Lots of discussion about surges and how to protect equipment against them. What I'd like to understand better are the dangers associated with under voltage and how to protect against that.

To what extent will electronics experience accelerated wear due to under voltage, and can anything be done to protect this equipment aside from putting them on UPSs? Thanks.

cant speak to specific damage, but undervoltage is just as bad as overvoltage.

Any good surge unit (panamax M4300PM for example) will protect from over, as well as under, voltage. At 90v it (4300pm) will shut off.

Now if you constantly have equipment running at say 95 volts, that cant be good.

Characterize 'undervoltage'. Long term or a few seconds of brown-out? 50V? 90V?

Most decent switching power supplies can handle near full load below their usual rating of 90VAC. If the voltage goes down, the current will go up, so either you will blow the input fuse, or possibly a rectifier. A good power supply will shutdown without damage. More likely though is the brown-out is accompanied by a spike or surge of some sort that does the real damage.

The question is in connection with a home that suffers from very poor quality power service. The home suffers from surges, brown outs, black outs, and probably any other type of power issue you are likely to find in the U.S.

I am trying to help the home owner understand what protection is required for their equipment beyond surge protection. The home is actually under construction. Neighboring homes that do not have special power conditioning/regulation apparently need to have all electronics (including refrigerators, AC units, etc.) replaced every year or two. Lightbulbs go way faster than that.

Any thoughts about how to handle this? Thanks.

I don't know- how about contacting the power utility? They're responsible for the supply, right? Is this a rural location?

Personally, I would go off the grid if the power utility couldn't do the job.

A surge protector will only open if the voltage drops. It will not correct the situation. You will need a line interactive ups to maintain voltage.

OK. But, how detrimental to equipment and light bulbs is it to address the under voltage only by turning off power as opposed to maintaining it? Thanks.

Furthering Kevin (licensed electrician)'s thoughts

Every device in the house that is impacted by "brown out" needs to be attached to it's own ups. Every ups needs to be sized appropriately to meet the current demands of the attached device.

Please clarify - what do you mean by "is impacted by"? The impact of a brown out on various electronics is what I am asking about.

What will happen to various types of devices (AV, kitchen appliances, light bulbs) when exposed to brown and protected only by passive devices that turn off - rather than maintain - voltage? This is what the home owner (and I) are trying to assess. I don't want to tell them they need to add UPSs everywhere without qualifying the negative impact on their electronics of not doing do.

It depends on the device. Some will fail prematurely, some more than others. Depends on the power supply and the tolerance of the components among many other factors.

Unfortunately, I don't have an easy way to assess that impact. You may have to do the research at a more technical level.

Aside from UPS products, which require maintenance to keep a good battery in the units to feed the inverter, there are more robust products that tackle the task of voltage stabilization.

These products do not use inverters attached to batteries like a UPS, they use taps on a very large transformer where the electrician/installer can plug it in and basically walk away forever.

The AC-1215 is the one that every live sound veteran knows. It has 8 taps to take an incoming voltage between 80 and 140 and step it up or down to voltage in the proper range. They also adjust so if there is additional voltage sag when the AC compressors kick on, they automatically re-adjust.

Furman makes the models that I am most familiar with.
[Link: furmansound.com]

Is the feed to the house sagging?

If so, don't mess with band-aid fixes all over the house... call the utility company.

If the voltage is on the low range when measured at the panel, they can move the service feed lines to the next tap on the transformer out at the pole (or the pedestal if your lines are underground).

Learn what has been well understood by engineers for generations. Tom MacIntyre on 7 Sept 2001 describes how engineers routinely test all designs:

If a low voltage damages any electronics, the design did not even met standards that existed more than 40 years ago.

Voltage can drop so low that incandescent bulbs dim to 50% intensity. That is perfectly normal and ideal voltage to all electronics. But sags can be harmful to appliances at greater risk - motorized appliances such as the refrigerator, air conditioner, furnace, and dishwasher. So the utility will disconnect power long before a voltage drops that low. How often are your light bulbs dimming to 50% intensity?

Light bulb life expectancy is completely different. A 120 volt light bulb will fail in about half the time when voltage is 127 volts. Just another reason why utilities maintain voltages well within what is normal voltage for all electronics. If yours is not, then get the problem fixed. Don't cure it with mythical solutions that costs $hundreds.

Nothing can be installed in a house to correct line voltage or frequency variation. Nor should it be necessary. Each transformers serving hundreds of customers adjust voltages as necessary.

If installing surge protection, then work should have started before footings were poured. Surge protection is always about the earthing. More reliable facilities use a solution that makes surges irrelevant even in munitions dumps. And that costs the least. ie Ufer ground. Every delay makes surge protection more expensive. If a house has not yet been backfilled, then best protection might be a buried ground wire encircling the foundation. Other solutions may still be implemented if not too late. Unfortunately, planning too late has only increased costs.

All electronics operate normally at low voltages. Power off is nothing more than electronics seeing voltage drop below a fixed point. Some better motorized appliances (ie air conditioner) contain circuit to do same. Since brownouts are harmful to motorized (not electronic) appliances.

What else do you want to protect from other than another type of surge that requires lightning rods?

Power=Current*Voltage

During a low voltage condition, current increases in order to maintain the correct power output. An increase in current results in a increase in heat to components.

Normally this would be a bad thing and certainly is in regards to AC motors.
Fortunately most electronics are designed with sophisticated power supplies which compensate for fluctuations in voltage. A low voltage condition is isolated in the power supply in most cases with an increase in heat and really isn't a major problem.

Chuckle