Surge Protection

[walkerj]

Can someone explain to me how whole house surge protection works.
How does it "suppress"?
Is it the same as a plug strip?
I'm clueless

 

[nakulak]

never used a whole house surge, but you might try looking up TVSS, there are several good articles about how they work - using a semiconductor to basically bypass (shunting) spikes to reduce them on the line

 

[Billy_Bob]

So far as I know, many of these devices use MOV's (Metal Oxide Varistors).

Varistors are normally "off", but will turn "on" when the voltage reaches a certain level. These will then short the hots or each hot to ground or both until the voltage falls to the correct range. More at the link below...

The second link below discusses the "types" of suppressors.

Metal Oxide Varistor...
http://en.wikipedia.org/wiki/Varistor

Significant changes - surge protective devices...
http://ecmweb.com/power_quality/electric_ul__nec/

 

[megloff11x]

Most do use TVSS devices, usually MOV's, as described above. These have an energy rating. If your surge has more energy than the rating, then it may weaken or even blow up the TVSS. Then you have no more protection.

The standard drill seems to be run a MOV between all lines, neutral, and ground. In a house this would be:

L1-L2
L1-N
L2-N
L1-G
L2-G
N-G

This may seem silly on the last one since N & G are bonded, but bonded by what? A wire? The transient surge is a fast event, a wire is an inductor, and at high frequency (a fast event) an inductor has a high impedance.

Placement is key with all connections. The wires tend to behave as inductors and you want to shunt the Voltage spike quickly.

The MOV's connected as above will make the spike common to all incoming lines (no big Voltage difference to blow stuff) as well as try to dump its energy into the ground.

Your own connection may vary as the TVSS unit may have other stuff.

 

[dereckbc]

For a whole house or service entrance protector there is no need for any other modes other than N1-N, and N2-N. Anything else is a waist of material and money..

All surge protectors using MOV's or SAD's work exactly alike.
They simple short or shunt when the specified voltage is reached called "Clamping Voltage" and release once the voltage falls below the threshold.

 

[nc5p]

For a whole house or service entrance protector there is no need for any other modes other than N1-N, and N2-N. Anything else is a waist of material and money..

All surge protectors using MOV's or SAD's work exactly alike.
They simple short or shunt when the specified voltage is reached called "Clamping Voltage" and release once the voltage falls below the threshold.

Silicon Avalanche Diodes have lower energy limits than MOV's and in general should not be used on a service or large feeder. They are much faster than MOV's and are thus good for nuclear EMP protection. One way around this issue is to install a large MOV in parallel with the SAD. Rate the SAD at a higher clamp voltage than the MOV so that the SAD "catches" the fast rising part of the surge, but it's clamp voltage is just above the MOV so the MOV takes over and clamps the bulk of the current. Once the MOV fires the SAD will stop conducting before destruction occurs. I use the Littlefuse 15K SAD's on AC power systems, but they are hard to find in stock. The others are too small and I've blown them up on the bench testing. If the customer does not require EMP level protection it is probably best to stay with MOV's. To do it right requires a lot more than just surge protection.