OK, relating to my remote stat sensor thread, it appears I may in fact need shielded UTP. when calling around, almost no one even knows what Im talking about. Graybar - no go. All the HD, Lowes, etc - no go. Asked a few local HVAC contractors - no go. A@@D says they can get it, but suggested I try Graybar instead for cost reasons.

Is it really that rare?

If I had to choose between the two, which would offer better protection from interference Regular (un-shielded) UTP, or regular (non UTP) shielded wire. One of the local HVAC guys suggested using just shielded speaker wire,etc.

You may find shielded speaker wire just as hard to find. I would not take the tin knocker's suggestion; if the tstat mfr specifies it, stick with it.

I use Windy City Wire here in Chicago for oddball stuff like this, and they almost always have what I need. I ordered and received some shielded Cat 5 from them recently, and even had a choice of colors from their in-stock inventory.

UTP stands for Unshielded Twisted Pair. You are looking for STP as no one will have shielded unshielded twisted pair. :)

Or indeed FTP; foiled twisted pair.

Ditto what jayson said, my graybar rep said they have some colors in stock...

Who is the TStat manufacturer? I've never heard of a stat that specs shielded cat 5/6.

Anixter and Graybar both stock shielded. I consider the likelihood that you truly need shielded slim to none, as the transmission properties of the cable are for *practical purposes* the same, other than the shielding, and the TStat specs may well have been drawn up by an engineer who just chose shielded for the spec because he didn't have a clue and figured "a shield's better than no shield", but if you want to follow spec...Anixter or Graybar stock it.

Belden cable makes a lot of this type of wire.

One thing I have done in the past is to add a ferrite core to the wire. Depending upon where the interference is coming from, and at what frequency it is, this sometimes does the trick.

Its an HAI remote temp sensor. See this thread
[Link: remotecentral.com]
I ended up trying the 18/7 that is curenlty in the wall, but my luck ran out. I am getting some erratic readings from the sensor. It will be 68 one second, and 73 the next. I at least wanted to TRY the spec'd wire (outside of the wall) and see if it helps

I did try Grybar, and they didnt have it here in Ohio.

I can guarantee you Anixter stocks it, we've bought tons of it there.

Just to clarify, I was saying that unshielded Cat 5 would likely work as well as shielded Cat 5, regular old thermostat wire might indeed be problematic if the spec calls for shielded (or unshielded) twisted pair.

Maybe he's looking for unshielded Universal Twisted Pair?

Just to clarify further, all of my posts up until now assumed you were looking for shielded Cat 5 (or 6) because of the terms you used. However, I just reviewed the actual spec ([Link: homeauto.com]) and I see it's not calling for Cat 5 or 6 at all. It says:

Run a twisted pair, shielded cable from the Omnistat to the Remote Temperature Sensor location. For distances up to 100 feet,
typical twisted pair, PVC-insulated, shielded cable may be used. For distances from 100-150 feet, twisted pair with
polypropylene insulated conductors, shielded must be used. For distances from 150-250 feet, twisted pair with foam-polyethylene
insulated conductors, shielded must be used. Wire runs must not exceed 250 feet.

That is the most ridiculous joke of a spec I have ever seen. How about giving a f**cking model so people can just refer to a cable? How about giving a required guage?! I can't even imagine the number of support calls that have had to take answering questions about that instead of just supplying a useful spec. And you're supposed to use, depending on distance:

PVC-insulated (<100')
OR
polypropylene insulated conductors (100' - 150')
OR
foam-polyethylene insulated conductors (150' - 250')

Someone who wrote that was smoking a crack pipe. Get on the phone with them and tell them to give you the wire you should be using. What a joke, this is the stuff that drives me nutty. We've got enough to worry about throughout the day without having to waste time because some moronic company puts this type of garbage in their specs.

I have an HAI temp sensor connected to an HAI panel with CAT5 UTP. The distance is probably 50 feet, no problems.

I think it's very clear. If they gave you an exact type of wire to use, and it wasn't what you saw available locally, you'd want to know the above info.


There isn't a required gauge, because this is a thermistor. The wire is carrying a voltage less than a volt and the currents used to excite the thermistor are quite low. They run a small current through the wire, probably about 1mA, and measure the voltage using an A/D converter. They then run a larger current and again measure the voltage. The two currents and two voltages let them determine what the resistance of the thermistor is, as opposed to the resistance of the wire. It is the resistance of the thermistor that they want to determine as that varies directly with temperature.

The shield is connected to the thermostant, as it is used as a guard ring in this circuit. The voltages they are dealing with are very low, and small amounts of noise introduced into the circuit will cause readings to vary. Do your best to keep the wire and sensor away from 110VAC, and any speaker runs. If you're going to be close to any of these, regardless of the length of the run, use the shielded wire. They specify the insulation, because the leakage current for the wire is such an issue in this application.

The person who spec'd this was obviously an engineer, and he spec'd it in a way that other engineers will immediately understand. I'm just trying to translate for you, as I know how these circuits work.

We have used standard Cat5e UTP for both the HAI thermostat and the HAI temp sensor with no problems whatsoever. Just stay away from any electric wires and you will be fine.

If you really want STP, call Kimberly @ Windy City. I know they stock it, and are very reasonable on price.