Should my boiler be hot to the touch?

As your boiler’s most important task is to heat up water, it should come as no surprise that it will get warm.

Not only are there gas flames burning in there, but there’s also piping hot water flowing out of it. If you put your hand on a boiler that has been heating up water for a few minutes, you should certainly not feel any discomfort or pain – but if it’s just a little warm to the touch, it’s probably working fine.

The size of the boiler might make a difference, however. A smaller one will have less of a gap between the internal components and the outer casing, which could make it warmer than you’re used to.

In contrast, a more modern boiler will have more insulation to make it efficient, in which case you might not feel any warmth at all.

Finally, a boiler that’s kept in an enclosed space can get warmer than one that’s left out in the open. You should check that your boiler is designed to be hidden away, however – many boilers require airflow all around them to operate safely and efficiently, but not all fitters or previous property occupants know this.

So to answer the main question – “Should my boiler be hot to the touch?” – the answer is no, but some will indeed get quite warm. Remember that an overly warm boiler is almost certainly an inefficient one, as heat will be leaking out around it rather than into the cylinder, radiators and taps. It could be time for an upgrade.

In theory, a boiler that’s hot on the outside does represent a risk of damage, or potentially even an explosion. In practice, any boiler made in the past 30 years should have a host of physical and electronic safeguards to prevent it getting that far, and it is more likely to shut down. If you suspect there’s a problem, however, do call out an engineer to check it out – don’t wait for your annual service.

If a boiler is hot to the touch, there must be something overheating inside. The heating parts of the boiler (the burners and the heat exchanger) get very hot, but rely on a free flow of water to keep the temperatures below the maximum safe levels.

So, in all likelihood, a hot boiler will be caused by something slowing down the free flow of water. There are a few likely candidates:

• A buildup of limescale in the heat exchanger or system
• The pump not working properly
• The thermistor not sensing the correct temperature
• A fault with the printed circuit board
• A blockage in the central heating system

None of these issues can be safely diagnosed or fixed by an unqualified person, so it is vital that a boiler engineer has a look at the boiler to identify any problems.

For more information on overheating boilers, have a read of another of our blog posts – but as we say there too, a professional boiler expert will understand your problem, so please get in touch with us to arrange a quick visit.