COP26 has got everyone talking about how we heat our homes. And what changes we’ll need to make to reach net zero carbon emissions by 2050.
The government’s ambition is to be installing 600, 000 heat pumps per year by 2028. Heat pumps need to run at low temperatures to maximise their efficiency. But low temperature heating isn’t just for heat pumps.
Until we all have a heat pump; low temperature heating is a more cost effective and environmentally friendly way of running our gas boilers.
When we’re talking about low temperature heating, we don’t mean simply turning your thermostat down from 21 to 19 degrees.
And we’re not suggesting you just put a jumper on and sit in a cold house, either!
Low temperature heating systems have cooler water running through them, without compromising your comfort.
If you want to learn more about this, read on!
What is low temperature heating?
As we’ve already mentioned, low temperature heating doesn’t mean that your house is cold.
Your house will be a comfortable temperature; while the heating system runs at a lower temperature.
In a traditional heating system; the temperature of the water flowing around your radiators is between 70 °C and 85 °C.
With a low temperature heating system; the temperature of the water could be 25 °C to 50 °C; whilst keeping you nice and warm.
The main advantage of low temperature heating is that it’s much more efficient. Or in other words, your boiler will be burning less gas to do its job. This will save you money on your energy bills, as well as being better for the environment.
Why is low temperature heating more efficient?
Low temperature heating makes your boiler more efficient. Because when you reduce the water temperature in your system, it allows your boiler to condense properly.
Thanks to changes to the law in 2005 and Boiler Plus, all modern boilers are condensing boilers. They can potentially extract 90-92% of heat from fuel, compared to 50-80% with an old non-condensing boiler.
But the key word here is ‘potentially’. Just because a modern condensing boiler says it’s 92% efficient on the box, doesn’t mean it will achieve this. It must be given the right conditions – specifically, the correct flow and return temperatures.
Low temperature heating and condensing boilers
To understand why low temperature heating is more efficient; you need to know a bit about how condensing boilers work.
A condensing boiler works by recycling the wasted exhaust gas that is created during a boiler’s normal operation.
By re-using the exhausted gas; water vapour; and steam; back through the system; some of the heat and water is retained making the boiler’s operation more efficient.
But boilers can only get into this efficient sweet-spot known as ‘condensing mode’ when operating at lower temperatures. The water in the heating system needs to be less than 54°C when it returns to the boiler. This enables the heat to turn back into water (or condense).
At 54°C a condensing boiler will start to recover its lost heat.
Only when the return temperature is 45°C or lower; will the boiler recover enough heat to reach its full efficiency potential.
The problem is, most boilers aren’t meeting their efficiency potential because they’re set up to have much higher return temperatures.
According to The Heating Hub; most gas boilers are set up to have a flow temperature of 80°C and a return of 60°C. But this is too high for condensing mode.
Why aren’t boilers being set to lower temperatures then?
Since we know that the key to energy efficiency is to get boilers into condensing mode; why are most boilers set to flow at around 80°C?
This is a very good question. And unfortunately, the answer seems to be either laziness or lack of training in central heating design.
Manufacturers know that setting a boiler to flow at 80°C and return at 60°C means there’ll be loads of heat; and the homeowner won’t have a problem getting their house warm. It doesn’t matter to the manufacturer how high your energy bills are, or whether most of that heat is wasted!
Another problem is that many installers fail to carry out heat loss calculations to find the correct size of boiler for your needs. And install an oversized one ‘just in case’.
If you’ve read our blog: What size boiler do I need? You’ll know that oversizing a boiler results in boiler cycling, and also prevents your boiler from getting into condensing mode.
The Heating Hub says that 99% of installers have not been trained to set up condensing gas boilers properly. This is why it’s vital to get a reputable Gas Safe engineer to install your boiler.
Rest assured that The Heating People are certified Heat Geeks (see link at the end of this blog) and follow industry best practice.
What are the benefits of low temperature heating?
Let’s look at some of the benefits of low temperature heating…
Low temperature heating is more energy efficient
As we’ve explained above, the efficiency of condensing boilers (and heat pumps) is higher when they supply heat at lower temperature.
Reducing the return temperature of the water in your heating system could increase the efficiency of your boiler to over 90%.
Low temperature heating is more cost-effective
Since low temperature heating is more energy efficient, you should save money on your energy bills.
A recent report by the Heating and Hot Water Council (HHIC) found that households can save around 6-8% on their gas bill just by turning down the flow temperature on their condensing combi boiler.
Low temperature heating creates a more comfortable heat
Despite the common misconception that low temperature heating means you’ll be cold, a benefit of lowering the temperature in your central heating system is that you’ll get a more consistent and gentle heat.
Although your rooms may take a little bit longer to warm up, you won’t get the spikes of over and under heating where your boiler blasts on and then quickly switches off.
Low temperature heating is practical
Installing a low temperature heating system is a practical choice. Because the consistent lower temperature means that you won’t need to turn down your thermostat when you go to bed or you’re nipping out.
Low temperature heating creates cleaner air
Now this is a surprising one! But low temperature heating produces less airborne dust around your home, which is good news if you suffer from asthma or allergies.
The reason for this, is that despite their somewhat misleading name, ‘radiators’ produce most of their heat through convection (not radiation). Convection works by circulating heat around your room.
Unfortunately, it’s not just heat that circulates in the convection current. All the grim dust and allergens that are hiding in your radiator fins will be carried around too!
With lower temperature heating, your room will get warm through more radiant heat (rather than convection) and this settles the air.
Low temperature heating is kinder on your heating system
Although your boiler has been designed to cope with high temperatures, setting your heating system to a lower temperature is kinder on it.
Nobody likes stop-starting, and the same is true of your boiler!
Constant heating and cooling can take its toll on the component parts of your boiler.
Think of it as being a bit like a car. You know that if you’re constantly flooring the accelerator and then slamming on the brakes, this will use up more petrol and increase the general wear and tear on your car. It’s far better to tootle along at a lower steady speed.
Low temperature heating is the equivalent of doing a nice consistent 50 mph in your car!
Can I turn down my boiler’s flow temperature?
If you have a condensing combi boiler you can reduce the flow temperature on the front of your boiler. The Heating Hub has an excellent article on how to do this. We’ve linked to the article at the end of this blog.
What do I need to have low temperature heating?
Let’s look at the different ways of achieving a low temperature heating system.
Increased radiator sizes
Your radiators need to be sized correctly to make sure that they can deliver the same amount of heat at a lower flow temperature.
Larger radiators have a larger surface area which will maximise the amount of heat that can be transmitted to the ambient air.
Radiator balancing
In addition to checking that your radiators are the correct size to deliver enough heat at lower temperatures, they should be balanced. Setting the radiator flow rates or ‘radiator balancing’ prevents the boiler from putting too much energy into the heating circuit and improves efficiency.
Increased insulation
You might hear the phrase ‘Fabric First’ mentioned a lot when people are talking about efficient heating. This phrase is referring to the fact that to get the most out of your heating system (especially at lower temperatures) you need to have decent insulation to minimise heat loss.
Buildings with poor (or no) insulation will lose their heat much faster than buildings with insulation. So, if you’ve got a poorly insulated home, you’ll need to be burning more fuel to keep it warm.
If you want to heat your home with low temperature heating, insulation is even more important to keep your home feeling warm.
Check out our related blog on how you can reduce heat loss at home.
Modulating controls
For a low temperature heating system to work, suitable controls need to be used.
Weather compensation devices use an outside sensor to adjust your boiler’s operation accordingly.
On a cold day, heat will be lost from your home more quickly than on a warm day. So, when the outside temperature falls, the boilers flow temperature is increased using a correctly determined ‘curve’ to compensate for the extra heat loss.
Conversely, when it’s warmer outside, there’s less heat loss and the boiler will reduce its flow temperature, thereby running more efficiently.
Load compensation controls work in a similar way to weather compensation because they also use intelligent communication between temperature sensors and your boiler.
But unlike weather compensators, which use an external sensor, load compensation controls use an internal sensor to achieve your desired indoor temperature.
Load compensators measure the difference between the current temperature in your room, and the desired temperature that you’ve set. The controller then tells your boiler to increase or decrease its output to precisely close the gap.
If your desired temperature is dramatically different from the current room temperature, the load compensator will tell the boiler to increase its flow temperature to the maximum.
As the room temperature gets closer to your desired temperature, the boiler is told to reduce its flow temperature.
Final thoughts…
Thanks to COP26, people are finally starting to appreciate that optimising the efficiency of our heating systems is vital in the fight against climate change.
The government is taking the first steps towards the decarbonisation of heating, but it’s not going to be an overnight fix.
In the meantime, there are lots of things we can do with our current heating systems to improve their efficiency.
But as people are also starting to realise… a boiler is only as good as the installer that fits it.
If you want to get the most out of your new boiler and allow it to operate at its A-rated efficiency, book your free survey with The Heating People today.
Useful Links:
Heat Geek article: Benefits of low temperature heating systems
Energy Stats UK: Low temperature heating
Energy Saving Trust: Quick guide to low carbon heating
The Heating Hub – article on gas prices and boiler inefficiency
