Ac Power And Third-Wire Ground Test; Alternate Or Additional Ground - Toshiba STRATA CTX100 Installation And Maintenance Manual

AC Power and Third-wire Ground Test

Test the "third-wire ground" for continuity by either measuring the resistance between the third
prong terminal (earth ground) and a metal cold water pipe (maximum: 1 ohm), or by using a
commercially available earth ground indicator. If neither procedure is possible, perform the
following earth ground test procedure.
WARNING! Hazardous voltages that may cause death or injury are exposed during the
following test. Use great care when working with AC power line voltage.
➤
To perform the earth ground test procedure
1. Obtain a suitable voltmeter, and set it for a possible reading of up to 250VAC.
2. Connect the meter probes between the two main AC voltage terminals (white and black wires)
on the wall outlet. The reading obtained should be between 100~125VAC.
3. Move one of the meter probes to the third terminal (green wire ground). Either the same
reading or a reading of zero volts should be obtained.
4. If the reading is zero volts, leave one probe on the ground terminal and move the other probe to
the second voltage terminal.
CAUTION! If a reading of zero volts is obtained on both voltage terminals (white wire to
green wire, black wire to green wire), the outlet is not properly grounded. Omit
Steps 5 and 6, and see following CAUTION!
5. If a reading of zero volts on one terminal, and a reading of 100~125VAC on the other terminal
is obtained, remove both probes from the outlet.
6. Set the meter to the "OHMS/Rx1" scale. Place one probe on the ground terminal, and the other
probe on the terminal that produced a reading of zero volts. The reading should be less than 1
ohm.
If the reading is more than one ohm, then the outlet is not adequately grounded.
CAUTION!
If the above tests show the outlet AC voltage is not in range or is not properly
grounded, the condition should be corrected (per Article 250 of the National
Electrical Code) by a qualified electrician before the system is connected.

Alternate or Additional Ground

If the "third-wire" AC ground can not practically be improved or if extreme motor noise or other
disturbance causes system malfunction, or if local area lightning storms exist, a separate direct
ground may be warranted.
Connect an alternate earth ground from a cold water pipe or earth grounding rod directly to the
screw terminal on the CTX100 power supply (see
Strata CTX I&M 10/02
AC Power and Grounding Requirements
Figure 2-2).
Strata CTX100 Installation
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