Furnace commissioning Flashcards
What type of pump would be used to lift water in below grade submersed situations?
Sump pump
What is the purpose of a foot valve?
Prevent water from leaving the suction line
How is a sump or sewage pump controlled?
Float switch
What are materials that readily give up their electrons called?
Conductors
What must happen when measuring resistance of a device in a circuit?
Disconnect the device being checked and place the test leads in series with the device
Which type of pilot burner draws primary air into the burner at the point of combustion eliminating the chance of dust to be present?
Post aerated pilot
What can happen if a pilot burner is not adjusted properly and metal is impinging in the pilot flame?
The flame will cool and cause incomplete combustion
Describe a heating thermostat.
Temperature sensing switch that closes on temperature fall
What happens in the furnace when the high limit switch opens?
Gas flow is turned off and the blower is energized
What is the purpose of a draft hood in a gas appliance?
Provide a break in the stack action and prevent the products of combustion from down drafting and entering the heat exchanger
What device can control one or more initiating devices in a circuit?
Relay
What type of capacitor would be used with a single phase motor?
Run capacitor
What unit of measure is used for testing capacitors?
Farads
When referencing flow of the products of combustion, where in a gas furnace is the inducer motor located?
Downstream of the burner and heat exchanger
Which safety limit switch automatically resets?
Main high limit
What is the recommended spark gap for the pilot ignition spark?
1/8”
What is the purpose of a dirt pocket when installed at the appliance gas line drop?
Collect filings and foreign materials
What gas line material is used above ground, can be cut to any length, uses manufactured specialty fittings and is flexible for fewer connections?
CSST-corrugated stainless steel tubing
How far must the vent of a regulator be from a moisture exhaust vent?
3’
What needs to be done to a gas appliance when installing at high altitudes as per specifications?
Derate by 10% for altitudes between 2000’ and 4500’. Over 4500’, the input rating shall be reduced at the rate of 4% for each additional 1000’. (Decrease BTUH)
What is required for the safe operation of a water boiler if the system drains?
Low level cut off
What are 2 main principles in flame rod detection?
Flame rectification and flame conductivity
What type of ignition system, on a call for heat, lights the pilot, proves the pilot is lit, lights the main burner, proves the main burner and then shuts off the pilot as it is no longer needed?
Interrupted pilot ignition
What type of system uses a spark to light the main burner?
Direct spark ignition
What is required for the flame proving circuit to become rectified?
The larger ratio between the ground and flame rod allowing current to flow more in one direction
What function does a CPU perform in a gas furnace?
Executes a series of stored instructions
What can be used to adjust fan off timers in a gas furnace?
Dip switch
What are the more reliable hot surface igniters made of- silicone carbide or silicone nitride?
Silicone nitride
Name 3 approved gas leak detection methods?
Soapy water solution, test dial, electronic leak detector
What type of venting must be used when installing a condensing gas appliance?
BH vent
If the temperature rise in a furnace is too high, what must be done according to the rating plate?
Increase fan speed
What type of pilot burner uses primary air and secondary air for combustion and burn continuously?
Aerated standing pilot burner
What needs to be done to the pilot burner when converting fuels from natural gas to propane?
Change the insert orifice to a smaller sized orifice
What does a heat anticipator accomplish in a mechanical thermostat?
Lessen room temperature swings
Which high limit safety device comes with a manual reset button?
Flame roll out
What 3 components make up the atom?
Electrons, neutrons and protons
What are the electrons in the outermost orbit of an atom called?
Valence
Materials that easily give up electrons are known as?
Conductors
Current can be described as the flow of ____________ which is measured in ____________?
Electrons, amperes
What is the unit of measure for the number of cycles per second, when referencing alternating current?
Hertz
Name 3 examples of electromotive force that can produce voltage?
Magnetic, heat and friction
What 3 things are required for electricity to flow?
Path, source and load
In this electrical circuit, what component would be considered the load-
battery
light bulb
switch or
transformer?
Light bulb
What is a continuity test used to determine?
If an electrical circuit is complete
What can be used to check an electrical circuit for live voltage?
Voltage pen or test light
What type of meter should never be connected to an energized circuit?
Ohmmeter
When comparing schedule 40 and schedule 80 pipe, what happens to the inside diameter as the wall thickness increases?
Inside diameter decreases
When threading pipe, what is the cutting fluid used for?
To help keep the pipe and threading dies cool
When the pipe has been cut to the correct length, what must be done before threading begins?
Clean die threads, ream pipe and oil
What type of piping cannot be used in above ground installations?
Polyethylene
What is the definition of thread engagement?
The amount of pipe that is added to a face to face measurement
Why is teflon tape used on an iron thread?
Lubricate the joint
What is type M copper used for?
Potable water
In HVAC, where can aluminum tubing be used?
Pilot gas from gas valve to pilot burner
What must be done if a gas furnace heat exchanger is deemed defective?
Replace with same approved heat exchanger
What must be installed in conjunction with a regulator?
Shut off valve
What would a plugged regulator vent cause?
An increase in outlet pressure
What is it called when the flow of gas has stopped completely by the regulator?
Lock up
What is the minimum distance between a regulator vent termination and mechanical air intake?
10’
What is the area of the common manifold when venting 2 or more regulators together, without internal relief?
2 x the total area of the connected bleed vents
What is the maximum pressure setting of the 1st stage regulator in a residential propane installation?
No more than 10 psig
What are the 3 main elements of a regulator?
Orifice (the restricting element), diaphragm (the measuring element) and spring (the loading element)
What is an orifice designed to do?
Control rate of flow of gas to the burner
What is the proper way to verify the actual size of an orifice?
Using the shank of the orifice drill
What is a leak limiting device used for?
To limit the amount of gas escaping if the diaphragm ruptures. (1cu.ft/hr for propane and 2.5cu.ft/hr for natural gas
When is a leak limiting device used?
On 2psig or lower pressure systems in a well ventilated space only
What 2 devices on a regulator, are used to control excess pressure?
Internal and external relief valves
How is a regulator freeze up identified?
By a lack of gas to the burners (slow or sluggish operation)
What does a plugged regulator vent cause?
Excessively high outlet pressures
What position does a gas valve fail in?
Closed position
Name 4 types of pressure regulators?
Service, system, appliance and servo
What closes the regulator valve stem?
Gas pressure
How do you change rotation in a belt drive motor?
Reverse the wires under the cover plate
How do you test a low water cut off control on a boiler?
Drain the boiler
What type of valve is used on a propane tank for liquid withdrawal?
Excess flow valve
How close to the side of a building can an RTU be located?
6’
How far from a masonry wall does a 7500L propane tank have to be located?
10’
What needs to be checked on a transformer if it has been replaced multiple times?
VA rating
How many support legs minimum are needed on a horizontal propane tank?
2
What type of pipe is not allowed for liquid propane and cannot be used in above ground installations?
Polyethylene
What are the LEL and UEL for propane?
2.3% to 9.5%
What are the LEL and UEL for natural gas?
5% to 15%
What is the piping between the well head and the processor called?
Production lines
What is the piping between the city gate and the building called?
Distribution lines
What type of venting is used on a high efficient oil fired furnace?
L vent
How must a steam boiler be wired for an operator control and a safety control-
series and series
parallel and series
parallel
Series and series
What class category is a 24 volt transformer?
Class 2
What common voltage, used in furnaces, is found on the secondary side of a transformer?
24V
When testing resistance, how must the meter be hooked up and is the circuit energized or deenergized?
The circuit is deenergized and the meter leads are hooked up in series
On a gas fired residential furnace, where would the main high limit switch be located?
Next to the heat exchanger
What is determined by clocking the gas meter?
BTUH input of the appliance
Calculate the BTUH for a natural gas fired furnace that took 45 seconds to complete 1 revolution on a 1 cubic foot dial?
1/45=0.0222 x 3600=80
This gives you the cubic feet of gas, now you need to multiply that by the calorific value of the fuel to get the BTUH.
80 x 1000= 80,000 BTUH
What must be done to the fan speed if the temperature rise in a furnace is too high according to the rating plate?
Fan speed should be increased
How do you test the high limit in a gas fired residential furnace?
Disconnect the heating fan speed wire from the terminal and do a call for heat.
What happens to the pilot in an intermittent and interrupted ignition system?
Intermittent-pilot stays on after main burner is lit
Interrupted-pilot turns off after main burner is lit
What is the included angle of a NPT (National Pipe Thread)?
60 degrees
What is cutting oil used for in threading pipe?
Keeps the pipe and threading dies cool
What is the purpose of gas Teflon tape on a pipe thread?
Lubricate the joint
What is the amperage of a 120 volt circuit that has a 10 ohm light and a 50 ohm fan motor wired in series?
Add up the ohms and divide this into the volts to get the amps.
10 + 50 = 60 ohms
120/60 = 2 amps
What is the voltage of a series circuit with 4-15 ohm lights and a 5 amp draw?
Add up ohms and multiply by the amperage.
15 + 15 + 15 + 15 = 60 ohms
60 x 5 = 300 volts
What is the purpose of a draft hood in a gas appliance?
Prevents down drafts from enter the heat exchanger
From the list, which safety switch automatically resets?
Roll out
Spill
Blocked vent
Main high limit
Main high limit-once cabinet cools down, the limit switch will reset.
What is the area of the common manifold when venting 2 or more regulators together, with internal relief?
The manifold (single vent line) has an area equal to the largest relief valve opening plus 50% of the total area of the other relief valve openings.
What can cause damage to the copper fins of a heat exchanger on a boiler?
Low or no water
How do you set the heat anticipator on a thermostat?
The amp draw stated on the gas valve
What is formed when you chemically combine 2 elements?
A compound
What 2 things can turn on the blower motor on a standard or low efficient furnace?
Fan control
Summer switch
