DISTECH,Calling all Distech Reps!!!Shielded Lon or NOT
Guys, DISTECH reps or dealers only, Please, I want to hear first had expierence as to how they were instructed by Distech to install Shielded Lon applications.
I have a building that is suspect for a lot of noise, Water Source Heat pumps, mounted close to lighting and such, controller will be HPU100,mounted on the outside of units, we cannot relocate them and we are not going to put them in an enclosure. I cannot get a good answer as to how Distech Handles using Shielded Lon cable on a Job, I have been told that they will allow it, but I cannot find the document on thier web site to specify how they require termination. I have been told that they require a certain proceedure unlike conventional shielding. (landing at one place and Twisting and taping it off at each unit conncetion.) Has any one used shielded Lon on a Distech project and how were you instructed to handle the shielding proceedure, were you required to use terminating drain resistors at each unit???I was told something about this but I have not seen anything in Print. ANy help would be great. Any thing is print form from Distech would be even better. I am not a direct customer, so I cannot get the answer or info Direct from them.
This is taken from the LonWatcher 3 User Guide:
Figure 5-12: Grounding Shielded Twisted Pair Cable
It is recommended to use shielded cable only when the network cable is outside of thebuilding since it will be subjected to electromagnetic interference (EMI).
The twisted pair is terminated according to the guidelines listed in the previoussections. The cable shield should be grounded using a capacitor to tie the shield to earthground and a large value resistor should be used to bleed off any static charge on theshield.
Tie the shield to earth ground through a capacitor, instead of with a direct connection.
This prevents DC and 50/60 Hz ground paths from forming through the shield.
Typical values for Cc and Rb are as follows:
Cc = 0.1 μF, 10%, Metalized Polyester, ≥ 100V
Rb = 470kΩ, 1/4W, ±5%
The cable shield should be grounded at least once per segment, and preferably at each node. Grounding the shield at every node (using the shield grounding circuit attatched) will assist in suppressing 50/60Hz standing waves.
Its alot of work but it should work.
We install distech controllers just like any other when using shielded cable. Ground at one location but I have never had to use a resistor. Most of our jobs are pretty noise free dispite running lon wire within two feet of flourecent lighting, sometimes you just can't avoid it.
Distech-Controls do not recommend using shielded cable and suggest only to use the echelon specified Beldon cable. If a job is a refit from RS 485 and it is not possible due to costs Distech have given suggestions on how, which is from Echelon's manuals
Look at Echelon's standards and follow that for termination.
Just as important afterwards to utilize that protocol analyzer you better have already purchased.
Distech like every other LON based company purchase their network transceivers form Echelon. This isn't a Distech issue, it's an Echelon issue and Echelon's 's pretty specific about using non-shielded cable.
As has been re-published here, you can use shielded cable if you choose, but you need to follow the rules. I've tried short-cutting those rules and not used the recommended capacitor/resistor combo and have not been happy with the results.
I would also recommend watching "Network Troubleshooting - the tools and techniques" The link is below.
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