Most of us now have condensing gas boilers in our homes. What this means is that when running at lower temperatures condensation form within the heat exchangers. This leads to a significant increase in efficiency with less heat being wasted out through the flue.
Sounds great but unfortunately most of us do not have thermostats which can take advantage of this. Most common are dial thermostats which are based on bi-metalic strips, Victorian technology, or digital and app-controlled versions of said Victorian technology. This includes Hive and depending on the setup Tado and Nest.
These simply send power to the boiler telling it to come on full blast. When the boiler comes on it will condense, but only briefly, then be running too hot for condensation to form. The 95% efficient boiler you’ve got is unfortunately now running in the low 80s. After running for a while, the thermostat will tell the boiler the room is at a comfortable temperature and to turn off.
Even though the thermostat has told the boiler to stop, your radiators are still holding a lot of heat which will cause the air in your house to carry on heating, leading to an often uncomfortable and too hot overshoot. Depending on how well your house retains heat there is then a wait before the house cools down and the thermostat says it needs heat again and restarting the on/off cycle.
I need you to forget everything you know about controlling heating as we can do so much better than the Victorian technology. This is where weather and load compensation comes in.
Weather compensation relies on an outdoor sensor and following a pre-set curve the boiler and radiators then only get as hot as they need to in order to keep the house warm and comfortable. If it’s cold out the radiators will be hot, likewise if it is mild, they will only be tepid.
The list of benefits is extensive: the boiler is running much more efficiently, therefore lower gas bills and CO2 emissions, the house maintains a much more even temperature without the swings an on/off thermostat will give, less wear and tear on the boiler and pump as they aren’t running as hot, cooler radiators means lower risk of burns to young children and elderly residents.
Load compensation when applied correctly is similar but uses a more 21st Century appropriate thermostat which tells the boiler how hot it needs to be in order to maintain the room temperature rather than the old fashioned on/off.
My preference has always been to fit Viessmann boilers. I’ll explain in more detail why in another article but for now want to talk about the built-in advanced weather compensation.
Originally weather compensation was included as the primary control in top end Viessmann Vitodens 200-w but is now included in the more budget friendly 100 and the cheap and cheerful 050 boilers too. Rather than using expensive app controlled thermostats which are often inefficient and ineffective as already mentioned they often only need a £20 sensor to unlock the benefits weather compensation brings.
When I ask my customers how they are getting on with their new controls they have often complement how they have become used to the heating being there in the background rather than the constant fight with their old thermostat.