[RE-wrenches] Cat 5 cable in 240 AC power conduit with #2 alum entrance wire.

[Daniel Young]

Well, I don’t think anyone on this list is a network specialist, which is what I would consider an expert…. But…

 

Running cat5 (really any data cable) parallel to a power line (especially and AC line) is listed as a bad move in almost every installation guide I have ever seen. Data and power are supposed to cross paths in a perpendicular fashion whenever they get “close” to each other. If the clients wants to pay for a letter from a network specialist, just so they can spend more money putting the right stuff in, I would just have that done. But everything I’ve ever learned about this says that power running in the same conduit as communications is a cardinal sin (they run parallel, and as close as is physically possible while in the same conduit). To borrow a phrase from Joe Lstiburek “That’s what we call a Barry Bonds problem…..stupid on steroids”.

 

The bare minimum is to make sure the cable is shielded, and the bleed wire is terminated at a grounding point at one end only. This is the only way there is a prayer for Ethernet signals to make the 120’ journey with any reliability. The more noise in the line, the slower the connection, as more and more packets will get rejected and have to be re-sent until they make it through without too much distortion, at some point the noise will prevent any data packets from making it from A to B and you need to break out the string and Dixie cups.

 

The standard phone line may function, but it might sound like you’re talking to one of the adults from Charley Brown.

 

As for the inverter signal…. I bet that would work if you use a solid state relay that requires just a few milliamps to trigger, even 28AWG cat 5 wire can handle that I bet. When we use a shielded cat 5 to transmit MODBUS and a small amount of signal power, we usually use two pairs of wire and parallel them just to give more copper for the amps to go through. You just make sure you run the + using the striped wires from both sets, and the - on the solid wire from both sets (or vise versa) so that your power is truly running in twisted pairs still and so it will not create any added noise in the cabling.

 

When a client wants to do something like this with us and we cannot convince them it’s a bad idea, we simply put it in writing that any issues resulting from “XYZ” will not be covered by our warranty, as it was done counter to industry best practices, and against our advise.

 

With Regards,

 

Daniel Young, 

NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90

 

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of John Blittersdorf
Sent: Monday, August 22, 2016 9:26 AM
To: RE-wrenches <RE-wrenches at lists.re-wrenches.org>
Subject: [RE-wrenches] Cat 5 cable in 240 AC power conduit with #2 alum entrance wire.

 

Wrenches,

  I have a customer who has pulled a cat 5 cable through his power conduit (2" PVC) to a new barn for about 120' and wants to use it for ethernet and telephone.  Wants me to use a pair if wires in the cable to trigger a relay to disconnect a direct grid tie inverter (AC Coupling) when batteries are full on his double GVFX3648 backup system   He wants it in writing from experts that it is not a good idea.  Has anyone done this and had good luck with it or have opinions?

 

John Blittersdorf

 

formerly owner of Central Vermont Solar & Wind

now working for the new owner Rob Stubbins Solar 

(I get a regular paycheck and (usually) regular hours. 

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