305A/305B/305C Flashcards
What is the main difference between an intermittent pilot gas valve and a direct ignition gas valve?
The direct ignition gas valve has no pilot connection
When using electronic ignition, what is the process of proving the flame called?
Flame rectification
What is the minimum flame rod to ground electrode area that is immersed in the flame?
1:4
Why have the flame conductivity systems not been used for proving the flame?
The system will not distinguish between flame and a short to ground
What’s the first step in the sequence of operation for any heating appliance with electronic ignition?
Call for heat
What’s the importance of the connection diagram?
It shows where the wires go and the colour of wires.
What is the importance of a ladder diagram?
Shows how the appliance works for troubleshooting
What device has a capacitor connected to it?
Blower motor
Two main principles in Flame rod detection systems are?
Flame rectification
Flame conductivity
In conductivity systems the ground electrode must be at least ____ times that of the flame rod?
4 times
4:1 ratio
Flame rectification is measured in what
DC micro amps
What is the spark gap on an Intermittent pilot spark ignition system?
1/8” gap
What’s the difference between intermittent pilot ignition and an interrupted pilot ignition system?
In Intermittent pilot system the pilot is not extinguished after ignition of the main burner
What are the different types of electronic ignition systems?
Intermittent pilot using spark
Intermittent pilot using Hot surface
Direct ignition using spark
Direct ignition using hot surface
What is DSI?
Direct spark ignition
What is IP
Intermittent pilot ignition
What is HSI?
Hot surface ignition
An automatic ignition system uses what for a flame sensing device?
Flame rod/ flame rectification
What is the igniter on a HSI made of typically?
Silicon carbide
What happens when lockout occurs?
De energizes spark ignition and burners
Adjustable components in a mid efficiency furnace?
Blower fan off time delay
Blower fan speeds
List 5 parts of a relay
Coil
Core
Return spring
Armature
Contacts
4 common arrangements for the contacts of a relay
SPST-NO - Single Pull Single Throw Normally Open
SPST- NC - Single pull Single throw Normally Closed
SPDT- Single pull Double Throw
DPDT- Double Pull Double Throw
2 Types of capacitors?
Run Capacitors
Start Capacitors
Material used to seperate 2 plates in a capacitor?
Dielectric
What activates the Pressure Switch?
Pressure switch is activated when the IDM starts turning and creates enough pressure
What is flame rectification?
It is an AC electrical circuit that sends a small current from the furnace board to the flame rod.
When the flame is established the flame acts as a conductor or path which allows current to flow across from the flame rod to ground burner completing the circuit
Where is the CPU located?
Control board
What way is a ladder diagram read?
Left to right
What’s HPS stand for
High Pressure Switch
What’s LPS
Low Pressure Switch
What is a better HSI?
Silicone carbide or silicone Nitride?
Silicone Nitride
What commonly use Run Capacitors?
Air handler blower motors,
Induced or forced draft fan motors on high efficiency furnaces, condenser fan motors, compressors and pumps for hot water and chilled water
Common applications for Start capacitors?
Typically only used to start compressors
Voltage classification for Run Capacitors?
370V and 440V
Voltage classification for Start capacitors?
125V, 250V and 330V
Is it safe to inspect electrical components with the power on?
No
Typical circuit board on any furnace will only have one voltage ?
False
List 3 acceptable methods to check for gas leaks ?
Test dial
Commercial leak detectors
Electronic leak detector
What direction must venting on the furnace slope?
Upwards and away from the furnace
What the maximum distance supports can be apart on a 636 system?
5 Feet
What should the heat anticipator be set to?
The amperage draw of the 24-volt circuit
Formulas for converting gas quantity into BTUh?
Hourly consumption =( size of test dial / # secs. 1 revolution) x 3600
BTUh = hourly consumption x calorific value
How is an ignition system energized?
Ignition module
What is the usual voltage for a system control module?
24V
What gas control valve is used for DIS, IP and HIS?
Combination Gas Valve
A redundant gas valve can provide protection against what?
The main operator failing in the open position
Which ignition system energizes only the first main valve to open and allows gas to flow to the pilot?
Direct ignition
What’s the function of a flame sensor?
To prove there is a flame
A flame sensor rectifies a AC signal to a _________________
Micro Amp DC current
What does a system pre purge mean?
The inducer motor runs to clear out the vent of products of combustion
What does trip ignition mean ?
The time it takes to light the main burner and prove there is a flame
What does lockout mean?
After 1 or multiple attempts to light the burners and it fails system will go into lockout.
What are 2 things that can be done to reset Lockout?
Turn off main power or turn off call for heat @ TSTAT
How should Venting be installed?
Venting shall be installed with no dips or sags
