100Q Code Exam Failed Questions

Question 1

What is the maximum distance that the base of an extension ladder must be placed out from a vertical wall that is 900 cm high?

Answer 1

300CM as Max. Min would be 225. 3:1 to 4:1 ratio

Question 2

Can non-conductive, optical fibre cables used for industrial communications be run in the same raceway as a 480V electric power circuit?

Answer 2

Yes. Only for industrial applications 56-200(3)

Question 3

Before closing the secondary of a delta transformer bank, a voltmeter indicates twice the rated voltage. Is this good?

Answer 3

No. It should read 0V. One transformer is wired backwards.

Question 4

What is the smallest size available for neutral-support (NS90) cable?

Answer 4

8. Use table D1 (Page 533.) Don’t use table 36A or 36B. They will mislead you!

Question 5

What is the maximum ampacity rating for four 1250 kcmil RW90XLPE aluminum conductors, when installed in a run of rigid metal conduit for a 3Ø, 4-wire feeder terminating on a circuit breaker?

Answer 5

485A. See 4-004,(2) b, (3), 4-006 (2), and Table 4.

Use T.2, 75° column…no de-rating for the neutral

Question 6

The secondary circuits of instrument transformers, like this CT, should be grounded when the primary circuits are connected to ____ or more.

Answer 6

300V. See 10-116 (1)

Question 7

What is the maximum voltage allowed between the conductors seen here in this unmarked surface raceway?

Answer 7

300V. Look up raceway surface index. 12-1608

Question 8

What is the minimum size disconnect, shown here, for a 15 kVAR, 208V, single-phase, dry-type capacitor?

Answer 8

See 26-214

15000 VARs ÷ 208V = 72.1 FLC

72.1 amps x 135% = 97.35 amps..it will only fit into the next larger size disconnect.

Essentially, we size the disconnect to the fuse, if known, and at the very least the conductor size

Question 9

What is the minimum number of straight threads that must be fully engaged in a rigid metal conduit threaded joint in a zone 21 hazardous location?

Note: The area contains Group IIB gasses.

Answer 9

See 12-1008.

Section 18 does not provide any special requirements for the number of threads, so we refer to the general section.

Question 10

If replacing an ungrounded receptical with a grounded one. Can you ground to the cold water pipe?

Answer 10

Yes. 26-700(7)

Question 11

If 120 VAC is placed across the input of this full wave bridge rectifier, what would be the expected DC output?

Answer 11

108V. 120VAC x .9 = 108

Question 12

Medical electrical equipment is fed from an isolated system within a hospital.

What is the grounding requirement, if this equipment is permanently connected?

Answer 12

A conventional grounding system, installed in the separate raceway.

See 24-200(2)

Question 13

What is the maximum distance that 1000 kcmil RW90XLPE aluminum conductors can be run unsupported in a raceway vertically in a shaft?

Answer 13

25M. See 12-120 & T.21

Question 14

Explain how 3 light ground fault light indicators work fro 3 phase systems.

Answer 14

Will need to look this up.

Question 15

What is the maximum rating of the overload relays that are used to protect this 25 hp, 575V, 3-phase refrigeration compressor, seen here?

Answer 15

37.8 Amps. See 28-710 (a) & T.44

FLA x 140% = max setting.

27 FLA x 1.4 =

Question 16

Inserting more resistance in the starting controller of a wound rotor induction motor (WRIM) would:

Answer 16

The torque produced by an induction motor is function of stator flux, rotor current and rotor power factor.

By adding resistance at starting, the added resistance improves the rotor power factor and at the same time decreases the inrush current.

This gives high starting torque and reduced inrush amps.

Question 17

A 3Ø, squirrel-cage motor is rated at 480 V, but is connected to a 600 V supply. What will happen?

Answer 17

Motor will run with 20% more power.

Question 18

What is the full-load current rating of a 5 hp, 240VDC motor? What is the full-load current rating of a 5 hp, 240VDC motor?

Answer 18

20A. DC Motor FLA’s are found in Table D2

Question 19

What is the torque formula?

Answer 19

T = (5252 x HP) ÷ N

T in lbs-ft
N in RPM

Question 20

Why can’t you use a series excited DC motor on a belt drive?

Answer 20

Motor runaway will occur if belt breaks. Destroying motor.

Question 21

What is the maximum size of non-time -delay (NTD) fuse that is permitted to protect a 50 kVA, 600- 120/208V, 3-phase, 4-wire liquid filled transformer?

Answer 21

80A. See 26-254 (2)a

50 000 VA ÷ (600V x √3) = 48.1 A primary

48.1 A x 150% = 72.2 A fuse…round up.

Question 22

At what % of speed does a start split-phase motor should have its centrifugal switch open?

Answer 22

75%

Question 23

Where pendant lamp holders are used the conductors must be twisted together when?

Answer 23

The conductors exceed 900 mm in length. See 22-104 (2) & 30-608(5)

Question 24

A 3-phase, three-wire system has ground fault indicator lamps, all working properly.

What will happen if A-phase goes to ground?

Answer 24

A-phase light goes off.

Question 25

Here is a 100 amp temporary service for a residential construction site. What is the minimum trade size of circular service conduit allowed for this service?

Answer 25

Trade size 21. See 76-002 (3) points us to see 6-306 (c).

Question 26

Ground fault protection is required on a main service.

What is the maximum allowable time-delay setting, if the ground fault current is greater than 3000 amps?

Answer 26

1 second. See 14-102 (2)

Question 27

What is the maximum standard fuse size to protect the primary of the the following liquid-filled, step-down distribution transformer?

1. 5 MVA
13. 8 / 2.3 kV, 3-phase

Answer 27

100 Amps. See 26-252 (1) a & (2)

1.5 MVA ÷ (13.8kV x 1.73) = 63.94A x 150% =96 amps…round up!

Question 28

What would be the color code for a 15 K Ω resistor?

Answer 28

Brown,

Green, &

Orange

Question 29

What is the minimum size of a eight-conductor cable that can be pulled into an ENT raceway for a Class 2 circuit?

Answer 29

24 Awg. See 16-210 (4) e

Question 30

This flow switch is installed in an operating FA system.

If the lid is removed, what signal would be seen at the control panel?

Answer 30

Trouble. It gives the same “trouble” alarm it would as if it lost supervisory current on one of the detection or signal zones

Question 31

This synchronous motor, illustrated here, has 16-poles and operates at a 0.8 leading power factor at full-load.

This motor will be operating at ____% speed regulation.

Answer 31

0%. This question fools many on the IP exam…

Speed regulation is based on how much the rotor speed changes with load.

In this motor, the rotor speed never changes with load or power factor.

it should always be 0% speed regulation as speed changes 0%.

Question 32

Illustrated here is a wireway that measures 50 mm by 75 mm.

According to this Code, how many stranded control conductors can be installed within it, if the following wire is to be used:

#14 AWG, RW90 XLPE, 600V, unjacketed.

170
200
421
168

Answer 32

168.
See 12-2104 (4) & (5) & T.10A

50 mm x 75 mm = 3750 mm2

However, we can only use 40% of this amount.

3750 mm2 x 40% = 1500 mm2 to be used for control wires.

Use T.10A to find wire dimensions.

1500 mm2 ÷ 8.89 mm2 = 168.7 wires

Question 33

What tables do you use to find the mm Sq area of stranded and non-stranded cable?

Answer 33

Table 10a and 10c

Question 34

The centrifugal switch on this single-phase, capacitor-start induction motor is stuck in the closed position.

What would be the probable effect on this motors operation?

The motor will never reach full speed.
Correct Answer

The start winding will overheat.

The motor will not even start.
Incorrect Response

The run winding will overheat.

Answer 34

In this closed position, current will stay in the start winding for a long period of time.

This small AWG winding is not designed for long periods of current and will burn out fairly quickly.