I have the same tower and remote package.
Jim is correct. The controller uses 120VAC and it would be a code violation
to run it in the same conduit as low voltage cables. Period.
It's irrelevant that low current flows in the control lines when operating
the tower. This is only true because the relays at the tower draw a
relatively small amount of current. But there's no current limiting at the
source (the switch box in the shack), so If a short occurs between a control
line carrying 120VAC and one of your low voltage cables, you could be
exposed to dangerous voltage/current or your low voltage devices could be
damaged. The code recognizes this and the possibility that damage to cable
jackets can occur when pulling them through conduit. My advice: don't do it.
I was unware of US Tower's unfortunate design when I installed my conduit
and cables. I have three separate 265-foot conduits: a 4" conduit for two
runs of 1/2" hardline, a 2.5" conduit for all the control cables and a 1"
conduit for 240VAC AC to the tower (where there's a breaker subpanel that
splits the 240V AC into two 120VAC circuits, one for the tower and one for a
utility outlet.) Had I know about the AC control signals, I might have run
the control cable for the tower through the AC conduit (and would have
selected larger diameter tubing for that run.) That said, I don't know if
it's OK to run 240VAC and 120VAC through the same conduit.
Once I realized that AC was going to run inside my control cable conduit, I
built an interface and control box to translate a safe 12VDC in the shack
and conduit to 120VAC at the tower. It's actually a very simple circuit that
uses the same control cable as the AC-based system (I used 8-conductor rotor
cable). The interface consists of a six 12VDC relays that switch the 120VAC
relays in the remote control box mounted on the tower. The board is only a
few inches square and there was plenty of room to mount it in the metal box
at the tower. The control system simply consists of switches and LEDs built
into a project box. The arrangement is basically the same as the original
control box. There's a SPST Power-On switch, a SPDT three-position
Raising-Off-Lowering Switch, and a SPDT Local-Remote switch. There are three
pairs of green and red LEDs: a pair to indicate Raising and Full Up, a pair
to indicate Lowering and Full down, and a pair to indicate Remote and Local.
The power switch is connected to the shack 13.8V supply.
I have PDFs of the interface circuit, the 12VDC control box and the original
120VAC control box that I'd be happy to email to anyone who wants them. US
Tower has a schematic (of sorts) for the components in the remote control
relays that could be helpful for making connections at the tower. If you
didn't get that, ask for it.
73, Dick WC1M
> -----Original Message-----
> From: Jim Brown [mailto:jim@audiosystemsgroup.com]
> Sent: Thursday, November 06, 2014 6:28 PM
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] RMC-1000 remote - what type of cable to run?
>
> On Thu,11/6/2014 11:55 AM, Howard W6HDG wrote:
> > I then emailed him again and double checked that it could run in the
> > same conduit with coax and rotor cables and he replied, "Yes, as I
> > said, it would be off while transmissions/radio operation ".
>
> Sorry, that's a wrong answer. If the cables carry 120VAC, they MUST NOT be
> in the same conduit with low voltage wiring. As I recall, the break point
is
> something like 48V.
>
> 73, Jim K9YC
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