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Table of Contents
Chapter 1 Administration
Chapter 2 Definitions
Chapter 3 General Regulations
Chapter 4 Ventilation.
Chapter 5 Exhaust Systems
Chapter 6 Duct Systems
Chapter 7 Combustion Air
Chapter 8 Chimneys & Vents
Chapter 9 Specific Appliances
Chapter 10 Boilers, Water Htrs
Chapter 11 Refrigeration
Chapter 12 Hydronic Piping
Chapter 13 Fuel Oil Piping
Chapter 14 Solar Systems
POLICY
OTHER
Chapter 1 Administration:
(A) (Q) Is it the responsibility of a plans examiner or inspector to inform a designer or contractor
of additional requirements of other State agencies or licensing boards?
(B) No. It is not the responsibility of the inspector or plans examiner. It shall be the
responsibility of the permit holder, design professional, contractor, or occupational license
holder to determine whether any additional requirements exist. 101.5
Chapter 3 General Requirements:
1) (Q) What are the requirements for systems installed in a flood plain?
(A) Section 301.13 Flood hazard: For structures located in flood hazard areas, mechanical
systems, equipment and appliances shall be located at or above the design flood
elevation. Exception: Mechanical systems, equipment and appliances are permittedto
be located below the design flood elevation provided that they are designed andinstalled
to prevent water from entering or accumulating within the components and to resist
hydrostatic and hydrodynamic loads and stresses, including theeffects of buoyancy,
during the occurrence of flooding to the design flood elevationin compliance with the
flood-resistant construction requirements of the International Building Code.301.13.1
High-velocity wave action. In flood hazard areas subject to high-velocity wave action,
mechanical systems and equipment shall not be mounted on or penetrate walls intended
to break away under flood loads. See also section 602.4 for similar the requirements
covering the duct system.
2) (Q) Would the discharge line of an appliance condensate pump need to be protected from
freezing temperatures?
(A) Chapter 307 does not address the protection of condensate discharge lines, installed in
areas subject to freezing temperatures, however, we would be remiss if we did not
require this protection in areas such as a ventilated attic space. Other areas of concern
would be where the line exits the foundation wall. We would “recommend” that these
installations be sloped downward and increasing in pipe size to limit blockages.
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3) (Q) What type of access would be required for a boiler installation where the boiler devices
may be subject to vandalism or component theft?
(A) Chapter 306 covers the typical installation of equipment. Section 105.1 Would allow us
the flexibility to allow alternative access on a case by case basis.
4) Q) Where are the seismic strapping requirements for air conditioners and/or heat
pumps in the NC Mechanical Code?
(A) Seismic requirements and zone information is in the Building Code as
referenced by 301.15 of the Mechanical Code.
5) (Q Do copper condensate lines or return piping of heating/cooling units that are in direct
contact with galvanized sheet metal duct and/or plenum constitute a potential for galvanic
action?
(A) It is recommended that piping be protected from potential corrosion by protecting or
isolating the piping. 307.2.2
6)  (Q) What is the proper way to protect an appliance in a residential garage?
(A) From the information we have from DOI and past practice if you pulled a straight
edge from the garage door opening to the rear of the opening, if the appliance in
question was not in the normal path of the vehicle, then no protection is required.
No what if’s Ref: 303.4
7)  (Q) A mechanical contractor requested an interpretation as to whether traps were required
on the condensate from an evaporator coil and if we knew of any conflicts with the
energy code involving cleanout vent/ tees on a blow-through unit discharging into an
unconditioned area (attic/crawl space)?
(A) The code requires the inspector to rely on the manufacturer’s data to determine if a
trapped drain is required. If any conflicts with other codes are apparent then the
contractor may need to consult with the manufacturer to resolve the problem and
inform the inspector of the issues. Ref: 307.2.4
Chapter 4 Ventilation:
1) (Q) What is the minimum ventilation required for toilet rooms?
(A) Toilet rooms are not considered to be habitable space and so their
ventilation requirements would be found in table 403.3 which would require
mechanical exhaust and not natural ventilation. Note: We have allowed natural
ventilation in the past and we will begin enforcing the mechanical ventilation
requirement on permits obtained after April 1, 2011.
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Chapter 5 Exhaust Systems:
1) (Q) Does Mecklenburg County allow an alternative method for type I hood
clearances?
(A) Mecklenburg County allows the use of NFPA 96, Chapter 4.2.3.2 based
on an interpretation by DOI dated 2/2/2004.
2) (Q) In an automotive repair garage with a vehicle exhaust source capture system per NCMC
502.14, is it permitted to have one (1) –exhaust capture connection for every two (2) bays
or is one connection only allowed per bay?
(A) The Mechanical Code is silent on this question, however the code language gives the
inference that it requires a singular; “a source capture system” for each vehicle or
service bay. One per bay is required. Ref: 502.14
3) (Q) Even though the code requirements have been met for the installation of the grease duct
the contractor wants to add several more cleanout openings because he also has the
maintenance contract on the grease duct system. The duct is only 10 inches by 10 inches
and the code access door manufacturer informs him the smallest door approved for
grease duct installation per code is 12 inches by 12 inches. Can the contractor make his
own door to access the grease duct?
(A) Yes. Where the duct is smaller than the 12 by 12 minimum the mechanical contractor
may provide cleanouts approved by the mechanical official at least equivalent to the
minimum requirements of the code for manufactured access doors. Ref: 506.3.9
4) (Q)The Mechanical inspector has turned a residential range exhaust installation down
because the contractor has used screws to join the pipe together and then sealed the pipe
joints with mastic. The pipe extends up through the roof and is terminated per code. Is this
inspector correct? Is this a code violation?
(A) The inspector may consider this a code violation; reference is 505.1 “smooth inner
walls,” however there are minimal code restrictions on residential hood installations.
While the code reference says smooth we would accept small screws and mastic to
fasten the duct joints together. Ref: 505.1
5) (Q) A contractor asks the inspector if he can combine the bathroom exhaust with the dryer
exhaust to value engineer the job for the owner and appease the Architect who is
complaining about all of the exterior wall penetrations disturbing the ambiance of his
finished exterior walls. Can the inspector allow this installation? Will a redesign in duct
sizing, fittings or joints be required?
(A) No. No comingling of the dryer exhaust is allowed by code. Ref: 504.1
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6) (Q) A battery room is installed in an existing multistory building. The designer says it is
virtually impossible to run the exhaust duct up to the roof because of the tenants and
space in the ceiling above so he wants to run the duct into an area way in the middle of
the building that is enclosed on all four sides similar to an interior courtyard in an office
building. The only thing located in the area way are 10 compressors for AC to the
various building tenants. His problem with running the duct to the area way is that he can
only get 3 feet of clearance to terminate the exhaust duct. Can this installation be allowed
per Code?
(A) No, Ref: 501.2.1 sub (1) for conveyance of flammable/explosive vapors.
7) (Q) A UL listed grease duct installation for a type I hood is called for inspection. Duct joints
are not welded per code requirements; however, the installation instructions show
approved joint connections without welded joints. What would the inspector be required
to inspect? How does the inspector look at the installation for code compliance? What
tests are required for system approval?
(A) Inspection of the manufactured system would have to comply with all standard tests
for grease duct required for type I hoods including 506.3.2.5. Any tests specified in the
manufacturers literature will also be the responsibility of the field inspector. Ref:
506.3.2.5
8) (Q) Under what conditions can an outdoor grill and hood be installed under a covered porch?
(A) The hood would be approved if installed per the manufacturer’s installation
instructions, including the correct fan, and unit sizing-and it is used in a single family
detached dwelling. No townhouse/condo/apartment use would be allowed. Ref: 506.4.1
9) (Q) A manufacturer has submitted a dryer booster fan to be used in a residential application
per IRC 1501. Would the inspector approve the booster fan if the contractor has the
letter on site for the inspection?
(A) Dryer booster fans are not allowed by the code. There is no code language to allow
their use. Ref: 504.1
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Chapter 6 Duct Systems:
1) (Q) What method can be used to protect the opening in a floor/ceiling or roof/ceiling
assembly where supply duct from the HVAC unit penetrates the assembly? NOTE: There
is not a fire damper currently manufactured that is approved for this application when the
multi-story building is classified as an R2 occupancy with type V construction.
(A) The current code approval for this application requires a smoke detector to be
installed in the same room as the HVAC unit that will shut down the unit if smoke is
detected. The smoke detector shall tie in to the smoke detector circuit provided for the
apt/condo unit. A static damper is required at the ceiling penetration of the HVAC duct
penetrations from the unit. This method of protecting the ceiling penetrations is only
approved until a Fire Damper is manufactured that provides adequate protection for
the openings.
2) (Q) What are the minimum requirements for plenum rated materials within an open air
plenum space?
(A) Not required. See plenum definition. Open air returns are typically in habitable areas
and do not have to conform to the material requirements of enclosed plenums.
Example: Home Depot. Ref: Chapter 2 plenum definition. & 602.2.1
3) (Q) Unlisted duct tape has been installed on the metal to metal and flex to metal airduct joints
of a furnace installation in a single-family dwelling. Is it required that the unlisted duct
tape be removed before installing the approved tape or mastic?
(A) No, approved tape may be installed over unlisted duct tape unless the listing, labeling
or manufacturer’s instructions supersede the allowance of such material. Ref: 603.9
4) (Q) What is considered proper access for smoke/fire dampers?
(A) MC 607.5 states that the damper must be accessible for removal/maintenance.
5) (Q) Are fire dampers, smoke dampers, or combination dampers required in walls that
separate a garage from the residential living space in a single family dwelling?
(A) The code has no provisions for a fire damper of any type to be required in this
residential installation. 603.1.2
6) (Q) Are longitudinal seams required to be sealed in a duct used to exhaust a bath fan?
(A) Yes. Our policy has always been to seal the seams in a longitudinal duct run in a
residential application to prevent any duct leakage on the ceiling. Recent DOI
interpretations of the 2012 code MC Section 603.9 back the department position to
seal the exhaust duct. The 2009 code vaguely describes “contamination prevention”
in 601.4 but exempts one and two family dwellings. Ref; 603.9
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7) (Q) A listed and labeled product (return air grill) is being installed in a panned 2 by 4 wall
stud cavity. A return air grill is being installed in the wall cavity at a depth of 1 inch
leaving only 2 inches between the return collar and the filter. Is this installation allowed
by Code?
(A) The inspector must look at the surface area to determine if this installation will meet
code. Ref: 602.3, 605.2
8) (Q) Charlotte Pipe has a new CPVC pipe called ChemDrain with a Zero flame spread rating
and a smoke developed rating of between 8 and 22 based on ULC S102.2. Can we allow
this new pipe in return air plenums?
(A) Yes. As long as it is tested and approved for at least 25-50 smoke and flame spread
rating we would allow the product in return air plenums. Ref: 602.2.1
Chapter 9 Specific Appliances, Fireplaces and Solid Fuel-Burning Equipment:
1) (Q) What is the minimum clearance of a microwave oven hung under an existing stove cook
top? The manufacturer’s instructions require a 24 inch clearance. This clearance will work
but just barely because of the existing cabinet height. The house is in a historic district and
the governing board does not allow removal or alteration of existing cabinets in the district.
Can the inspector allow the manufacturers approved clearance?
(A) Yes. Install the equipment per manufacturer’s clearances. Ref: 917.4
Chapter 10 Boilers, Water Heaters and Pressure Vessels:
(1) (Q) An out of state jurisdiction ask the department about the enforcement of ASME Boiler
and Pressure vessel regulation enforcement for the state of North Carolina. Who
enforces regulations for UNFIRED pressure vessels for (1) Newly installed pressure
vessels to comply with ASME Boiler and Pressure Vessel Code, (2) Repairs and
alterations for existing boilers, and (3) Other regulations or codes that also apply to
boilers?
(A) The Department of Labor Boiler and Pressure Vessel division has primary
responsibility over boiler inspections, however there is a list of exempt boilers. The
exempt boilers are governed by the North Carolina Mechanical and Fuel Gas codes
as enforced by the Office of the State Fire Marshall through the Department of
Insurance. Ref: Ch. 10 and NCGS 95-69.10/ BPV Rules.
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Chapter 11 Refrigeration:
1) (Q) An existing chiller is being replaced. The existing chiller uses R-22. The chiller is in an
existing mechanical room. The new chiller will be using the more environmentally
friendly R-410-A refrigerant. The existing chiller room has a volume of 925 sq. feet and a
cu ft. volume of 12,025. The new chiller has 160 lb of R-410A in its largest refrigerant
circuit. The chillers quantity exceeds the capacity of the room as provided for in the chart
in tbl. 1103.1 2009 NC mech. Code. Table 1103.1 has been changed in the 2012 North
Carolina code and the quantity of R-410 has been reduced to 25lb/1000 cu. ft. There are
no other changes in the code that would change the quantities. Can the code official
allow the new code quantities to be used so a separate mechanical room will not be
required?
(A) Since there are no other changes that would require the designer to build a separate
mechanical room the new table quantity is approved as an alternate design. Ref:
Table 1103.1- 2012 and Table 1103.1- 2009
Policy: Includes Energy Conservation and Re-Hab Codes
1) (Q) When is a refrigeration permit required?
(A) A refrigeration permit is required for any refrigeration equipment required to be
assembled (excluding the walk-in cooler box) OR any equipment required to be hard
wired electrically (not cord and plug type).
2) (Q) Is the outside air make-up air duct located on the non-insulated side of an attic space in
a single family dwelling required to be insulated?
(A) No. The temperature difference between the air in the make-up air duct
and the air temperature in the attic are not sufficient to cause condensate
that would require insulating the duct. Ref: 503.2.7, Exception #2, North Carolina
Energy Conservation Code
3) (Q)When does a Mechanical Inspector enforce the Carbon Monoxide Alarm requirements
adopted by the NC Department of Insurance in One-and-Two-Family Dwellings and
Townhouses? Effective date: January 1, 2011.
(A) 2009 NC Residential Code revisions to Section R313 as provided below:
R313.1.1 Carbon Monoxide alarms. In new construction, dwelling units shall be
provided with an approved carbon monoxide alarm installed outside of each separate
sleeping area in the immediate vicinity of the bedroom(s) as directed by the alarm
manufacturer. R313.1.2 Where required-existing dwellings. In existing dwellings,
where interior alterations, repairs, fuel-fired appliance replacements, or additions
requiring a permit occur, or where one or more sleeping rooms are added or created,
carbon monoxide alarms shall be provided in accordance with Section 313.1.1.
R313.1.3 The required carbon monoxide alarms shall be audible in all bedrooms over
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background noise levels with all intervening doors closed. Single station carbon
monoxide alarms shall be listed as complying with UL 2034 and shall be installed in
accordance with this code and the manufacturer’s installation instructions.
4) (Q Can R-4 insulated Flex be used in Icynene insulated attics where a thermal barrier is
above the ductwork?
(A) Yes. It can be used as long as the attic is now part of the thermal envelope and properly
sealed. Ref: 503.2.7, NC Energy Conservation Code
5) (Q) Does the code limit the noise level produced by heat pumps and air conditioners?
(A) No. There are not any requirements restricting the noise levels of this equipment in the
current code. Local ordinances dictate noise levels and are not enforced by building
code enforcement officials in Mecklenburg County.
6) (Q) When extending gas pipe to non-electrical gas equipment (barbecue, insert, are you
required to bond the existing gas pipe connected to an existing gas or electrical appliance?
(A) No, unless the alteration creates the potential to be energized.
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