Heat Recovery


The HWHPTS is vastly different, both in design and operation
to all other known heat pump systems


The water storage cylinder is connected to the cold water supply at its base. As soon as the refrigeration plant starts to operate, cold water flows out of the cylinder base and into the inner tube of the double pipe heat exchanger where it passes in contra-flow with refrigerant flowing through the outer tube and is heated. The refrigerant is fully condensed. Water flows by natural thermo-dynamic action through the superheat region of the refrigerant, which causes it to be heated 5-7° C above condensing temperature before entering the top of the insulated cylinder where it is stored until required. This hot water does not mix with the cold water in the cylinder, thus the user is provided with a supply of sufficiently hot water, eg at 55° C based on a condensing-temperature of 48° C, within a few minutes of plant startup.

Boost heating using costly primary energy is necessary only in exceptional cases. The Permanent Transfer System even sub-cools the refrigerant, resulting in a further energy gain. If desired, this energy gain can be utilised to increase the condensing pressure and hence hot water temperature to provide an instantaneous supply of pasteurised water.

One of the most important features of the Permanent Transfer System is the location of the heat exchangers. These are arranged beneath the insulation jacket and are wound spirally around the cylinder but have no contact with the cylinder wall. The exchangers are continuously supplied with “mains cold” water from the cylinder base even when no hot water is being drawn off. All of the waste heat is transferred until the cylinder is filled, from top to bottom, with hot water. This is attributable to a further unique Permanent Transfer System design feature whereby the hot and cold water layers are maintained separate throughout the heat recovery process. The hot water produced is deposited gently at the top of the cylinder and spreads horizontally to form a clearly defined layer above the cold water block. The volume occupied by this hot water is the same as that flowing from the cylinder base through the exchanger. When the hot layer reaches the cylinder base, the refrigerant is diverted directly to the normal condenser using a by-pass circuit recommended by Eureka. This prevents both scaling of the exchanger and unnecessary operation of the refrigeration plant at an elevated condensing pressure.

Benefits of recovering refrigeration waste heat using an ultra-optimised system


The HWHPTS is designed for a wide range of applications including supermarkets, hospitals, nursing homes, bakeries, hotels, restaurants, food processing, and wherever a refrigeration plant from 2-400kW is operating.

• HOT WATER AT 50 – 60°C

The HWHPTS `harnesses waste heat from refrigeration to generate hot water at typically 50-60°C which is approximately 7°C above refrigerant condensing temperature. Hot water is available within minutes of the refrigerant plant running. Virtually 100% of the available condenser waste heat can be recovered.


The hot water produced is stored in a cylinder insulated against heat loss with an environmentally friendly, CFC-free polyurethane or foam filled jacket. Hot water can be stored over a prolonged period without significant temperature loss. The cylinder is internally lined with two coats of vitreous enamel and incorporates a magnesium sacrificial anode for corrosion protection. The cylinder is also equipped with a TUV-approved, push-button control unit for monitoring the effectiveness of the corrosion protection system both during and after the guarantee period. This enables the user to exploit the life-expectancy of the cylinder to the fullest.


AII heat exchangers incorporate a safety circuit using a pyramidal tube with leak detector. By means of this specially-developed system all of the waste heat energy can be transferred into water. All exchangers are Australian Watermark-approved and are registered with and monitored by the DVGW (German Association of Gas and Water Engineers). Test Mark: DIN-DVGW NW 9401 AR 3328. All exchangers are manufactured as standard in high-grade copper and are suitable for refrigerants R 134a, R 404A, R 407C, R 410A, R 507, R 22. Internal nickel plating is an available option for special applications.


The design of the HWHPTS has been developed from a considerable amount of practical experience. It operates automatically and without pumps. Because of Eureka’s special design, each water molecule flows through the exchanger only once and within the space of one minute. This contact time is too short for any significant lime scale formation. Should in extreme cases de-scaling become necessary, the exchanger can be quickly and economically cleaned using special connection points provided. It is not necessary to disconnect the water or refrigerant circuits.


HWHPTS models PTSAU 300, PTSAU 450, and PTSAU 500 incorporate water storage cylinders of 300, 450, and 500 litres volume, respectively. The storage capacity can be increased by parallel-connecting water storage cylinders of the same size. For very large capacities a variant model is used, the Permanent Transfer unit (PTE), which contains only heat exchangers. The PTE unit is parallel-connected on site with a water storage cylinder selected to match the exchanger capacity and/or the required water storage capacity. All water storage cylinders are fabricated from steel. Cylinders up to and including 2000 litres are lined with two coats of vitreous enamel. Cylinders 3000 litres and larger are synthetically lined internally with Rexit. All cylinders are suitable for providing potable water and feature a TUV-approved corrosion protection device.


The design and construction of the HWHPTS is such that virtually all known forms of corrosion have been eliminated. Based on the proven longevity of the unit, we guarantee the cylinder for five years while all other parts carry a two-year guarantee.