User & Installation manual Appendix
Ground connection
What Should Be Grounded?
Any equipment that is or could become energized, even accidentally, should be
grounded. Current from lightning, strikes objects in a random fashion. Accounts of
lightning strikes reveal scenarios most of us could not predict.
Electric circuits should be wired with a 3-wire conductor consisting of hot, neutral and
grounding wires. The grounding wire should be attached cleanly and securely to
devices or systems to be grounded. The other end of the grounding wire should be
attached to the ground bus on the main panel.
Lightning Protection
1. Connect the shield to the ground at one end (controller side) of long shielded
wires such as for temperature and humidity sensors. When extending cables
for temperature sensors and humidity sensors also connect the shield through
the extension.
2. Run a heavy wire directly from the ground terminal to the ground rod, which
must also be connected to the electrical service ground. The Ground should be
less than 5 ohm resistance.
3. Do not use light wires for these ground connections. They must carry heavy
lightning currents, sometimes exceeding thousands of amperes. The
galvanized plate of the NMC-64 is the ground reference for it. You may
connect the heavy ground wire using spare screws on it. Do not use the
shielding of sensor and low voltage wiring as lightning grounds.
4. Ensure that all ground connections go to a single local point. When lightning
strikes, grounds a foot or two apart will be at significantly different voltages. If
you have several electronic boxes with individual grounds, connect all these
together to a single point. This should continue to the ground rod or the
electrical service. In particular, avoid grounding any controls remotely through
shield wiring.
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