Intermatic Whole House Surge Protector ?

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Old 04-17-08, 09:40 AM
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Intermatic Whole House Surge Protector ?

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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Old 04-17-08, 10:36 AM
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Originally Posted by Robert111 View Post
one nearby strike fried the control board on our furnace !
Unfortunately that's a very common occurance.

Any of you folks ever used this model ?
Not that particular one, but there are several similar ones. I think it's a good idea to install a panel surge protector. There is of course no guarantee that it will save anything from damage, but a good first line of defense.

If they do ever take a big hit, do they (usually) fail open or closed ?
Depends on how big of a hit and how close to your house -- lightning is an incredibly powerful force. I've seen the aftermath of some strikes that ripped buried lines out of the ground.

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 ?
Yes. It's hooked up through a breaker so once the MOVs short out, the breaker will trip. The MOVs would need to be replaced before the circuit could be switched back in.
 
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Old 04-17-08, 01:18 PM
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I just installed one very similar in a recent main panel upgrade. For things like furnaces, AC, garage openers, etc. I believe a main panel surge suppressor is invaluable. But still install high quality point of use suppressors on your computer, expensive tv equipment, etc.

The instructions on these units are straight forward but often include a few different ways to wire them. The Leviton I just installed had an option to install it on the main lugs, or via a breaker - and the breaker could be 20A or 30A. Basically, as long as you (or your electrician) follows the installation instructions, you should be good to go. The other comment that is often included in the instructions is to make the wires as short as possible. Presuming you install with a breaker, try to keep the breaker in a position close to the main disconnect and cut the wires reasonably short. A few extra inches of resistance when you're talking tens of thousands of volts can make a difference.

Also, usually once these units take a hit, they need to be replaced. Most of them don't allow you to user-replace the MOVs.
 
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Old 04-17-08, 01:28 PM
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Square D and Cutler-Hammer also offer panel mounted surge protection. Check the warrantee offers and check the limits of coverage and see what is covered. Most have indicator lights to show that the protection is in force.

Nothing will protect you from a direct strike, however, a panel mount in conjunction with surge strips at the point of use are the best bet for protection.

As surges can come through the cable tv and phone wirng make sure they are protected also.
 
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Old 04-17-08, 02:24 PM
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there's hits, and there's big hits..

Originally Posted by Robert111 View Post
Hello,


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 ?
MOV's are non-linear resistors. Once a breakdown voltage is met and exceeded, they start conduction. The conduction time and the conduction current both factor in the equation if the MOV's will survive. During the conduction interval, they heat up. That's why box mounted devices are typically larger MOV's and even are paralleled up. The joule rating is a measure of how much energy they can dissapate as heat before they fry.
If significantly overloaded, they will flame, maybe even liberate material rapidly (explode). Most installations include a series fuse, and this is used as the basis of the "little green light". If the fuse is good, the green light is on. I understand they can fail in near short mode.
 
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Old 04-17-08, 02:33 PM
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And then there is R F damage

While the box or other protectors do a lot of good, the radio frequency energy from a near miss can still fry electronic parts. One, some years ago blew transistors out of several radio scanners I had lying on the desk. Sad to say, neither one was plugged in or turned on. That thousand foot long spark gap transmitter (lightening) fried them.
 
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Old 04-17-08, 02:42 PM
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impressive!

Originally Posted by goldstar View Post
While the box or other protectors do a lot of good, the radio frequency energy from a near miss can still fry electronic parts. One, some years ago blew transistors out of several radio scanners I had lying on the desk. Sad to say, neither one was plugged in or turned on. That thousand foot long spark gap transmitter (lightening) fried them.
And then there is the lead box buried underground trick. (for even more protection)
 
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