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Posted by w_tom on June 5, 2008, 9:15 pm
On Jun 5, 4:50 pm, letter...@invalid.com wrote:
> My service panel is grounded at the pole, which is right outside the
> house. This is a farm, and that pole provides power to multiple
> buildings. However, the electric service is not the problem, it's the
> phone line. This is a trailer house. When the phone company
> installed the phone line, they grounded the phone line to the steel
> beam under the trailer. Since the trailer beam has cinder blocks
> under it, it's really not grounded at all. Maybe I should add a
> ground rod and connect the phone line. I always thought this was not
> an adaquate ground. ...
In a previous post, repeatedly stated was something critical - 'less
than 10 feet'. Whereas that 50 foot wire might be sufficient for
safety grounding (protect from electric shock), that same wire is too
long for surge protection.
Every telco subscriber has a 'whole house' protector installed for
free; located in what others have called the demarcation block or
NID. But and again, that protector is only as effective as its earth
ground. Bonding to a trailer does not connect lightning energy into
earth. Earthing at the utility pole is only a primary surge
protection =91system=92. Required is secondary protection where all
utilities make that 'less than 10 foot' connection to the structure's
(trailer's) single point earth ground.
Why would that telco installed =91whole house=92 protector not protect?
No earthing. Protection means lightning's energy must be dissipated in
earth. That telco 'whole house' protector must be earthed to an
electrode that also earths AC electric, cable, and satellite dish.
Those other requirements are also important: 'less than 10 feet, no
sharp wire bends, separated from all other wires, etc.
In most cases, a single 10 foot ground rod provides a massive
increase in protection (as also noted by John Grabowski). Soil is
also relevant. For example, if sandy soil, then some will massively
expand their earthing for a little more protection:
http://members.aol.com/gfretwell/ufer.jpg
http://scott-inc.com/html/ufer.htm
All that to make the protector more effective. The point: a
protector is only as effective as its earth ground.
AC electric pole earth ground only earths their transformer and its
internal protector. A pole's earth ground does not earth a trailer or
any other building. Each structure must also have its own single
point earth ground.
Teleco installed 'whole house' protector without earthing (only
trailer bonded) means that protector acted as if it never existed.
How to create superior telephone line protection? 'Telco
provided' (demarc or NID) protector must connect short ('less than 10
feet') to the best earthing electrode also used by AC electric, TV
cable, and satellite dish where all wires enter the building. Bonded
to the trailer would explain telephone appliance damage. No telephone
appliance damage for 20 years means a properly earthed NID.
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