How should we prepare for too high and too low voltage coming into our homes next year? What things in our homes are liable to be damaged or ruined by this? I have heard that low voltage will kill your refrigerator and computer. What about other things? What about voltage spikes? What to do? I asked this Q within a related thread, but got no answers. Would one of you electrically savvy folks please advise?

-- Shivani Arjuna (odnsmall@aol.com), May 14, 1999

Answers

Shivani

I posted this answer a few days ago. perhaps you missed it. You will need a power conditioner. That is, a device that gives constant voltage with fluctuating input voltages. They can be found in the Grainger catalog, and will cost from $500 to $1250 , based on size. A licensed electrician should install it for you

hope this is of help to you,

Bob Pilcher Electric Lic #11234

-- Bob P (rpilc99206@aol.com), May 14, 1999.

For "voltage spikes" (extremely short duration, extremely high voltage) use surge supressor.

For consistent high or low voltage, about all you can do get a "line conditioner". This is a transformer which monitors the input voltage (within reason) and holds the output voltage at 110 volts (or so). Only affordable for low-current loads.

Big risk is motors in brown-out condition. In a brown-out (low voltage), motors draw excessive current - so much that the motor will burn-out. Good trick is to get a slow-blow fuse for the motor that will blow if it starts drawing more than normal current.

My advice is worth what you paid for it!

-- Anonymous99 (Anonymous99@Anonymous99.xxx), May 14, 1999.

Bob,

Is this a whole house power conditioner for $500 or more? I've got a Grainger near by and an account there.

Sincerely, Stan Faryna

-- Stan Faryna (info@giglobal.com), May 15, 1999.

Years ago I worked for a major catalog company in the office of the service department, and more home appliances were damaged by brown outs than any other cause. This is much worse on appliances than just a shutdown. When you consider that a modest priced fridge begins at around $500.00, the cost of protection is worth considering.

-- gilda (jess@listbot.com), May 15, 1999.

Stan

The motor loads need to be transferred to a separate panel that will be fed by the power conditioner. Choose the power conditioner based on 125% of the total load. I would delete Air conditioning and electric dryers, as these will be too large of a load to be practical. Al this may have to be integrated with your generator, so consult a licensed electrician who has experience in this type of installation

regards, Bob Lic #11234 NJ

-- Bob P (rpilc99206@aol.com), May 15, 1999.

Bob P,

Any thoughts on putting a slow-blo fuse on the line-cord for each motor to be protected? I thought I might try:

• Measure current drawn by device (fridge, for example) use amp- meter.
• Multiply amperage by some factor (suggestion needed here!), yeilding fuse amperage "F"
• Place slo-blo fuse, of amerage "F" on line-cord to device
• Assume fuse will blow if motor starts drawing too much current

-- Anonymous99 (Anonymous99@Anonymous99.xxx), May 15, 1999.

Stan - Bob lists the range of power/price in his reply in thread http://www.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=000oGQ but I have a question for Bob.

Since power conditioners are so pricey (but nice) does there exist in the market a following device? Three relays, #1 is small capacity and is inactive and closed at 120VAC and will activate and open when voltage gets above a certian voltage, #2 is small capacity and is normally active and closed at 120VAC and will trip open when voltage falls below a certian voltage, #3 is large capacity usually closed and whose windings are in series with the switches of #1 and #2. Ie, smaller relays break the circuit to #3's coil in over or under voltage conditions opening #3's switch turning of the load. Idea being that IF something like this is inexpensive, many people would be happy to just have something shut down completly during a power problem if the price of a line conditioner is too much. To prevent the relays for clacking on/off/on/off and attempting to start/stop/start/stop the load, both of the small relays should probably be a locking type that need a manual unlock. hmmmm, this is sounding more expensive and complicated as I type this.......

-- Ken Seger (kenseger@earthlink.net), May 15, 1999.

Ken,

There are line monitors with user-adjustable high and low trip settings. You set the trip levels where you want them, connect the monitor to the line in question, and wait. If one of the trip settings is exceeded, the monitor responds in any one or more of a number of ways, depending on the manufacturer.

One unit I worked with years ago had a user port for relay contacts that would open or close when the trip occurred. Then, of course, it was up to the user to decide what the trip "signal" would do: trip a breaker, sound an alarm, switch to an alternate power source, etc. The unit also had a strip chart that would continuously record line voltage.

These were available 20 years ago to anyone that wanted one. Bob P. would know if they're still available, and what they can do. I wouldn't be surprised to learn that they were digitized, and had microcontrollers (embedded chips) in them.

-- LP (soldog@hotmail.com), May 15, 1999.

Relays might work, but within the limited range of the operating characteristics of "each" motor. If you have a cutoff at say 105 Vac and another at 125vac, this 3 relay would work. A timer could be used to elliminate the on/off pulses caused by fluctuating voltages, or the manual reset.

My reeling is , the line conditioner is more practical, and even less expensive unless you are capable of designing these relays yourself.

Remember that home brewed controls are not UL approved, and will open up other liabilities for you. Again get your local electrician involved on this, do it the right way, and you will be happoer in the long run.

best to you,

Bob P Lic #11234 NJ

-- Bob P (rpilc99206@aol.com), May 15, 1999.

anon

sorry, but the fuse idea won't work

fuses are used for branch circuit protection and shorts occurring in a load (motor, etc) Motor protection (overloads) are used as well in commecial and industrial applications to protect the motor

The motors in you home have built in thermal overload protection, and when stalled, they will yurn on/off as they cool and reheat.

Unfotunately, this will not occur on a brownout situation most likely. low voltage will just damage the motor in time.

You had better get the power conditioner, thats what the job calls for.

Good luck,

Bob P Lic #11234

-- Bob P (rpilc99206@aol.com), May 15, 1999.