Potential Power Factor Problems in LED & T5 Retrofit Tubes Australian businesses are embracing the opportunities to improve energy efficiency within their workplaces, and reduce electricity consumption operating costs. Lighting upgrades provide businesses with significant energy savings with ROI’s typically between 30-70%. A popular investment choice for businesses is replacing their existing T8 1200mm 36W Fluorescent Tubes with retrofit LED (18W-22W) and T5 Fluorescent (22W-28W) Tubes. Picture 1 – T8 LED & T5 Fluorescent Retrofit Tubes These types of retrofit tubes provide a cost effective solution for reducing energy costs. However; if installed into a magnetic iron core ballast lighting fixture without any modifications (i.e. bypassing the ballast and capacitor), then the power factor (pf) of the circuit is reduced which means the electrical efficiency of the circuit has been degraded. Unfortunately there are some wholesalers, sales people and installers of LED and T5 retrofit products that advise that their products can be simply swapped over, without any modifications performed by a qualified electrician, and do not advise on the increased current (A) that is introduced due to poor power factor. This approach should not be considered as best practice. What is Power Factor (pf)? The power factor of an AC electrical power system is defined as the ratio of the real power flowing to the load, to the apparent power in the circuit1, and is a dimensionless number between -1 and 1 which highlights the efficiency of the electrical circuit. Real power (W) is the capacity of the circuit for performing work in a particular time, and is what most businesses are charged in their tariff in the form of kWh. Apparent power (VA) is the product of the current and voltage of the circuit, and is what the electrical utility needs to deliver to a client’s site to operate the electrical loads. 2 x 36W T8 Tubes Picture 2 – pf measurement of a 2 x 36W Fluorescent tubes in a standard office troffer lighting fixture (fixture using magnetic iron core ballast) As highlighted in Picture 2; a standard twin 36W fluorescent tube troffer has a power factor (pf) of ~0.85, which means that 85% of the total power drawn through the electrical circuit is used for “real work”. The other ~15% is due to inefficiencies within the electrical load that restricts the 100% conversion of total power drawn (Apparent Power) into electrical work achieved (Real Power). LED + T5 Power Factor (pf) in Unmodified Lighting Fixtures (fixtures using magnetic iron core ballasts) When LED and T5 retrofit tubes are used to directly replace T8 Fluorescent tubes (without modifications), the following power factor measurements are recorded: 2 x 26W T5 Tubes 2 x 18W LED Tubes Apparent Power Real Power Picture 3 – pf measurement of a 2 x 18W LED & 2 x 28W T5 retrofit tubes in a standard office troffer lighting fixture (fixture using magnetic iron core ballast) As highlighted in Picture 3; an unmodified troffer with LED or T5 retrofit tubes installed can have a power factor (pf) of ~0.25, which means that 25% of the total power drawn through the electrical circuit is used for “real work”. The other ~75% is due to increased inefficiencies, introduced by the retrofit tubes, within the electrical load that restricts the 100% conversion of total power drawn (Apparent Power) into electrical work achieved (Real Power). Even though the wattage has reduced by 56%, the current (A) has increased by 53% compared to the original 2 x 36W Fluorescent tube troffer. LED + T5 Power Factor (pf) in Modified Lighting Fixtures (bypassing magnetic iron core ballasts & capacitor) When LED and T5 retrofit tubes are used to directly replace T8 Fluorescent tubes (with bypassing modifications), the following power factor measurements are recorded: 2 x 26W T5 Tubes 2 x 18W LED Tubes Apparent Power Real Power Picture 4 – pf measurement of a 2 x 18W LED & 2 x 28W T5 retrofit tubes in a standard office troffer lighting fixture (bypassing magnetic iron core ballast & capacitor) As highlighted in Picture 4; a modified2 troffer with LED or T5 retrofit tubes installed can have a power factor (pf) of ~0.98, which means that 98% of the total power drawn through the electrical circuit is used for “real work”. The other ~2% is due to decreased inefficiencies, introduced by the retrofit tubes and modified troffer, within the electrical load that restricts the 100% conversion of total power drawn (Apparent Power) into electrical work achieved (Real Power). The power factor has improved, the wattage has reduced by 57%, and the current (A) has decreased by 61% compared to the original 2 x 36W Fluorescent tube troffer. Summary of Performance Lighting Fixture Real Power (W) Apparent Power (VA) Power Factor (pf) Amps (A) Standard 2 x 36W Troffer 90W 106VA 0.85 0.428A Unmodified 2 x 18W LED Troffer 40W 164VA 0.24 0.654A Unmodified 2 x 26W T5 Troffer 57W 159VA 0.36 0.633A Modified 2 x 18W LED Troffer 39W 41VA 0.95 0.167A Modified 2 x 26W T5 Troffer 57W 58VA 0.98 0.232A As highlighted in the table above; poor power factor and increased current (A) draw is introduced into the lighting circuit when LED & T5 retrofit tubes are installed without bypassing the magnetic iron core ballast and capacitor within the linear lighting systems. Consequences from poor Power Factor A load with a low power factor draws more current than a load with a high power factor for the same amount of useful power transferred. The higher currents increase the energy lost in the distribution system, and all components of the system such as generators, conductors, transformers, and switchgear would be need to be increased in size (and cost) to carry the extra current drawn throughout the network3. The poor power factor issue in unmodified LED & T5 retrofit linear lighting systems may be insignificant when reviewed in small installations, but if allowed to be installed in significant numbers across Australia this will work against reducing the CO2e even when a financial ($) benefit is achieved for the business that invests in retrofit LED & T5 tubes, unless Power Factor Correction systems are installed at their site. The key issues to consider when LED & T5 retrofits are installed in unmodified linear fluorescent lighting systems are as follows:  Increased current (A) draw within the lighting circuit, causing potential overloading issues.  Increased pressure on power generation requirements due to increased inefficiencies.  Increased CO2e associated with sites that do not have power factor correction systems installed. References: 1 IEEE Std. 100 Authoritative Dictionary of Standards Terms, 7th edition ISBN 0-7381-2601-2 2 Electrical Regulatory Authorities Council (ERAC) Website: http://www.erac.gov.au/images/Downloads/0001%20-%20T8T5%20flourescent%20lamp%20adaptor%20retrofits.pdf 3 Power Factor definition - Wikipedia Website: http://en.wikipedia.org/wiki/Power_factor