Please explain a UPS is and its purpose - AVS Forum | Home Theater Discussions And Reviews
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Old 09-08-2013, 09:23 PM - Thread Starter
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This is my first post so please bare with me. smile.gif I am finishing our basement and included in this project is a longtime wanted dedicated home theater room. I have read all the posts in the "what would I do different in a home theater build". That may not be the exact name but after 27 pages of posts I forgot the name of the thread. Anyway in a couple of post some of the guys were talking about a UPS to use with a projector which I had never heard of after a little research I understand it to sand for Uninterrupted Power Supply. Is this the same as a battery backup that I use for my desktop computer? One of the guys posted a link and I looked it up and it looked like a extension cord with a outlet on the end of it... but I'm not sure what that would do to keep the power supply uninterrupted? Any help would be greatly appreciated as I don't want to miss out on something that I should of put in after it is too late. confused.gif


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Old 09-08-2013, 10:17 PM
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The purpose of an uninterruptable power supply (UPS) is to continue to supply power to mission critical devices after the power company's power fails completely, or goes too low or too high in voltage. Your "battery backup" is a UPS. The power is provided from a battery that is charged while the power from the power company is OK. How long the UPS will continue to provide power after the power fails is a function of the battery size and the load imposed by the connected equipment. There are three common types of UPS: standby, line interactive, and double conversion. A standby UPS switches to battery power when the power company's power fails or the voltage goes too high or low. A line interactive UPS does the same, but also adjusts for low and high voltages within limits while the load is running on power company power. You can get the same voltage regulation in a device that is not a UPS. You really don't need it in either case because the power supplies in your gear are designed to work properly across a range of input voltages. A dual conversion UPS is analogous to always running on battery, pretty much separating your gear from typical power quality problems like sag, harmonics, etc. This is generally not a problem for AV gear. The power supplies usually handle these things just fine.

The question you have to answer for yourself is what is mission critical. A lot of folks think that keeping a projector from shutting down without a cool down cycle is important to keep the bulb from being damaged. It isn't. The bulb is actually happier cooling down slowly. The cool down cycle is there for other reasons. Some people think their DVR is mission critical. They cannot stand to miss an episode of their favorite program. This makes more sense to me. Some people put their AVR on a UPS. Makes absolutely no sense to me in most cases.

UPSs typically provide some degree of surge protection. But that is not a reason to buy a UPS.
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Old 09-08-2013, 11:09 PM
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For most AV purposes, a UPS is good for "surviving" temporary (a few seconds) glitches in power. DVRs and other computer / hard-drive gear can take a long time to reboot after a power loss, so the UPS can save you some frustration. I have my DVRs on one for both reasons - the temporary glitch (which for me is very rare, although I had one in a storm two weeks ago), and to run an hour or so and keep recording while the power is out. Note that in order for that to work, all the gear that supplies signal(s) to the devices have to remain powered as well. Otherwise you're recording snow. biggrin.gif

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