WattMaster WCC III part 10 - Manual (Page 10)

10. RS-485 COMMUNICATIONS
WCC III Technical Guide 10-8
Lightning Suppression
Lightning Suppression
Lightning is an act of nature and as such cannot be predicted or
controlled. There is NOTHING that will COMPLETELY protect
any electronic equipment from the massive effects of a direct or
near hit from lightning. WattMaster Controls has taken a number
of steps to protect the electronic components and the incoming
pathways of its equipment from voltage surges that may enter
them. These incoming pathways are defi ned as: 24VAC power,
RS-232 data communications, RS-485 data communications, input
wiring, and relay control circuits. All of these pathways have been
protected using a variety of devices, including varistors, diodes,
transorbs, and excessive ground planes on all of our circuit boards.
There are several “General Rules” that can be applied towards
lightning protection:
General Rule Number One:
Any time the WCC III /Satellite
RS-485 communication’s loop enters or leaves a building, there
needs to be a properly installed and grounded lightning protection
device or lightning suppressor device.
General Rule Number Two:
No lightning protection devices
or lightning suppressor devices will protect against a direct
lightning hit.
General Rule Number Three:
For a lightning protection
device or lightning suppressor device to work properly, there needs
to be an actual earth-ground connection point as near as possible
to the lightning protection device or lightning suppressor device.
Being feet away from the actual earth-ground connection does not
work, Being inches away is always the best possible connection
point for this actual ground connection.
At some point you have to ask the question: “What
exactly are you trying to protect?”
Lightning could enter the building via an analog input on a TUC-2R,
and then it could cause problems with the RS-485 communications
loop on the SAT 3C/D/F TUC communications loop along with
more problems on the SAT RS-485 communications loop. You
could have your entire building’s control system go down due to a
close lightning strike. The most likely path that lightning would take
to do the most damage would be on the RS-485 communications
loop that connects the Satellite controllers to each other. You may
decide to put multiple lightning protection devices or lightning
suppressor devices on every RS-485 communications loop as a
preventive safety measure.
WattMaster Controls sells an RS-485 communications loop
lightning protection device. The WattMaster part number is
OE437-03.