Sequence of operation of residential controls Flashcards
From the following description identify the component listed below. Is usually a single-phase, fractional hp motor.
Fan motor
Transformer
Fan control switch
Thermostat
Fan motor
From the following description identify the component listed below. Is the operating controller for the appliance.
Fan motor
Transformer
Fan control switch
Thermostat
thermostat
From the following description identify the component listed below. Supplies a millivolt signal to the automatic pilot valve section in the combination gas valve.
Transformer
Fan control switch
Thermocouple
High-limit switch
thermocouple
what is the maximum VA output rating for a class 2 transformer
100 VA
the temperature to which a thermostat is set is called the:
Set point
What term describes a furnace that starts and stops frequently due to a lack of air movement through the heat exchanger?
High-limit cycling
If the circulating air fan continues to run after the heat exchanger is cooled past 90° F, the air that is circulated to be quite cool in the building. Which Fan-limit control setting must be adjusted to correct the problem?
Fan-off switch
While troubleshooting a thermostat a technician measures 24 V across the “R” and “W” contacts with the switch in the closed position. What is the most likely problem?
Heat anticipator is burned out
A technician is troubleshooting a “No Heat” call on a 24 Volt control system. After the control circuit has been verified and power has been confirmed at the gas valve, how can the integrity of the gas valve be confirmed?
Using the continuity function of a multimeter, check the gas valve coil and replace the gas valve if this test shows an open circuit
The 120 V heating system derives its name from its control circuit power rating 120 V.
T or F
True
A transformer is typically required for a 120 V heating system.
T or F
True
Thermostats utilized for commercial applications most likely have heat anticipators incorporated in their construction.
T or F
false
With direct reference to the operating cycle of a commercial unit heater, what should be the next occurrence after the “Fan-on” setting has been reached?
The fan starts
What adjustments to the fan-limit settings should be made by the technician when commissioning or performing routine maintenance on a commercial heating appliance?
As per manufacturer
What is a common design incorporated into the gas valve of larger heating appliances?
Two stage (step) design
What significant design change was incorporated in thermostats due to environmental concerns January 1, 2006?
Prohibited use of mercury filled bulb contacts
Older mercury bulb thermostats can be disposed of in any trash receptacle.
T or F
false
Spring-Activated, snap-action exposed contacts utilize what control principle to operate?
Bimetal
For a cooling application, the thermostat contacts must __________when the room temperature falls.
open
Name the terminal connections on basic heating and cooling
R
W
Y
G
C
R - Power
W - Heat (WARM)
Y - Cool (CHILLY)
G - Fan (FANG)
C - Common
From the list below, which of the following would not be recommended when installing a thermostat?
Near other sources of heat or any position subjected to cold drafts, out of direct sunlight, away from any heat producing appliances
It is recommended to use the built-in thermometer when calibrating a thermostat.
T or F
False
The thermostat anticipator is wired in___________ with the thermostat contacts on a heating thermostat and in parallel to the contacts on a cooling thermostat.
Series
The purpose of the anticipator is to compensate for the extra heat that is put into the room after burner shuts down.
T or F
True
Any measurable temperature above or below the thermostat set point is called;
Offset
The recommended way to calibrate a heat anticipator is;
Physically measure the control circuit amperage and set the anticipator to the measured amperage
The anticipator may also be adjusted to change the cycle times of the appliance.
True
Programmable thermostats;
a) Provide multiple set-point values
b) Allow for appliance operation during different
day time periods
c) Increase efficiency of the heating/cooling
system
d) All of the above
All of the above
What term describes a combustion fan operating for a predetermined time prior to the ignition sequence?
Pre-purge
With direct reference to the operational sequence of a mid-efficient furnace, what device must be last be activated before the ignition sequence can occur?
Air proving switch
A mid-efficient furnace would fall under which category of the B-149.1 gas code?
class I
The high-limit switch located in the heat exchange area of a mid-efficient furnace is normally of what design?
Snap-disc bimetal
Where would a technician locate a VSS on a mid-efficient furnace?
Located near the vent outlet of the furnace
A VSS or FRS would typically be;
Manual reset
Spark and hot surface ignition systems would have trial for ignition time than an intermittent pilot ignition system.
A shorter
Newer hot surface ignitors are constructed from .
Silicon nitride (NEWtride)
Older mid-efficient furnaces would normally have blower speed/s.
a) one
b) more than one
c) non-adjustable
d) adjustable
More than one AND Adjustable
Many of the new high-efficient furnaces utilize _________to improve operational efficiency through all firing rates and heating loads.
VAriable speed DC motors
Which of the following would not be considered an input to an electronic control board?
Hot surface ignitor
With reference to the operational sequence of a mid-efficient furnace, the delay-on timing sequence for the circulating air fan is adjustable.
T of F
False
With reference to the operational sequence of a mid-efficient furnace, if the combustion fan is operating but the hot surface ignitor fails to operate, what would be the first component for a technician to check?
Air switch
How can a technician determine the proper circulating fan speed required for a mid-efficient furnace?
air temperature test
If the measured heat rise in a furnace is higher than the manufacturers specification, how can a technician correct the problem?
Increase circulating air fan speed
Changing circulating air fan speed on a mid-efficient furnace is done;
Manually
Blower off delay adjustments are typically set by the manufacturer and are non-adjustable.
T or F
false
While verifying blower off delay setting on a mid-efficient furnace, a technician observes that the circulating air fan is de-energized with a discharge air plenum temperature of 120 °F. What can be done to correct this problem?
Increase the delay off time
Some electronic control boards or ignition control centres come equipped with light-emitting diodes (LEDs). What is the primary purpose of these LEDs?
A) Identify operational sequence
B) Show fault conditions
C) Assist with troubleshooting
Show fault conditions AND Assist with troubleshooting
Manufacturers provide generic troubleshooting guides that apply to any appliance of the same design.
T or F
False
If a technician were to perform an upgrade to an existing heating system to a cooling, where would the evaporator coil be installed?
In the discharge (warm) air plenum
What speed is typically used by default for the circulating air fan during cooling mode?
High
What component of the control system must be checked (verified) for capacity when adding cooling components to an existing system?
Transformer VA
DO this when adding any component
