Joules - surge protector question

[JoeH]

I see surge protectors with differing values for joules.... but it doesn't say what is better ... is higher better than lower values ?

thanks

[MEXICOWANDERER]

Lucky thing they fail open circuit. And 300 joules into a 100 joule MOV means much of the transient continues on its merry way right into your wallet. Even at 10 joules bit by bit it consumes a MOV.

Personally I have never seen a shorted MOV. TVS and GDTs yes. MOVs no.

[Salvo]

MOV's get "used up" when they get heat stressed. They get heat stressed because there's not enough of them. If you got a MOV rated at 100 joules and along comes a 300 joules transient, guess what, the part will get heat stressed.

Again, it all boils down to more is better.

MEXICOWANDERER wrote:
When a metal oxide varistor is "used up" the show is over.

[MEXICOWANDERER]

When a metal oxide varistor is "used up" the show is over. Their weakness is relatively slow reaction time which limits usefulness with high frequency events. I did not spend extra money for 20mm devices for the heck of it. BTW the response time for a bi-directional TVS diode is four-billionths of a second. They compliment a MOV nicely. But the TVS need individual fuzing which makes them less attractive to gizmo manufacturers. A 180 volt rated TVS chops all transients off at 180-volts but they are fragile and that's where MOVs "should" take the load off.

[Salvo]

You misunderstood wiki.

They state more is better. I concur.

SoundGuy wrote:

JoeH wrote:
I see surge protectors with differing values for joules.... but it doesn't say what is better ... is higher better than lower values ?

As with many things in life there's much more to the story of surge protector joule rating than simply saying "higher is better" ... because in fact it may not be necessarily so, particularly when we're talking about RV specific surge protectors which use MOVs (Metal Oxide Varistors) to direct excessive current surge & spikes to ground. From this wiki article ...

"The joule rating is a commonly quoted but very misleading parameter for comparing MOV-based surge protectors. A surge of any arbitrary ampere and voltage combination can occur in time, but surges commonly last only for nanoseconds to microseconds, and experimentally modeled surge energy has been far under 100 joules. Well-designed surge protectors should not rely on MOVs to absorb surge energy, but instead to survive the process of harmlessly redirecting it to ground. Generally, more joules means an MOV absorbs less energy while diverting even more into ground"

[MEXICOWANDERER]

There is "apparent" then there is reality. The "official" printed number for CFE power and Mexican registered (NOM) power devices is 127 vac 60Hz.

127

254

508

No way on the face of the earth are Mexico-bound appliances any different than USA appliances other than language tags. NOM is a trade law gimmick used to sanction illegal importation of less expensive electrical merchandise.

In Mulege Baja California Sur 30-years ago living on Ice House Rd. I was measuring 560+ volt 12 millisecond transients when the 150 horsepower ammonia compressor motor started and stopped. On a 127 volt line. Fluorescent lamp ballasts failed almost immediately. When a phase goes offline to my place it causes a ringing of several seconds before a breaker trips and relay shunts to ground. The first harmonic is in excess of 800vac on the remaining pair of conductors. You would think the transmission to distribution transmission step down would isolate this. I have a fresh set of Panasonic caps for the Sola line tamer upon my return. My refrigerator in my kid's restaurant has a 700va Sola protecting it.

I am grumbling. Thinking how nice a bi-directional 100-amp avalanche rectifier would be. 155,000 1/4 wave amp capacity. Absurd. Six hundred dollars.

I've been thinking about making a modular TVS board strictly plug in components. TVS and MOVs on modules. Half dozen modules per unit. CFE has 890 Mw of generation capacity at Lazaro Cardenas. So this is like unzipping for a forest fire.

[time2roll]

Are microwaves and other appliances sold in MX rated for the higher voltage in MX?
Just curious what the power label actually says.

[SoundGuy]

MEXICOWANDERER wrote:
Some folks are slow to catch on why there are so many microwave oven failures in RVs.

I'd be one of them. :S The microwave oven in our previous KZ Spree worked just fine for a couple of years then suddenly out of the blue just quit entirely ... this was long before I began using any form of line protection and in looking back now I'm sure it was a surge of spike that did it in. :M

[MEXICOWANDERER]

Ooooo why did I check the power strip? My little Daewoo 600-watt microwave played Permanent Possum last weekend and this thread jogged my suspicion. I picked up a brand-new scratch & dent Oster 900 watt Oster for 60 dollars eqvt Pesos.

At home I have ultra-quality power while on the road-in-the-toad the BORG will work fine 85-140 volts.

Some folks are slow to catch on why there are so many microwave oven failures in RVs.

[MEXICOWANDERER]

Smkettner X2

Campground voltage and connections are a circus in the US. Down here connections are reliable and guaranteed (BAD) so there's no guesswork. But my opinion differs from senor Kettner's on the transients importance in snubbing them. Microwave oven boards last about a year down here before lights out. And voltage in many places is stable. And comparing the voltage quality in a dirty campground network to a clean dedicated transformer service drop in the US is a cruel joke.

Remember that pricey Belden power strip I laughed about here on the forum a few months ago? Well I took it apart last night and found all 5 MOVs deader than a doornail. Today I snip and hurl and solder in 5 20mm MOVS. I like the strip because it has an eight foot 14-gauge wire and eight taps.

[time2roll]

Don't dwell on surge rating too much. Primary faults are voltage, polarity and ground connection.

If it has surge protection you should be covered for most events.

Also check length of warranty.

[MEXICOWANDERER]

Spike protectors are voltage specific. Two sets of MOVs, 2-sets of TVS 2 sets of gas gischarge tubes. L1 and L2 to L0. L1 and L2 to earth on a 240 volt suppressor. On a GOOD setup each component has a fuse. Device taken off line and a continuity check confirms if fuses have been faulted. Multiple discrete components protected by a single fuse is idiocy.

[wa8yxm]

JoeH wrote:
I see surge protectors with differing values for joules.... but it doesn't say what is better ... is higher better than lower values ?

thanks

Two answers: First the direct answer: More is better (higher is better)

Second the warning answers: There are two classes of devices we call surge protectors.. One has a digital or alpha-numeric display of some kind (the best of these give you Amps, Volts and stuff like that) the other has only a few (less than 5) indicator lights.

The alpha-numeric display may be an LCD or it may be muti-segment LED's but it too will give you either error codes (With a translation table usually stickered nearby) or error messages like "240 VOLTS"

The ones with out will not protect you from 240 volts.. Or low/high voltage, or anything other than very brief SPIKES.. Even a surge (Which can last for several seconds) which will overwhelm thise devices.

I have both on my RV.. First is the LCD type.. The LED type comes later.

[MEXICOWANDERER]

Great Post IMHO SoundGuy

The ubiquitous "MOV" works well only on some transient voltage spikes, but not all.

Compare a MOV to a shock absorber or prize fighter. They can only take so much, then it's all over. They wear out. Having a bunch of MOV capacity means they will wear out more slowly.

Really fast acting high voltage short-duration transients is like placing a light middle-weight in the ring. Much faster and quicker than the heavyweight MOV. These faster transients can destroy integrated circuits just as certainly as slower longer duration voltage spikes.

Stick oscilloscope probes on a large transformer winding, load the transformer then shut it off and what you will see in the oscilloscope screen will make your hair stand out on end.

The same thing happens when motor windings are switched off under heavy load.

Design of a transient voltage suppression device is as much an artform as it is engineering skill. The art comes in when trying to make the thing work, live a long time and be affordable.

I loved it when I encountered a TVS diode rated 1,000 times higher capacity than my purchased Transient Voltage Suppressor diodes. Unfortunately the monster TVS was a thousand times the cost.

When it comes to purchasing a good voltage spike protector, beware of shady advertising that makes it sound like you are getting a big bowl of beef stew but you end up with a cup of hot water and a bouillon cube.

[SoundGuy]

JoeH wrote:
I see surge protectors with differing values for joules.... but it doesn't say what is better ... is higher better than lower values ?

As with many things in life there's much more to the story of surge protector joule rating than simply saying "higher is better" ... because in fact it may not be necessarily so, particularly when we're talking about RV specific surge protectors which use MOVs (Metal Oxide Varistors) to direct excessive current surge & spikes to ground. From this wiki article ...

"The joule rating is a commonly quoted but very misleading parameter for comparing MOV-based surge protectors. A surge of any arbitrary ampere and voltage combination can occur in time, but surges commonly last only for nanoseconds to microseconds, and experimentally modeled surge energy has been far under 100 joules. Well-designed surge protectors should not rely on MOVs to absorb surge energy, but instead to survive the process of harmlessly redirecting it to ground. Generally, more joules means an MOV absorbs less energy while diverting even more into ground"

Rather than accept WAG commentary from those who claim "more is better" you'd be far better off to accept that manufacturers such as TRC and Progressive Industries know what they're going and have selected joule ratings appropriate for the task at hand. One also needs to understand the very real possibility that MOVs in these various surge protectors, exposed to sufficient strikes, can be expected to fail ... in other words, a surge protector is not necessarily a one time, lifetime purchase. The potential for MOV failure is the very reason I chose to invest in a hardwire Progressive EMS-HW30C which is field serviceable by myself rather than the portable equivalent which is a sealed unit and must be returned to the manufacturer for repair.