>
> Message: 6
> Date: Wed, 11 Dec 2019 16:33:53 -0800
> From: Jim Brown <jim@audiosystemsgroup.com>
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] Special grounding and/or cable routing?
> Message-ID:
> <0ac881be-ecd5-0a1f-33ff-ffc0250970fd@audiosystemsgroup.com>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> On 12/11/2019 5:49 AM, Paul Beckmann wrote:
> > I'm writing the reflector members today to get their thoughts on my plans
> > for coax and cable routing, grounding, and lightning suppression. Should
> > suppression be installed at the base of the tower before it makes the 15'
> > underground run? Should the tower ground and garage ground be directly
> > interconnected?
>
> Absolutely yes -- one of the most fundamental rules of grounding and
> bonding is that ALL grounds must be bonded together. The only time you
> would NOT bond tower ground to other grounds is if it was more than
> 60-100 ft from the building housing the shack. I would place arrestors
> on a panel near ground level where it enters the garage so that bonding
> from that panel (the arrestors) has the shortest practical path to the
> earth.
>
> > If so, should the ground be placed inside or outside the
> > coax and rotator cable conduit?
>
> In general, it's good practice to route all cables together. This would
> be a great application for steel conduit (EMT) if it's practical to
> install it. Bond it to ground at both ends, and it shields the wiring
> AND acts as a very robust bonding conductor. It is NOT, however,
> permitted to run power and low voltage wiring in the same conduit, and
> equipment grounding conductors associated with power (the Green Wire)
> MUST be run in the same conduit with power conductors.
This is not true. So long as all cables have a rating equal to the highest
voltage encountered you can bundle all cables in the same raceway. Even
ether net can be purchased with 600VAC insulation ratings. Along with most
other style of wire.
We currently use 0 to 10v dimmers and they have both the 0 to 10 and the
120 to 277 volt based 'mains' wires in the same metal clad spiral conduit.
This meets BOTH UL and at least back to 2011 NEC.
It is a common myth that they can't all be in the same raceway. But that
doesn't make it right.
Also, he has both underground and above ground runs. You don't use EMT in
the ground. You SHOULD use it above ground, along with what is called BOND
BUSHINGS on both ends. This will keep everything at the dame rf and DC
potential, as well as provide some shielding.
If you want to use metal conduit in the ground, use rigid pipe along with a
good installation of plastic tape. Not normal electric tape, but what
electricians refer to as pipe wrap. I don't. I use schedule 40 pvc
underground and then transistor to metal pipe when it comes above ground
for any appreciable length.
Also you must have a sheathed ground to pull into your conduit. You may
not use bare ground wire inside a raceway with sheathed wires. Reason
being the bare copper will (can) abraxe the insulation, especially when
being installed and / or pulled in. Some AHJ (authorities having
jurisdiction may argue this, but it is code where I work in California).
These statements will ring true to current NEC guidelines, California
Electric Code and my local AHJ)
--Shane
KD6VXI
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