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Weather Comp V Load Compensation - What is Best For Me?

Their is a lot going at on in the industry at the moment with regards to saving energy and gas usage. The majority of boilers in the UK are oversized and we recorded the third highest boiler sales in the whole world. In 2015 the Energy Related product Directive (erp ) was launched to try to help cut European carbon emissions by eliminating low efficiency heating products. In April 2018 Boiler Plus was launched, meaning any new boiler installation had use one of four energy saving features (weather compensation, flue gas heat recovery, load compensation or smart controls - see our last blog, to meet the standard.

Today we are going to talk about weather compensation and load compensation.

So firstly what exactly are they..

Well they are actually similar in the way they work. Weather compensation will use an external sensor on a outside wall, preferably north/north westerly unless you have a Baxi and you can use their flue sensor IFOS, it measure the external temperature and adjusts the boiler flow temperature on how hot or how cold it is outside. Load Compensation works more or less the same but is reactive to the internal temperature.

Although they work similar there is a big difference between them. With weather compensation you are trying to keep the house at a comparable temperature and as it’s using an external sensor it’s less reactive to changes inside the house, I have found the best way of using weather compensation is to have a long running time, letting it come on at say 6am and go off at 10pm, this way it can modulate down and just keep the whole house comfortable. Each individual room can then be controlled by thermostatic radiator valves at your required comfort level, you shouldn't ever really be hot or cold. Think of it like boiling a pan of water on a gas hob, you use a lot of gas to heat that water up in the first instance, if you then turned the gas down to a low flame you could keep that water at a desired temperature without using a lot of energy, where as if you let it go cold, to get it back to the temperature you had before you would need to turn the gas back up, in heating terms this is called boiler cycling. Cycling causes stress on boiler components, turning on and off all the time much like stopping and starting in a car, reducing the life of components and causing repairs, it also uses more gas this way as it’s using more energy to heat the water that has cooled down. You may also find that your house is hot/cold/hot/cold. It allows the heating to run at low temperatures which inturn keeps the boiler in “condensing” mode longer allow the boiler to be at its most efficient. But weather compensation isn’t for everyone, this is where load compensation will come in. 

For load compensation controls to work the heating control and boiler must be able to communicate in a common language, most boilers use a protocol called OpenTherm although there are others out there. This protocol allows the boiler and controls to communicate which allows the boiler to modulate the alter the flow temperatures correctly to the internal demand.  The traditional way to control a central heating system is with a basic ON/OFF or TPI room thermostat. The room thermostat is set to a temperature and will switch the boiler ON and OFF; when the room temperature falls below the temperature set point, the thermostat switches the boiler ON and then when the room temperature goes above temperature set point, the thermostat turns the boiler OFF. OpenTherm provides much more precise control of the boiler, by continuously adjusting the boiler's water temperature set point (the 'Control Setpoint'). OpenTherm always assumes that the room thermostat calculates the amount of heat required from the boiler and this is matched to the varying demand requirements. By setting the boiler's water temperature to the correct temperature set point as it leaves the boiler, OpenTherm not only maintains the correct room temperature set point but also helps the boiler's efficiency by running at lower flow temperatures for longer periods; this ensures more of the boilers heat exchanger is at condensing temperatures, which is the boilers most efficient point. I have found that load compensation is ideal for people who have irregular life patterns and want there heating to be more reactive for them when they are home. People who work away or are out of the house for long hours. You can also get load compensation controls that use a local weather station as well for external temperature, although not as reliable as the external sensor due to areas having micro climates, it is still something to thing about when choosing the correct set up for your house.