Trouble shooting
When voltage is read across a fuse, this indicates the fuse is...?
Blown
When receiving a flame verification code, what should the issue be?
Dirty flame sensor
What does BTU stand for?
British thermal unit
What is the IDF
Induced Draft Fan
What can cause a motor to over amp
Low cap range or bearings wearing down causing friction
When 24v error code is presented, what does this mean?
There is no 24v power after the fuse
When a system over heats three times consecutively, what error code will be presented?
Limit circuit lockout
For a 4 ton system, how many CFM is required?
1600 CFM
What is a TRAN
Transformer
Whys is a bypass humidifier worse than a fan powered?
Bypasses steal air from the system and re-circulate heat
When testing for a bad wire, what are you searching for on your meter?
Continuity
When given an ignition lockout error code, what has happened?
System failed to prove flame was present, so the furnace went into a 3 hour lockout
What can cause the breaker to pop when a furnace turns on?
Direct short to ground
A stack switch is what kind of switch?
Limit switch
This wire is mandatory for a thermostat that is powered by furnace?
Common wire
What is the main cause of a limit switch lockout?
Air flow
On a Carrier furnace, what does rapid LED flashing mean?
Line voltage polarity is reversed
To measure with a sealed system so reading as accurate
What is an ILK
Blower door interlock switch
How often should ducts be cleaned?
Every 5-10 years
Why is it important to inspect venting on a pressure switch error?
If venting is too close together it can cause air circulation issues, and if there is a dip in the venting it can cause water build up which restricts air flow out the exhaust
When receiving a pressure switch code for a 90% furnace, what four things should you check?
Inducer function
Pressure switch function
Condensate trap/Drain line
Venting
What is the sequence of operations for a furnace
Thermostat calls for heat, control board does safety check, IDF turns on, pressure switch closes, igniter turns on, gas valve opens, furnace lights, flame sensor proves flame, 30-60 second blower delay, thermostat satisfies
What is a GVR?
Gas valve relay
How does a modulating gas valve work?
Modulates gas pressure size based off negative pressure through collector box