HVAC Flashcards
What type burner is usually installed in high-efficiency furnaces with forced-draft?
A mono-port burner
Round or square supply ducts that are connected to and branch off the extended duct are called?
Side takeoffs.
On low-pressure boilers, the PRV is set to open at what pressure?
15 psi
A warm-air supply duct that runs horizontally from the furnace plenum to a riser is called what?
A leader
How much does one cubic foot of water at 68° F weigh?
62 pounds
The intermittent pilot is the main distinguishing characteristic of which furnace?
The mid-efficiency furnace
What causes the air of a gravity warm-air furnace to circulate through the house ?
The different weights of warm and cool air.
According to plumbing standards, gas meters should be what?
Lockable
Where should air filters be installed?
in the plenum or duct in the
path of the return air.
The flue pipe of a fuel-burning heating system should at least be the same size as what?
The furnace’s connector.
On a furnace with a standing-pilot light, the thermal couple has to do what before the gas valve opens?
Determines if there is a flame.
What is the minimum efficiency rating for furnaces?
78%
A hydronic heating system is what type of system ?
A forced hot-water heating system
The older gas furnaces have what type of pilot light?
A standing-pilot light.
What is the loop in the return pipe that prevents the loss of water if the line develops a leak called?
A Hartford return.
Which type of furnace has a fan that pulls air into the combustion chamber, through the heat exchanger, and blows it out through the venting system?
An induced draft furnace.
A conventional low-efficiency, natural-draft, gas-fired furnace requires how many cubic feet of air per cubic foot of gas burned?
About 30 cubic feet.
How is the efficiency of cooling systems
in a residential installation is expressed?
Seasonal Energy Efficiency Ratio (SEER).
Heating systems can be categorized in what four ways?
Gas, Steam, Hydronic, or Electric.
A Hot-surface ignition device on a furnace is also called what?
A glow plug or glow stick
A downflow, counter-flow, or downdraft furnace are the_______?
Same thing.
This transfers the heat from the air passing over it to the refrigerant passing through it on an AC unit.
The evaporator
For an oil-fired furnace, what automatically reduces (or dilutes) the chimney draft to the optimal amount?
The barometric damper
How can an up flow forced-air furnace be designed for low clearances?
By located the warm-air outlet and return-air inlet at the top of the furnace?
Boiler water pressure is reduced from plumbing water pressure by using what?
A PRV.
When inspecting an evaporating cooler, the report should state if the unit is one-______ or _________?
one-speed or two-speed
What’s the typical cooling load per square foot for the south?
One ton per 450-700.
A condensing furnace has an average SEER of what?
90%
Heating/Plumbing pipes that pass through unheated space should be insulated to a minimum of what?
R-4
A gas furnace with a yellow flame indicates what?
Insufficient primary air
What control on an electric furnace ensures that the individual elements don’t all turn on at the same time?
A sequencer
On an evaporator cooler, what is the minimum air gap between the water discharge at the float and the water level?
1-inch
For a 110-volt window/portable ac, what is the maximum cord length?
10-feet
When a heat pump system is switched from cool to heat, what is activated?
The four-way reversing valve.
How many BTUs are in a kilowatt hour?
3412 btus.
Which burner has a larger output: Monoport or Ribbon?
Monoport
Vent pipe should slope upward at what per foot?
1/4-inch
For a boiler, what is the typical setting for a low temperature limit or primary control?
140F
High-efficiency boilers commonly have problems with their what?
Heat exchangers.
What color should the flame of an oil-fired heating system be?
Orange and yellow
Any heating system that does not operate should be reported as?
In need of correction.
Which furnace uses a fan to pull air into the burner?
An induced-draft
Flue pipes from two fuel-burning appliances should not not enter a chimney from opposite sides at what ?
The same height.
