If all 3 are single-point-grounded, why does A/C need a surge suppressor but phone & cable do not?
From: Flea Ridden (flea_at_flea.ridden)
Date: Fri, 09 Jul 2004 14:20:59 GMT
Why don't all manufacturers sell models like the Intermatic PanelGuard IG1300-2T-1C which protects phone
and cable inputs too?
If protection like this is not needed for phone and cable lines, why is it needed for A/C lines?
> Yes communication ports are easily damaged where they are used beyond
> what they were designed for. Two examples are RS-232 ports and
> outside speakers to a stereo amp. However first one must ask where
> was the incoming and outgoing path for that damage.
> Does a surge enter on communication port, damage that port, then
> stop? Of course not. First a complete circuit is established from
> cloud to earth. After that circuit is conducting electricity through
> everything in that circuit, only then does something fail. If that
> circuit is incoming and outgoing via appliance - a condition where
> 1000+ volts means the 'whole house protector system was defective -
> then the solution is not to supplement the protector. The solution is
> to fix the 'whole house' protector and its so critically necessary
> earth ground.
> As noted previously, many communication ports, to communicate with
> devices not adjacent to the computer, already have effective internal
> protection. For example NIC (ethernet) port is typically good for in
> excess of 1000 volts. That is effective protection that can be
> overwhelmed if the necessary 'whole house' protector system is not
> installed. Most critical component of that system? Single point
> earth ground.
> Do we fix the single point ground or do we install 'point of use'
> protectors on every of well over 100 appliances inside the house?
> Remember, GFCIs in kitchen and bathroom, furnace, electronic timer
> switch, dishwasher, clock radio, portable phone, microwave, alarm
> system - are but a few of the electronics that each need a $15 or $50
> protector if the 'whole house' system is not properly installed.
> Better and less expensive to fix the 'whole house' (secondary)
> protection system.
> Charles Perry cites a paper that is a 'must read' for anyone who
> needs surge protection:
> Same authors make same point in an applicaton note for builders and
> other structural contractors - again must read:
> In the Cozy Cabin example, simple principles of single point earth
> ground are violated. Damage was made possible by human failure. The
> Rambling Residence suffers from a similar failure. For example,
> outside speakers are incoming wires that did not first connect to
> single point ground before leaving the building. Where did that
> transient enter or leave? The authors suspect induced electromagnetic
> transient. However those wires easily could have been connected to a
> direct surge by being buried, routed over conductive materials such as
> concrete, or even in contact with another conductor - the tree. But
> again, wires entered the building without first making contact to the
> single point earth ground system. A blantant violation.
> Other suspects could have contributed to the problem. Electrical
> controls for the sprinkler system also complicate the installation of
> a single point ground. Where or how did another structure - the
> exterior pool - connect to building? Were building and pools
> interconnected at a single point or did they too create ground loops?
> Both pool and building should have been connected as if each were a
> separate structure. If not, then the building could have ground loop
> problems - no single point earth ground existed.
> Earthing is the primary solution to surge protection which is also
> why new homes should have Ufer or halo grounds. Grounding installed
> bfore the foundation is even constructed. Purpose is to make earth
> beneath equipotential - make the single point ground more effective.
> Plug-in or 'point of use' protectors do not adaquately compensate for
> a defective earthing system. Furthermore those plug-in protectors are
> typically undersized and grossly overpriced - on the order of tens of
> times more expensive per protected appliance.
> That is the point of that nist.gov paper and so many other
> industry professionals. Protectors are not the protection. Earthing
> - the thing often forgotten because it is out of sight - is the most
> important aspect of surge protection.
> And we are only discussing secondary protection. What is the
> primary protection? Examples of failures in a building's primary
> protection system:
> Again, the less expensive and essential solution is earthing even in
> the primary protector system.
> "Charles Perry" <firstname.lastname@example.org> wrote in message news:<2l2bmtF7im90U1@uni-berlin.de>...
> > The problem is not with the power supply, it is with the communications
> > ports. Nine out of ten failed appliances that we examine have failures
> > associated with the communications ports. If you don't provide the proper
> > TVSS that ties the power and communications references together, then you
> > will damage equipment.
> > http://www.eeel.nist.gov/817/817g/spd-anthology/files/Enlightening.pdf
> > A very good paper that mentions this.
> > Charles Perry P.E.