When running an electrical circuit through studs along the length of a wall, is it OK to make a dead straight line for 20 feet or so, or is this likely to cause noise in some electronic equipment?
-- "For it is only of the new one grows tired. Of the old one never tires."
-- Kierkegaard, _Repetition_
James Owens, Ottawa, Canada
On Mon, 27 Sep 2004 09:02:13 -0700, James Owens wrote (in article ):
James -
I have not seen a lot of reliable info on EMF problems with household wiring (as opposed to problems with EMF from transfomers or high voltage transmission lines). It's apparently a developing and highly debated area.
AFAIK, you want to avoid running communications wiring in proximity to power wiring. In particular, you want to avoid running them in parallel within a foot or so. If communications cable has to cross power cable, then it should be done at a right angle.
Aside from those rules, I have seen no reports of straight cable runs at household voltages causing unacceptable electromagnetic radiation. Assuming the cable contains the hot and neutral (or return) circuit conductors, the radiated fields largely cancel.
If the circuit run will be in proximity to particularly sensitive equipment, say in a wall directly behind audio equipment or a computer installation, you can always install it in grounded metal conduit (flexible if necessary). The conduit blocks EMF radiation.
Regards,
- Kenneth
It all depends on what "communication" is. If you are talking about "data", LANs and such they have pretty good 60hz rejection. If you are talking about straight audio, 60hz is going to show up if you don't use shielded twisted pair and without good grounding/bonding it can still be a problem.
Thanks. I know I could use a grounded shield, but I wondered if normal practice was to run the line higher and lower here and there to avoid an antenna effect. (I realize that the wavelength of 60 Hz is considerably bigger than my house!) I gather people don't worry about it though; perhaps 20 ft isn't significantly worse than 5 ft.
Computer monitors and electric guitar wiring are particularly sensitive to EMF at this frequency, so if there is a way to minimize it that doesn't involve conduit (or grounded metal sheeting), it would be good to know about.
-- "For it is only of the new one grows tired. Of the old one never tires."
-- Kierkegaard, _Repetition_
James Owens, Ottawa, Canada
Wandering the wire around a bit isn't going to make any difference. 20' is
20', whether it takes 20' of wire, or 30' ;-)For the most part, with modern romex, the wires are so close that most of the EMF self-cancels.
I've seen a really really intractible computer monitor problem, but that was a monitor less than 30' away from a major distribution feeder.
A computer monitor isn't going to be bothered by the EMF/magnetics in your typical house. A guitar might, but flapping a cable or two around a bit won't help. Make sure you have decent quality shielded audio cable, and don't get too close to the fluorescent fixtures.
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