So you need an uninterruptible power supply unit, but you're having trouble sizing it. How do you figure it out? Some uninteruptible power supply (UPS) systems are rated in kilowatts (kW) and others in kilo-volt-amperes (kVA).  First, let's review the confusing terminology and facts: For years, large UPS systems have been designed based on a PF of 0.8, which means that a 100 kVA UPS will only support 80 kW of "real" power load. Most UPS systems continue to be designed that way, even though the majority of technology today has power factors of 0.95 – 0.98. Neither the kW nor the kVA capacity of the UPS can be exceeded, but because of the higher PF numbers, it is usually the kW rating that governs today. There are, however, some UPS systems on the market that are PF-corrected so that the kW and kVA ratings are the same. Nameplate data on UPS systems The biggest problem when figuring size requirements for UPS units is determining their actual load. Many data hardware manufacturers still provide very inadequate or erroneous power data on their equipment.

Bigger manufacturers are usually linked to or have a configurator on their websites. ac unit to buyThese tend to give quite accurate information.small one room ac unit Beware of using the nameplate. estimated cost to replace ac unitThis is a legality rating, and will usually give a much higher volt-ampere rating than the unit will ever draw. For example, consider a unit with a nameplate that reads 90 – 240 volts at 4 – 8 amps with a 500 watt power supply. First, the numbers are backwards. The larger amperage goes with the lower voltage. If you assume a nominal 120 volts at 8 amps, you get 960 VA. A pf of 0.95 would yield 912 watts. No power supply is that inefficient, and a power supply almost never runs at full power. Therefore, it is highly unlikely that this device will ever draw more than 500 watts of power, but if you want to be really conservative, multiply by 1.1 and figure 550 watts of input power.

And don't get trapped by dual-corded equipment. The power supplies share the load and either one is supposed to be able to carry the full load. Therefore, a unit with two 500 watt supplies should still be figured as if it had only one. ABOUT THE AUTHOR: Robert McFarlane is a pioneer in the field of building cabling design. He has been asked to speak at countless seminars on building infrastructure for electronic communications, evolving technologies and the requirements of trading floor and data center design. Mr. McFarlane served for twelve years as President of Interport Financial, Inc., a firm specializing in designs for financial trading floors and critical data centers.Subscribe in a reader Enter your email address:Delivered by FeedBurner Book of the Week: The Millionaire Next Door More Bad News on Retirement What's the Top Financial Stress in Your State? You Can Retire Early on an Average Income Star Money Articles for Week of September 19 Save a Ton by Having Your Wedding on a Thursday

Why People Quit Their Jobs Star Money Articles for Week of September 12 Any information shared on Free Money Finance does not constitute financial advice. The Website is intended to provide general information only and does not attempt to give you advice that relates to your specific circumstances. You are advised to discuss your specific requirements with an independent financial adviser. Per FTC guidelines, this website may be compensated by companies mentioned through advertising, affiliate programs or otherwise. All posts are © 2005-2012, Free Money Finance.Honeywell Indoor Portable Evaporative Air Cooler Honeywell Indoor Evaporative Air Cooler Honeywell Wi-Fi Thermostat - Smart, Programmable LG 10,000 BTU Portable Dehumidifying Air Conditioner LG 14,000 BTU Portable Air Conditioner/Heater w/Remote Honeywell Indoor/Outdoor Evaporative Air Cooler Honeywell Air Conditioner with Heat Pump - Black/Silver Honeywell 8,000 BTU Portable Dehumidifying AC w/Remote

LG 12,000 BTU Window-Mount Air Conditioner with Remote LG 7,500 BTU Window-Mount Air Conditioner with Remote Keystone 6,000 BTU 115V Window Air Conditioner LG 14,000 BTU Portable Air Conditioner w/LCD Remote Honeywell 12,000-BTU Air Conditioner - Black/Silver Honeywell 14,000-BTU Air Conditioner - Black/Silver Frigidaire Window-Mounted, 8,000-BTU Air Conditioner Frigidaire 18,500 BTU 230V Window Air Conditioner Honeywell 10,000-BTU Portable Air Conditioner Trim Kit for 26" Through-the-Wall Air Conditioners Stamped Aluminum Rear Grille for 26" Wall Sleeve EZ-AC Air Conditioning Support Bracket De'Longhi Pinguino 14,000 BTU Air Conditioner w/Wi-Fi De'Longhi Portable Air Conditioner Storage Cover LG Stamped Aluminum Rear Grille for 26" Wall Sleeve LG 26" Sleeve for Through-the-Wall Air Conditioners De'Longhi 14,000 BTU All-Season Portable AC w/Heat Pump De'Longhi Pinguino 3-in-1 13,000 BTU Portable AC