low and high voltage distance? ...power bleed?

[kyles974]

hey guys.... I just learned that you should run high voltage and low voltage away....or not close together because of "power bleed."

I'm going to be running power out to garage. (220v about 140ft)
Also will be running another PVC for alarm wires, overhead door remote wire, etc., etc., in a seperate PVC.

What is the rough distance you would keep these apart? 3ft? 4ft? etc.,

Also, is power bleed an issue where they run into the garage? If so, what would you guys suggest using to enter the garage?

 

[matt151617]

I think side by side in seperate conduit in the trench is fine. Leave a foot or so distance between them. The width of a shovel should be good enough for 2 lines. Many run a bare ground in the low voltage conduit to help with any interference.

 

[eljefino]

They're probably worried about inductive interference. If you run "twisted pair" wire you should be fine. Ethernet cable is fantastic for this and you can use it for phone service, alarm, etc as well. I would just not run "zip cord" speaker wire, not that you have a reason to.

 

[ddawg16]

4-6" (yes, inches) and you will be fine. You could actually run the Cat 5 or 6 in the same conduit and it would not be bothered by it.....at least the mutual inductance....the bigger issue is if there was a bare wire.....you could engergize the ethernet cable with AC voltage...that is the main reason for the physical seperation.

 

[kyles974]

Ok, so I understand here.......if I have my (buried) 220v in one 2" PVC and around a foot or two over I have these in the other 2" PVC:

Two (2) Cat 5 E 350MHz pvc (one for ethernet and one for extra or ??? future misc.)

One (1) "fire and alarm" 18 AGW 2 C cable pvc

One (1) coax cable for TV

......then I should be fine?

Also, where the two will come into the garage, should I get some can of protector to prevent this so called "power bleed/interference" or is this from longer runs side by side?

 

[kyles974]

anyone?

 

[Gary S]

4-6" (yes, inches) and you will be fine. .

I agree. To isolate high voltage away from low voltage, things need to be grounded.
If you think about it, that crumbly stuff you dug out of the trench and you use to backfill between the two conduits is what?????????????? Yes, ground.

 

[matt151617]

It'll be fine, since the power wires will still be in conduit as you come into the panel.

 

[kyles974]

It'll be fine, since the power wires will still be in conduit as you come into the panel.

cool, thanks matt

 

[ForceFed70]

Code here is 1' of seperation and if lines must cross they cross at 90* angle.

 

[Falcon67]

Code here is 1' of seperation and if lines must cross they cross at 90* angle.

So the people that wrote that code don't know anything about shielding, twisted pair phone or networking cable. You cross plug wires at close to 90 degrees. We have all kinds of ethernet cable laying on 277V ballasted light fixtures, etc.

 

[jeffmoss26]

We have all kinds of ethernet cable laying on 277V ballasted light fixtures, etc.

That's not how it should be done!

 

[theoldwizard1]

......then I should be fine?

You are going to leave a good quality nylon string for possible "future" cabling, aren't you ?

 

[ddawg16]

Your 240Vac is 60 Hz
Your Ethernet is 100Mhz +

All moderan Ethernet switches are transformer coupled...hence, any induced AC will be filtered out.

As for the alarm wires....DC....you would have to have the alarm wires in the same conduit as the AC to get any mutual inductance.

You would be surprised at how quickly the field strength drops down with distance.....if the alarm wires have any source impeadance below 1000 ohms, you will have nothing to worry about, even if the conduits are side by side.

As I mentioned above...the reason for not running them in the same conduit is for protection in case you had a couple of nicked wires that could end up touching.

 

[ForceFed70]

So the people that wrote that code don't know anything about shielding, twisted pair phone or networking cable. You cross plug wires at close to 90 degrees. We have all kinds of ethernet cable laying on 277V ballasted light fixtures, etc.

Not sure what your point is here.

Best practice is to avoid excessive noise due to EMI and to avoid induced current. Regardless of whether there are other methods in place to prevent this from causing problems with the equipment. The old saying about curing the disease instead of treating the symptoms seams fitting in this case.

Our networking guys would soil themselves and fire the contractor if they found any low voltage cabling resting on top of a florescent fixture.

 

[kyles974]

Your 240Vac is 60 Hz
Your Ethernet is 100Mhz +

All moderan Ethernet switches are transformer coupled...hence, any induced AC will be filtered out.

As for the alarm wires....DC....you would have to have the alarm wires in the same conduit as the AC to get any mutual inductance.

You would be surprised at how quickly the field strength drops down with distance.....if the alarm wires have any source impeadance below 1000 ohms, you will have nothing to worry about, even if the conduits are side by side.

As I mentioned above...the reason for not running them in the same conduit is for protection in case you had a couple of nicked wires that could end up touching.

cool.....got a much more understanding now, thanks

 

[Norcal]

"High voltage"? There is no high voltage in residential, even 480* volts is considered low voltage, it would be better to refer it as line voltage & low voltage.

*Pretty ****** rare for 480 in a residential setting, But I have found 277V lighting in a bootleg mother in-law unit.(I am not joking.)

 

[ddawg16]

"High voltage"? There is no high voltage in residential, even 480* volts is considered low voltage, it would be better to refer it as line voltage & low voltage.

*Pretty ****** rare for 480 in a residential setting, But I have found 277V lighting in a bootleg mother in-law unit.(I am not joking.)

Don't tell them that 4160Vac is considered 'Medium Volatage'....

 

[MrMark]

Code here is 1' of seperation and if lines must cross they cross at 90* angle.

This is the general rule here in the states too.

At least according to ATT.

 

[Falcon67]

That's not how it should be done!

You got a field of buildings built from 1930 to 1950 retrofitted with God knows what - you don't always get to choose. I actually lose more network equipment to power problems in newer buildings built to current codes. Figure that one out. Our contractors do a good job, and we run under when possible - but sometimes the route to a drop is the route to a drop. I have networking equipment next to giant 480V 3 phase air handling equipment and coolant pumps because that's the only space.

Yes, agree - don't do it but I'm just saying shielded twisted pair was made to put up with that.