The Efficient Way Forward
In recent years, the emergence of the 4-pipe chiller & heat pump has allowed engineers to heat and cool large buildings without the need for two separate pieces of equipment. Here we look at how the modern 4-pipe chiller can be the right technical solution for better cost-and-energy-efficient HVAC systems.
What are multifunction 4-pipe chillers?
A 4-pipe chiller (aka multifunction chiller) combines the function of a chiller and a boiler in a single machine, allowing for simultaneous heating and cooling. Until recently, a building required two separate systems – typically one chiller and one gas-powered boiler – to have heating AND cooling. This required complex pipework, extra plant room space, and higher maintenance costs.
Multifunction 4-pipe chillers are heat pump-based technology units that recover the thermal energy normally rejected and expelled outdoors by air-cooled condensers.
By recovering this lost heat, a multifunction 4-pipe chiller can harness it for hot water production, increasing the heat pump effect. This can potentially increase the Total Efficiency Ratio (TER) from 300% to over 700%.
How is a 4-pipe chiller more efficient?
A traditional, 2-pipe system can only heat or cool a building at any time – it cannot do both at once. In the process of cooling, a chiller generates thermal energy or heat as a by-product. In a 2-pipe system, this heat dissipates into the surrounding environment. The heat wasted by a traditional system can be up to 25% more than the cooling it provides.
In a 4-pipe system, the heat is captured and used to power the heating needs of the building. This means that far less energy is required to produce the same heat, resulting in improved energy efficiency, reduced operational costs, and a smaller carbon footprint.
How are water volumes and system applications important?
System water volumes are an important consideration for multi-function chillers. When considering initial applications, a good rule of thumb is 10L per kW of cooling capacity.
Stable operation is provided by having sufficient water volume. This is best served in a primary/secondary HHW/CHW water system by using the buffer tank as a decoupling device and making the secondary pumps variable flow. The buffer tank is like a thermal battery which the chiller will charge as required and the field will draw from it as needed.
Learn how to size your buffer tank here.
How can I cut expenses?
As the requirement of removing gas from commercial buildings increases, it’s now becoming more popular to replace gas-fired boilers with more efficient multifunction chillers.
The simultaneous heating and cooling cuts capital and maintenance expenditure because instead of the traditional need for both a chiller for cold water and a boiler for heat, you can have a range of hot and cold temperatures from one piece of equipment.
The efficiency of this combined with the cut cost of one complex piece of equipment means your client will be saving money and reducing their carbon footprint as less energy is wasted.
Who uses simultaneous heating and cooling?
4-pipe chillers are best suited for use in large commercial buildings that spend a significant portion of the year in those “in-between” temperatures (neither extreme heat nor extreme cold). Both heating and cooling might be called for in different sections of a given building depending on the preferences of the residents, exposure to the sun during that time of day, and a variety of other factors. A 4-pipe chiller can handle this.
Boilers work independently, rejecting heat outside and burning fossil fuels.
Using the heat absorbed from the cooling load of the chiller to produce heating water as a bi-product is far more efficient and environmentally sustainable, potentially eliminating or reducing reliance on the burning of fossil fuels.
Simultaneous heating and cooling works in buildings and hotels with facades exposed to different points of the compass/internal office equipment, people and lights.
It’s also appropriate for hospitals with various medical processes and comfort conditions for patients and staff, manufacturing and production requiring hot and cold water for various processes, and commercial applications such as supermarkets, shopping centres, and retail outlets.
What’s the Total Efficiency Ratio?
TER (or Total Efficiency Ratio) in 4-pipe chillers is the point where the cooling and heating loads are balanced – this doesn’t mean they’re equal.
In the case of an air-to-water 4-pipe chiller, TER refers to the available recovery heating capacity at 45 degrees Celsius, leaving heating hot water temperature and cooling capacity when the leaving chilled water temperature is 7 degrees Celsius.
Therefore, no heat is being rejected or absorbed from the external heat exchanger, and no fans are running. In other words, it’s heating capacity + cooling capacity / compressor power input only. In this situation, the heating capacity will almost always be 20-25% higher than the cooling capacity.
Masterflow’s 4-pipe chillers
Masterflow offers a range of combined chiller and heat pumps that are selected and priced locally. The SPINchiller Multifunction by Clivet is an exceptionally efficient liquid chiller and heat pump. The SPINchiller can supply hot and cold water simultaneously and deliver cooling with an outdoor temperature of up to 52°C. The system features an advanced heat recovery device that can harvest thermal energy created through cooling to cover the heat load required.