Interference between AWG and CAT 5

Interference between AWG and CAT 5

 (Hard facts courtesy of Marcus Ernst, Humor by Brad Hartman)

 One of the issues with buildings is that there are a large number of systems in a building that don’t play well together when they are mixed.  Two of the systems that tend to fight on the playground are electromagnetic (power lines, fluorescents, etc.) and radio frequency (multiple transmissions on the same wireless frequency). 

 So with both systems occurring in buildings, how do you protect the systems from interference?

 Not as simple as just asking it to stop.  There are 2 types of interference, radio frequency (RFI) and electromagnetic (EMI).  CAT 5 cable is designed to mitigate RFI due to the fact that the wires are in twisted pairs.  Electromagnetic interference is typically eliminated by using shielded cable.  The shield, aka drain, is typically grounded at 1 end to remove the EMI charge.  CAT5 does not have a shield as it also known as UTP cable (unshielded, twisted pair). 

The cables are designed, or cladded in a way to minimize the interference.  To ensure that EMI is not an issue, you can put the wires feeding the fixture in question, in EMT and use compression connectors and couplings.  This way there is a good bond between the sections of EMT.  Also, make sure that the EMT is grounded at one end.  Any stray EMI will be captured and grounded.  At this point you have eliminated any RFI and EMI issues. 

As a general rule, you should try to maintain a separation between line and low voltage (data) of a minimum of 6”.  All crosses should be done at 90 degree angles.  This is given the typical construction materials used MC and EMT with set screw connectors and couplings.  When this is not possible, bonded, grounded EMT will serve to mitigate the EMI.


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