Dealing with cronic VOLTAGE SPIKES

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  #1  
Old 12-15-10, 08:32 PM
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Dealing with cronic VOLTAGE SPIKES

I'm retired and living in the Philippines. The power here is 230 VAC to ground and we have huge voltage spikes.

A tech here says there are 1000 spikes of at least 4000 v per day. The duration is very short. I THINK he was saying it was less than 1/100000 second. This is so brief it doesn't bother electric motors, etc. but long term its fatal to any electronics. The repeated spikes eventually break down the semi-conductor junctions, he says.

So in 5 years I've lost 3 computers and thousands of dollars of other stuff including a couple voltage regulators that are supposed to stop the spikes. I'm trying to do something about it.

There are power cords and AVR's that claim to protect but it that's largely a scam. Maybe I'm drastically wrong but this is the way I understand it.

In anything less than a $200 device protection is provided by components called MOV or Metal Oxide Varistor. They are connected between "hot" and ground. When a spike reaches the activation voltage (270v for example) they turn on in 3 or 4 micro sec grounding out the spike. When the voltage drops a few micro sec later they switch off just as fast. The problem is they are "sacrificial" in that each spike damages them a little bit until they fail. Then they do nothing. There is no cheap way of testing one. They rated in "joules". The more J the more spikes it can handle. A power cord or AVR will typically have one MOV rated for 50 to 100 joules. A 50J MOV will absorb MAYBE a half dozen good spikes before failure.

So you think you are protected but likely you are not. So what to do?

There are MOV's with 300J or more online for about $0.40 each (Q:100) and if wired in parallel the effect is cumulative. One could add several AVR and change them a couple times a year on general principle but you still could not trust it for expensive electronics. I need some way to detect when they fail.

One doc says "when a MOV fails, for a very brief time it acts as a dead short to ground. Then it fuses into an inert block." No hint what a "very brief time" is but I have had many failed MOV's and no blown fuses so it must be pretty short duration.

So what if one placed a small glass fuse in line with the MOV. When the MOV failed, the fuse would burn out. No protection but it would be a visible and cheap indicator to replace the MOV. If I put several like this AVR and checked it frequently I'd know for sure.

Problem is that I have no idea what size fuse to use. If it's too small it might burn out every time a spike is grounded out. If it's too big it might not have time to melt when the MOV fails.

Any suggestions?

Any ideas for a more complex setup that might turn on a LED or something if the fuse is blown?

Many thanks for your kind attention.
 
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  #2  
Old 12-15-10, 09:26 PM
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Originally Posted by johnb0647 View Post
In anything less than a $200 device protection is provided by components called MOV...
Everything you posted about MOVs is true.

So what if one placed a small glass fuse in line with the MOV. When the MOV failed, the fuse would burn out.
I believe a fuse would be much too slow compared to the MOV. MOV response time is usually measured milliseconds (1/1000 sec) whereas fuses might take up to a couple seconds to burn.

Any ideas for a more complex setup that might turn on a LED or something if the fuse is blown?
Most of the whole-house and panel mounted surge protection units have LED indicators which tell you when the MOVs are still good. They make these for most North American panel models, so I assume the big brands would also have the units compatible with your system.

Something else you should check is your home's grounding electrode system. In the US, the minimum requirement is that your panel be grounded to the incoming municipal plumbing pipe and to two additional 8' (2.5 m) ground rods with a #6 (14 mm˛) or larger copper wire. You also need to have a "single point ground" which means that your telephone, data, antenna, cable, satellite systems, etc all must ground to the same electrode system as your electrical service using substantial copper wires. Most electronics that are damaged by bad power are because they connect to two separate systems that have different grounds (power and CATV for example); single point grounding helps to prevent that problem.

Finally, you can get some top-of-the-line surge protectors that use a series choke coil instead of sacrificial MOVs. This is the type of protector you might find at a telecom company facility. They are more expensive but very effective at blocking voltage spikes and are not degraded over time. There is a company called Brickwall which sells this type of protector. Most of their products are for North American voltage, but I believe they do take custom orders.
 

Last edited by ibpooks; 12-16-10 at 09:02 AM. Reason: Added metric conversions
  #3  
Old 12-15-10, 10:09 PM
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I use a Brick Wall for my computer and I have never had any problems. I used them with industrial instrumentation also, a good product.

Brick Wall
 
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Old 12-15-10, 11:22 PM
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Johnb0647 If I may ask an off topic question, have they stopped using a mixture of 120v and 240v circuits in the same house. Always found it scary that some of the receptacles in a house were 120v and some were 240v but were all 1-15R. Or does that vary by island?
 
  #5  
Old 12-16-10, 08:23 AM
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Originally Posted by Furd View Post
I use a Brick Wall for my computer and I have never had any problems. I used them with industrial instrumentation also, a good product.
If I had serious concerns about surges, I would look at the Series Mode units, of which BrickWall is one brand. I researched these a few years back and solicited detractors and opposing opinions. No takers.
 
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