Legislation is having a big impact in the ventilation sector. Les Fish examines European Directives in the fans sector.
On April 6, 2011, the European Parliament issued an Official Journal which has far reaching implications in terms of the types of fans which will be acceptable for use within the European Union in future. Fan manufacturers, OEM customers of fan manufacturers and end-users of fanrelated products are all affected, and the focus of attention is 'efficiency'.
Directive 2009/125/EC of the European Parliament is the legal document referred to above, and the directive covers fans driven by electric motors with an electrical input power ranging from 125W to 500kW.
In 2007, EU leaders endorsed an integrated approach to climate and energy policy and committed to transforming Europe into a highly energy efficient, low carbon economy. They made a unilateral commitment that Europe would cut its emissions by at least 20 per cent of 1990 levels by 2020.
The thrust of the European legislation is to establish minimum efficiency standards for the various types of fans commonly in use, introducing these minimum efficiency standards in what have become known as 'two tiers'.
'Tier 1' becomes effective on 1 January, 2013, when the first round of minimum efficiency standards come into effect. Tier 2' becomes effective on 1 January, 2015, when the bar is raised, and the minimum efficiency standards in this Tier are more onerous than those in 'Tier 1'.
The regulation relating to fans is preceded by regulations aimed at reducing energy consumption in light bulbs and electric motors.
The efficiency of a fan in simple terms is the ratio of output (air) power and input (electrical) power. Output (air) power is the result of multiplying air flow volume (m3/s) by pressure (Pa). The pressure used in the calculation can be either static pressure or total pressure.
Total pressure = static pressure + dynamic pressure and fan efficiency can be stated as total efficiency (using total pressure) or static efficiency (using static pressure). Depending upon how the fan performance is measured, in terms of ducted or nonducted outlet, one or the other (static efficiency or total efficiency) is used.
(Ducted or non-ducted outlet places the measurement method into a measurement category).
Input (electrical) power for a three phase motor directly driven fan is given by: √3 x voltage (volts) x current (amps) x cosф (power factor) The fan performance is measured to determine peak efficiency (static or total, depending upon the measurement category), and the electrical power absorbed at this point is used in a calculation to determine the target energy efficiency'.
The selection of the correct calculation is dependent upon whether:
· the performance is measured with or without outlet duct and
· the electrical input power at peak efficiency is greater than 10kW or less than or equal to 10kW.
For the purpose of the Directive, fans are grouped into six fan types:
· Axial fan
· Centrifugal forward curved fan and centrifugal radial bladed fan
· Centrifugal backward curved fan without housing
· Centrifugal backward curved fan with housing
· Mixed flow fan
· Cross flow fan
For each fan type there are similar but different calculations to determine the 'target efficiency', this being the minimum efficiency the fan must achieve to be compliant with the Directive.
Consider the determination of 'target efficiency' for an axial fan for Tier 1 compliance:
Assume input electrical power of axial fan measured without ducted outlet is 500W (0.5kW)
ηtarget =2.74 x ln(0.5)-6.33 + 36
= 2.74 x (-0.69315) - 6.33
= 27.77 per cent
If the measured peak efficiency of the fan achieves or exceeds this minimum efficiency value, it is considered compliant with the Directive, often referred to as ErP 2102 compliant.
Consider that, in 2015, the values of (N) for axial fans increase from 36 to 40, and from 50 to 58.
There is a degree of latitude which the Directive allows (measured efficiency must be at least target energy efficiency x 0.9), which will be interpreted by different manufacturers in different ways, the riskier option being to apply the full 10 per cent. Manufacturing tolerances would suggest this is unwise; discovery of a non-compliant fan being offered as a compliant fan will prove less than helpful for the manufacturer in question.
There is also the possibility within the Directive of allowing the use of fans which are very nearly compliant to be used as long as they are only used with a frequency inverter. This is a curious concession, which is based upon the premise that the fan will be speed controlled, and the inverter will indeed realise a reduction in energy consumption (compared with voltage-based speed control). If the fan runs at full speed, however, the inherent losses in an inverter will actually increase the energy consumption.
There is, of course, much more to this Directive than is shown here, and the original document should be referred to for absolute clarity.
• Les Fish is managing director of Ziehl-Abegg UK