Using a decentralised water loop heat pump system could be the answer to meeting the challenges of providing year-round heating and cooling says Andy Mayes of Clivet UK
THE current trend in air conditioning design is based on the following considerations: the need to provide a flexible solution to the year round heating and cooling requirements; minimal impact on the environment; low energy consumption, operating and maintenance costs; and simple and fast installation costs.

Accommodating all these considerations in a single solution can present a challenge, but there is a tried and proven solution. For many applications this can be resolved by utilising a decentralised water loop heat pump system, which provides controllable heating and cooling as circumstances demand.

Why decentralised systems?

In the majority of buildings, factors such as the actual occupancy, lighting, solar gain etc, are, for the majority of the time, variable for year- round design of the air conditioning system. Although diversity factors can be taken into account, it is important that the air conditioning system employed is able to respond to both peak demand and part-load whilst still maintaining high efficiency.

If this is not the case, the system is, in effect, oversized or undersized for much of the year and can result in poor climate control and high running costs. Many centralised systems provide lower efficiencies during periods of part load and this can be for as much as 95% of the season. Typical load profiles for different types of building illustrate this point with restaurants, bars and offices requiring very different peak loads.

The majority of buildings not only require efficiency throughout this variable load profile but also demand simultaneous heating and cooling in different areas of the building. It is important for the designer to understand how the system will perform in such situations, as many centralised systems may be operating at reduced efficiency during simultaneous heating and cooling.

One of the most efficient decentralised systems is the water loop heat pump system which also boasts minimum impact on the environment. It has proven reliability, is flexible and more able to adapt to changing building requirements.

Most significantly, this system does not suffer from the disadvantages that some airside direct expansion heat pumps exhibit when trying to operate in low ambient conditions.

Clivet offers a large range of terminal units suitable for inclusion on a water loop and which are designed with a minimal quantity of hermetically sealed HFC refrigerant to reduce any risk of leakage. The terminal units are designed with a high COP and low TEWI.

What is a reverse cycle water loop system?

In its most basic form, a water loop system both for heating and cooling will consist of a two-pipe water loop, a means of heat injection and rejection, water circulating pumps and a quantity of packaged terminal water source heat pump units.

The system provides both heating and cooling around the building, with terminal units either taking heat from the water loop or injecting heat into it as required.

Unwanted heat is taken from areas requiring cooling and transferred to the water loop. Conversely, areas requiring heating will take heat from the water; thereby for a large part of the year restoring the thermal balance within the water loop and providing energy reclaim capability.

The benefits of a water loop system?

One of the main reasons designers are turning to water loop systems is due to the cost benefits that can be gained. Running costs can be very attractive with terminal units offering heating COPs in the region of 5, and when compared to traditional systems, major savings can be gained. Installation costs are also very low due to the simple uninsulated two-pipe water loop required.

Furthermore, with packaged terminal units there is no need for expensive refrigerant skills; the terminal units simply require a local electrical supply, flow and return water connections and a condensate drain.

A major benefit of packaged terminal units is that they can be easily isolated and maintained without disruption to the rest of the system. This is because each terminal unit has its own sealed and self-contained refrigerant circuit designed with a minimal refrigerant charge, thereby ensuring both minimum environmental impact and low maintenance costs.

Simple system design is also a major benefit to be gained when employing a water loop system, for each element of the system design is well established and proven, factors that are essential in reducing risk to clients.

The range of water source units suitable from Clivet for inclusion within the system extends from the smaller capacity Versatemp range to larger capacity cabinet and roof-top units. With careful design, consideration can be given to future building requirements, allowing for expansion of the water loop and the introduction of further terminal units, none of which reduce the efficiency of the initial design stages. Additionally, water loops can capitalise on waste heat and cooling from industrial processes.

Frequently this heat or cooling is dissipated into the outside ambient with users paying both to generate the energy and also to reject it. However the water loop is a good means of utilising this energy for the purposes of heating or cooling other areas of the building.

Controlling such a system may at first sight appear to be complex. However, the only requirement is a water loop controller to ensure the correct heat injection and rejection, together with a suitable water flow rate prior to initialising the individual terminal units, ensuring a simple yet powerful system.

The terminal units may be supplied with various control options, factory-fitted for individual control or for BMS interface ensuring that all clients’ needs are catered for.



Is there a choice in terminal units?

The range of reverse cycle heat pump units manufactured by Clivet for installation on water loop are designed to provide both cooling and heating to ensure a comfortable all-year-round environment is achieved. The units are capable of automatic heating and cooling as required to ensure they reach their individual set points.

The extensive product range starts with wall mounted units suitable for small offices giving just 1.5kW of heating and cooling and increases up to the larger ducted rooftop units suitable for shopping centres and public buildings with heating and cooling capacities exceeding 300kW. These units are also designed for specific applications including offices, hotel bedrooms, theatres and cinemas.

Additional water loop products

Clivet has recently added two new products to its water loop catalogue, these being the EVH Room and EVH Space product ranges. The EVH Room range consists of terminal units with heating/cooling duties from 1.7kW-7.1kW and offer high COPs and EERs. Each unit incorporates a high quality rotary compressor, thermostatic expansion valves and brazed plate heat exchanger, the result being a highly efficient unit.

The units come as standard with the Clivet Talk Electronics and HID controller designed to offer the customer a range of options including differential pressure switch and solenoid valve control of the water flow for variable flow water loop systems.

The EVH Space range builds on the capabilities of the EVH Room by extending the heating and cooling capacities from 9kW-36kW. In addition the EVH Space range incorporates scroll compressors and can include a serial converter on the controls enabling up to 127 units to be controlled via a MODbus protocol.

Clivet UK 01489 572238