A condensing boiler is the type of central heating boiler for your home. If installed and commissioned correctly, it’s a highly efficient model that can save you money on your energy bills. It’s also very efficient at heating your home. However, there are some things you should know about how this type of boiler works. Read more to learn about them!
How to Tell if your Boiler is a Condensing Boiler
Condensing boilers have been installed for the past 20 years, they can be identified in the home as they will have a white plastic pipe coming out the bottom of it as well as the normal copper pipes. If your house does not have a hot water tank and a boiler, you’ll have a condensing boiler which in this instance is called a combi-boiler.
How a Condensing Boiler functions
A condensing boiler is a type of boiler that uses the waste heat from the flue gas to pre-heat the feed water before it is pumped through the heat exchanger. The heat exchanger is usually a coil of steel pipe in the hot side of the boiler.
Because there are two separate systems, this allows for greater efficiency as well as safer operation since there are no combustible materials being used during combustion (e.g. coal or wood).
From 1st April 2005 new regulations were made that meant all new boilers fitted in domestic properties need to be condensing type. Initially they were standard boilers (those with hot water tanks as well) but we now have mainly combi boilers fitted (with no hot water tank.) Combi boilers tend to be set up better however it is still worth checking how well these are set up.
Most UK Condensing Boilers not set up correctly
You may have heard that condensing boilers are a great way to save money on your heating bill, but if it’s not set up correctly, you could be wasting energy without even realising it. Most UK condensing boilers are not setup correctly, which means they don’t work as efficiently as they could and can cost you more money in the long run.
Condensing boilers will run quite happily outside of the sweet spot where they will condense which is the most efficient. To achieve the sweet spot you need to have your Hot Water Flow running at 65°C and your Return running at 45°C.
Outside of this sweet spot you lose efficiencies to either too much heat input or longer burn times trying to achieve the control settings. Lots of UK condensing boilers are set up to run like their predecessors with the flow temperatures in the 70-85°C range and the system balanced only on the radiator flows. This will work but it is not efficient and will burn more energy than you need to use.
How are Condensing Boilers set up incorrectly?
This stems back to their introduction and their fundamental change in how they function. Traditional central heating boilers used high temperatures to heat water to as hot as practicable then pump it round the radiators that heat the rooms they are in. These would then be shut off when either a Room Thermostat achieves its temperature and deactivates the boiler or a Thermostatic Radiator Valve shuts off the water supply to the radiator when it’s desired setting is achieved.
Central Heating technicians (and DIYers) where trained to balance radiators based on this high heat and continued to do so even when condensing boilers where introduced.
Incompatible condensing boiler heating controls
There are a number of smart devices available now that although help greater control of your central heating can defeat the higher efficiency that a condensing boiler can delivery.
Likewise Thermostatic Radiation Valves (TRVs) can, if not used wisely, work against a condensing boiler.
Balancing a Condensing Boiler system
Balancing a condensing boiler system is the process of making sure that all parts are working together efficiently and as they should be. When your system is balanced, it will run smoothly, produce hot water quickly and efficiently and save you money on energy bills.
A balanced system means that the water temperature in the boiler is as close a possible to 65°C in your flow and your Return is 45°C.
Frustratingly very few boilers have the ability to tell you this key piece of information. New boilers are starting to show these temperatures or at least indicate you are running efficiently. The most accurate method is to put thermometers on flow and return and measure.
Is your Condensing Boiler Oversized?
The most important thing to remember about your Condensing Boiler is that it needs to be sized correctly. This means that the boiler should be able to heat your home with the amount of heat loss from your property.
It is a fact that most Houses in the UK that have condensing boilers will have been over specified for the size of House.
Quite often what happens is a calculation is carried out to see what capacity the boiler needs and then the next size up boiler is selected, this could cause your property to be oversized. Unless you can adjust it’s input power it is unlikely you’ll ever be able to achieve high efficiency on you boiler.
Setting condensing boiler up with lower flow temperatures
The first thing you need to do is set your condensing boiler up with flow temperature of 65°C. Most condensing boilers will have the ability to adjust this. It is often the most common thing that gets adjusted upwards to get more heat, which defeats efficiencies.
If you don’t have the user manual for your boiler, it will probably be available online. Failing this, there is a wealth of videos on youtube showing you how to adjust your flow temperature. If you search by entering your make of boiler and add setting flow temperature you should get some results.
Make sure your radiators are balanced
Like the Boiler you need to make sure your radiators are balanced. To achieve this you need to aim to get a 20⁰C differential between the flow in pipe and the flow out pipe.
If you have TRVs you need to put this to maximum and then adjust the flow using the valve on the other pipe. Once adjusted you can put the the TRV back to your desired setting although this will throw the balance out and could affect the boiler efficiency.
To make this easier you can get inexpensive clip on thermostats that you can put on the flow and return pipes to see the temperatures and adjust accordingly.
Once all the radiators are balanced you should see an improvement in the boiler flow and return temperatures.
Check your Hot Water Tank temperatures
Your hot water tank has a thermostat that call for heat if it is below the temperature set, if your boiler was set to high it is possible this was set too high also. Ideally it should be some where about 60⁰C this will ensure it is not always calling for heat and hot enough to be safe.
By safe we mean that hot water should be stored above 55⁰C to kill of any bacteria, especially Legionella bacteria which can thrive at lower temperatures.
To measure the temperature in the tank you can use an infrared digital thermometer and check the temperature of the hot water either by :
- measuring the temperature of the outlet pipe of the tank (typically the pipe at the top of the tank) or,
- measure the temperature of the water coming out of a hot tap.
Household often already have these digital thermometers that they use for measuring their body temperature. They often have different modes and you can use one of these set to the mode that measures surface temperature.
Maximising Condensing Boiler Efficiencies
Getting your condensing boiler working efficiently is a must for anyone trying to save money on their energy bills. A condensing boiler has a much higher efficiency than non-condensing boilers and can save you hundreds of pounds per year depending on the size of your property.
Is 90%+ efficiencies possible
Yes, it is possible to achieve 90%+ efficiencies. But it requires a lot of attention to detail and investment on your part. It also requires a lot of time—and this is where many people get frustrated.
In order to reach the high efficiency levels that we discussed above, you need to make sure that you are doing all the right things with your condensing boiler system
One off tasks:
- Check your pipes are insulated with sufficient lagging.
- Check your hot water tank is lagged
- Make sure your radiators are balanced if any alterations to the system has been made.
Check on a regular basis:
- Ensure your boiler is serviced regularly.
- Check the temperature of your hot water tank, if you have one
- Make sure your radiators are balanced
- Don’t adjust the flow temperature.
How much will an efficient Condensing Boiler Save?
This is very dependent upon how your current system is set up. Typically you could save 12% on your energy costs by making your condensing boiler ‘live’ in the condensing zone.
Conclusion
If you’re looking to get your condensing boiler working at optimal efficiency, we recommend following these steps:
- Check for leaks and ensure the system is balanced
- Adjust the flow temperature of hot water from the boiler to match its most efficient temperatures.
- Use a programmable thermostat that can automatically reduce power when it senses less demand on heating needs (this will help save money!)
Good luck with this process!
