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