Furnace Flashcards
(25 cards)
What does ‘R’ signify on a control wiring?
24Vac CONSTANT POWER
What does ‘W’ signify on a control wiring?
HEAT or
HEATING RELAY
What does ‘Y’ signify on a control wiring?
‘COOL’/ ‘COOLING RELAY’ or
more ACCURATELY
‘COMPRESSOR’
What does ‘G’ signify on a control wiring?
‘FAN RELAY’
What does ‘O/B’ signify on a control wiring?
REVERSING VALVE
O is Reversing Valve energized in COOLING mode
B is Reversing Valve energized in HEATING mode
What does ‘C’ signify on a control wiring?
Common, 24 VAC grounded
What are the two wires called coming off of the secondary side of a step-down transformer for a typical furnace.
‘R’ and ‘C’
What is the minimum clearance to combustible for type ‘BH’ vent?
0” Clearance to combustibles
What is the minimum clearance to combustibles for type “B” vent.
1”
What is the minimum clearance to combustibles for type ‘C’ Vent?
6”
What is used to detect blocked vent on a furnace?
A N/O Pressure Switch
What is used to prove draft inducer motor start up?
N/O Pressure Switch
What proves the draft inducer motor has succesfully sped up to full capacity on a two stage furnace allowing gas valve to fully open?
N/O High Fire Pressure Switch
What is the minimum Clearance from a Propane Gas regulator relief to a fresh air intake
10’
What is the minimum Clearance from a Natural Gas regulator relief to a fresh air intake
3’
What does a GAS VALVE on a furnace do?
Allows gas to flow through at a specified pressure in order to maintain a BTU per Hour in conjuction with inducer staging and the blower fan speed.
What does a burner do?
EVENLY BLENDS AIR and FUEL to make a very efficient (BUNSEN) blue flame that produces VERY little CARBON MONOXIDE
What does an ignitor do?
IGNITES the air/fuel Mixture INSTANTANEOUSLY, in order to prevent DELAYED IGNITON/ or FLAME ROLLBACK
What does a HSI do and what does it stand for?
HOT SURFACE IGNITOR
Reaches 2400F to INSTANTANEOUSLY ignite air/fuel mixture
How does a standing pilot work?
Uses a present flame to INSTANTANEOUSLY ignite the air/fuel mixture coming out the main burner.
Pilot is located next to the main burner and mostly uses a thermocouple to insure flame is present.
How does an Direct Spark Ignitor(DSI) function?
Has a module that steps up voltage very high to cause a ‘spark’ to jump across a small gap creating a small, very hot source that will INSTANTANEOUSLY ignite the air/fuel mixture
What is a flame sensing safety?
A component used to PROVE flame is present.
Thermocouple, flame rectification sensor and occasionally Thermopile
How does a Flame Rectification Sensor work?
Grounds itself in the flame, using flame ionization to rectify a A/c signal into a D/c signal
SAFETYYYYY
