Maple Systems HMC7000 Series - Manual (Page 13)

HMC7000 Series Installation Guide
Maple Systems Inc., 808 134th Street SW, Suite 120, Everett, WA 98204-7333 • www.maplesystems.com .
1010-1042 Page 11 of 22 Rev. 02, 09/25/2013
Control Panel Grounding
The control panel must be connected to a good, high-integrity earth ground both for safety considerations and shielding
purposes. Maple Systems cannot overemphasize the importance of good grounding. If you fail to use good grounding
procedures during installation, sporadic malfunction of the HMC may occur. Connect the HMC chassis ground terminal
to a reliable earth ground with a low-resistance path.
Route all earth ground wires that lead from the HMC, the PLC, the power supply, and the line filter to a central earth
ground point such as a barrier strip. This will ensure that no ground current from one device influences the operation of
the other devices.
Connect the HMC chassis ground terminal to the control panel door using a heavy-gauge short braided cable or ground
wire to minimize resistance. Connect the power cable‟s shield wire to the HMC chassis ground terminal. Connect the
control panel to earth ground using a copper grounding rod close to the HMC and control panel.
Hinged doors on control panels do not provide a long-term electrical connection to the rest of the enclosure. Corrosion
develops over time and prevents good electrical contact. For this reason, a separate wire braid should be installed from the
hinged control panel to the rest of the enclosure.
For a more in-depth overview of ground wiring techniques, refer to Technical Note #1027, “OIT Ground Wiring and
Electrical Noise Reduction,” which you can find in the Tech Notes section on our web site.
Connect HMC Chassis Ground to Control Panel
To reduce the possibility of electrical interference, connect the chassis ground terminal of the HMC to a clean earth
ground. Ensure that the HMC is grounded separately from other high-power systems. Use a single-point ground if
grounding more than one unit.
If the control panel is metal, make sure it is properly grounded. Then connect a short heavy gauge wire (#14 AWG) from
the chassis ground terminal of the HMC to a mounting bolt on the control panel door. The mounting bolt must have good
electrical contact to the control panel; scrape away any paint that may be covering the panel to provide a good connection.
NOTE: If the control panel is made of a non-conductive material, it is essential that you connect the chassis ground
terminal of the HMC to a clean earth ground point located close to the panel.
Figure 2: Chassis Ground Connection
NOTE: Do not use a ground that has an unstable impedance, such a painted screws, or ground subject to vibration.