Hey all.. forgive the "blast from the past".. for some reason a bunch of
emails showed up as new, but in reality, were from a long time ago..
Jim Lux wrote:
> Tom Anderson wrote:
>> Jim and fellow tower talk members:
>> I'm in the process of having a 220 line run into the shack for a new
>> Alpha 9500 amp my XYL and I picked up at the plant in Boulder a month
>> ago. Still waiting on the electrician showing up though.
>> While I had him on the phone I asked him (and yes I've known him for
>> years (I was his son's Eagle Scout advisor) and he's done work for me
>> before and does a lot of commercial work near us) about a whole house
>> protector and in his opinion he felt a good individual unit for the
>> plugs and equipment you wanted to protect was better than a whole
>> house protector. He said many strikes, surges, etc. come into the
>> house via phone lines, TV cable, satellite dishes, etc. and often
>> bypass the whole house protector before getting into the home
>> electrical system, which is why he prefers good single unit protectors
>> when needed.
> Not to be argumentative, but it would seem that the peer-reviewed
> transient protection literature doesn't agree with the single unit
> protection philosophy.
> (i.e. things that aren't sales material or field application guidelines
> from one company or another.. but stuff that has been independently
> produced, or at least reviewed by folks without a financial or other
> interest. Sure, the guys from Erico publish papers on transient
> suppression, and Erico sells products that do this, but the journal's
> pre-publication review process generally makes sure that 2 or 3 other
> folks take a look at it and make sure it's not all bushwa.)
> Your friend is right that lots of transients come in other ways, which
> is why you need protection on *all* of them, and why everyone is so
> obsessed with all those "bonding" rules. However, there's a whole raft
> of reasons why protection at the entrance is needed, and preferred, and
> which should be properly coordinated with the downstream protection.
> The guidelines for things like safety critical installations (e.g. the
> FAA guidelines and DoD guidelines) all talk about transient protection
> at the service entrance, but make little or no mention of "point of use"
> Also, a lot of protection devices get a lot of their protection ability
> by absorbing the transient (and getting spectacularly destroyed in the
> process). I think I'd rather have the spectacular failure out by the
> meter, rather than on some plugstrip behind the desk.
> Really, the only hazard that point of use protection protects against is
> a transient being induced in your house wiring closer to the equipment
> than to the service entrance, because of the time delays involved.
> (transients from outside, which are MUCH more common, get suppressed at
> the service entrance) Or, if you have something in your house that puts
> big transients on the power wiring (like that 1kW tesla coil you fire up
> in the garage.. been there, done that, cooked my garage door opener and
> a UPS.)
> Of course, a decent series mode suppressor (i.e. a LC low pass filter)
> will solve that problem. Most modern electronic equipment already has
> fairly decent low pass input filters on the AC line connection (to
> prevent signals inside the box from coming out and creating EMI havoc),
> so the sub microsecond transient resulting from that spurious induced
> voltage, and reflecting back from the clamp will get smoothed out by the
> filter to a level that is lower than the damage threshold for your device.
> For folks wanting to spend some time and about $20, get the book by
> Standler on overvoltage protection. (google standler overvoltage and
> you'll probably find it) He's got all the data, the impulse waveforms,
> the theory of what works and what doesn't. His website also has some
> info. I can't recall which off hand, but in one place or the other, he
> talks about the UL1449 standards, and the problem with "joule ratings"
> and "clipping voltage".
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