Intermatic Whole House Surge Protector ?

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Hello,
Having a new service box installed in a residence.
Electrician has never used these before, so thought I'd ask here.
Was thinking of purchasing, and having him install, an Intermatic Whole House Surge Suppressor Model 4870 in the new box. Have had several large lightning storms in the past, and one nearby strike fried the control board on our furnace ! The Intermatic unit isn't all that expensive, about $80 or so.
Any of you folks ever used this model ?
Worth doing ? Thoughts on ?
BTW: If they do ever take a big hit, do they (usually) fail open or closed ?
e.g., would the MOV's be shorting the hot to neutral/ground after a big hit, such that the unit would have to be removed prior to re-initiating service ?
Thanks, Bob
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After a major strike costed our insurance co 10000 + we installed one and a Lightning arrestor, there is better stuff out there but it costs more. An electrician that hasnt used one? Maybe you need one who is up to date on these issues and what you really need.
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From what I see on the web, the unit would be fed through a standard 15A dual-pole breaker, so if it shorted, the breaker would trip, and you'd be running normally, with no protection, until you replaced the unit (and maybe the breaker).
The write up on the LPS unit, which another responder has linked to, says it pretty clearly: "These SPDs are not repairable. A defective SPD fails short circuit, in which case the line/branch fuses or breakers operate. A prolonged short circuit may open, and in the process cause rupture of the SPD elements. " My guess is the sames goes for the Intermatic.
Chip C Toronto
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Robert11 wrote:

Intermatic surge protectors do not use MOVs - they are electronic. The one you are considering handles 1200 joules and 48,000 Amps. Usually this is adequate to handle typical power-line surges (blown transformer, re-connect time, etc.). It they take a hit, they keep on working (unless it's a direct lightning strike!). They indicate when they no longer are working (I think by yelling "help").
Use of this device does not remove the need for more modest surge protectors on individual devices. The Intermatic protects against surges from outside your home, but it's possible a device inside your home could generate a surge affecting stuff on the house side of the Intermatic.
We have one on our office service (not this model, but the same idea). We've never been bothered by a power surges. We've never been bothered by stampeding elephants either, so that's not much of a testimonial.
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Why would the intermatic not absorb in-house surges?
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Bob F wrote:

The suggestion comes from the Intermatic web site.
I presume because everything on the same side of the device causing the surge - including the Intermatic - is exposed to the surge. It's not the path of least resistance; it's everything.
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wrote in message news:VM2dnfrrp-

I would imagine that the suppressor would absorb the surge to keep it from passing on to other circuits at the breaker panel.
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What is this claim based on? If they don't use MOV's what exactly do they use? Also, this would seem to imply that MOV's are not considered electronic components, but I believe by any reasonable definition, they are electronic components.
The one

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snipped-for-privacy@optonline.net wrote:

You're right, of course. MOV are classified as "electronic" components. But metallic-oxide-varistors work like reverse fuses: they short their terminals together. And, like fuses, they (usually) only work once with no indication (other than sometimes smoke) that they won't work again.
Sophisticated electronic circuitry can bleed off surges to ground and continue to function indefinitely. It is the existence of this circuitry that's the difference between a $3.00 "surge-suppression" outlet strip and a $50.00 one.
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HeyBub wrote:

MOVs will continue to work indefinitely if their rated clamping current isn't exceeded, so they will readily clamp on the modest surges seen every day. The mega surges from a really close lightning strike or a tree branch dropping the primaries into the secondaries is what will cause the MOV to self destruct and usually trip the circuit breaker in the process thereby sacrificing itself to save the stuff downstream of it.
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Pete C. wrote:

While MOVs are good with very short duration surges, dropping a primary wire onto secondaries will rapidly destroy a MOV as you describe. Then protection is gone.
UL requires thermal disconnects for failing MOVs. The specs from trader4 include 200k AIC Surge Rated Fuses which indicate that suppressor can be used on in a panel with an available fault current (not surge related) of 200,000A. The suppressor may also trip a circuit breaker, but protection should be internal.
I believe the maximum likely surge current on one of the hot service wires is 10,000A based on a very strong 100,000A surge hitting the high voltage wire on the pole behind your house. The spec from trader4 is 40,000A per wire for that suppressor, which is well beyond what is likely.
MOVs also have an energy (Joule) rating, which is cumulative. The 40,000A rating goes with a very high Joule rating, which means the suppressor can take many hits. If a MOV had a 1000J rating, it is for a single surge. If the individual hits were much smaller, like 100J, the cumulative rating is much higher than 1000J. When the energy rating is exceeded, the MOV starts to conduct at lower voltages, eventually conducting at normal voltages and failing in thermal runaway.
Without a service panel suppressor, there will be arc over to panel ground at about 6,000V. After it is established, the arc voltage will be hundreds of volts. That dumps most of the surge energy to earth. For plug-in suppressors, the impedance of the branch circuit wiring greatly limits the current, and thus the energy, that can reach the suppressor. Combined with arc over, the energy that can reach a plug-in suppressor is surprisingly small (unless the branch circuit is very short).
--
bud--

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I think I've answered the question myself. Below is an excerpt from Intermatics datasheets from both a residential and also a commercial/ industrial unit that clearly say both do in fact use MOV's and say nothing about any alternate "sophisticated electronic circuitry." I don;t know of any such alternate components that can handle the huge currents that MOV's can which is why they are used in all the surge protectors that I've seen.
If you have any alternate reference, we'd like to see it.
Residential: Features and Applications: The IG1240RC features six modes of protection and is recommended for residential and light commercial applications. It is intended for installation on 120/240 volt AC panels. The IG1240RC incorporates the newest developments in MOV technology and provides individual component thermal protection and monitoring.
Commercial: For installation in Category "C & B" locations ! Service Entrance, Distribution Panels and Sub-panels ! Parallel installation ! 125k Amps Peak Surge Capacity per mode ! All mode suppression for systems with a neutral ! Line-to-Line, Line-to-Neutral, Line-to-Ground, Neutral-to-Ground ! 6 mode suppression for systems with no neutral ! Line-to-Line, Line-to-Ground ! Integral Disconnect Switch with safety interlock ! Easily replaceable master surge module ! 40k Amp MOVs ! 200k AIC Surge Rated Fuses
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snipped-for-privacy@optonline.net wrote:

Ah, okay. Thanks for the info. I thought a quality company like Intermatic would rely on something other than MOVs, such as zener diodes or gas-discharge tubes. Maybe even motor/alternators.
If they, in fact, are relying on piece-of-shit MOVs (probably made in China), well, might as well stand naked in the rain.
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HeyBub wrote:

According to the IEEE guide, "the vast majority (>90%) of both hard-wired and plug-in protectors use MOVs to perform the voltage-limiting function. In most AC protectors, they are the only significant voltage limiters."
Zener diodes and gas discharge tubes don't have the energy dissipation capacity of MOVs in a small volume. MOVs dissipate the energy throughout the volume of the device, where a zener diode dissipates the energy at a 'junction'. Other devices with high capacity are arc gaps and silicon carbide devices (another form of MOV). I don't see a practical component solution in your list.
You have not said why MOVs are a POS.
You could certainly use a motor/alternator. Depending on how much you are protecting it might only cost a few thousand dollars. Or a full-time conversion UPS for your house? (But what protects the UPS?) Or maybe a ferroresonant transformer? You could use it to help heat the house.
Or maybe a full-time off-grid generator? And get rid of the troublesome phone and cable lines?
--
bud--



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Lightning wants the shortest path to earth. Make sure that the electrician installs at least two ground rods and although the code allows them to be a minimum of six feet apart I suggest at least sixteen feet between rods.
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Robert11 wrote:

If you want comments, provide a link to information for the model. The Intermatic site did not find 4870 in a search.
>

MOVs normally fail in thermal runaway and low resistance. All surge suppressors (US) should be listed under UL1449. UL1449 requires overheating MOVs be disconnected by a thermal disconnect.
Carefully follow the manufacturers instructions. Keeping connecting wires short is very important.
Everything I saw at the Intermatic site indicated that their service panel suppressors were MOV based.
I didnt see anything at lightningprotectioncor.com on why their suppressors would be superior.
Equipment most likely to be damaged has connection to both power and signal (phone, cable). If a strong surge produces a 1000A current to earth, and the resistance to earth is a very good 10 ohms, the voltage at the service ground will rise to 10,000V above absolute ground. The way to protect equipment is to keep the ground reference for power and phone and cable at the same potential. That requires a *short* ground wire from phone and cable entry protectors to the ground at the power service.
With adequate ratings, using service panel suppressors, and plug-in suppressors on sensitive electronics with power and signal connections, you can protect against almost all lightning (not including a direct strike to the house - very uncommon).
If using a plug-in suppressor, all wiring (power, phone, cable, ...) going to a set of protected equipment must go through the suppressor.
--
bud--

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That means that you regular old circuit breaker in you main panel will "protect" the MOV from thermal runaway. Trouble is that once the CB trips you lose protection until to notice the open breaker.
One would think that "someone" would make a MOV equiped device with a self-resetting thermal breaker as part of the design. ALL of them seem to have either fuxes or the MOV self-destructs in a way that doesn't set the device on fire or create a short.

Well, it takes te impulse a little more than a nano-second to travel a foot. If the response time of the MOV is measured in micro or even mili seconds, the length of the wiring just doesn't make any difference.

Amen!
Yep!
That's why all utility wires are supposed to come into the house at the same general location so that the grounds can be bonded together. The "cable folks" often don't bother. Ditto for the "dish" folks.

Well, you can get "local" break out boxes that will protect AC plugs and 1 or 2 coax and/or 1 or 2 phone lines. If the grounds are bonded well at the electric service grounds I suspect that your local suppressor may have a shorter than expected life.

AMEN!
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John Gilmer wrote:

The UL required "thermal disconnect" must be close proximity to the MOV and responds when the MOV gets hot at end of life (thermal runaway). It is inside the suppressor.
It operates at end of life - the MOV conducts at "normal" voltages.

A well designed suppressor matches internal protection to the MOVs. They disconnect the MOVs when they are at end of life. For overvoltage (much longer duration than surge and will rapidly destroy MOVs) a few plug-in suppressors will disconnect and save MOVs and protected equipment.

The response time of MOVs is negligible. And surge rise times are over a microsecond.
The problem is voltage drop. Surges are short duration events and thus basically high frequency. The inductance of wire dominates over resistance. The IEEE guide on surges and surge protection: http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_May051.pdf has information on lead length and voltage drop (pdf page 32). At 3,000A surge current, 6 inches of lead adds 70 volts to the clamp voltage.

It seems like a fairly common problem for signal services to be at distant points. Cable installers are notorious for not correctly bonding to power service grounds. Dish is probably worse.
The IEEE guide has an example of a cable service with too long a ground wire causing a high voltage between cable and power wires (starting pdf pabe 40). The guide says that if a short interconnect cannot be made "the only effective way of protecting the equipment is to use a multiport [plug-in] protector." (You could also run the cable to near the power service, install a second ground block, and distribute from there.)

"Local suppressor" is plug-in suppressor? Should have easier life if interconnection at services is short - would have less use of voltage limiting device from signal to plug-in suppressor ground.

--
bud--


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If the MOV got that 'hot' as to open a thermal fuse, it was grossly undersized operating in complete violation of its manufacturer. Grossly undersizing is common with plug-in protectors since profit margins are more important than effective protection. MOVs much shunt (clamp, divert, connect) surges to earth AND remain *functional*. Those promoting plug-in protectors forget to mention that a protector must not fail by blowing the thermal fuse.
Any MOV that gets so hot as to trip a thermal fuse was violating MOV manufacturer specs and providing no effective protection. The only acceptable MOV failure means no excessive heat - no MOV vaporization. But such failures get the naive to recommend more protectors - increase sales. Again, which is more important profits or protection?
Scary pictures demonstrate problem with grossly undersized protectors that still have UL 1449 approval. Not only do we instead install one properly sized 'whole house' protector. We also do not want protectors located on a rug or adjacent to a pile of desktop papers. The scary pictures demonstrate a 'too common' problem with plug-in protectors that Bud promotes for: http://www.hanford.gov/rl/?page=556&parent=554 http://www.westwhitelandfire.com/Articles/Surge%20Protectors.pdf http://www.ddxg.net/old/surge_protectors.htm http://www.zerosurge.com/HTML/movs.html http://tinyurl.com/3x73ol http://www3.cw56.com/news/articles/local/BO63312 /
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w_tom wrote:

In w_s mind, plug-in suppressors have minuscule ratings and service panel suppressors have mega ratings. But plug-in suppressors are readily available with very high ratings for relatively low cost. And branch circuit impedance greatly limits the current, and thus energy that gets to a plug-in suppressor.

None of w_s links say any damaged suppressor even had a UL label.

Lacking technical arguments about plug-in suppressors, w_ tries to discredit people who expose his drivel. All I promote is accurate information.

Lacking valid technical arguments all w_ has is pathetic scare tactics.
His hanford link is about "some older model" power strips and says overheating was fixed with a revision to UL1449 that required thermal disconnects. That was 1998. The hanford failure was in 1999 - a one year old suppressor? There is no reason to believe, from *any* of these links, that there is a problem with suppressors produced under the UL standard that has been in effect since 1998.
For accurate information on plug-in suppressors read the IEEE and NIST guides. Both say plug-in suppressors are effective.
--
bud--

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