CHILLERS
technology and heat exchanger designs that maximise the effi ciency and heat transfer capabilities of propane. An important aspect to consider for any system is the heat loads that the unit will be expected to run. When peak heating loads (in winter) or peak cooling loads (in summer) dictate additional capacity requirements, a two-pipe reversible heat pump provides an economical solution. A modular confi guration enables defrost periods and
improves system part load effi ciency even further. At low operating temperatures, defrosting the heat pump’s heat exchanger is a necessary process to maintain system performance and effi ciency. A quick and simple method involves reversing the function of the heat pump to take heat from the water circuit and reversing the function of the outdoor heat exchanger from evaporator to condenser. It’s essential to maintain suffi cient hot water content to support temporary reverse cycle operation, which is necessary to defrost the outdoor unit’s heat exchanger.
With multiple heat pumps bolted together, it is important to sequence the defrost cycle so that heating can still be delivered to the building during this process. When designing a system, it’s also important to consider that heat pumps all have a minimum water volume requirement, as well as low operating temperatures. A buff er vessel will ensure that the heat pump runs for a minimum amount of time in order to reduce the number of times that the compressor will switch on and off , therefore reducing the wear and tear of the compressor. Using buff er vessels can be very benefi cial as they can help to minimise any potential fl uctuations in the supplied fl ow temperature.
Download the ACR News app today
Safety fi rst
Ensuring safety when designing a propane heat pump system is vital in all situations, and there are very stringent standards in place to ensure proper ventilation, leak detection, and positioning are all taken into consideration. Due to its high fl ammability, the use of propane in
refrigeration systems is governed by strict safety standards, such as EN 378. Propane heat pump systems are required to have built-in leak detection and ATEX-approved fans. ATEX is the term commonly used for the two European directives for controlling explosive atmospheres, which are Directives 99/92/ EC and 2014/34/EU. The water circuit is required to have an automatic air purge system to release refrigerant and a water pressure relief valve in the event of a water heat exchanger fault (Site-Installed). These must be installed or ducted outside of the building, away from potential ignition sources. However, it’s important to note that because propane is
highly fl ammable, it requires careful handling and adherence to strict safety protocols. Reputable suppliers of propane heat pumps should always issue guidelines with their products, and it is imperative that installation, maintenance, service and commissioning are always carried out by qualifi ed class A3 refrigerant engineers. Always check, never assume! The adoption of propane in modern HVAC heat pump systems represents a signifi cant step towards more sustainable and energy-effi cient cooling and heating solutions. With environmental benefi ts, high performance, and cost- eff ectiveness, propane is poised to play a crucial role in the future of HVAC technology.
If we consider the overall life cycle, fi nancial and environmental benefi ts of such a
change, in my experience, they
usually far outweigh any inconvenience or upfront capital cost.
www.acr-news.com • June 2025 31
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52
