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55 Cards in this Set
- Front
- Back
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What would happen if the fan on an electric unit heater burned out? |
The heater would remain energized until the fusible link melts OR the interlock switch would de-energize the electric heater. |
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If a duct-mounted electric heater is to be installed and it is discovered that the heater is too long to fit inside the duct, what can the technician do to properly complete the installation? |
Return the heater to the supply house and obtain the correct size heater. |
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The resistance wire used in electric heating elements is usually |
nickel chromium |
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Radiant heat is trasferred by |
infrared rays |
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Electric baseboard heaters are classified as |
natural draft convectors |
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Quartz and glass panel electric units are classified as |
radiant heaters |
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An electric heating unit in a duct system is classified as |
forced draft convector |
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How do you measure Btu/h out of a 10 Kw furnace rated on 240V? |
10,000 x 3.413 = 34,130 |
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The limit switch is used on the electric element assembly to |
open the circuit to the element if the furnace overheats |
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T or F: Generally speaking, electric heat is very efficient but costs more when compared to oil and gas. |
True |
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T or F: For maximum element life, the element must have sufficient air over all parts of the element to prevent any part of the element from glowing red. |
True |
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T or F: Electric heating units provide amost instant heat. Therefore, anticipators are not needed in electric heat thermostats. |
False |
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T or F: If the number two contact on a package sequencer fails to close, the number three contact can still close |
False |
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T or F: One potential safety hazard that all technicians should be aware of when working on an electric furnace is that there are many exposed electrical connections. |
True |
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In order to prevent a duct-mounted electric heater from being energized when the fan is not on, an ________ should be used |
interlock |
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A set of contacts actuated by a magnetic coil is called a ________ |
relay |
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the amount of heat energy in 1 watt of electrical energy is ________ |
3.413 |
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If the fan were to fail and the limit switch stuck closed, the element would be cut off by the ________ |
Safety device |
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In order to provide time delay between stages of electric heat, the controls that are used are called ________ |
sequencer |
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How do you calculate CFM in an electric furnace? |
Watts x 3.413 / (1.08 * ΔT) |
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How do you calculate CFM in a gas furnace? |
Btu output / (1.08 x ΔT) |
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A gas valve system that has the gas valve and igition control all in one unit is called a |
smart valve |
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When a pilot flame or a main burner flame is sensed (or proved) through the flame it is called |
flame rectification |
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The manifold pressure of a natural gas furnace at low fire would be |
1.7" WC |
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When two furnaces are setup side by side to act as one furnace with multi stages of heat this installtion is called |
Twinning |
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The orifice is a precisely sized hole in the |
spud |
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The manifold pressure of a natural gas furnace at high fire would be |
3.5" WC |
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The typical manifold pressure of a propane furnace would be |
11" WC |
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What will shut off a gas valve if the furnace overheats? |
Aux limit switch |
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The specific gravity of natural gas is |
0.60 |
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The proper color of a gas flame is |
blue with slight orange tips |
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T or F: A gas flame will carry electrical energy |
True |
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T or F: A gas furnace designed for use with natural gas can be used with liquified petroleum (LP) with no system modifications. |
False |
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T or F: When a pilot flame or main burner flame is sensed by the IFC, the current it sees is measured in Milliamps. |
False, Microamps |
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T or F: A thermocouple when it is heated generates around 20-30 microvolts |
False |
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If the combustion gases are pushed through the heat exchanger the furnace is said to have a ________ draft. |
forced draft |
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A ________ is located between the gas valve and the burners |
orifice |
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Spark ignition is important for rooftop or package units located outdoors because of ________ problems. |
draft problems |
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The dangerous byproduct of poor combustion of gas is ________ |
CO or Carbon-monoxide |
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Three products of complete combustion of natural and LP gas are ________, ________, and ________. |
Water vapor, heat, and CO2 |
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If the combustion gases are pulled through the heat changer, the furnace is said to have a ________draft |
Induced draft |
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Why is "inches of water column" used to measure gas pressure instead of psig? |
The pressure is too small to accurately measure in psig. |
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When the burners ignite, the burner flame is normal until the blower starts. At this time, continuous roll out occurs. What is the problem? |
A leak in the heat exchanger + not getting complete combustion |
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7 intermittent Pilot steps |
1. Call for heat 2. Gas to pilot opens 3. Pilot is lit + proven 4. Gas valve opens. 5. Burner comes on. 6. Burner proves 7. Blower comes on |
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8 HSI steps |
1. Call for heat 2. Combustion blower comes on 3. Prove combustion blower 4. 16 second HSI 5. Gas valve opens 6. Burner gets lit 7. Burner gets proved 8. Blower comes on |
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7 Spark-Ignition steps |
1. Call for heat 2. Combustion blower comes on 3. Prove combustion blower 4. Spark/gas valve on 5. Burner gets lit 6. Burner gets proved 7. Blower comes on |
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6 Standing pilot steps |
1. Call for heat 2. Gas valve opens. 3. Pilot lights burner 4. Burner comes on. 5. Burner proves 6. Blower comes on |
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When a gas furnace ignites and is under "full-fire," why does the fan not come on immediately? |
The furnace needs to heat up |
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What is the purpose of a gas regulator? |
To control the amount of gas coming in and out. |
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Primarily used in crawl spaces |
Horizontal furnace |
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Blower located above heat exchanger |
downflow furnace |
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Blower located below heat exchanger |
Upflow furnace |
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Return and supply ducts are both on top |
low boy |
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What is a forced draft furnace? |
Push/blow with a positive pressure Mounted on the inlet of the heat exchanger |
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What is an induced draft furnace? |
Pull/suck air with a slight negative pressure Mounted on the outlet of the heat exchanger |
