Testing and Troubleshooting Flashcards
What three items does a combustion analyser sample when testing efficiency?
CO2, O2, and Excess air
What is a draft gauge used for?
To measure flue draft and pressure drop across air filters
What are four types of efficiencies?
Combustion, steady state, thermal, and annual fuel utilization
Which dial is used for the purpose of clocking the meter
The proving dial
What is the calorific value of natural gas?
1000 BTU
What is the calorific value of propane gas?
2500 BTU
What are the conditions that could possibly cause low O2 in the flue gas?
Insufficient combustion air, burner over firing, and low vent (stack) draft
What are 3 conditions that may cause low vent draft in an appliance?
Improperly sized vent, vent system blocked, and poor workmanship
On the PCB, What can be used to aid in the diagnosis of a fault in a furnace?
The LED
Every manufacturer uses LED fault codes on their circuit boards. True or False?
True
Should the power be turned on or off before you read the fault codes?
Turned on
What are the possible causes for a pressure switch not closing?
Blocked vent pipe, faulty tubing, faulty induced draft motor, and dirty or worn induced fan wheel
What are the possible causes for a limit switch to open?
Plugged filter, restriction in the duct work, loose blower wheel, faulty blower motor, and faulty switch or electrical connections.
Where is the rollout switch located?
Beside the burner
A flame sensor is checked by measuring the amount of ___ flowing through it.
DC microamps
All HSI are supplied with 110 V. True or False?
False
What can happen to an HSI if the furnace is oversized?
It can shorten the life of the HSI
The troubleshooting procedure for a direct drive multi-speed motor is exactly the same as it is far an electronically commuted motor. True or False?
False
What are the variety of test instruments used for testing a furnace?
A gas analyzer, manometer, tachometer, multimeter, and thermometer
What is the air to gas ratio?
10/1
What device is used to measure gas pressure and pressure drops in ductwork?
A manometer
What device is used for measuring the speed of motors and fans in HVAC equipment?
A Tachometer
What device combines a voltmeter, ohmmeter, and an amp meter in one to perform service and electrical readings?
A multimeter
What device is used for taking temperature readings?
A Thermometer
What gauge is used for determining draft pressure?
A draft gauge
What is Annual Fuel Utilization Efficiency (AFUE) ?
A thermal efficiency measure of combustion equipment like furnaces, boilers, and water heaters.
What is combustion efficiency?
It is a calculated measurement in percent of how well the appliance converts the fuel into useable heat at a specific point in time.
What is steady-state efficiency?
It used to describe combustion efficiency
What is running efficiency?
It is defined as the point at which combustion gas content reaches equilibrium and stack temperatures stabilize.
What is annual fuel utilization efficiency (AFUE)?
It is the off cycle losses of equipment
What is the stack temperature and running efficiency in a standard low-efficient furnace?
Stack temperature 500 degrees F and a running efficiency of 70 - 79 percent
What is the stack temperature and running efficiency in a mid-efficient furnace?
Stack temperature 350 degrees and a running efficiency of 80 - 83 percent
What is the stack temperature and running efficiency in a high-efficient furnace?
Stack temperature 110 degrees F and a running efficiency of 90 - 98 percent
What is the smallest dial on the gas meter?
The test dial
What is the formula for flow rate?
Vol of dial X 3600 / time
With less gas would you have a larger or smaller orfice?
A smaller orfice
How do you convert the amount of gas used into Btuh?
You must multiply the cubic feet of gas consumed by its calorific value.
What is the difference between low oxygen and high oxygen O2 and High CO levels?
Low oxygen has insufficient combustion gas, burner is over firing. and has a low vent draft. High oxygen combustion has too much combustion air, burner is underfiring, and has loose access panels.
How do you diagnose a pressure switch?
By checking both the electrical and the diaphragm that is in the switch.
What is a limit switch?
A simple auto resetting, on-off switch that opens due to excessive heat in the heat cabinet.
What is a rollout switch?
It is a manual reset switch that is normally closed that opens when the temperature at the burners gets too high.
A flame sensor has power going to it all the time. True or False?
True
What are some causes of excessive on/off cycling?
Installation of an over-sized furnace, dirty filter or squirrel cage blower, or a dirty evaporator coil or heat exchanger.
What are the two types of gas valves?
Solenoid and diaphragm
What are the two basic types of indoor blower motors?
Direct drive and belt drive
What is an electronically commuted motor (ECM)?
It is an ultra-high efficiency programmable brushless DC motor that uses a permanent magnetic rotor and built-in inverter.
