Mechanical Q&A 2009
Attention: 3 Denotes a new question!
z Denotes a revised/revisited question.
Quarter
Land Use and Environmental Service Agency
(Code Enforcement)
December 2009
4)
5)
6)
7)
1
nd
2
rd
3)
3
2)
(Q) What does a contractor/permit holder have to supply for an
inspection?
(A) Section 107.2 of the NC Administrative Code states that it is the
duty of the permit holder “to provide access to and means for
inspection of the work for any inspections that are required by this
code.”
(Q) An existing home with a package unit, installed prior to the
requirement for lintels where the duct penetrates the foundation wall is
being replaced with equipment and duct of the same size. Would a lintel
have to be installed at this time?
(A) No, provided there is no increase in size of the foundation
opening.
(Q) The Mecklenburg County inspection department preaches strongly
about how hard it works to combat inconsistency in inspections and
interpretations. When are you going to be consistent with other counties?
(A) Mecklenburg County Code Enforcement prides itself on
achieving a high level of consistency within the confines of
Mecklenburg County. We however do not have authority over other
counties or the decisions they render. We make interpretation
recommendations and/or requests to the NC Department of
Insurance from time to time and will continue to do so in and effort to
provide consistent code enforcement within “Mecklenburg County”.
(Q) What is the inspection department’s policy on wearing hard hats on
construction sites?
(A) We are to wear hard hats anywhere job sites are posted “Hard
Hat Area”!
(Q) Is a permit and inspection required when replacing or installing a free
standing appliance?
(A) Yes, if the appliance is directly connected to the building utilities
and just plugged into an outlet.
(Q) How do you calculate the ventilation rate for an upfit that contains
multiple types of uses?
(A) You split the upfit’s square footage into the various uses before
applying table 403.
(Q) Is “on demand” ventilation design allowed under section 403.3 of the
2009 NC Mechanical Code?
(A) The designer does have prerogative to use on demand as the
criteria for their design provided the system has the capacity to
achieve the ventilation rate prescribed in table 403.3, the sensors
used are correctly placed (plenum, near return, etc.) and the primary
4th
1)
st
General:
Mechanical Q&A 2009
Attention: 3 Denotes a new question!
z Denotes a revised/revisited question.
December 2009
Quarter
Land Use and Environmental Service Agency
(Code Enforcement)
General continued:
4th
contaminant is carbon dioxide. Occupancies such as a hair solon
would not be suitable for on demand ventilation design. (Designs will
be evaluated on a case by case basis and it will be the responsibility
of the designer to convince the code official that the design meets
intent of section 403)
Mechanical Q&A 2009
Attention: 3 Denotes a new question!
z Denotes a revised/revisited question.
Quarter
Land Use and Environmental Service Agency
(Code Enforcement)
December 2009
3)
4)
5)
6)
7)
2
rd
2)
(Q) Are hinges required on roof mounted exhaust fans (506.5.3)?
(A) If the exhaust system has code approved cleanouts and removal
of the exhaust fan for duct cleaning is not necessary, then a hinge
would not be required.
(Q) Does equipment installed in an enclosure, accessed by a louvered
door, have to be supplied with a high and low combustion air duct?
(A) The louvered door can not be used to meet the combustion air
requirements (per DOI). Transfer ducts or ducts to the outside are
acceptable.
(Q) Is a well acceptable to achieve the termination (clearance to grade)
requirements on a downdraft exhaust for a domestic range?
(A) In cases where there is no possible alternative to achieve the
required clearance to grade, a well with positive drain to open air
may be provided.
(Q) Does the Code require that combustion air openings be screen for
pest control?
(A) Section 304.11, item #5 of the NCFGC prohibits screening of
ducts terminating in the attic.
(Q) What is the definition of an alcove/closet as it applies to required
combustion air openings?
(A) An alcove or closet applies to a space typically large enough to
accommodate the appliance only. A space containing a sink with
standing room would NOT be considered an alcove or closet.
(Q) May two water heaters piped together be placed in an alcove, one in
front of the other?
(A) Yes, provided that both equipment’s controls are fully accessible
for service or replacement without removing the other water heater.
(Q) Would the 16’ rule apply to a roof whose slope exceeds the 3 in 12
limitation listed in section 306.5?
(A) Actually the Code in section 305.6 is addressing two different
issues.
1. Section 306.5. When the roof or elevated structure exceeds 16’
in height, a permanent means of access (steps/ladder) shall be
provided.
2. Section 306.5.1. When the slope of the roof exceeds 3 units in
12 units, a platform and railing is required for equipment
needing periodic servicing. A catwalk may be required to
provide access between the equipment platform and the roof
access.
3
1)
nd
Equipment:
Mechanical Q&A 2009
Attention: 3 Denotes a new question!
z Denotes a revised/revisited question.
December 2009
Quarter
Land Use and Environmental Service Agency
(Code Enforcement)
Equipment continued:
(Q) Do decorative appliances such as fire rings, fire bowls, fire pits or fire
fountains have to be listed?
(A) Yes
9)
(Q) Are low voltage electrical permits required for a residential furnace
replacement?
(A) The mechanical permit covers associated low voltage devices
typically installed by the mechanical contractor. Replacement of an
HVAC thermostat would be considered service work and no permit
would be required.
10)
(Q) What is the required scuttle access required for a residential
equipment replacement?
(A) The access door would have to be large enough to remove the
largest component.
11)9 (Q) May HVAC equipment be turned such that the equipment could be
serviced from the steps of a disappearing stair?
(A) No. The intent of the Code is to provide the technician a safe area
from which to work. The intent of exception 1 of section 306.3 is to
access the appliance through a scuttle opening either standing on
the ground, lift, scaffold or ladder.
Note: The definition: Disappearing stairs are any configuration for stairs
that can be used to move from one floor to another, but is not fixed in
place permanently. Some designs for these types of stairs call for
retracting sections that fold and can be recessed in the floor between the
two levels. Other designs call for stairwells that fold to a more or less flat
position against a wall.
4th
8)
Mechanical Q&A 2009
Attention: 3 Denotes a new question!
z Denotes a revised/revisited question.
Quarter
Land Use and Environmental Service Agency
(Code Enforcement)
December 2009
4)
5)
6)
7)
1
3)
nd
2)
(Q) May a contractor use the merchant coupling provided with each stick
of gas pipe, to assemble the permitted gas piping system?
(A) The NC Gas Code does not prohibit the use of all thread
merchant couplings.
(Q) How many gas tests are required for a single gas pipe installation?
(A) The Code would require two tests. One before you cover the work
and one on final inspection. We require an additional test if you
would like “temporary heat” which would result in a total of three.
(Q) Does gas piping have to be steel where the piping terminates at the
meter?
(A) The Code does not require a steel termination, but many gas
utility providers (Piedmont Natural Gas) will refuse to connect to
CSST or copper piping.
(Q) May the valve for a free standing range be placed behind the range?
(A) Yes. The valve is for servicing and does not have to be placed
where it can be accessed without moving the appliance.
(Q) Does the Code require a cut-off to be placed at the base of decorative
gas yard lights?
(A) Yes! The light is considered an appliance and would require a
cut-off within 6 feet and accessible (box/vault).
(Q) What is the minimum length for an appliance drip leg (sediment trap)?
(A) Drip legs shall be a minimum of 3” long or per the equipment
and/or regulator manufacturer’s installation instructions, whichever
is greater.
(Q) How do you test a new gas line extension or branch, added to an
existing gas line within the structure?
(A) Section 406.1.3 (2009 NC Gas Code) states that only the new
branch has to be tested. Section 406.1.4 states that you must use
two valves in series with a telltale piece, with valve, between the two
valves to vent any pressure.
2
1)
st
Gas Piping:
Mechanical Q&A 2009
Attention: 3 Denotes a new question!
z Denotes a revised/revisited question.
Quarter
Land Use and Environmental Service Agency
(Code Enforcement)
December 2009
4)
5)
1
nd
2
3)
rd
2)
(Q) What does the new 2009 Energy Code require for duct insulation?
(A) Section 403. of the NC Energy Code states residential supplies
and returns shall be R8 in unconditioned areas. Duct running
through the web of floor truss systems may be R6 to limit duct
compression. Duct installed between conditioned floors need not be
insulated provided there is no condensation. Commercial supplies
and returns shall be R5 in unconditioned areas. Commercial outside
duct shall be R8.
(Q) The new 2009 NC Mechanical Code requires that grease duct be
tested with a light. How will this be accomplished?
(A) The contractor/installer shall call for an inspection after the job is
ready for inspection. The ladders should be in place, the drop
cord/light shall be fished through the duct and any obstacles such as
fans or grills that might obscure the inspection shall be removed.
The light inspection will commence upon arrival. Should the
contractor have concerns about open duct or would like the
inspector on the job for more time, the contractor may secure an
inspection by appointment (Call J. Aidoo (704)353-1273).
(Q) What are the new requirements for duct wrap on type I grease exhaust
in lieu of shaft requirements?
(A) In January 2009 UL, OPL and ICC-ES withdrew the listing and
Legacy reports for enclosure materials that used UL1978 as the
basis for approval instead of the more appropriate ASTM E2336
standard. Projects with permits issued on or after May 1, 2009 will be
required to meet the ASTM E2336 standards.
(Q) Is flex duct allowed in a residential garage?
(A) HVAC systems whose equipment room is located within the
garage shall be constructed of metal (26 gage, Minimum) for all
portions located within or penetrating the rated floor or ceiling.
Systems that serve the living area shall not supply or return from the
garage. Systems dedicated to the garage with not portions
penetrating the rated enclosure may be of duct board or flex duct.
(Q) What are the requirements for an exhaust fan serving a shaft with 22
inch subducts from the several floors of bath rooms.
(A) The fan must be located at the top of the shaft, operate
continuously, and be connected to emergency power.
3
1)
st
Duct:
Mechanical Q&A 2009
Attention: 3 Denotes a new question!
z Denotes a revised/revisited question.
December 2009
Quarter
Land Use and Environmental Service Agency
(Code Enforcement)
8)
9)
3
7)
(Q) When does an architectural ceiling made of decorative lattice become
a smoke or fire contaminant as it pertains to return plenums?
(A) When it is placed above the height of the walls in the room it
serves which would be classified “plenum space”.
(Q) Is there a minimum R rating for ventilation makeup air duct on a
residential structure?
(A) No
(Q) Would the Code require that this ventilation makeup air duct be
filtered?
(A) Yes
(Q) can a duct from an existing heating system be extended to a sun room
addition?
(A) Section 402.3 of the NC Energy Code would allow the extension
provided the duct was zoned.
4th
6)
rd
Duct continued:
Mechanical Q&A 2009
Attention: 3 Denotes a new question!
z Denotes a revised/revisited question.
Quarter
Land Use and Environmental Service Agency
(Code Enforcement)
December 2009
2)
3)
3
(Q) What is the definition of light duty as it pertains to equipment exempt
from exhaust hood requirements?
(A) LIGHT-DUTY COOKING APPLIANCE. Light-duty cooking appliances
include gas and electric ovens (including standard, bake, roasting, revolving,
retherm, convection, combination convection/steamer, conveyor, deck or
deck-style pizza, and pastry),electric and gas steam-jacketed kettles, electric
and gas compartment steamers (both pressure and atmospheric) and electric
and gas cheese melters.
Exception #3 of section 507.2.2 would allow a single light duty appliance to be
exempt from a type II hood as long as the designer accounts for the load in
the HVAC design.
Note:
We may allow a second Light Duty Appliance provided the total grease laden
discharge does not exceed 5 mg/m3 when tested to EPA 202.
(Q) How much area is required to be cleared at the termination of a
residential dryer exhaust installed below grade?
(A) The Code requires 200 square inches be cleared.
(Q) May wooden shelves be placed under a type I hood?
(A) No
4th
1)
rd
Hoods and Exhaust: