With rising energy costs and increasingly ambitious environmental goals, heat pumps have been gaining recognition as an efficient heating and cooling solution for a wide range of commercial, institutional and industrial buildings, says Richard James
Heat pumps rely on one of themost energy-efficient methods of heating a building: the transfer of free thermal energy from outside to inside based on the difference in temperature between the two. Reversible-cycle heat pumps offer both heating and cooling, depending on what is required. Compared to a boiler and chiller system, reversible cycle heat pumps offer the distinct advantage of combining heating and cooling in one piece of equipment.

Keeping pace with the increasing demand for heat pumps is the growing number and variety of heat pumps currently on the market. Defining your priorities and requirements will simplify your final decision about which heat pump to install. This article discusses seven criteria that are important, in varying degrees, for most buildings.

Today, commercial buildings account for over 33 per cent of total energy consumption in the European Union (EU). It is estimated that 32 per cent of the energy used in EU commercial buildings is consumed by heating, ventilation and air-conditioning (HVAC) systems. Reducing that percentage, and therefore energy costs, is a priority for most building owners. Both regular and reversible-cycle heat pumps offer significant energy savings because of their inherently efficient heating technology. Still, not every heat pump offers the same results. If energy efficiency is your top priority, look for heat pumps that come with Eurovent certification, have an Energy Efficiency Ratio (EER) higher than 3.2 and have a Class A energy efficiency rating for meeting the highest European standards.

Rising noise levels

As acoustic requirements for a variety of building types have grown increasingly stringent, sound is likely to become more important for building owners. However, improving heat pump energy efficiency has always come at the expense of rising noise levels due to more or larger fans and other components. Building owners typically face a trade-off: low noise and low energy efficiency or high energy efficiency and high noise.

Recent advances in casings, heat exchangers, compressor enclosures and fans offer a solution with the introduction of new a generation of heat pumps, lead by the Trane AquaStream3G, that are both quiet and efficient. So if you feel you are compromising on energy efficiency or sound levels, there are better options available.

Building owners must be able to rely on their HVAC system working efficiently with limited or no downtime. A number of factors can be considered when thinking about the reliability of an HVAC system, including the reputation of the manufacturer, the product testing the manufacturer undertakes on every unit, the quality controls in place during production and the location of their after-sales service departments.

A number of system features help ensure maximum heat pump reliability. For example, smart defrost cycles significantly reduce energy consumption and possible unit downtime. Electronic expansion valves provideb etter part-load performance and superior refrigerant control. The quality and integration of the unit and system controller can also guarantee stable and reliable operation.

Optional technologies are currently available to increase the energy efficiency of heat pumps even further. Heat recovery is one such option, whereby heat rejected through a condenser is recovered and then used for another purpose. Partial heat recovery, for example, allows the recovery of energy from the compressor's discharge.

The energy is used to heat the water in a secondary circuit up to 70°C. Another option is variable frequency drive technology, which reduces energy consumption by adjusting the flow control to meet actual requirement.

One aspect of an HVAC system that doesn't often receive the attention it deserves is maintenance. There is a simple correlation between the time taken for maintenance and the costs, both direct costs from the maintenance bills themselves and indirect costs due to downtime and effects on productivity of a less than optimal working environment. Plus, after the original purchase price, maintenance costs constitute an important part of the total cost of ownership
of the HVAC system.

Making maintenance easy

In order to reduce maintenance costs, a heat pump system must be built to
make maintenance as easy as possible.

This can include:

open designs

;

positioning of all components

(including compressors, valves and
pressure ports) within 300mm of the edge of the unit;

fitting fans on hinges so they can be safely accessed from outside the unit;

an easily accessible pump package;

and

optimization of the controller for easy diagnostics and reports.

Experience has taught us that every customer is unique. What is more, geographical location, high or low ambient temperatures or extreme water temperatures can necessitate tailored solutions. Make sure to check whether the heat pump system you are considering offers the operating range for ambient and water temperatures your application or situation requires.

The total cost of ownership (TCO) comprises all costs associated with the heat pump. This includes the purchase cost of the system (design, development and installation), running costs (maintenance and repair costs and time) plus recycling costs or resale value at the end of its lifecycle.

Even though the initial purchase price of one system may be higher than another, the better system leads to a lower TCO over the course of its lifecycle because it is more reliable or easier to maintain. For this reason, it is important to look beyond the initial cost to see the bigger picture.

Innovations in HVAC systems have led to new heat pump designs that can offer significant benefits compared to the systems that they are designed to replace. As we have seen, it is important to decide on your priorities before investigating your heat pump options. Energy efficiency, noise levels, reliability, optional energy efficiency technologies, maintenance, options for customization and TCO all play a role in finding the heat pump that best fits your needs.

New generation heat pump

The Trane AquaStream3G is an example of a new generation heat pump claimed to provide a solution to the traditional trade-off between energy efficiency and low sound levels.

The AquaStream3G comes with a Eurovent Certification and Class A energy efficiency rating. At the same time, the AquaStream3G offers three low sound levels: Compact (typical sound levels currently on the market); Super-Quiet (5 dB(A) quieter than Compact); and Comprehensive Acoustic Package (8 dB(A) quieter than Compact).

// The author is sales leader for Trane Commercial Systems, UK South //