OAs the Christmas festivities approached, Madeleine and Matt Cage* decided to replace their 19-year-old boiler which only worked in 20-minute bursts. When an engineer came to see what they needed, he simply looked at the system in place and recommended a similar machine.
What the couple soon realized was that the boiler that was in place – and which they had been told to replace with something similar – was far too big for their four-bedroom home.
A second engineer, who took more precise measurements of the size of the house and how it used its heating, recommended a much smaller system that would be more efficient and cost less to run.
An oversized boiler is a common problem, according to Jo Alsop of The Heating Hub, an independent consultancy that focuses on energy efficiency, and it’s a problem that’s only adding to the rising cost of heating our homes. houses.
As we enter the coldest time of the year, in the midst of an energy crisis that has sent bills soaring, consumers have also been advised that there are simple measures they can put in place to save money. related to the use of the boiler.
“There is latent efficiency in every boiler, some of which can be harnessed by occupants with a few simple and safe DIY changes,” Alsop says.
Is your boiler too big?
Most boilers (around 80%) sold in the UK are combination units, which provide heating and hot water. The others are either ordinary heat-only boilers or system boilers, which work with a hot water tank.
All types have similar issues, in that they are often too powerful for household needs. As Alsop explains, “It’s like trying to boil water with a small saucepan on a large hob – there’s no way it won’t boil over. That’s what a big, oversized boiler does. This is too large for the building’s heat loss.
“Boilers are at their most efficient when they match the heat loss,” she says, with studies finding that oversized boilers are 6 to 9 percent less efficient.
An average UK house can be heated with a 6-10kW boiler in cold weather. Most heat-only and system boilers start at 11-13 kW. Combi boilers need at least 24kW, but that’s for instant hot water, and have heating outputs of around 18kW, still too much for most homes, she says.
Due to a misunderstanding of heat loss, some installers are installing larger and larger boilers, installing systems up to 50 kW, according to Alsop. Oversized boilers are subject to greater wear and tear, which can lead to higher fuel bills.
To solve the problem, modern boilers must have two separate outlets, one for heating and one for hot water. Combi boilers have this automatically. But for heat-only and system boilers, the installer must configure the system correctly and install the correct heating controls, which in most cases doesn’t happen, she says.
When configured correctly, the boiler can be “scaled” down or adjusted to the maximum heat demand by installers.
Get the right throughput
The flow temperature determines the temperature to which the boiler heats the water and is usually set between 70°C and 80°C when the combi boiler is installed. But that’s too high for many boilers to operate efficiently, according to energy company EDF.
At lower temperatures, they go into condensing mode more frequently, allowing more heat to be captured and recycled back into the system.
Combi boilers often work best when they heat the radiators to 60°C or less, according to Nesta, the agency that promotes innovation. This doesn’t mean the temperature in your home will be lower, but the radiators will take a bit longer to heat up.
Adjusting it yourself is possible, but it’s not the same as changing the temperature on your thermostat. The controls for changing the flow temperature are located on the front of the boiler.
“A government report found that 70% of homes could stay warm at flow temperatures of 60°C, which is 20 degrees cooler than most homes currently installed,” Alsop says.
“If an owner is particularly mindful of it, they can adjust it to 50°C in the milder months and drop it back to 60°C as it gets colder, so the temperature relates to the temperature exterior.”
Nesta estimates that lowering the temperature could save an energy bill of £112 a year.
Turn off preheat
As combi boilers are usually placed some distance from the bathroom, it can take time for water to reach the taps.
A preheat function in some machines keeps a small amount of hot water ready, which can be sent quickly to the hot water tap.
But to do this, the boiler must fire every 90 minutes or so, using a little gas at a time. This can add up over time: the Heating Hub says there’s a potential saving of up to £90 a year if this is turned off.
How to turn it off depends on the type of machine, and not all models have this feature, while some that have it cannot be turned off.
Making changes to the way you heat your home can result in significant savings. Turning down the thermostat just one degree can save money. In France, owners of private buildings have been encouraged to lower thermostats to 19°C when occupied, and lower them further to 16°C at night.
“It’s always a little dizzying. But it really works. It’s one of the biggest savings to go from 20C to 19C,” Alsop says. A single degree can save £117 a year on the average bill, it is claimed.
Some homes leave their boiler on “long and low”, or permanently at a lower temperature all day, so the machine has less work to do and spends less time in an inefficient mode trying to achieve a certain temperature.
However, Alsop says this has been shown to use more gas and a timed scheme – where the boiler is on for set periods, such as two hours – is more efficient and can save £130 a year.
* The name has been changed
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