t know when to produce hot water and when to stop. If you find yourself in a similar situation, this quick read can help!

Types of Thermostats

Before you go foraging for the contact of your boiler installer, there are a few things you can try out that might save you the trouble of having to wait for an engineer. Before identifying the problem, you need to know what kind of thermostat your system is on. It will make it easier to narrow down the problems.

Electrochemical Thermostats

These are fitted on older and more basic models. They have a very simple mechanical principle that works on the basis of a strip of two different metals joined together. At times, the strips are in the shape of a coil.

The coils or strips expand and contract as the temperature fluctuates activating the contacts on either end of the thermostat. The mechanism is connected to a mercury switch which is responsible for opening and closing the point of contact.

Electronic Thermostats

These are more advanced varieties fitted in modern boilers. They are programmable, versatile and flexible. They have wireless options that you can connect to the boiler through a Wi-Fi connection and control the boiler remotely.

You can set the adjustments of the electronic thermostat to your preferred settings which is why they are often preferred. With the additional hardware and software, these types of thermostats are more sophisticated and also cost more.

Read our latest blog: How Much to Move a Boiler.

Room temperature and setting don’t match

One of the most common faults with a thermostat is having the room temperature and settings not matching. This can cause the boiler to delay when starting up or fail to start running when it should.

It’s slightly hard to tell if your thermostat is failing but, there’s a neat trick you can use. Tape a small thermometer next to the thermostat. To get the most accurate reading, place a paper towel behind the thermometer.

Wait for about 15 minutes then check the reading of the thermometer and that of the thermostat. If the readings differ by more than a degree, there’s a fair chance the thermostat is not correct. You might have to recalibrate the thermostat or replace it.

Check settings on the thermostat

If you have recently changed the thermostat, it could just be a matter of the settings not being right. There are a few things you can check that could be causing the boiler not to respond to the thermostat.

Start by checking if the thermostat is set to heat and is calling for heat. You can tell this by the ‘Heat On’, flame icon or a shimmering sun icon displayed on the panel. The thermostat should call for heat as soon as the temperature falls below the heat setpoint.

Once you’re certain the thermostat is doing its job right, check to see if the boiler is switched on and the circuit breakers are on. Lastly, check to make sure that the wires are matched correctly and connected securely to the thermostat.

If the reason for changing the thermostat was the boiler not responding, it could be the boiler at fault. Call in an engineer to have the system diagnosed.

Other factors to consider

If you’re still having problems and the boiler still refuses to respond to the thermostat here are a few other factors you can look into when diagnosing the thermostat:

  • Check to see if the inside of the thermostat is clean
  • Make sure the thermostat box is level. If the box is not level, it can affect the accuracy of the internal components
  • Make sure the box is not placed under direct sunlight or in front of drafty windows. Poor positioning can affect the readings and accuracy of the thermostat.
  • Check if the anticipator is properly set. For mechanical thermostats, check for a little metal tab usually mounted on the round dial inside the thermostat. You can try pushing the tab gently to either direction to see if that solves the problem. If you’re not sure if it’s set correctly, you can compare with the owner’s manual.

Some thermostat problems are easy to deal with, however, if you’re not sure of what the problem could be, it’s best to have a professional boiler installer or engineer come and assess the system and recommend the best solution.

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