Electronic ignition and system controls and schematics

Question 1

4 types of electronic ignition systems

Answer 1

Intermittent pilot using spark
Intermittent pilot using hot surface
Direct ignition using spark
Direct ignition using hot surface

Question 2

Another type of electronic ignition system is the interrupted pilot system but it is not widely used. Why is this?

Answer 2

Due to the additional cost of controls it is not widely used

Question 3

How do intermittent and interrupted pilot systems differ?

Answer 3

With an intermittent pilot it is not extinguished after ignition of the main burner

Interrupted pilot systems extinguish after ignition

Question 4

What spark gap is recommended with pilot spark ignition?

Answer 4

1/8

Question 5

What is a flame rod?

Answer 5

A rod that is immersed in the burner flame. Current is passed from the module to the flame rod via the burner flame then returned back to the module. This current path proves the flame

Question 6

What is the difference between flame rectification and flame conductivity?

Answer 6

Rectification changes AC to micro amp DC through the flame.

Conductivity is only AC current (this method is easily tricked)

Question 7

Two types of HSI

Answer 7

Silicon carbide
Silicon nitride

Question 8

What ratio is required for a flame rod?

Answer 8

4:1 ground to flame rod.

Question 9

What is a recycling control in regards to an ignition control module?

Answer 9

When an ignition module tries two or three times to ignite before lockout occurs

Question 10

What is the warm up time and temp of an HSI

Answer 10

17-34 seconds at 2600 degrees F

Question 11

What is the ignition temp of natural gas?

Answer 11

1000-1200 degrees F

Question 12

Two types of wiring diagrams?

Answer 12

Pictorial diagram (connection)

Schematic (ladder)

Question 13

True or false. Wiring diagrams are shown in an energized state?

Answer 13

False. Diagrams are shown in a de-energized state

Question 14

Characteristics of silicon nitride and silicon carbide HSI’s

Answer 14

Carbide - brittle and porous

Nitride - strong, smooth

Question 15

What is the main difference between intermittent pilot gas valve and a direct ignition gas valve?

Answer 15

The direct ignition gas valve has no pilot connection

Question 16

Why have flame conductivity systems not been used for proving the flame?

Answer 16

The system will not distinguish between a flame and a short to ground

Question 17

What is the first step in the sequence of operation for any heating appliance with electronic ignition?

Answer 17

A call for heat from the thermostat

Question 18

What is the importance of a connection diagram?

Answer 18

It shows where the wires go and the colour of the wires

Question 19

What is the importance of a ladder diagram?

Answer 19

It shows how the appliance works for troubleshooting

Question 20

Should you clean a flame rod with sandpaper?

Answer 20

No, flames rods should only be cleaned with materials that are not too abrasive (scotch brite, 000 steel wool) if the flame rod receives deep scratches from more abrasive materials it will increase the ground-to-flame ratio and the system will not prove flame

Question 21

In standby mode the R terminal should have power to it?

Answer 21

Yes

Question 22

In standby the W terminal should have power to it?

Answer 22

No

Question 23

When the thermostat is calling for heat what two terminals are closed?

Answer 23

R and W

Question 24

A high limit switch and a rollout switch both have a built in reset?

Answer 24

No. Only rollouts have a reset switch. High limits use bi-metal disc to disconnect when a specified temperature is achieved. Once the cool down they will automatically reset

Question 25

What is a relay?

Answer 25

An automatic remote control device that uses one or more initiating devices, such as a switch, to operate or control another device

Question 26

Two methods a relay can be controlled by are?

Answer 26

Electro-magnetically Electronic solid state components

Question 27

What are the 6 parts of a relay?

Answer 27

Coil Core Return spring Armature N.O. contacts N.C. Contacts

Question 28

What are the two types of capacitors?

Answer 28

-Run capacitor (power capacitor) used to increase running efficiency -start capacitor used to give the motor a boost on startup

Question 29

What unit is used to measure capacitors?

Answer 29

Microfarads (looks like a weird u next to an F - uF or mfd)

Question 30

What are the two methods to discharge a capacitor?

Answer 30

High wattage resistor Socketed 100 watt light bulb

Question 31

Before you test a capacitor what must be done?

Answer 31

Discharge capacitor

Question 31

All furnaces have pressure switches?

Answer 31

No, only mid and high efficient

Question 32

What is the purpose of a pressure switch?

Answer 32

Safety device. Pressure switches prove that there are no obstructions in the venting system

Question 33

What are the two components of a pressure switches and where do they connect?

Answer 33

Diaphragm - connected to inducer motor assembly Micro switch - wired in series to the gas valve

Question 34

What is the purpose of an inducer motor?

Answer 34

To assist in the venting of flue gasses

Question 35

What are the three components of an inducer motor?

Answer 35

Motor Blower wheel Housing

Question 36

Where is a flame rollout switch typically located? How many are typically used?

Answer 36

Located on the burner box. Typically two. One on each side of the burner box

Question 37

What is the purpose of a CPU (central processing unit)?

Answer 37

To execute a sequence of instructions.

Question 38

Four steps that nearly all CPU’s use in their operation

Answer 38

Fetching Decoding Executing Writeback

Question 39

What is an electronic control board?

Answer 39

It contains the CPU and all other necessary electrical connections within the furnace

Question 40

What would happen to the control board if 120 vac was applied to the thermostat terminals?

Answer 40

It will destroy the board

Question 41

What is the insulating material used to separate the two plates in a capacitor?

Answer 41

Dielectric

Question 42

What is a High Pressure Switch (HPS) and where is it located?

Answer 42

A protective device for the compressor in refrigeration units. Located between the discharge side of the compressor and the condensing coil

Question 43

What is the function of a low pressure switch (LPS)?

Answer 43

Monitors refrigeration system for a loss of refrigerant and may also be helpful in stopping the evaporator coil from freezing due to a dirty filter or low airflow

Question 44

What is a time delay relay (TDR) used for on an air conditioning condenser?

Answer 44

To avoid short cycling of the compressor and chattering of the of the contactor due to power interruptions

Question 45

What is the purpose of post purge?

Answer 45

To remove unburnt gases

Question 46

What causes a HSI to glow?

Answer 46

High resistance