Weather compensation is a system available to some heat pumps which reduces the water set-point temperature against ambient temperatures.
Ambient temperatures are monitored by the heat pump and the water set-point or air temperatures, in air source heat pumps is set to reduce as external temperatures increase.
Similar to boiler flow temperature, weather compensation is automated on some heat pumps and kicks in automatically if it makes economic sense to do so.
Unlike flow temperature in a boiler, you don’t need to think about adjusting your heat pump based on ambient temperatures. Heat pump models with weather compensation will adjust return water set-point temperatures.
What is Weather Compensation?
Essentially, the warmer the weather and hotter the temperature outside, the cooler the temperature of the return water set-point.
This reduction in temperature allows heat pumps to run more efficiently in warmer weather because they’re not required to heat the return-water to such a high temperature in warmer conditions, so less electricity is required to run the heat pump.
Heat pumps employ sophisticated systems to monitor actual temperatures and manage return water set-point temperatures to appropriate levels, through a system known as weather compensation.
Condensing boilers also use similar technology to keep flow temperatures low.
Why do Return Water Temperatures Matter?
In countries that don’t have access to discounted overnight energy or cheaper tariffs, heat pumps save money by reducing the flow temperature.
If less heat is needed to generate heat, relative to the ambient temperature, less energy is needed to produce the overall heat, therefore on warmer days, the heat pump can work at optimal efficiency using a cheaper electricity to amass heat into the property faster.
This means you can have warmth through radiators faster and sooner, heat more rooms and fill hot water tanks, whereas in countries or regions without discounted electricity, operating the heat pump at a steady state of efficiency, relative to the ambient temperature of external air, makes considerably more economic sense.
Should You Change Your Heat Pump Weather Compensation Settings?
Whether you should change your heat pump setting to optimise it for running with weather compensation enabled or without depends on your energy tariff.
If you’re currently on a tariff which offers reduced electricity rates, discounts for overnight use or you’re generating electricity yourself through solar panels or wind turbines you’ll likely want to avoid weather compensation, because your electricity deal should mean you can generate enough heat energy, through cheaper, discounted or even free electricity, with the heat pump running at a maximum return water set-point temperature, to reliably heat and store heat for your home continuously.
If you’re on a fixed rate tariff without discounts or incentivised electricity, then you may want to consider enabling weather compensation. However, if you’re operating a ground source heat pump, weather compensation may already be operating.
If it isn’t, then you may find any savings you make are minimal, Ground Source Heat Pumps generate heat from the ambient temperature in the ground, through boreholes or underground loop array systems, the temperature underground varies very little, even during the heat of summer and the colder winter months.
So you may find weather compensation makes little to no difference in your overall savings.
If you have an air source heat pump, weather compensation may make more sense, even in the U.K. however, our climate differs in temperature much less than some climates, so again, savings may be negligible.
How do Weather Compensation Systems Work in Heat Pumps?
Weather compensation systems are advanced automated systems which help determine the perfect return water set-point temperature based on real time up to date temperature readings. They work by;
Continuously monitoring ambient temperatures with sensors
Data is collected via sensors to monitor the indoor and outdoor temperatures.
Default Set-Point Temperature
A default or baseline temperature is set for the heat pump, this is often around an ambient temperature and can be between 22°C and 35°C
Sensors Monitor External Temperatures
External air temperatures are monitored continuously. This helps determine the heat loss of a building, i.e. the difference between the internal temperature and the external temperatures.
Calculations
The required set-point temperature is calculated based on the outdoor temperature and any potential “compensation curve” – which is how much the set-point temperature should change in response to changes to the external temperatures.
So, if external temperatures are 5°C the set-point temperature may be 35°C. If external temperatures were to rise to 15°C the set-point temperature may also change to 25°C.
The compensation curve will keep the set-point temperature at a point relative to the ambient temperature based on real-world conditions.
Manual Fine Tuning
Most systems with a weather compensation setting allow for manual adjustment and optimisation for homeowners or qualified technicians based on pre-defined parameters or to account for particularly unusual properties.
Continuous Optimisation
Ongoing adjustment and optimisation will occur based on the changes measured by the sensors, user temperature settings and compensation curves.
All of these systems work together to help keep the heat pump system working to an optimal level and ensure that utmost efficiency is achieved for the heat pump.
