This may make me seem like a tard, but...
2007-Apr-07, Saturday 09:00 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
ssurgulI FINALLY found a quick summary of what the difference is between the watt and the VA rating on computer equipment. From my early physics classes, I was always, always confused by how a 'VA' different from a 'W', given that they were the same measurements. But here at least is the distinction.
http://www.refurbups.com/FAQs#presales7
(For the lazy and equally uninformed, the VA rating is used to size wiring and breakers, and seems to be the maximum expected draw, whereas watts in this case, is the 'actual' power drawn down the lines, which will always be equal to or less than the VA rating.)
Watt Ratings Differs From Volt Amp Ratings
Answer:
Introduction
This note helps explain the differences between Watts and VA and explains how the terms are correctly and incorrectly used in specifying power protection equipment. Many people are confused about the distinction between the Watt and Volt-Amp (V-A) measures for UPS load sizing.
Background
The power drawn by computing equipment is expressed in Watts or Volt-Amps (VA). The power in Watts is the real power drawn by the equipment. Volt-Amps is called the "apparent power" and is the product of the voltage applied to the equipment times the current drawn by the equipment.
Both Watt and VA ratings have a use and purpose. The Watt rating determines the actual power purchased from the utility company and the heat loading generated by the equipment. The VA rating is used for sizing wiring and circuit breakers.
The VA and Watt ratings for some types of electrical loads, like incandescent light bulbs, are identical. However, for computer equipment the Watt and VA ratings can differ significantly, with the VA rating always being equal to or larger than the Watt rating. The ratio of the Watt to VA rating is called the "Power Factor" and is expressed either as a number (i.e. 0.7) or a percentage (i.e. 70%).
The power rating of the UPS
UPS have both Watt ratings and VA ratings. Neither the Watt nor the VA rating of a UPS may be exceeded. In most cases, UPS manufacturers only publish the VA rating of the UPS. However, it is a standard in the industry that the Watt rating is approximately 60% of the VA rating, this being the typical power factor of common loads. Therefore, it is safe to assume that the Watt rating of the UPS is 60% of the published VA rating.
How to avoid sizing errors
Equipment nameplate ratings are often in VA, which makes it difficult to know the Watt ratings. If using equipment nameplate ratings for sizing, a user might configure a system which appears to be correctly sized based on VA ratings but actually exceeds the UPS Watt rating.
By sizing the VA rating of a load to be no greater than 60% of the VA rating of the UPS, it is impossible to exceed the Watt rating of the UPS. Therefore, unless you have high certainty of the Watt ratings of the loads, the safest approach is to keep the sum of the load nameplate ratings below 60% of the UPS VA rating. Note that this conservative sizing approach will typically give rise to an oversized UPS and a larger run time than expected. If optimization of the system and an accurate run time are required, discuss your requirements with RefurbUPS Power protection representative, for product recommedations to meet your needs.
Note that this conservative sizing approach will typically give rise to an oversized UPS and a larger run time than expected. If optimization of the system and an accurate run time are required, use APC sizing and Worldwide Web configuration tools.
Conclusion
Power consumption information on computer loads is often not specified in a way that allows simple sizing of a UPS. It is possible to configure systems that appear to be correctly sized but actually overload the UPS. By slightly over sizing the UPS compared with the nameplate ratings of the equipment, proper operation of the system is ensured. Over sizing also provides the side benefit.
http://www.refurbups.com/FAQs#presales7
(For the lazy and equally uninformed, the VA rating is used to size wiring and breakers, and seems to be the maximum expected draw, whereas watts in this case, is the 'actual' power drawn down the lines, which will always be equal to or less than the VA rating.)
Watt Ratings Differs From Volt Amp Ratings
Answer:
Introduction
This note helps explain the differences between Watts and VA and explains how the terms are correctly and incorrectly used in specifying power protection equipment. Many people are confused about the distinction between the Watt and Volt-Amp (V-A) measures for UPS load sizing.
Background
The power drawn by computing equipment is expressed in Watts or Volt-Amps (VA). The power in Watts is the real power drawn by the equipment. Volt-Amps is called the "apparent power" and is the product of the voltage applied to the equipment times the current drawn by the equipment.
Both Watt and VA ratings have a use and purpose. The Watt rating determines the actual power purchased from the utility company and the heat loading generated by the equipment. The VA rating is used for sizing wiring and circuit breakers.
The VA and Watt ratings for some types of electrical loads, like incandescent light bulbs, are identical. However, for computer equipment the Watt and VA ratings can differ significantly, with the VA rating always being equal to or larger than the Watt rating. The ratio of the Watt to VA rating is called the "Power Factor" and is expressed either as a number (i.e. 0.7) or a percentage (i.e. 70%).
The power rating of the UPS
UPS have both Watt ratings and VA ratings. Neither the Watt nor the VA rating of a UPS may be exceeded. In most cases, UPS manufacturers only publish the VA rating of the UPS. However, it is a standard in the industry that the Watt rating is approximately 60% of the VA rating, this being the typical power factor of common loads. Therefore, it is safe to assume that the Watt rating of the UPS is 60% of the published VA rating.
How to avoid sizing errors
Equipment nameplate ratings are often in VA, which makes it difficult to know the Watt ratings. If using equipment nameplate ratings for sizing, a user might configure a system which appears to be correctly sized based on VA ratings but actually exceeds the UPS Watt rating.
By sizing the VA rating of a load to be no greater than 60% of the VA rating of the UPS, it is impossible to exceed the Watt rating of the UPS. Therefore, unless you have high certainty of the Watt ratings of the loads, the safest approach is to keep the sum of the load nameplate ratings below 60% of the UPS VA rating. Note that this conservative sizing approach will typically give rise to an oversized UPS and a larger run time than expected. If optimization of the system and an accurate run time are required, discuss your requirements with RefurbUPS Power protection representative, for product recommedations to meet your needs.
Note that this conservative sizing approach will typically give rise to an oversized UPS and a larger run time than expected. If optimization of the system and an accurate run time are required, use APC sizing and Worldwide Web configuration tools.
Conclusion
Power consumption information on computer loads is often not specified in a way that allows simple sizing of a UPS. It is possible to configure systems that appear to be correctly sized but actually overload the UPS. By slightly over sizing the UPS compared with the nameplate ratings of the equipment, proper operation of the system is ensured. Over sizing also provides the side benefit.