On 5/4/2012 4:19 PM, dpb wrote:
On 5/4/2012 3:40 PM, genius wrote:
Hey all,
I am trying to move my sprinkler controller (an Orbit digital job
about 4 years old) to a more convenient spot in the garage. It has
very thick, I would guess 12 gauge, wire going from the valves to the
controller box. Is that the required thickness? I was thinking if I
used cat5e, there's 4 twisted pair so I can get a unique colored wire
to each of my 8 zones...

As another poster says, it'll depend on what the actual current draw is
and that'll depend on what the number of valves/zone is and the power to
control each and the operating voltage level. My guess is that the
answer is 'no'; there's not enough ampacity in signal cable or the
spec's wouldn't go to anything as heavy as what you've quoted.

Cat 5 is, afaik, not specified specifically by conductor diameter but by
digital transmission performance spec's but I believe it generally is in
the 22-24 AWG range. From the following table for power transmission you
see you're going to be very limited in how much current you can draw. 22
AWG is as little under 1 A; 24 AWG is under 0.6 A.

I _think_ I've seen typical lawn valve spec's at 24 VAC/200 mA holding
current but inrush is probably 2-3X that.

If there's only a single valve of that size on each conductor pair you
_might_ get away with it for such a short run, but the answer is you
really probably need a minimum of 18 AWG and probably out to think more
like 16 or so. Of course, if your valves are higher draw or more/zone,
needs will go up, too.

Your surest bet is to match wire size to what is already there; one
would assume the installer didn't waste materials for no good reason.

--

also take into account voltage drop. smaller wire will have a larger
voltage drop than larger wire.