Boilers that are located in cold areas of your house, including garages and lofts, can be prone to freezing, and this can wreak havoc with the system, causing blocked or burst pipes. Frost protection is just another safety feature that’s built into your boiler to keep your family and your home safe, but how exactly does it work? Read on to find out more.

What does frost protection mean?

Any system that uses water and is located in a cold environment has the ability to freeze. This doesn’t always mean that it definitely will, but there is a likelihood that it could happen. Frost protection is a built-in safety feature that can stop this from occurring. If water in your heating system were to freeze, it could cause all sorts of problems, some of which we go into in more detail at the bottom of this guide. However, frost protection means the water in the system never drops low enough for this to happen.

What is frost protection on a boiler?

The frost protection setting turns your boiler on when it senses that the water in the system has dropped below a specific temperature. This temperature is usually around five degrees, and you wouldn’t necessarily want it any lower than this, as the water could freeze before the boiler has a chance to warm up. Alternatively, if you set it any higher than this, the boiler could turn on more frequently than you need it to, causing higher energy bills.

When it senses that the water within the system has dropped to five degrees, the boiler will begin to heat the water to 10 ℃, at which point the boiler turns itself back off again. The boiler will do this as many times as necessary to ensure that the water in the system doesn’t drop below that all-important five degrees.

It’s a misconception that this safety feature can significantly increase your heating bills. However, as the water that is heated won’t be circulated around your heating system or sent to the water tank for storage, you shouldn’t really see any change in the amount of energy the boiler is using. The boiler will only heat the water that is located within it, and the amount of energy it takes to do this is very minimal.

Do I have to protect my boiler from frost?

Only boilers that are located in cold places will need to use frost protection, and so an appliance that’s located inside your house won’t ever use it, unless of course your home drops to below five degrees, which is unlikely.

Gas boilers that are installed in cooler areas, like a garage or loft, will need some form of frost protection, but this feature is usually built into modern boilers. If you have an older boiler, there are frost protection thermostats that can be bought and installed separately so that your boiler will turn on when it senses a drop in temperature. We’d recommend that you invest in one of these to prevent any issues in the future.

For extra protection, you can buy insulating jackets to wrap the pipes in. Not only can this prevent them from freezing, but could also keep them warmer for longer when the heating is on, increasing the efficiency of the system.

What happens to frozen central heating?

Frozen pipes can cause all sorts of problems but the main problem is that you often don’t know they’re frozen until it’s too late. The only pipe you can visibly see in your central heating system is the condensate pipe, which will exit from your home via an external wall. If this has frozen, you will likely be able to see ice on the end of the pipe.

You’ll be able tell if your central heating has frozen at any point if:

  • You have no running water
  • You have a burst pipe
  • There is a blockage in the system
  • There is water damage to the property

Modern or newer boilers may also show a fault code on the screen. You can use your boiler’s manual to determine what the fault code means or, if you have a Viessmann boiler, you can use our fault code checker.

Frozen water can begin to cause damage to your boiler, particularly to the heat exchanger, as it expands when it becomes ice, therefore it’s best to solve this problem as soon as possible, or put some preventative measures in place so it doesn’t happen in the future.

You should try applying warm (not hot) water to any outdoor pipes to help thaw the ice. You may also wish to turn off your water supply using the stopcock just in case a pipe bursts. Try to keep your home warm using portable heaters if you have them, as this will also help to defrost any pipework. Once everything’s thawed, turn the water back on and check for leaks. 

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