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Fasttrack
04-20-2009, 12:53 AM
Hey guys, I know this came up on the board before, but I couldn't find the thread...

My sister has problems with some components getting damaged from, according to the service rep, low line voltage. They live out in the country and occassionally the line voltage drops pretty low. I was trying to come up with an energy efficient device that would keep the voltage at a constant 115 or something.

I know someone posted something about this but now I can't find it...

Ken_Shea
04-20-2009, 01:07 AM
Fasttrack,
Depending on the size requirements I believe that a common UPS is designed to do just that.

Also double check the tightness and cleanliness of the connection at outlets and power distribution box. (With caution) :)

kendall
04-20-2009, 01:49 AM
That's what I do with most of my 'critical' things, my power is very bad here.
All the electronics are on various UPSs, and the things that are too large to use a UPS are used alone. (if the fridge is running when the furnace comes on, the lights go dim, and the UPSs start to beep a nice tune)

Works, but I have some money tied up in them.

If you get the bigger ones, you can replace the batteries when they die with an externally mounted deep cycle battery and have plenty of backup for power outages.

Ken.

Paul Alciatore
04-20-2009, 02:18 AM
Some UPSs work that way and some do not. Check the specs before purchasing one.

barts
04-20-2009, 02:53 AM
Hey guys, I know this came up on the board before, but I couldn't find the thread...

My sister has problems with some components getting damaged from, according to the service rep, low line voltage.

Also look out for a "floating neutral"; I've had problems w/ that; figured it
out when our lights got brighter when the neighbor started his ski-saw.

The power company was skeptical, but came out anyway and once they figured out we were right, fixed it...

For computer gear that need protection, try something like this:

http://www.apc.com/resource/include/techspec_index.cfm?base_sku=LE1200&tab=features\

JoeFin
04-20-2009, 03:04 AM
You could do it the old fashion way with a "Phase Failure Relay" and a contactor to switch off your critical loads

http://cgi.ebay.com/SQUARE-D-8430-DWU-PHASE-FAILURE-RELAY_W0QQitemZ290284936514QQcmdZViewItemQQptZLH_D efaultDomain_0?hash=item290284936514&_trksid=p3286.m20.l1116

macona
04-20-2009, 03:24 AM
Hey guys, I know this came up on the board before, but I couldn't find the thread...

My sister has problems with some components getting damaged from, according to the service rep, low line voltage. They live out in the country and occassionally the line voltage drops pretty low. I was trying to come up with an energy efficient device that would keep the voltage at a constant 115 or something.

I know someone posted something about this but now I can't find it...

There are several types of line stabilizers out there both electromechanical and full electric.

These are good assuming it will handle the load. What is she frying?

http://www.tessco.com/products/displayProductInfo.do?sku=483372&eventPage=1

The Artful Bodger
04-20-2009, 03:28 AM
If the voltage is consistently low you could ask the power company for a change of transformer tap. If that is not possible you could use an auto transformer in a voltage-boost mode, the transformer does not have to be big.

Sparky_NY
04-20-2009, 07:39 AM
Research the power companys standards. Here, they must maintain the voltage within +/- 5%. I have had low voltage problems at customers and the power company installed new transformers and rewired the primary distribution in the immediate area to correct the situation. Over the years peoples comsumption has increased with all the new toys we have these days. In many areas they have far too many homes being fed off a single transformer. Not uncommon here, in older areas, to find 12 houses fed off a single 25KVA transformer (100amp).

The problem is getting the power company to confirm the problem exists. They are not eager to spend a lot of money and evade the issue commonly. Here, they are known for checking the voltage at 10am and finding it within spec, of course it is, everyone is at work, the demand is low at that time. I insist they put a recorder on and that monitors it for 3 days storing the highs/lows and periods. Once the problem is confirmed, here they have to correct it.

Other areas may have different operating standards imposed on the power company, you will have to research it. Here we have "the public service commission", a state group that oversees utility companies and sets the standards they must maintain.

Evan
04-20-2009, 08:04 AM
Most UPSs cannot do anything about low line voltage except switch to battery power. I used to sell them and the brand I sold for use in this area is Cyberpower. Cyberpower has a line of UPSs that contain a saturating core transformer which will correct the line voltage from a low of 90vac to a high of 140ac without switching to battery power. I have 4 of them here at home for that reason.

I use the Cyberpower CP685AVR model. They sell a range of models but it is the AVR (automatic voltage regulation) that you need. The 685AVR will supply 390 watts. It bypasses the AVR transformer when the voltage is good to avoid hum. If the voltage goes out of spec then it switches in the AVR transformer which can maintain correct voltage with an input of 90 vac to 140 vac. If it goes out of that range it switches to battery power.

MSRP is $85. They have larger units as well for good prices. I have no interest in the company but used to sell their products. I never had one returned.

Ken_Shea
04-20-2009, 08:23 AM
APC makes a UPS that will automatically boost and trim voltage with out using the battery.

http://www.apc.com/products/family/index.cfm?id=251&tab=features#anchor1

JMS6449
04-20-2009, 10:07 AM
The main issue to be concerned with for computers and sensitive equipment is
an isolated ground. I have seen upward of 10 volts neutral to earth ground.

Evan
04-20-2009, 10:37 AM
Neutral to ground voltage is always a problem. It is usually caused by a loose connection on the neutral though, rather than a floating ground. If the ground is poor but the neutral is solid then there will only be the voltage drop of the wire resistance of the neutral that can appear against ground. If the ground is entirely floating, as in disconnected, the measurements to ground are meaningless. The ground will act as an antenna and all sorts of strange readings are possible especially with a high impedance meter input.

Fasttrack
04-20-2009, 12:29 PM
Thanks guys - I'll check out the neutral to ground voltage and check for a floating ground next time I'm out there. I know those can wreak havoc in the lab, especially when your working on a scale of pico amps - i.e. floating ground can unexpectedly reverse the flow of current!

This is actually for a freezer! The only computers in the house are laptops and they don't seem to have problem with line voltage issues with their onboard batteries. They have a desktop in the office in the shop, but it may be on a UPS, I can't remember. Anyhow, they have a 1 year old Kennmore freezer and they've had to replace this digital panel (the temp control unit) three times now. They've also had similiar problems with a temp control unit on a hot tub. There's no need for all the USB ports and other goodies that alot of the UPS come with - I was sort of hoping for a simple circuit that I could put together but those UPS that Evan recommended sure are priced right...

Evan
04-20-2009, 01:18 PM
Tell them to get one of the larger Cyberpower units. Freezers don't draw a lot of power and Cyberpower offers a lifetime "as long as the device whatever it is, is plugged into our unit" insurance policy that replaces both the UPS and the plugee in the event of power damage, like lightning. Make sure they register it.

airsmith282
04-20-2009, 02:10 PM
get your self a big desil genny that can run the house and the shop hassle free and get off the grid , that or several solar pannels that put out enough 12 volt power to power up 3000 watt inverters or higher and have battery back up for the inverterers for night time use..

just and idea why pay for power when you can use the energy of the sun
for the solar stuff or desil for the genny idea