Energy Efficient Air Conditioning 25
CHIEVING EFFICIENT DESIGN in DX air conditioning systems is somewhat more complex than just locating indoor units and outdoor units within a building’s structure. There are some basic top tips to help keep systems as efficient as possible: - Keep pipe runs to a minimum. Designs tend to locate the outdoor units within a single area on the roof or close to a building. This can lead to longer pipe than necessary, while manufacturers will allow ever increasing lengths of inter-connecting pipe work to be used. With systems up to 1km it is best to reduce these to manageable distances, as a significant amount of energy can be adsorbed in distributing the refrigerant around a building.
Ensure that air flow distribution is understood. When locating outdoor units it is best to allow free air flow around the systems. If site restricts the location of
Top tips for energy efficient systems A
outdoor units to confined areas such as light wells or internal plant rooms make sure that the locations are not overloaded and the air flow from the discharge and returns should not be mixed. While the outdoor units are normally able to deal with a degree external static pressure and higher than normal on coil temperatures, a bad design can create situations where systems will not achieve the predicted energy use due to the high temperatures created by the rejected heat and conversely areas of cold during heating.
Indoor unit location is critical. Designers should ensure that these units are located to prevent air flow recirculation. This can be an issue particularly with ceiling mounted type units, as the use of the correct grille types and checking air flow patterns can adversely affect end users comfort by causing cold drafts or stratification, especially if
the indoor units vary their fan speeds below the threshold of the grilles’ capacity.
The use of zoning and individual set points is becoming intrinsic in a system’s design, but control systems should also allow for set point resetting and possible restricting set point changes so that end-users cannot over-cool or heat a space.
Further increases in efficiency can be gained by using a mixture of heat pumps and heat recovery systems together. Typically heat pump systems on internal loads and heat recovery systems where there is a constant cooling load, such as a computer room, and mix this with a constant heating load for low grade hot water or air curtain applications. It is also a good practice to mix external loads in the same way as it allows for solar or internal heat gains to be distributed to cooler areas with in a building.
It cannot be over-emphasised that system maintenance is
vital. Dirty coils, blocked air filters and restricted air flows will have a significant effect on a system’s performance and life expectancy. Actively managing a system’s time scheduling to ensure it meets the occupants’ needs can also reduce running costs.
While these procedures may appear to be relatively simple it should be recognised that building surveillance studies have concluded that poorly performing systems within buildings tend to be badly designed and/or poorly maintained. Given the focus that building regulations is putting energy efficiency we should ensure that these systems are kept to optimum performance levels. The IoR Service Engineers Section Air Conditioning and Heat Pump Group provides regular guidance on news and technical tips for engineers for subscribers.
See more tips and advice at
www.ior.org.uk/achpi
Frimatech
Visit ACR News online at
www.acr-news.com
ACR News February 2015
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