TREC Home Inspector National Exam –
HVAC with complete solutions.
For mechanical systems, a level working space at least _____________________
inches deep and _____________________ inches wide shall be provided in front of the
control side to service an appliance. Correct Answer -30"; 30"
When mechanical equipment is located in attics, it shall not be further than
_____________________feet from the attic access. Correct Answer -20'
Attics containing mechanical appliance shall be provided with an opening and a clear
and unobstructed passageway to allow removal of the _____________________
appliance. Correct Answer -largest, 22 by 30inches
Mechanical appliances installed in attics shall have a luminaire controlled by a switch
located at the required _____________________ _____________________ and a 120
volt receptacle outlet provided at or near the appliance location. Correct Answer -
passageway opening
Mechanical appliances suspended from the floor shall have a clearance of not less than
_____________________inches from the ground. Correct Answer -6"
Mechanical appliances having an ignition source shall be elevated such that the source
of ignition is not less than _____________________above the floor in garages.
Correct Answer -18"
Supports and foundations for the outdoor unit of a heat pump shall be raised at least
_____________________ inches above the ground. Correct Answer -3"
A 4-inch radius mitered 45 degree elbow dryer exhaust duct fitting shall reduce the
maximum 35-foot length of a dryer duct by _____________________ feet,
_____________________inches. Correct Answer -2'; 6"
Where a space for a _____________________ _____________________ is provided,
an exhaust duct system shall be installed. Correct Answer -clothes dryer
Under-floor plenums shall be _____________________ in new structures. Correct
Answer -prohibited
Outdoor and return air for a forced-air heating or cooling system shall not be taken from
_____________________. Correct Answer -closets, bathrooms, toilet rooms,
kitchens, garages, boiler rooms, furnace rooms, unconditioned attics, or other dwelling
units
,For mechanical system installations in flood hazard areas, _____________________
_____________________ openings shall be located at or above the required elevation.
Correct Answer -combustion air
Manually operated vent _____________________ shall not be installed except in
connectors or chimneys serving solid-fuel-burning appliances. Correct Answer -
dampers
Freestanding or built-in ranges shall have a vertical clearance above the cooking top of
not less than _____________________ inches to unprotected combustible material.
Correct Answer -30"
Sauna heaters shall be equipped with a thermostat that will limit room temperature to
not greater than _____________________degrees F. Correct Answer -194⁰F
Confined Space and Combustion Air
If the volume of space where the appliance is located is less than 50 cubic feet of space
per......BTU per hour of aggregate input of the appliance, then it is a confined space.
50 cubic feet = 2.5 feet x 2.5 feet x 8 feet
In unconfined spaces in buildings, infiltration may be adequate to provide air for
combustion, ventilation and dilution of flue gases. However, in buildings of tight
construction -- for example, doors and windows that have weatherstripping, walls that
are heavily insulated, openings that are caulked, floors and walls with vapor barriers,
etc. -- additional air may need to be provided.
Solution
Two permanent openings to adjacent spaces could be provided so that the combined
volume of all spaces meets the requirements. If the building is sealed so tightly that
infiltration air is not adequate for combustion, combustion air should then be obtained
from outdoors Correct Answer -1,000
All Air from Inside the Dwelling
If all combustion air is taken from the inside of the dwelling, then two permanent
openings should be installed. One opening should be within ........ inches of the top and
one within ...... inches of the bottom of the space. Each opening shall have a free area
equal to a minimum of 1 square inch per 1,000 BTU-per-hour input rating of all
appliances installed within the space, but not less than 100 square inches. Correct
Answer -12,12
All Air from Outdoors
, If all combustion air is taken from the outdoor air, then one opening should be within 12
inches of the top and one within 12 inches of the bottom of the space. The openings are
permitted to connect to spaces directly communicating with the outdoor air, such as a
ventilated crawlspace or ventilated attic space. Each opening should have a free area of
at least 1 square inch per 4,000 BTU per hour of total input rating of all appliances in the
space when using ......ducts, or 2,000 BTU per hour if using .......ducts. Correct
Answer -vertical ducts 4,000 BTU/ horizontal ducts 2,000 BTU
Louvers
In calculating the free area of a combustion air opening fitted with louvers, the inspector
should note that metal louvers obstruct about ........ of the opening, and wooden louvers
obstruct ...... of it. Correct Answer -metal 25%, wood 75%
Backdraft
The lack of dilution air (the air used for draft) may cause a condition of backdraft at the
furnace. Backdraft occurs when the combustion gases are not drafting or rising up
through the chimney but are, instead, coming backward into the living area of the
building. This is a hazardous situation, since carbon monoxide could be entering the
dwelling.
Backdraft can be caused by various conditions, including: Correct Answer -
inadequate dilution air;
flue restriction or blockage;
chimney downdraft;
exhaust fans causing draft and pressure problems within the building; and
improper chimney or flue connector size.
Roughly 15 cubic feet of air are needed to burn 1 cubic foot of natural gas. Gas
furnaces also need draft air (or dilution air) to maintain a draft of the combustion gases.
Another 15 cubic feet of air is needed for every cubic foot of natural gas. This air helps
with a chimney draft. Therefore, a conventional low-efficiency, standing-pilot gas
furnace requires about .................cubic feet of air (15 dilution plus 15 combustion) for
every cubic foot of gas burned.
If combustion air is inadequately supplied to a gas furnace,................will likely be
produced. Carbon monoxide can be lethal. Correct Answer -30 cubic ft of air (15
dilution plus 15 combustion)
carbon monoxide
Draft Types
There are three types of burners relative to the draft. They are:
natural-draft burners; Gravity Warm-Air Heating Systems
