Emerson Signal Reference Grid, Grounding Electrode Conductor for FPCs With Transformer

Installation Instructions

Signal Reference Grid

If the unit is used to supply power to a computer room or area that is equipped with a signal reference grid or a grounded raised-floor stringer system, a grounding conductor should be connected from the system ground bus to the grid or floor system. This conductor should be stranded or braided #8 AWG or larger, and as short as practical. Less than 3 ft. (1m) is recommended.

1.3.4Grounding Electrode Conductor for FPCs With Transformer

Required by code - The Liebert FPC with transformer must be grounded according to the safety practices of NEC 250-26. A local grounding electrode conductor is recommended in addition to the equipment safety ground which is normally run with the input power conductors. (See Figures 5 through 8.)

As shown in Figure 12, the grounding electrode conductor is run from the unit to the nearest effec- tively grounded location (listed in order of preference):

•Building steel

•Metal water pipe

•Other made grounding electrode

The grounding electrode conductor’s size is based on the secondary circuit conductors. Table 10 shows the minimum recommended grounding electrode conductor according to the NEC (Table 250-66).

Table 10 Minimum grounding electrode conductor size (AWG)

	Output Voltage
kVA
	208V	380V	415V
15	8	8	8
30	8	8	8
50	4	8	8
75	2	6	6
100	0	4	4
125	0	2	2
150	00	2	2
200	00	0	0
225	00	0	0
300	00	0	0

AWG wire size based on 75°C copper conductors

Recommended methods for running the grounding electrode conductor (arranged by preference for system performance; as acceptable by local and other applicable codes):

•Outside of conduit (where not subject to damage)

•Inside non-metallic conduit

•Inside non-ferrous conduit

•Inside ferrous conduit, bonded to the ferrous conduit at both ends, as acceptable by local and other applicable codes

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