| Have you ever wondered why some power ratings | | | | you will use a 60% load factor on the UPS. If you |
| are expressed in WATTS, some in AMPS, some in | | | | overload a UPS it is almost certain to fail during a |
| VOLTS, and some in KVA? For many in the hosting | | | | power outage, as the draw on the batteries will |
| business this can be a very confusing topic. Face it, | | | | exceed the capacity of the UPS. Most new UPSs will |
| professionals in the content business are probably not | | | | automatically go into battery bypass when an overload |
| electrical engineers, and most electrical engineers know | | | | condition occurs. The 60% load factor accounts for |
| nothing about the creation and delivery of content. | | | | the high probability that most of the equipment drawing |
| This article will explain in simple terms the difference | | | | power through the UPS will be of a category that has |
| between the major power ratings, and describe when | | | | a power factor of between.55 and.75. |
| each should be used in your network architecture | | | | Example 1 |
| planning. | | | | You have a 10KVA UPS. Your data center has racks |
| According to APC, the main difference between | | | | of low end self-assembled computers with a total |
| watts and volt amps is the watt rating determines the | | | | estimated rating of 9000 watts. Your UPS will most |
| actual draw of power from a power source and the | | | | like fail, as the power factor is probably around.70. You |
| heat generated from equipment. The VA rating is used | | | | would need at least 12.85KVA to adequately backup |
| for sizing equipment such as circuit breakers, wiring, | | | | the data center. |
| and UPS. The VA rating is normally equal to or higher | | | | Example 2 |
| than the watt rating, as it includes the "power factor" in | | | | You have a 10KVA UPS. Your data center has racks |
| its calculation. | | | | of low end self-assembled computers with a total |
| Power Factors | | | | estimated rating of 6000 watts. Your UPS will be able |
| The Power Factor is a calculation used to account for | | | | to handle the load, as the power factor corrected |
| the difference in power supplies used to convert AC | | | | rating will require approximately 8.5KVA of UPS. |
| power into DC for use in electrical appliances and | | | | Some modern UPSs will actually tell you the average |
| computer equipment. There are two types of power | | | | power factor and real time load capacity of the UPS. |
| supplies - the capacitor input supply and the power | | | | Some Useful Conversion Factorso Refrigeration |
| factor corrected supply. | | | | - 1 watt =.86 kcal/h |
| Power factor corrected supplies are used in most high | | | | - 1 watt = 3.412 Btu/h |
| end computing and switching equipment, and have a | | | | - 1 watt = 2.843 x 10-4 tons |
| ratio of 1VA:1W - allowing a very simple calculation for | | | | - 1 ton = 200 Btu/min |
| scaling electrical equipment and UPS. Thus, in theory, if | | | | - 1 ton = 12,000 Btu/h |
| your power factor is 1:1, and your UPS is an 80KVA | | | | - 1 ton = 3,517.2 Wo kVA Conversions |
| UPS, then you would be able to load the UPS to 100% | | | | Three phasekVA = V ï?--ïEUR A |
| of its rating. | | | | ï?--ïEUR √3 ⁄ïEUR 1000 |
| Older electrical equipment, as well as most lower end | | | | Single phasekVA = V ï?--ïEUR A |
| computers and video equipment use capacitor input | | | | ڕEUR 1000 |
| power supplies and have a power factor anywhere | | | | FormulaskVA = Voltage x Current (amps) |
| from.55 to.75 times the VA rating. | | | | Watts = VA x PF |
| Typically when scaling a UPS for use in a data center | | | | BTU = Watts x 3. |