Running data and speaker wire with AC


Active Member
I was not sure where to put this, so I placed it here. I will be running AC power (220) in a two foot deep trench to an irrigation pump near a dock. I also need to run a cat5 cable (used for a weather station, not a network) and speaker cable to the same general location.

If I put the AC line in 2' deep then fill with a 1' of dirt or so, then place the cat5 and speaker cable on top of that, would there be any reason to be concerned with interference?


it would be best to run seperately, but if it is not "critical" then you may be alright. just keep in mind that 220 produces a lot of noise ...
i was going to suggest that, but digging another hole is a much better justification of cost, IMO ... sheilding on CAT5 is almost a $100 jump in cost for a box of 1,000ft ...
Based on my own experience, I think this would work, I have done much worse without any issues. I guess he could always run the cat5/speaker wire in tubing approved for burrial?
he could, but it would have to be water tight, otherwise he needs to use cable rated for direct burial. noise wouldnt really be an issue if he were dealing with 120v, but 240 is bad.
This would not be a problem. Normal recommended separation in air is 2" to 12" depending on who you talk to. However, in the damp ground, there will be enough moisture to completely squelch any magnetic field which may try to cause interference.
that is the rule i know for 120v.

whenever i am dealing with 120v and data lines, i allow for between 8" to 2'. whenever it is 240v, i allow for a minimum of 2'. but, you are absolutely correct, the rule of thumb changes with the circle you run in. when i took my Cisco course, that was the advice i was given, so i took that as fact.

its all dependant on who you talk to, i am probably one of the more paranoid people when it comes to data runs. but every line i run must be certified, and the smallest amount of noise could fail it so i avoid all electrical at all cost.

Thanks for all of the input. I am going to put in in a conduit just in case I need to run anything in the future.

Based on the responces, I think I will try one trench and if it is not to bad I will do another one a few feet over and put the low voltage in it. I have never used one of those trenchers before so I am not sure how difficult it will be.

Thanks again...

make sure to call your local digtess company ... cutting a high voltage line, or a gas line. either would make for a big headache or possibly an un-necessary trip to the hospital. :)
InsanePhotoGuy said:
that is the rule i know for 120v.

whenever i am dealing with 120v and data lines, i allow for between 8" to 2'. whenever it is 240v, i allow for a minimum of 2'.
Insane: You are apparantly unaware that 240V is just two 120V circuits of opposite phases. 240 is still 120. There will be no difference in the magnetic fields derived from 120 than from 240. They are both 120. Besides, the magnetic field is derived from current not from voltage.

If there is any noise induced in the data wires it will be when the pump motor starts. That's when the current momentarily surges. The voltage will stay relatively constant, but will drop if anything.

CT, save some money and use PVC conduit. It won't shield the magnetic field but will not corrode like steel will. Also, be sure to use direct burial cable, as the conduit will eventually fill up with water.

What no one has asked yet is the distance that you need to run these wires? It's been mentioned that shielded cable cost more money (which it does), but if you're trenching 2ft deep for more than 20-30ft (you may be going hundreds) the cost of labor and tool rental if your not doing it by hand would far outway this.

Sandpiper's given you some good advice... 240v has the "potential" to cause more interference as it's usually only run for devices which require lots of current. There's really no difference that I know of between 120/240 as far as EMI is concerned, it's all determined by what's plugged in at the other end.

As InsanePhotoGuy mentions, you should have concern if that CAT5 was going to be used for high speed data, but your weather station is likely RS-232 or RS-485 so shouldn't be a problem with proximity to the High Voltage. Same with the speaker wire... you'd need to place speaker wire right next to high voltage for some distance to get any interference (and this provided there is a high current, electrically noisy device on the high voltage line).

Here's the advice I would give (most of which is just sumarizing what the others have posted:

-Do use PVC conduit

-Do use "weather-proof" cable for both the CAT5 and Speaker wire. This can be different than "direct burial" cable which will always have a tougher and UV resistant jacket, but may not be gel filled which is what's important for your use. Check the package because companies mark/market cable differently... ie durect burial vs weather-proof.

-Size your speaker wire accordingly to the distance from amp to speaker. 16g is good up to around 100ft, 14ga will get you around 200ft, anything longer you should use 12ga.

-If you're unsure if/where any utilities are buried, call to get them marked. Especially if you'll be using something mechanized to trench like a Ditch Witch.

-If the run is longer than 300ft, you might want to consider installing a vault somewhere along the middle to act as a pull point which will make it easier to pull the wire (high and low voltage).

-Don't forget to install pull strings while putting your conduit together.

-Use large enough conduit to make the pulls easy and to leave room for future low voltage wire if needed.

-Always pull a new string in with the wire so you can leave one behind for future use.

This is all fresh in my mind as we've just burried ~1400ft of 2" conduit for a customer job to get Cable TV and Phone from the road to a new house, and intercom & gate control from the house out to the front gate.

I have used black plastic "water pipe" that comes in big coils for underground runs of 100 feet or more with great success. I like the continuous coil because I don't have to worry about water entering the pipe at a connection point (there are none). Use a shop-vac at one end to suck your pull string through and remember to run and extra pull-string with your cable.

A different perspective:

I do concert and television lighting professionally.
For temporary lighting setups we often run unshielded Cat5, 5e and 6 wiring along with all the other power runs. From dozens of feeds to hundreds of feeds, 10-20 amp circuits across 3 phases of power up to 100 meters (330 feet) and I have never noticed a perceptible degradation of the signals. We use the Cat 5/e/6 wiring for 100 base and gigabit ether networks, KVM extenders, Video baluns, and lighting control.

Is there a difference? I'm sure if I hooked up test equipment it would show I'm not getting optimum performance from the wiring. Is that difference enough to affect anything? Not likely.

Do I prefer shielded ethernet cabling? Absolutely! However often it is simply not an option available to me. If it is good enough for multi-million dollar entertainment productions, it is probably good enough for home use.
(NEC rules not withstanding.)