Shielded Wire

Alan(CaliforniaRadiant)Forbes

We've had a few problems in the past when using regular thermsotat wire for outdoor sensors; you get them too close to any line voltage wiring and it messes up the signal.

My supplier sells "plenum wire" - 18 gauge. They assure me it's the same thing. Is this the right stuff to use?



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KCA_2

If you

use a shielded wire you can't go wrong however, I've only used it were we might run along side a 110V or so wire. If you cross a wire there shouldn't be a problem.
Same thing if you use the Tekmar RTU's. Or any such other animal.

:-) Kca

BillW@honeywell

wire

Plenum wire refers to the type of insulation on the wire. Ordinary PVC releases all sorts of nasty stuff in a fire, so it can't be used in a plenum since air currents may carry these toxic gases to another area. Plenum wire is coated with Teflon. Shielded wire is a good idea, especially for remote sensors, or when you must run low voltage wire in close proximity to line voltages. Just look at the end of the wire...you'll see conductors, insulation and a metal spiral wound shield, then the external insulation. It prevents the line voltage wire from inducing a current into the low or micro-voltage line, causing false readings.

HBW

Proper Use

We typically use 18ga shielded stranded plenum wire for all our sensor wiring to prevent unwanted electrical signal noise. It should be pointed out that there are several ways to terminate the shields. The most basic way would be to fold back the drain wire and tape it off at the sensor location and then ground the opposite end at the controller. This acts like a hugh antenna to "drain" away the un-wanted noise.

tombig

seek and ye shall find

Pre-internet I was looking for a good shielded wire for a friend for a communication application. Wound up at a wire and cable warehouse with 12' spools all over the shop. They hooked me up with a product I swear would last if run under a lake. 4 conducter,twisted pair 18ga.,foil shield,rubber jacket,stainless braid shield,pvc outer layer. Haven't had a use for it since. Hmmm. Now I know why 1/2 roll has been bouncing around the shop for 5yrs.

Boilerpro_2

Where to buy

> Pre-internet I was looking for a good shielded

> wire for a friend for a communication

> application. Wound up at a wire and cable

> warehouse with 12' spools all over the shop. They

> hooked me up with a product I swear would last if

> run under a lake. 4 conducter,twisted pair

> 18ga.,foil shield,rubber jacket,stainless braid

> shield,pvc outer layer. Haven't had a use for it

> since. Hmmm. Now I know why 1/2 roll has been

> bouncing around the shop for 5yrs.

Boilerpro_2

Where to buy

Johnstone carries shielded wire....pretty nice stuff too. 2, 4, 6 conductor. I use it on all sensor wiring, the only problem is that while the control companies want you to use it, at least some don't leave enough space in the terminal blocks to connect the shield easily.

Boilerpro

hot_rod

Johnstone Supply

is where I get mine. Within a week if they have to order it. Should be a branch near you or go online. I started using it for t-stat and sensor wiring recently.

hot rod

Alan(CaliforniaRadiant)Forbes

Not the same

as what I bought; I think what I have is plain plenum wire since there's no additional shielding other than the plastic jacket.

But this stuff worked on my last job; I was getting high resistance readings on cold days and the boiler wasn't coming on becuase it thought it was 90* outside. I replaced it with this plenum wire and the resistance came down to match the outside temperature.

I'd better spring for the good stuff at Johnstone; don't want to take any chances. Thanks, you guys.

Nice threaded rod cutter, hr. Too bad they don't make one battery powered with short handles that you can put in a holster.

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jack_4

To be more correct

To be more correct, it provides a path of least resistance and the energy will be shorted to the ground rather than induced into you signal wire.

But you got the point correct. Connect the drain (shield) to ground on at least one end.

Dave_23

Outdoor wiring

Folks,

Wire and cable run outdoors should be Ultraviolet (UV) rated and specified for outdoor use so as to prevent deterioration over time.

Plenum-rated wire does not provide this feature.

However, if the wire is run in conduit, the outdoor rating requirement disappears as does the plenum-rating requirment.

-Dave