Friday, April 12, 2024

Turn it down – using built-in boiler controls and external sensors for efficient heating system design

Trevor Struck, Area Sales Manager at Hamworthy Heating

The way heating system design is approached can have a big impact on the energy-saving potential of a building. This not only concerns the choice of heating equipment including setup but also details such as room height and building occupancy. Making use of built-in boiler controls and ancillaries such as temperature sensors to feed information back to them offers an integrated approach to heating efficiency. This way, comfort levels are maintained, which has a positive effect on the wellbeing and productivity of people in the building. Maximising the use of control technology has benefits beyond heating costs.

‘One size doesn’t fit all’ approach to heating areas

When planning a heating system, you should consider what each part of a building is used for. Take kitchens for example, where heat is generated by appliances such as ovens, hobs but also fridges. Another so-called free contributor is solar radiation, especially where the sun shines through windows or large glass panels, causing space to heat up quickly. Where people are present, so is heat radiation. Additionally, lighting and IT equipment such as servers and computers also emit heat. This is why heat requirements in these areas are lower than in other parts of the building where no or little free contributions are present. On the other hand, corridors are only used intermittently and do not require constant heating, as they are only passed through to get to another part of the building.

It is essential to divide a building into different heating zones to avoid underheating one or overheating other areas. The energy is effectively minimised which reduces the costs to warm the building – heat is provided when it is needed, where it is needed, and at the right intensity.

This also needs to be regularly reviewed. With the current situation of Covid-19, many areas of a building will have drastically changed their occupancy and usage and therefore the amount of heat needed as well as the amount of ‘free heat’ being contributed.

How to track free contributions?

Internal space temperature sensors measure the air temperature and do not only monitor the performance of the heat generators and the various heating circuits but can also track heat produced by appliances, processes and people. The sensors should be positioned in carefully selected locations away from direct sunlight or other factors to avoid affecting measurements, giving an inaccurate picture of the actual room temperature.

Building layout and design as influencing factor

When it comes to building layout, there are many factors to review for efficient boiler control setup. For one, how quickly a space responds to heat, the thermal inertia of the building, needs to be considered. An office with low ceilings is an example of a space with low thermal inertia. With less air present, it will heat up faster and reduces the required start time before occupants arrive. In places with large volumes of air, such as in a church, high thermal inertia will increase the needed heat up time dramatically. High ceilings go hand in hand with poor heat distribution, unless suitable equipment to solve this issue is installed. It is vital to calculate an adequate time to switch on the boilers in the morning. On the other hand, an early switch off before occupants leave can help to achieve crucial energy savings. Modern controls will self-learn this when set up correctly, although fine tuning is still necessary and recommended throughout the first year of occupation.

Another issue to factor in is heat loss. It occurs on surfaces which make up the building envelope which separates a building from the outside (such as walls, floors, roof, windows etc.) but also from gaps in it where cold air can come through. These effects can be felt especially in the winter months with low temperature and winds. Therefore, monitoring the external temperature at any given time to estimate the heat loss from the building is necessary.

Multitasking as a standard

Modern boiler controls can ’multitask’. They can optimise the heat output of heat generators, heating circuits, and heating control. However, lack of knowledge means they are often not used to their full advantage.

Correct setup helps to improve efficiencies and extend the lifetime of the products, as it ensures even use across the installation. Given larger turndown ratios – the operational range of the boiler – increases with the number of boilers used, installing multiple boilers rather than one can reap significant energy-saving benefits. Heat requirements are matched by several boilers which operate in a more efficient mode together rather than only one providing all the heat at a higher, less efficient modulation. This is where built-in boiler controls are especially beneficial.

In multiple boiler arrangements, the boilers can be set to operate in different modes.

In unison control, the controller attempts to hold as many boiler modules firing at the same time to match the base load of the building. The aim of this setting is to have them all modulate to more efficient low fire together. In cascade control, the controller attempts to match the base load with as few boiler modules as possible. Each method has its own merits dependent on the hydraulic configuration local to the boilers.

Another benefit of multiple boilers is the availability of a backup during service or breakdown. While one boiler is out of use, others can step in to cover the heat demand without interrupting the heat supply. Using multiple boilers ensures even use across the installation for a longer product life, avoiding over- and underuse of individual boilers.

Looking beyond the boiler

To make the best use of modern technology, the heating system should be looked at as a whole. Efficiencies can be improved by using advanced boiler controls, sensors, mapping out high/low use areas of a building, and considering heat up time. With the use of multiple boilers in combination with built-in controls, further energy savings can be achieved. This benefits not only carbon emissions and energy costs but can also extend the reliability and lifetime of a system.

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