Would a UPS alleviate a voltage drop issue ?

I have a customer that is in a poorly wired warehouse . He has receptacles that are feed with #12 about 420 ' away. At times he is down to 95 vac. He does not want to spend the money to run new conduit and wire. My question is , would a UPS act as a regulator and keep the voltage at about 115 vac or so ?

Thanks so much

For voltage interuptions an online UPS might be your answer but I don't know if they follow the input line voltage or provide a constant voltage output. Here is a link for one model.
Link:
http://pcsupport.about.com/od/maintenance/gr/apcbr1500lcd.htm?utm_term=uninterrupted%20power%20supply%20ups&utm_content=p1-main-3-title&utm_medium=sem&utm_source=msn_s&utm_campaign=adid-54427d4f-80b7-46e7-a29d-8fa160f49197-0-ab_msb_ocode-12631&ad=semD&an=msn_s&am=broad&q=uninterrupted%20power%20supply%20ups&o=12631&qsrc=999&l=sem&askid=54427d4f-80b7-46e7-a29d-8fa160f49197-0-ab_msb

For voltage sags you probably are going to need something like a Sola Constant Voltage transformer. Something like in the link below.
http://www.clrwtr.com/PDF/Sola-Hevi-Duty/Sola-CVS-Constant-Voltage-Transformers.pdf

You might even need both.

Yes. A UPS will deliver regulated voltage. It is an inverter that generates an AC output from a battery. The incoming power for the UPS basically just keeps the battery charged. You should be aware that most UPS units also provide one or more non-battery backed power receptacles with surge protection and that the voltage on these outlets is not generated by the inverter. Therefore, you should take care to avoid connecting to one of these outlets.

Bit_Bucket_07 is right however success may depend on how often/long the voltage dips down to 95VAC; for example, the Phoenix Contact 5A UPS I have only takes 100-240VAC. So if it's down around 95VAC a lot, just make sure you find a UPS that takes that low of a voltage.

A ups may work, BUT, what is the current requirements of the receptacle?

a ups (uninterruptable power supply) that will carry 15 -20 amps at 120 volts for more than 5 minutes will cost more than correcting the wiring problem.
In addition, a ups has its own power input requirements in order to work correctly.

you will need one for each duplex receptacle (2 x 20 amps for a minimum of 5 minutes.

the strain on the wiring will be even more demanding.

regards,
james

If you get a UPS get a "Continuous On-Line UPS"

2. Continuous On-Line UPS - A UPS system for which the load is normally continually drawing power through the batteries, battery charger, and inverter and not directly from the normal AC supply.

3. Standby Off-Line UPS - A UPS system which normally connects your equipment to the normal AC line with the batteries and inverter in standby mode. When the line is weak or down it transfers the load to the batteries and inverter without any load malfunction and without any user action. When the line returns to normal the load is automatically retransferred back to the AC line.

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Rob S. said:

He does not want to spend the money to run new conduit and wire.

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Rob, I would stay away... if it was for you or you were doing a favor for a friend then go for it but there is nothing worse then a customer wanting to cut corners and do it right, we all have been there and cut ourselves but when it comes to a customer doing it I have found they will never be happy and always looking for you to 'fix it right' if the UPS does not work then it's on you

I have used many UPS's and save thousands of dollars (100's of thousands) by using them, here in the south we have storms that take out power for a minute or less a few times a month and installing a UPS will solve a lot of issues but the customer trying to make up for some dumb *** not knowing what they were doing on the install is not one and a job I would pass on.

Back to the original question... for me when I had brown outs the UPS would work or even a black out depending on the size, current draw and length of the outage (also what Mickey points out)

Short answer is: probably not.
I would start with replacing the outlet and the breaker and checking all the connections, especially the neutral bus in the panel. They are usually made of aluminum and tend to loosen up over time. This would be easy and cheap, and might solve the problem.
840 feet of #12 is only 1.33 ohms. He would have to be pulling close to 20 amps to drop that much voltage across the conductors. The problem is much more likely to be a loose, dirty, or corroded connection somewhere. Sometimes in a factory, breakers get used like light switches and that leads to failure.
Another thing to consider would be pulling new wire into the existing conduit, if the conduit size allows. If you could replace the #12 with #10 even just part of the way to a junction box it would help, especially if there are a lot of branch circuits. And of course, if there are a lot of branch circuits, those wire nuts could be a problem as well.