Control Wiring Shielded both ends

[Husky250]

Many opinions exist of the control wires that run between Indoor and outdoor units. The model Im speaking of is Sanyo Pac-i system that uses an 18 gauge 2 conductor control wire for commuication between boards. Sanyo Install manual states to ground both sides of the wiring. When you ground both sides is it possible to CREATE a conductor of interference? I have heard to only ground one side. Who is right in this case? How do you know for sure the communication is good ?

[mchild]

My tech manual shows to use shielded cable and to use the shielding to make the ground on each end.

[nike123]

Electrostatic shielding – Screen earthed at one end to a good earth (PLC end)
Electromagnetic shielding – Screen earthed at both ends

[Thermatech]

Mitsubishi Electric recomend for VRF multi systems that screen is only fixed to earth in one place.
To assist with this stratagy the control cable terminals at each indoor unit include a blank screen cable terminal which is connected to ,,,, nothing.

The control cable daisey chain around the system only needs to be tagged down to earth in one place to be effective against emf electrical interferance.

So for split system with only one lenght of communication cable between the indoor & outdoor unit ???? well you have to comply with the manufacturers specification. However I would suspect that making earth connection at one end will be make the screen effective.

[Husky250]

Electrostatic shielding – Screen earthed at one end to a good earth (PLC end)
Electromagnetic shielding – Screen earthed at both ends

What is the difference between electrostatic shielding and electromagnetic shielding? Also need to be clear about PLC end. Sorry to be so basic. Didnt know I should have taken electronics in college...Thanks for the help!

[nike123]

What is the difference between electrostatic shielding and electromagnetic shielding? Also need to be clear about PLC end. Sorry to be so basic. Didnt know I should have taken electronics in college...Thanks for the help!

Electrostatic shielding is protection of build up of high electrostatic voltage from atmosphere at cables who then can damage some electronic circuits like in RS485 networks.
http://en.wikipedia.org/wiki/Electrostatics

Electromagnetic shielding is protection from electromagnetic induction of undesired currents in signal cable from surrounding power cables (and other high power equipment) electromagnetic fields .

http://en.wikipedia.org/wiki/Shielded_cable

[frank]

Both end earthing can lead to multiple earth paths, interference and lots of problems.

Only earth at one end. This will quite easily provide an earth path in the case of the sheathing becoming live.

there is no other reason for earthing.

[Husky250]

I have always wondered why Sanyo calls for S-NET control wiring to be grounded on both ends. I do have to say however I have had auto address failures and until I grounded on BOTH SIDES the system would not auto address. Thank you all for the input!

[Refrigerologist]

As I understand it, it is usual to conect to ground at one end. This earth cable acts as a drain wire to drain back emf from other electrical fields to earth. If the drain wired is grounded at both ends the emf does not drain correctly and can cause interference.

[Husky250]

Thanks guys!