On July 10, 2012 at 17:08, westom said...
No protector does protection. A problem for most who want every solution inside a box. Reread those first paragraphs. What harmlessly absorbs hundreds of thousands of joules? What defines all protection? Earth ground. If you do not grasp that, then you are ripe to be scammed.
Facilities that cannot have damage do not waste money on protectors inside the building. The superior solution, that also costs tens or 100 times less money, is a 'whole house' protector properly earthed. Low impedance connection which means a wire length from protector to earth 'less than 10 feet'. Because wire length (not wire thickness) is the most critical parameter. No snake oil. Just fundamental electrical engineering knowledge.
Companies with better integrity sell the superior solution including Square D, Leviton, General Electric, ABB, Siemens, Ditek, Polyphaser, and Intermatic. A Cutler-Hammer solution sells in Lowes and Home Depot for less than $50. Money does not define quality. Science does. Worry little about the protector. Worry most about what defines protection - single point earth ground.
I see you did not respond to my quotes from NIST reference you provided. So I assume it was accepted as is. Now let's address this point where whole house devices provide such perfect protection no matter which brand or design.
First up is Eaton/Cutler-Hammer. This is actual failure mode in the field:
Notice the burned PC board traces rendering the device useless. The surge was shorted out by the MOV but the weakest path was the circuit board traces.
Another example:
On the left is the original device (Eaton Vanguard VGX). In the middle and to the right are catastrophic failures of the device literally blowing a hole through the enclosure! You were saying something about zero energy dissipated by these devices? What do you think created that damage?
Another example:
Smoked again. Why? Because details and the design matter in these devices as much as the $25 device. The mere classification of a device into this category does not give you license to say it all work just as well.
There are two problems behind these failure modes:
1. They hide behind the fact that UL testing is only for one mode at a time. This means the device is under-designed to handle higher heat buildup/energy when this is not the case.
2. Lack of "component level fusing" (CLF) where each MOV is properly protected. Remember, all this device is doing is creating a short to the ground. That will cause the MOV to start to cook as massive amount of current goes through it. Unlike what you are assuming, the device does not have zero impedance when it avalanches. You have to have a mechanism to keep it from smoking once its maximum rating is reached. A fuse does that.
Here is an example of good design:
And a company who stands behind it, repairing any failure of the device should its fuses blow.
So no, "better company integrity" is no assurance of device performance just because we are talking about whole house devices. You must perform the same due diligence into the design and understanding of its principal operation just the same. Quality and attention to key aspects of design matter and matter greatly. Imagine having these devices smoke in a $10M house where you were responsible for $500K of that cost! And the downstream device damage that would occur post these boxes failing.
As I noted in my first reply, you make some good points but they are marred by incorrect assumptions. Here is a great example of you thinking a $50 device works its wonders where data clearly shows that it can fail and fail just as catastrophically as point of use product.
