Alternatives to HCFCs in the Refrigeration and Air Conditioning Sector 57 S ection 02 such a plant and for chillers with a flooded system it could be expected to be 140 to 150 kg ammonia. C. To improve the energy efficiency, the chillers were equipped with inverters which facilitate a stable operation, thus avoiding start and stop operation as well as minimising the temperature differences in the heat exchangers. To optimise the energy efficiency and get early warning if D. any component’s performance deteriorates, a web-based remote monitoring system was installed. This allows the contractor as well as end user to monitor efficiency and also receive alarms if any values went out of normal range. Fig. 2.15 shows that the close control of temperatures in the system is possible with the inverter controlled compressor. The evaporation varies by approximately one degree with an average of -11.4 °C at a secondary temperature of -6.1 °C leaving the evaporator. The two ammonia chillers installed had been in operation for two years showing an improved energy efficiency and reliability relative to the old system. As the systems are factory-built, compact units with remote monitoring required little from the local operators. Supervision is mainly done remotely on the internet and the local staff can, if needed, request support from the manufacturer or contractor at any time if any value is out of limits or to discuss opportunities for energy optimisation. The COP of the ammonia chillers when supplying -6°C brine at condensing temperature 30°C is in average 3.0. The two compact low charge ammonia chillers operate reliably with minimum service requirements. Fig. 2.15 Graph of evaporation (green) and secondary temperatures show a stable operation during 24 hours without any compressor start/stops. 454035302520151050-5-10-1511:41:4212:43:4313:45:4414:46:4415:47:4416:48:4417:50:4518:51:4519:55:4820:56:4821:58:4922:59:4923:57:4600:58:4602:02:4903:06:5204:07:5205:11:5506:12:5507:16:5808:17:5809:19:5910:20:5911:23:0012:27:03Brine inBrine outEvaporation tempCoolant inCoolant outCondensing tempCompressor discharge28.1 OC29.7 OC5.7 OC-3.3 OC-5.5 OCPower in = 39.1 kWCOP = 3.3Cooling cap. = 179 kW29.9 OC58.9 OC1.71 Bar11.32 Bar20.9 OC20.7 OC-2.9 OC-2.8 OC-0.2 OCPower in = 0 kWCOP = 0Cooling cap. = 0 kW21.8 OC22.8 OC2.66 Bar8.06 Bar0.0 %72.4 % Fig. 2.14 Schematic flow chart from a web-based monitoring system showing relevant parameters for supervision and performance optimisation.