問題一覧
1
What kind meter reading indicate an open relay coil
infinite ohms
2
What is the first 120 volt load you see running a call for neat?
induced draft fan
3
What is the first switch to close on a call for heat
thermostat
4
What cause high temperature rise
clogged coil
5
What is a symptom on a block drain on a 90% furnace?
Open pressure switch
6
What can cause the limit switch to open
dirty filter dirty coil
7
What meter readings will indicate a short circuit when checking resistance of a motor
0 ohms
8
What is switching action of a heating thermostat
open on a rise
9
What does infinite Resisance across the switch mean
open switch
10
What is the symptom of short to ground?
blown fuse
11
Power must be off and a load must be isolated to test
resistance
12
If there’s 120 V to the induced draft fan and the motor doesn’t start, you should?
replace the motor
13
If there’s 0 volts from R to C but 24v at secondary what is wrong
Open limit switch
14
If there’s 24v from W to C and the induced draft fan Doesn’t start what’s wrong
induce draft fan relay has failed
15
When measuring heat to neutral What is being tested?
Low speed blower motor
16
If we have 24V R to C and 0 Volts W to C what is wrong?
failed thermostat
17
What could be wrong if the transformer primary has 0 V
Open motor door/ interlock door switch
18
If the pressure switch is open an induced draft fan running what is wrong
blockage in the venting
19
If the limit switch is open What could be the cause
high gas pressure
20
What meter reading can indicate open limit switch?
24V across / infinite ohms / outgoing Side to common
21
What are you do if you see bees
spray them
22
What happens after the inducer motor start
pressure switch closes
23
What conducts Electricity to ground from The flame sensor when the burner light
Flame
24
What is the typical igniter voltage
120v
25
What is the symptom of loose ground wire to IFC?
burner light and then shuts off
26
IDF relay closes
before burners ignite
27
Call for heat
before pressure switch closes
28
IDF relay closes
Before motor starts or pre-purge
29
Blower on delay
before blower off delay and T stat closes
30
120v to ?
Transformer primary
31
What is the symptom of a dirty A coil?
Open limit switch
32
What is the symptom of a plugged drain on a 90%
Open pressure switch
33
What is the symptom of a faulty t-stat
reading 0 from w to c
34
Which of the following is a symptom of an open induce draft fan motor winding
B
35
Which of the following symptoms of an Open blower motor winding
Open limit switch
36
Where is rollout switch located?
near the burners
37
Where is the auxiliary switch located
blower compartment
38
What does the pressure switch connect to
induced draft fan housing
39
Where is the IFC located?
blower compartment
40
Where is the flame sensor located?
near the burners
41
What could be wrong if there’s high temperature rise
High temperature rise
42
What is the manifold pressure in a natural gas furnace
3.5 inches of water column
43
What switch would be open if the flue pipe is blocked
pressure switch
44
What tool is used to measure gas pressure?
manometer
45
What could cause an Open rollout switch
crack in the heat exchanger
46
What winding of a blower Motor has the highest resistance
short winding
47
What is the minimum resistance or a hermetic motor winding to ground
1 million ohms 1 mega ohms
48
If we’re measuring a compressor from run to start what does that mean?
open winding
49
What type of load is a motor
inductive load