Article 250 - Grounding and Bonding

To qualify as an electrode, a water pipe must be in contact with the earth for at least — feet. 250.52 (A)(1)

10

When using a water pipe as an electrode you must connect to it within — feet of where the water pipe enters the building. 250.68(C)(1)

5

Structural steel may be used as an electrode if it is in contact with the earth for at least — feet. 250.52(A)(2)

10

A ground ring must consist of at least — feet of # — bare copper and must be buried at least — inches deep. 250.52(A)(4) and 250.53(F)

20, 2, 30

A concrete encased electrode must consist of at least — feet of — inch rebar, or # — bare copper. 250.52(A)(3)

20, 1/2, 4

A rod or pipe electrode must consist of — feet of at least — pipe or — inch rod unless listed or other diameters. 250.52 (A)(5)

8, 3/4, 5/8

Plate electrodes must have at least — square feet of surface area and must be buried at least — inches deep. 250.52(A)(7) 250.53(H)

2, 30

Rod or pipe electrodes must be supplemented by another electrode UNLESS the resistance to ground is not over — ohms. 250.53(A) (2) exception.

25

If a ground rod is supplemented by another ground rod you must space them at least — feet apart.

6

The only electrode that must always be supplemented is the — electrode. 250.53(D)(2)

water pipe

IF solid rock is encountered, you may lay a ground rod down in a trench that is at least — inches deep. 250.53(G)

30

Underground — piping, — ground rods, and the metal parts of an underground — structure may not be used as electrodes. 250.52(B)

gas, aluminium, swimming pool

If using aluminum for the GROUNDING ELECTRODE CONDUCTOR it must not be terminated to the electrode within — inches of the earth when outside. 250.64(A)

18

No matter what the service size, the largest copper Grounding Electrode Conductor ever required to a driven ground rod, pipe, or plate electrode is # — . 250.66(A)

6

No matter what the service size, the largest copper Grounding Electrode Conductor ever required to a concrete encased electrode is # — 250.66(B)

4

Generally, the grounding electrode conductor must be installed continuous without any splice or joint. But "if necessary" it may be spliced using either — connectors or — 250.64(C)(1)

irreversible compression, exothermic welding

Main Bonding Jumper found in — Grounding electrode conductors found in —

T250.102, T250.66

Table 250.102(C)(1) is used for sizing the grounded conductor, the — bonding jumper, the — bonding jumper, and — bonding jumpers. Table 250.102(C)(1)

main, system, supply side

Exposed non-current carrying metal parts of equipment must be grounded if located within — ft vertically or — horizontally of grounded surfaces. 250.110(1)

8, 5

Equipment grounding conductor sized # — and smaller must be green or bare their entire length. 250.119

6

Flexible metal raceway may not serve as an equipment grounding path if the total length is over — feet. 250.118(7)

6

Equipment grounding conductor is found in —

T250.122

When running conductors in parallel, the equipment grounding conductor must be installed in — parallel raceway 250.122(F) 

each

When installing a service raceway, an underground metal elbow installed in a run of PVC need not be grounded as long as it is buried at least — inches deep. 250.80 ex

18

The equipment grounding conductor ran to a pump motor must also be connected to the — 250.112(M) 

metal well casing

Frames of household ranges and dryers may only use the grounded neutral conductor for equipment grounding purposes for — circuits. 250.140ex

existing

The grounded conductor may be used to ground exposed metal parts only on the — side of the service disconnect. 250.142

line

If a ferrous metal raceway is used to protect the GEC, it must be bonded to the GEC at — end(s). 250.(E)(1)

both

Standard locknuts may not be used for bonding purposes at the — 250.92(B)

service

A locknut on an EMT connector is not considered to be adequate bonding if you encounter concentric knockouts AND the voltage is over — volts to ground. 250.96

250

The building or structure grounding electrode system is to be used as the grounding electrode for a — 250.30(A)(4) and (5)

separately derived system

For the bonding of communication systems, an IBT can be used or you could use a metal bar that is — inch thick and — inches wide. 250.94(B)

1/4, 2

Rooftop equipment supplied with metal raceways that use non-threaded fittings must have an equipment grounding conductor of the — type. 440.9

wire