Joules - surge protector question

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.

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.

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.

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.

Progressive Industries has some excellent units. Get the best you can afford. The consequences can be very great.

Good spike protection is not dirt cheap. The best kind chop voltage spikes off at the knees. An error would be to rate spike protection solely by Joule rating then shop for the cheapest protector. I'm a bit sensitive about this at the moment as I spent (for my pay grade).a fortune for big bags of MOVs, TVS diodes and Gas Discharge Tube devices so I can make my own spike protectors. It really hurt because I know one single stupid isolation transformer would filter and protect 100-times better than all those devices in all those bags put together. But isolation transformers are bulky, heavy and wuuwee pricey.

Try GOOGLE search term

TRANSIENT VOLTAGE PROTECTION

Higher the better. Don't go cheap on something that protects your life!
Joules info

Higher is better.