Great post Shane. For many years I have read on towertalk that running 120v
lines in the same conduit as the low voltage rotator and switching lines was
against code so I ran my 120v UF-B wire outside of tower's buried PVC
conduit. Thank for clearing this myth up.
73,
John KK9A
From: Shane Youhouse kd6vxi
Date: Fri, 13 Dec 2019 14:38:51 -0800
> 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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