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Posted by TWayne on July 7, 2008, 1:25 pm
> hallerb@aol.com wrote:
>>>
>>>> Does anyone know if surge suppresser protection can be increased by
>>>> "chaining" two or more together?
>>>> For example, I have two power strips that have surge suppresser
>>>> outlets. If I plug one of the strips into the protected outlet of
>>>> the other suppresser will the down-stream strip offer more
>>>> protection than the up-stream one?
> .
> I would get a single suppressor with high ratings. They are readily
> available at rather low cost.
>
> The division of the protection between the suppressors depends on the
> clamp voltage of the MOVs in the suppressors.
>
> If chained, I would plug-in only to the most downstream suppressor.
Actually, if you think about it, it really doesn't matter. All the
protection elements end up in parallel even though the plugins are in
"series". With one plugged into the other it won't make a bit of
difference. A "big" one and a "small" one will result in the small one
always being the guy to fail first anyway since it'll be the first to go
under fault cases.
So, a second one does add some protection, but not as much as one
would expect. Two identical units would not result in twice the juoles
of protection because one's components will always fire first and clamp
first, leaving the other one to sit there nice and cool. They won't
both clamp most of the time except under long, sustained faults and then
one will try to source it all, blow, and leave the other one to take its
place.
It's really better to have one larger, better designed unit than
multiple smaller ones. The conduction points, knees, and clamp
times/voltages are not very closely controled, especially in the cheap
units. All they're really there for are a few short duration spikes in
excess of about 600V, then once fired, try to pull that voltage down to
something lower until it burns itself out or the voltage goes away.
Do a Google for "how to's" & designs on surge supression; it's pretty
interesting stuff. I used to do safety testing on them for UL
certifications & componentry.
>
> Any manufacturer with a protected equipment warranty is likely to say
> the warranty is void.
>
> UL does not intend for any plug strips to be chained.
>
> Everything that is interconnected needs to be plugged into the same
> suppressor. External wires, like phone and cable, also need to go
> through the suppressor.
> .
>> Buy a UPS, far better design and protection.
> .
> UPSs, of the kind commonly used, do not intrinsically provide any
> surge protection. The surge protection included in a plug-in
> suppressor is commonly added.
Right; they're good protectors on the regulated side, but not on the
unregulated outputs. The batteries, caps & xfrms provide a lot of surge
protection just by having to be there for the design. And yes, I'm
including switching supplies.
Cheers,
>
> Compare surge ratings.
>
> And in the US get a UPS that includes UL1449 listing (surge
> suppressors). Many (most?) UPSs don't.
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