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#129693 - 07/27/05 07:26 AM TVSS
MaddMatt Offline
Junior Member

Registered: 07/26/05
Posts: 3
Loc: Glendale, AZ, United States
I live and work in the southwest, where we experience serious seasonal monsoon storms with a lot of lightning. As a result, we have to deal with power surges quite a bit, not only from the storms, but with the POCO switching around grids during the subsequent repairs.

Due to this, TVSS's are a growth market in the area, primarily for computer protection in all office situations. In studying the suppliers tech data on the various units available, I've found a hole in the available information. Perhaps one of you could fill me in;

1. What is the efficiency comparison between quality type plug-in units compared to a panel mount?

2. Which is better? A higher, or lower "clamping Voltage" rating.

3. From the data that I have read, (supplied by the manufacture's ), is it really adviseable to combine panel mount TVSS with Plug-in strip type tVSS?

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#129694 - 07/30/05 08:33 PM Re: TVSS
Surfinsparky Offline
Member

Registered: 07/29/05
Posts: 77
Loc: merritt island fl usa
Well I am no expert on this but living in florida the lightning capital.We use surge arrestors at the panel and surge suppressors downstream.I took a hit last month with a arrestor on my panel guess it went bad but it wiped out my phones my low voltage lighting my secruity system tripped my 200 amp main but it did'nt get my cpu.I use a true sine wave ups that I plug into a suppresors and then a plug it into a gfci.The gfci seems too go bad but that is it.Anyway the way I see it the more the merrier.It is also nice to get one with a indicator.I don't think they can handle too many spikes.

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#129695 - 07/31/05 08:17 AM Re: TVSS
NJwirenut Offline
Member

Registered: 09/15/01
Posts: 816
Loc: Bergen County, NJ
 Quote:
1. What is the efficiency comparison between quality type plug-in units compared to a panel mount?


Not sure how you would measure "efficiency" here, but a unit at the service entrance is FAR superior to ANYTHING installed at the point of use.

A TVSS relies on a short, heavy, low-impedance path to earth ground. The only reasonable place to get this is at the main service panel. A plug-in unit relies on the ground path back through the branch circuit wiring, which presents too much impedance to be of any value with fast-risetime events like a lightning strike.


 Quote:
2. Which is better? A higher, or lower "clamping Voltage" rating.


Lower, as long as the clamping voltage is higher than the peak voltage seen under any normal condition. In an area subject to high line voltage, a unit with a very low clamping voltage may be destroyed by firing continuously on mormal line voltage.

 Quote:
3. From the data that I have read, (supplied by the manufacture's ), is it really adviseable to combine panel mount TVSS with Plug-in strip type tVSS?


It certainly wont hurt anything, but the point of use units are pretty useless by themselves. They do often contain RFI filtering components, which may help in an interference situation.

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#129696 - 07/31/05 09:00 AM Re: TVSS
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
This is an area where, if ignorance is bliss, I am feeling quite happy right now.....

But it seems to me that the two serve separate functions, and would compliment each other.
The TVSS at the panel would protect you from stuff coming from the PoCo side of things, while the point-of-use stuff will protect you from stuff created within the house....by, say, a loose connection on a shared neutral.

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#129697 - 07/31/05 12:20 PM Re: TVSS
mxslick Offline
Member

Registered: 10/24/04
Posts: 785
Loc: Atomic City, ID USA
surfinsparky:
 Quote:
It is also nice to get one with a indicator.I don't think they can handle too many spikes.


Very true. Most units have MOV's (Metal Oxide Varistors) as the primary surge components, they are deliberately designed as "sacrificial" elements. Open up a strip that has failed and look for the remains of a disc-shaped component, that's your animal.
Their ability to absorb surges weakens with repeated surges. For a critical application in a highly-surge prone area, annual replacement would be a good idea. High-quality units have fuses which will open when the arresting capability is exceeded, protecting the connected equipment and the strip from catastrophic failure.

renosteinke:
 Quote:
while the point-of-use stuff will protect you from stuff created within the house....by, say, a loose connection on a shared neutral.


Probably, maybe, sort of. I say this from experiences, because a lot rides on the clamping voltage rating of the protector.

Case #1 was a P.A. amplifier on a portable genny. Standard surge strip, after a few hours of run time, the generator suddenly labored and almost stalled, this accompanied by smoke from the surge strip. Killed genny, opened strip to see the Line to neutral MOV burned out. Restarted genny, found that due to overspeed, it was outputting 158 volts!! P.A. amp was quite hot but not damaged.

Case #2 was an open neutral situation. Surge strip burned up, damaging the floor it was on, and the connected equipment (Sat dish, VCR, DVD and Surround Receiver) were all destroyed. After the fact (who knows how high voltage really got) measured 194 volts with my Fluke 36.

Many surge strips will still let through harmfully high voltages to the equipment with little or no clamping action. Perhaps one of the higher-grade with the fuses I mentioned above would've done better, but there is still a time factor which makes me think that they still wouldn't protect adequately.

American Power Conversion "APC" makes many high-quality products, including some line voltage regulators and UPS' which automatically bring out-of-range voltage to safe levels. Extreme overvoltage results in a shutdown to protect the equipment.
http://www.apc.com

In Case #2 I used their regulator to help protect against any further problems.

In any event, as others have stated, it doesn't hurt to combine panel-mount and point-of-use TVSS anytime there could be surge issues.
_________________________
Stupid should be painful.

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#129698 - 08/01/05 09:57 AM Re: TVSS
MaddMatt Offline
Junior Member

Registered: 07/26/05
Posts: 3
Loc: Glendale, AZ, United States
Thank you all for your clear, concise, and very helpful answers.

It never fails to amaze me that even after 20+ years in the trade, there is always something new to learn every day.

I can tell that this forum will be a valuable tool to enhance my business in the future, and I hope to be able to contribute in return as well.

Thanks again,

Matt

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#129699 - 11/09/05 08:43 AM Re: TVSS
mhulbert Offline
Member

Registered: 10/19/04
Posts: 133
Loc: Anaheim, CA USA
Nobody else has said it, but the lead length between the TVSS and your panel buss bar is critical. Most recommend 6" or less...this is harder than it seems to arrange in your typical residential panel.

The best setup is a unit that goes between your meter and your socket. However, most EUSERC utilities won't allow this. Second best is a unit that sits directly on the bus bars of your panel. Depending what you are dealing with, they make ones that look like breakers and pop on, all the way up to factory built in units that bolt next to the main lugs. Third best is an external unit that sits next to your panel. I have used ones from Leviton that have plug in surge modules, allowing for quick and easy replacement. They are also fused to prevent a n extended short. The way I usually hook these up is to order a meter main with a 200A breaker, and a 50A breaker, and run the 50A to the TVSS, and the 200A to a subpanel.

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#129700 - 12/13/05 08:45 PM Re: TVSS
dereckbc Offline
Member

Registered: 10/08/03
Posts: 158
Loc: Tulsa, OK
NJWIRENUT said:
"A TVSS relies on a short, heavy, low-impedance path to earth ground".

Sorry, but earth or ground has nothing to do with TVSS and has no function. Any TVSS device is just a clamp to fire at a prescribed voltage and acts as a short circuit between the two points it is connected too.

For example lets say you install a TVSS at the service entrance on a single phase 240 volt service. The best units (I am talking thousands of dollars) only have two surge protection (SPD) devices installed. One each from from line-to-neutral. You will not find a device installed L-G or N-G. Absolutely no need for one.

Once You get down stream from the N-G bond at the service, a SPD between L-G and N-G becomes usefull, but earth or ground still has no function. All you are doing is clamping the voltage between L-G or N-G at the receptacle or point of use. The EGC impedance is an open circuit to earth at lightning frequencies.



[This message has been edited by dereckbc (edited 12-13-2005).]

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#129701 - 12/14/05 07:02 AM Re: TVSS
Joe of NJ Offline
Member

Registered: 12/05/05
Posts: 24
Loc: West Orange, NJ, USA
If you are looking for some easy to read and understand info about TVSSs I suggest you to take a look at the following site: http://www.surgex.com/library/42001.html

For external transients suppression, panel mounted are the best option (Class “C” TVSS for ANSI/IEEE C62.41). There are many manufacturers available. I’ve used Liebert products in several occasions and they performed good (up to now). If pace of mind is important, you should provide both normal mode and common mode protection (LL, LN, LG, NG).

If you are concerned about budget (who’s not_?) you could (but I’m not recommending it) sacrifice LL protection because high external transients are more likely to be lighting induced common mode surges (all lines coming into the facility measured against ground). If the PoCo or another external facilities introduce in your panel high differential mode (surges between lines) transients, the LN, LG and NG sections of your TVSS together with a good grounding system will handle the job. If lightning is a concern you should check NFPA 780.

Hope this help,

Joe.-

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#129702 - 12/14/05 01:37 PM Re: TVSS
dereckbc Offline
Member

Registered: 10/08/03
Posts: 158
Loc: Tulsa, OK
Joe of NJ, if you are referring to a service entrance TVSS on a grounded system (even ungrounded), common mode is a waist of material, time, money, and serves no purpose.

The common mode is already provided in the "normal mode" via the MBJ on grounded systems. You cannot get any more protection than a dead short piece of copper. Only downstream of the entrance should common modes be used. As stated earlier ground (earth) has no function or purpose with TVSS devices.

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