Line C Troubleshoot Complex Circuits

Question 1

What is an arc flash?

Answer 1

The light and heat created from an arc fault explosion

Question 2

What is an arc blast?

Answer 2

The pressure wave created after an arc fault

Question 3

What is the major cause of an arc flash?

Answer 3

Voltage transients

Question 4

Referring to the figure below, what is arc flash boundary 1 referred to as?

Answer 4

Arc flash protection boundary

Question 5

Referring to the figure below, what is arc flash boundary 2 referred to as?

Answer 5

Arc flash limited approach boundary

Question 6

Referring to the figure below, what is arc flash boundary 3 referred to as?

Answer 6

Arc flash restricted boundary

Question 7

Referring to the figure below, what is arc flash boundary 4 referred to as?

Answer 7

Arc flash prohibited boundary

Question 8

What is defined as an arc flash protection boundary?

Answer 8

The calculated safe working distance from electrical equipment which would not expose the employee to the hazards associated with an electrical arc flash.

Question 9

What is defined as an arc flash limited approach boundary?

Answer 9

The minimum permitted distance that unqualified and unprotected personnel may approach a live component.

Question 10

What is defined as an arc flash prohibited boundary?

Answer 10

The boundary where no electrical worker is permitted unless proper procedures, PPE, training, energized work permits, and risk assessment are all in place.

Question 11

What is defined as an arc flash restricted approach boundary?

Answer 11

The minimum permitted distance where personnel need to have been trained in shock protection techniques, be wearing the correct PPE, and have a written and approved plan for any work in the zone.

Question 12

Referring to the DFMA Wiring Diagram, the DFMA supply fan isn’t running and you take the following readings with your multimeter:
- 120 Volts across terminals 1 and 2
- 0 Volts across terminals 1 and 12
- 120 Volts across terminals 12 and 13

What is the conclusion that you come as to why the DFMA supply fan is not running?

Answer 12

The inlet damper limit switch is open. Possible causes: the damper is not fully opening; the damper motor is not working; the damper linkages are disconnected; or the damper limit switch is not working.

Question 13

Referring to the DFMA Wiring Diagram, the DFMA burner is not firing. You take the following readings with your multimeter:
- 120 Volts across terminals 1 and 2
- 0 Volts across terminals 13 and 16
- 120 Volts across terminals 16 and 18
- 0 volts across terminals 19 and 20
- 0 volts at #7 terminal on the Fireye flame relay

What is the conclusion that you come as to why the burner is not firing?

Answer 13

The burner start contact is open. Could be a faulty relay (not energizing) or the start button has not been pressed.

Question 14

Referring to the DFMA Wiring Diagram, the DFMA burner is not firing. You take the following readings with your multimeter:
- 120 Volts across terminals 1 and 2
- 0 Volts across terminals 13 and 16
- 0 Volts across terminals 16 and 18
- 120 volts across terminals 20 and 21
- 120 volts from terminals 20 to 2
- 0 volts from terminals 21 to 2

What is the conclusion that you come as to why the burner is not firing?

Answer 14

High airflow switch is open. Causes could be: fan speed too high (sheaves not set correctly - too much velocity across the profile plates), improperly adjusted profile plates (too much velocity), failed switch, sensing tubing disconnected.

Question 15

Referring to the DFMA wiring Diagram, the DFMA burner is not firing. You take the following readings with your multimeter:
- 120 Volts across terminals 1 and 2
- 120 Volts across terminals 18 and 22
- 0 volts across terminals 20 and 21
- 120 volts from terminals 20 to 2
- 120 volts from terminals 21 to 2
- 0 volts at #7 terminal on the Fireye flame relay

What is the conclusion that you come as to why the burner is not firing?

Answer 15

Low airflow switch is open. Possible causes: the inlet supply filters are plugged, faulty air switch, a service door is open, fan speed too low (sheaves not set correctly - too little velocity), sensing tubing disconnected.

Question 16

Referring to the DFMA wiring Diagram, the DFMA outlet temperature is too low. You take the following readings with your multimeter:
- 120 Volts across terminals 1 and 2
- 0 Volts across terminals 18 and 22
- 120 volts at #7 terminal on the Fireye flame relay
- 120 volts across terminal 30 to 2
- 24 volts across terminals 34 and 35
- 0 volts across terminals 36 and 37

What is the conclusion that you come as to why the burner is not firing?

Answer 16

Burner modulation 0-10 Volt system has no voltage. This means the burner is stuck in low fire and can’t modulate/ramp up to high fire.

Question 17

Referring to the figure below, the loop current is measured at 29 mA. What are the possible causes of the excess load on the loop?

Answer 17

Miswiring, ground loop, a problem with the transmitter

Question 18

Referring to the figure below, what is the minimum power supply required for the 4-20 mA loop?

Answer 18

25 Volts

Question 19

If two points in a 4-20 mA loop are grounded it can create an alternate pathway for the loop current to flow through.

TRUE / FALSE

Answer 19

True

Question 20

Referring to the figure below, what should the resistance value be of the shunt resister given the following information?
- Source volts: 26
- Source current: 125
- Loop current: 20 mA max

Answer 20

125-20 = 105
26÷105= .2476 x 100 is 247.6 ohms
248 Ohms