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CHAPTER 3 GENERAL REGULATIONS
1) (Q) A cooling tower is being erected on the roof of a High Rise building. It is being
assembled using parts that are individually listed. Would this installation be allowed
under the 2012 code?
(A) No. The inspector would not allow the installation to be constructed, however, if the
design is sealed by a professional engineer, registered in the State of North Carolina, the
inspector must accept the design and construction of the equipment. Ref: 301.4,
Exception 2 , 2012 MC
2) (Q) Exhaust Ductwork is installed on the back wall of a garage. It extends out about 4 feet
from the wall into the garage area at an elevation of 6 feet above the floor. How
should the ductwork be protected from vehicle damage per code?
(A) Protection may not be required depending on what types of vehicles are worked on in
the garage, however, reflective tape or a bollard would provide adequate protection.
Ref: 303.4, 2012 MC
3) (Q) A barbeque grill has been installed on the covered porch of a residence. The owner has
constructed the hood himself per NSF requirements. Should the hood be allowed by
the Mechanical Inspector?
(A) NO. The grill is an appliance that is listed for outdoor use. To allow the grill to be under
a covered porch, indoors, per code, the grill would have to have either a type I
commercial hood or a hood built by the manufacturer that is approved and compatible
with the grill. 304.1, 2012 MC
4) (Q) A tractor trailer has a trailer 11 feet 6 inches high. It is backing into a loading dock
inside a public garage. The ceiling of the garage is 20 feet high. What is the minimum
height to the bottom of the unit heater from the top of the trailer if the unit heater is
installed directly over the trailer?
(A) Unless the manufacturers installation instructions specify a greater height the unit
heater shall be at least 1 foot 6 inches from the top of the trailer to the bottom of the
unit heater. Ref: 304.6, 2012 MC
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5) (Q) Can mastic be used in the joints for bonding stacked masonry instead of mortar or
surface bonding cement?
(A) Mastic is required to protect duct joints by adhering to metal duct which is generally
a non porous dry surface when applied. It is not approved for the installation specified
above. 304.1, 304.10.3, 2012 MC
6) (Q) If we are changing out a like for like roof top unit and it is over 16' above grade level
access does it have to have permanent access?
(A) No. 306.5, 2012 MC
7) (Q) I am installing a wood burning stove in my home. When installing the appliance I
will always be able to use table 308.6 for unlisted equipment to reduce clearances.
Is this a true statement?
(A) No. If the solid fuel burning appliance is labeled with clearances those
clearances shall be used when installing the solid-fuel burning appliance. Ref:
308.7, 2012 MC
8) (Q) What improvement in sizing mechanical equipment for single family dwellings and
duplexes has made it possible in the 2012 code to provide equipment that is properly
sized. (So equipment is not under sized nor is it over sized)?
(A) The use of Manual S for sizing requirements. Ref: 312.1, 2012 MC
CHAPTER 4 VENTILATION
1) (Q) To properly balance air flow and have a constant temperature exchange between all
spaces in an occupied building should ventilation be required at a constant value for
building occupants?
(A) NO. Ventilation shall be provided during the periods that a room or space is occupied.
Ref: 401.3, 2012 MC
2) Situation: We are working on a Nail Salon that will be going in a building downtown.
From speaking with the owner they will not be doing acrylic nails, and nearly all their
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products will be organic. In moving forward with the design it has been determined that
per 2012 NCMC (table 403.3 footnote b) we are not allowed to reticulate any air,
therefore, one would think all the air conditioning in the space must be exhausted. This is
not the case per DOI. In conversations with Billy Hinton concerning this section, it is his
interpretation that the reference to, “all air supplied to such spaces” means the
ventilation air supplied, and does not include the air for conditioning the space, therefore,
air for conditioning the space could be returned to the space, but not returned to any
other spaces. Due to the occupancy location on a lower floor of a multi-story building the
designer would like to utilize one of the existing exhaust shafts near the space. One of the
shafts is for toilet exhaust; one shaft is for the pool equipment room. Both exhaust fans
are located on the roof; therefore the shafts are negatively pressurized.
(Q) From reading through Chapter 5 of the code I cannot find any section that will not
allow me to combine the exhaust from the nail salon with either of the existing shafts.
Is this allowed?
(A) Yes. The ventilation requirement for a nail salon, (as determined by 2012 NC
mechanical code and footnote b in table 404.3), would require mechanical exhaust for
the entire amount of ventilation air supplied for the space for the nail stations. The
code would not require all the conditioned air to be exhausted from the space. The
exhaust from the nail stations may be connected to the exhaust for environmental air
since the system is negatively pressurized. Ref: 403.2.1, Table 403.3 foot note b, 2012
MC
3) (Q) We traded emails recently regarding the 2012 code requirement for exhaust in
residential kitchens, such as apartments and condos. The requirement stems from the
footnotes on the ventilation calculation schedule. I was told by another engineer
recently that Mecklenburg County will not require the kitchen exhaust if we are
utilizing natural ventilation for the apartments.
(A) We have not received an interpretation for the table below from DOI at this time.
For Natural verses Mechanical Ventilation we have sent a clarification document to
list conflicts between the two codes.(See charts below for comparisons) 401.2, 2012
MC vs. R303.4, 2012 Residential Building Code.
Date: May 11, 2012
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To:
DOI-David Conner/Dan Dittman
Re:
Differences in the 2012 NC Mechanical code vs. the 2012 NC Residential Code.
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Below is a comparison of the 2 codes (NCRC & NCMC) and the sections related to Natural
ventilation. There is some language in multiple sections that seem to conflict along with the available
commentary that shows some differences as well. Side by side comparison is listed below to
illustrate, question related to application are listed below.
NCRC (Residential)
NCMC (Mechanical)
R303.1 Habitable rooms. All habitable rooms shall have an
401.2 Ventilation required. Every occupied space shall be
aggregate glazing area of not less than 8 percent of the floor
ventilated by natural means in accordance with Section 402 or
area of such rooms. Natural ventilation shall be through
windows, doors, louvers or other approved openings to the
outdoor air. Such openings shall be provided with ready access
or shall otherwise be readily controllable by the building
occupants. The minimum open able area to the outdoors shall
be 4 percent of the floor area being ventilated.
by mechanical means in accordance with Section 403.
Exceptions:
1. The glazed areas need not be open able where the opening is
not required by Section R310 and an approved mechanical
ventilation system capable of producing 0.35 air change per
hour in the room is installed or a whole-house mechanical
ventilation system is installed capable of supplying outdoor
ventilation air of 15 cubic feet per minute (cfm) (78 L/s)
per occupant computed on the basis of two occupants
for the first bedroom and one occupant for each additional
bedroom.
HABITABLE SPACE. A space in a building for living,
sleeping, eating or cooking. Bathrooms, toilet rooms, closets,
halls, storage or utility spaces and similar areas are not
considered habitable spaces.
OCCUPIABLE SPACE. An enclosed space intended for
human activities, excluding those spaces intended primarily
for other purposes, such as storage rooms and equipment
rooms, that are only intended to be occupied occasionally and
for short periods of time.
R303.4.1 Intake opening. Mechanical and gravity outdoor
air intake openings shall be located a minimum of 10 feet
401.4 Intake opening location. Air intake openings shall
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(3048 mm) from any hazardous or noxious contaminant,
comply with all of the following:
such as vents, chimneys, plumbing vents, streets, alleys,
parking lots and loading docks, except as otherwise specified
in this code. Where a source of contaminant is located within
10 feet (3048 mm) of an intake opening, such opening shall be
located a minimum of 2 feet (610 mm) below the contaminant
source. For the purpose of this section, the exhaust from
dwelling unit toilet rooms, bathrooms and kitchens shall not be
considered as hazardous or noxious.
1. Intake openings shall be located a minimum of 10 feet
(3048 mm) from lot lines or buildings on the same lot.
Where openings front on a street or public way, the distance
shall be measured to the centerline of the street or
public way.
2. Mechanical and gravity outdoor air intake openings shall
be located not less than 10 feet (3048 mm) horizontally
from any hazardous or noxious contaminant source, such
as vents, streets, alleys, parking lots and loading docks,
except as specified in Item 3 or Section 501.2.1.
3. Intake openings shall be located not less than 3 feet (914
mm) below contaminant sources where such sources are
located within 10 feet (3048 mm) of the opening.
R303.5 Outside opening protection. Air exhaust and intake
401.5 Intake opening protection. Air intake openings that
terminate outdoors shall be protected with corrosion-resistant
openings that terminate outdoors shall be protected with
screens, louvers or grilles. Openings in louvers, grilles and
corrosion-resistant screens, louvers or grilles having a
minimum opening size of 1/4 inch (6 mm) and a maximum
opening size of 1/2 inch (13 mm), in any dimension. Openings
shall be protected against local weather conditions. Outdoor air
exhaust and intake openings shall meet the provisions for
exterior wall opening protectives in accordance with this code.
R303.1 Habitable rooms. All habitable rooms shall have an
screens shall be sized in accordance with Table 401.5, and
shall be protected against local weather conditions. Outdoor air
intake openings located in exterior walls shall meet the
provisions for exterior wall opening protectives in accordance
with the International Building Code.
[B] 402.1 Natural ventilation. Natural ventilation of an
occupied space shall be through windows, doors, louvers or
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aggregate glazing area of not less than 8 percent of the floor
area of such rooms. Natural ventilation shall be through
windows, doors, louvers or other approved openings to the
outdoor air. Such openings shall be provided with ready access
or shall otherwise be readily controllable by the building
occupants. The minimum openable area to the outdoors shall
be 4 percent of the floor area being ventilated.
other openings to the outdoors. The operating mechanism for
such openings shall be provided with ready access so that the
openings are readily controllable by the building occupants.
R303.1 Habitable rooms. All habitable rooms shall have an
[B] 402.2 Ventilation area required. The minimum openable
aggregate glazing area of not less than 8 percent of the floor
area to the outdoors shall be 4 percent of the floor area being
area of such rooms. Natural ventilation shall be through
windows, doors, louvers or other approved openings to the
outdoor air. Such openings shall be provided with ready access
or shall otherwise be readily controllable by the building
occupants. The minimum openable area to the outdoors shall
be 4 percent of the floor area being ventilated.
ventilated.
R303.2 Adjoining rooms. For the purpose of determining
[B] 402.3 Adjoining spaces. Where rooms and spaces without
light and ventilation requirements, any room shall be
considered as a portion of an adjoining room when at least
one-half of the area of the common wall is open and
unobstructed and provides an opening of not less than onetenth of the floor area of the interior room but not less than 25
square feet (2.3 m2).
openings to the outdoors are ventilated through an adjoining
room, the opening to the adjoining rooms shall be unobstructed
and shall have an area not less than 8 percent of the floor area
of the interior room or space, but not less than 25 square feet
(2.3 m2). The minimum openable area to the outdoors shall be
based on the total floor area being ventilated.
Exception: Openings required for light and/or ventilation
Exception: Exterior openings required for ventilation shall
shall be permitted to open into a thermally isolated sunroom
or patio cover of not less than one-tenth of the floor area of
be permitted to open into a thermally isolated sunroom
addition or patio cover, provided that the openable area
between the sunroom addition or patio cover and the interior
room has an area of not less than 8 percent of the floor area of
the interior room or space, but not less than 20 square feet
(1.86m2). The minimum openable area to the outdoors shall be
the interior room but not less than 20 square feet (2 m2). The
based on the total floor area being ventilated.
addition or patio cover, provided that there is an openable
area between the adjoining room and the sunroom addition
minimum openable area to the outdoors shall be based upon
the total floor area being ventilated.
R303.3 Bathrooms. Bathrooms, water closet compartments
and other similar rooms shall be provided with aggregate
glazing area in windows of not less than 3 square feet (0.3 m2),
one-half of which must be openable.
No separate listing for Bathrooms
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Exception: The glazed areas shall not be required where
artificial light and a mechanical ventilation system are
provided. The minimum ventilation rates shall be 50 cubic feet
per minute (24 L/s) for intermittent ventilation or 20 cubic feet
per minute (10 L/s) for continuous ventilation. Ventilation air
from the space shall be exhausted directly to the outside.
Questions:
1. The definitions between the 2 codes are different NCRC uses habitable rooms and the
NCMC uses occupiable spaces. It appears that the NCMC has more requirements than the
NCRC in that bathrooms, toilet rooms, laundry rooms, hallways, and possible closets if using
natural ventilation would be required openings to the exterior that match floor area, NCRC
has natural ventilation minimum opening for bathroom and toilet rooms but NCMC doesn’t.
Does the NCMC require hallways, laundry rooms, closets and bathroom/toilet rooms to have
windows to the exterior or adjoining room option if using natural ventilation?
2. In reference to both codes is a door or window considered an intake opening?
3. If a door/window is an intake opening is screening required for opening protection.
4. If a door/window is an intake opening, does the lot line or between building requirements
apply to NCRC as listed in the mechanical code, would this be the interpretation related to
potential contaminants.
5. The IRC and the IMC commentary that support the 2012 codes (2009 version) has conflicting
information related to what is a intake opening and when screening is required (Windows)
and Lot line issues. The IMC clearly has requirements for lot lines that the IRC doesn’t talk
about and the IRC has no reference to “except windows and doors” as listed in the IMC
commentary for intake openings. How should this be applied?
6. Should the requirements match in both codes?
4) (Q) Are screens allowed on outside vents?
(A) Yes. 401.5 MC and IBC, sizing Table 401.5, 2012 MC (Exception: Dryer Vents)
CHAPTER 5 EXHAUSTS SYSTEMS
1) (Q) What would be an adequate amount of make-up air in a residential occupancy if the
dryer is exhausting 50 cfm and the Kitchen hood is exhausting through the roof at the
same time at 40 cfm. How much make- up air would be required?
(A) It depends. Make up air is not required in residential occupancies if natural ventilation
is used per 402, however, if 403 is used then make up air would be required.
Ref: 501.3 exception. 2012 MC
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2) (Q) Would environmental air exhaust ever be considered hazardous or noxious per the
Mechanical code?
(A) No. 501.2.1 #3, 2012 MC “Such exhaust shall not be considered hazardous of noxious.”
3) (Q) A garage is installing a ventilation system to avoid consideration by the electrical code
to be a class 1 division 2 area. Should the fan motors be interlocked with the
electrical receptacles and /or equipment/appliances in the garage to shut down the
power to the apparatus above if the ventilation fans lose power?
(A) Yes. “Electrical equipment and appliances used in operations that generate explosive
or flammable vapors, fumes or dusts shall be interlocked with the ventilation system
so that the equipment and appliances cannot be operated unless the ventilation fans
are in operation.” 503.1 MC 2012
4) (Q) The contractor has the installation instructions for dryer vents for a specific make of
Maytag dryer that will be installed in all the apartments in a 40 unit complex. The
Manufacturers’ instructions show lengths of duct runs that exceed the minimum code
and no equivalent lengths for the fittings used with the dryer duct. Should the
inspector approve the installation?
(A) NO. The inspector should require the contractor to supply an equivalent length chart
for fittings from the manufacturer or re-calculate the runs using the equivalent length
chart in the code (table 504.6.4.1) Ref: 504.6.4.2, 2012 MC
5) (Q) A mechanical contractor is insulating the makeup air duct to a type 1 hood with
standard fiberglass insulation. He has installed the insulation all the way to the hood.
(a) Would this be allowed by the 2012 mechanical code?
(b) What should be used as an alternate method if this is not allowed?
(A) (a) The standard duct insulation should not be allowed within 18 inches of the hood
because of the heat generated by the hood. 506.3.6, 2012 MC
(b) A rated fire wrap material could be used to wrap the duct within 18 inches of the
hood termination. 506.3.6, exception # 3, 2012 MC
6) (Q) A placard has been provided five feet above the dryer exhaust duct connection on the
wall with the dryer manufacturer’s information for duct equivalent length. Does this
meet the identification requirements of the 2012 code for length identification?
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(A) Yes. It would be considered permanent identification. Ref: 504.6.5 MC 2012
7) Situation: A restaurant has installed two barbeque cookers under type I hoods which
exhaust high-medium- & low heat cooking appliances. The food services inspector
discovered the cookers and reported it to the Code Enforcement Department.
Answer a. through e. below.
a. (Q) The owner says the cookers are safe as installed and they are code compliant. (1) Is
the owner correct? (2) What are the obvious code violations related to this
installation?
(A) (1) The owner is not qualified to determine the safety of the equipment. The restaurant
installed the cookers without plans or permits. Require cookers to meet the code. Ref:
106.1, 106.2.1 Administrative Code.
(2) Since the cookers use solid fuel and gas for heat for cooking they are classified as
extra-heavy-duty cooking appliances and cannot be located under the same type I
hood with high-medium & low heat appliances. Ref: 507.3.4 MC
b.(Q)Three Type 1 hoods for the cooking equipment are connected to single grease
exhaust duct that exits the building into a covered parking garage. (1) Can the separate
hoods required for the two Extra-heavy-duty cooking appliances be combined with the
existing grease duct exhaust if properly sized? (2) May the grease duct from the extraheavy-duty appliances exhaust into the covered Parking deck?
(A) (1) No. Hoods for the two extra-heavy–duty barbeque cookers shall exit the building
through a separate exhaust duct system. The two cookers may, however, be under the
same Type 1 hood rather than having separate hoods or under a hood or hoods listed
for the application by the manufacturer. The exhaust systems may also be combined
since both are extra-heavy-duty cooking appliances. Ref: 507.2.4, 506.3.5 exception # 4
(2) No. It is a violation to have the current hood system grease duct exit the building
into a parking garage. The new grease duct shall exit the building either vertically or
horizontally to the outside. Ref: 506.3.12.2, 506.3.12.3, 506.5.5
c.(Q) Are there more stringent exhaust requirements for hood exhaust CFM and safety
devices for a hood over an extra-heavy-duty cooking appliance than over high-mediumlow & heat cooking appliances?
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(A) Yes, see ventilation tables. Ref: 507.13.1
d.(Q) The manufacturer of the barbeque cookers sends a letter to the Code Administrator
with information on the engineering of the cookers. The letter explains how the cookers
are engineered/designed to make it virtually impossible for a spark or ember to be
exhausted into the duct system. The letter also states the cookers can be located
under the same type I hood with high-medium-low heat cooking appliances. Further, the
letter states the information will be included in the manufacturer’s literature in the
future on the two cookers installed at the restaurant plus 5 other models of cookers with
similar exhaust characteristics. Should the Code Administrator accept the manufacturer’s
letter and approve the cookers? (note: The manufacturer does not have a registered PE
on their staff.)
(A) The code official may accept the letter under the conditions stated above if a
professional engineer who works directly for the factory provides a letter under his seal
that the changes to the literature will be made. The letter must also provide information
as to how the engineering/design of the product is such that a spark or ember can never
be exhausted from the cookers that may cause a grease fire in the ductwork and ignite
fires in heavy-medium or light duty appliances that may also be under the hood. Ref:
105.2 MC
e. (Q) Should the Code Administrator require a third party test that confirms the cookers
will not emit sparks or embers into the grease duct system before he approves the
cookers?
(A)This may be one solution the Code Administrator would allow. Ref: 105.3, 105.3.1,
105.3.2 (MC).
8) (Q) a. What is the new clearance requirement in the 2012 Mechanical Code from operable
openings for all environmental air ducts? b. Can environmental air ducts ever be
considered hazardous or noxious?
(A) a. Three feet, Ref: 501.2.1 (MC)
b. No. Ref: 501.2.1 (MC)
9) (Q) Is exhausted air ever allowed to discharge into walkways or hallways?
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(A) No. Ref: 501.2.1.1, 2012 MC
10) (Q) Will the mechanical code allow exhaust outlets to discharge at or below the design
flood level (elevation)?
(A) No. 501.2.1 # 4 required 2012 MC, interpreted as required by the 2009
code (2009 501.4 ref. Ch 6, [B] 602.4)
11) (Q) (a) Are all occupancies required to provide pressure equalization when the system is
exhausting quantities of air? (b) Are there specific occupancy exceptions for
appliances and fans and if so what are they?
(A) [note: The 2009 code exempted R 3 occupancies only with no mention of specific
appliances or exhaust exceptions.] (a) The 2012 code exempts dwelling units in R 2
occupancies. (b) The 2012 code does not require pressure equalization for domestic
exhaust systems in residential occupancies and similar uses (domestic clothes dryers,
domestic range hoods, domestic bathroom exhaust). 501.3 and 501.3 exception,
2012 MC
12) (Q) A Mechanical Contractor is installing a 100 cfm bathroom exhaust fan in the kitchen
ceiling for a new housing development to meet requirements of table 403.3 footnote
b in the 2012 Mechanical Code. He is not installing a kitchen hood over the 4 burner
electric range and the manufacturer does not call for a hood.
Does this installation meet the code for table 403.3 ft. note b requirements of the
2012 Mechanical Code?
(A) Yes. If a mechanical ventilation means is provided per 403.1 MC 2012.
[See 401.2. Ventilation shall be required either by using 402 (Natural Ventilation) or
403 (Mechanical Ventilation).] [See 505.1 Exception 1 “where natural or mechanical
ventilation is “otherwise provided” listed and labeled ductless range hoods shall not
be required to discharge to the outdoors.] Question: If the manufacturer does not
require a hood over the cooking equipment would a ductless hood be required? No.
13) (Q) Is a Type I or a Type II hood required over an electric egg cooker that operates under
3000 Watts?
(A) No hood is required. Ref: 507.2.2 Exception #4, 2012 MC
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14) Project Information: The mechanical design for the a Plant Upgrade consists of the
installation of an air cooled chiller and a chilled water pumping system on the roof adjacent
to the existing air cooled chillers.
The electrical design for this work included an electrical equipment room located within the
garage having a UPS system having closed cell batteries. The electrical equipment room
design has a 2 hour fire rating and includes an air conditioning unit for heat removal with an
exhaust air system, if required, for the removal of hydrogen gas vapors.
The closed cell batteries are limited to the UPS equipment and emit very little hydrogen gas.
As a result, these batteries do not require an exhaust air system by the mechanical code.
However, to be safe, the owner has designed an exhaust air system to protect the electrical
equipment room in the event of an emergency.
The exhaust air system will be normally off and will be controlled by a hydrogen gas detector
installed within the electrical equipment room. When activated, the hydrogen gas detector
will start the exhaust air system and provide a local audio and visual alarm at the electrical
equipment room and at the building BAS system.
The exhaust airflow rate from the electrical equipment room is 150 CFM and it discharges
into the garage which is open to atmosphere for its ventilation air requirements. As a result,
it is our opinion that the exhaust air system is discharging to the outside and that it will have
no impact on the garage environment. The plans examiner has turned the plans down
requiring the exhaust to go outside the building. He says garage or loading dock is not
considered outside the building per mechanical code. The exhaust duct also has fire dampers
in three locations where it penetrates fire rated walls. The plans examiner will not allow fire
dampers in a hazardous exhaust system and is requiring the installation to be in shaft from
the electrical room to the outside wall penetration.
(Q) What can be done to allow the protection as shown on the plans?
(A) The plans examiner is correct. If your intent is to protect the electrical room from a
possible emergency situation then the installation as described by the plans examiner
is in compliance with minimum code. You have two choices. Meet the code minimums
described or remove the emergency system.
Ref: 510.1, 510.5.7, 510.6.1, 510.6.3 MC 2012
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CHAPTER 6 DUCT SYSTEMS
1) (Q) DOI, September 1, 2011, 2012 MC
If two or more air-handling systems serve a common space and one or more of these
systems serve additional spaces and the aggregate capacity of the combined systems
exceeds 2,000 cfm, what are the requirements for smoke detectors per Section
606.2.2?
(A) Section 606.2.2 requires that when two or more air systems serve common supply or
return ducts or plenums with a combined design capacity greater than 2000 cfm, the
return system shall be provided with smoked detectors. Section 606.2 states that
smoke detectors are not required where the air distribution system is incapable of
spreading smoke beyond the closing walls, floors and ceiling of the room or space
win which the smoke is generated. If two or more systems serve a common space, but
do not share common ducts or plenums, and each system has a design capacity of
2,000 cfm or less, no smoke detector is required. If their combined design capacity is >
2,000 cfm, and no single unit has a design capacity of 2,000 cfm or more, no smoke
detector is required because they do not share common ducts or plenums.
If multiple systems share common ducts or plenums and the distribution system is
incapable of spreading smoke beyond the enclosure of the room or space where the
smoke is generated, and then no smoke detector is required.
Keywords: smoke detection system control. 602.2, 2012 MC
2) (Q) Is painting exposed galvanized duct allowed by code for weather protection?
(A) Weather protection would not be required if the ductwork installation is approved by
the manufacturer for outdoor locations. Ref: 303.6, 603.1, MC 2012
3) (Q) Does a filter box have to be manufactured of can it be constructed in the shop of the
Mechanical Contractor?
(A) The Mechanical Contractor may construct the box to meet the code. 603.1, 2012 MC
4) (Q) What method can be used to protect the openings in a floor/ceiling or roof/ceiling
assembly where supply air duct from the HVAC unit penetrates the membrane of the
assembly? The type of occupancy is R2 multi-story with type V construction.
Note: The Mechanical Code calls for either a shaft, 607.6.2 #1, or a listed ceiling
radiation damper installed at the ceiling line, 607.6.2 #2, and a listed ceiling radiation
damper installed at the diffuser with no duct attached 607.6.2 #3 (supply plenum).
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(A) There is an issue that needs to be addressed with 607.6.2 #2. UL 555C and 607.3.1
would require the radiation damper to have dynamic closure because the unit fan will
continue to run in a fire or smoke condition. 607.3.1 States; “Only fire dampers listed
or labeled for dynamic systems shall be installed in heating, ventilating, an airconditioning systems designed to operated with fans on during a fire.” There is no
shut down required by code for the fan of an air handler in an apartment HVAC
system for example, therefore, the code and UL 555C require a dynamic type
damper for this installation. Per current DOI information a dynamic radiation damper
listed for mounting in the membrane ceiling of the penetration shall be used. As an
alternate method the air handler must be shut down in case of fire. This can be
accomplished by installing a smoke detector in the room adjacent and open to the air
handler. You are no longer required to tie it into the smoke detector system of the
apartment unit. If you opted for the smoke detector you still are required to protect
the penetration with a radiation damper, however, since you have provided a means to
shut the air down via the smoke detector you can install a standard radiation damper
with static and not dynamic closure. These are the only two methods approved at the
present time. Ref: 607.6.2 #2, 607.3.1, UL 555 C, 2012 MC
CHAPTER 11 REFRIGERATION
1) (Q) What is the proper procedure to use for changing out the outside condenser only in a
mixed system where the old evaporator continues to be used? Current system
refrigerant is R22 and the new refrigerant will be R 407 C. (Both are Class A1)
(A) Recovered refrigerants shall meet 1102.2.2.2 requirements. 1101.8 notification of
code Official of change of refrigerant. 105.5 equipment re use. 304.1 manufacturers
data req’d. See also 301.1.1, All references in this answer are from the 2012 MC
.
GENERAL INFORMATION (Admin. Code/ Mech. Code Admin. Section/ Policy)
1) (Q) Are permits required for B vents when a re-roof permit is pulled for a building with gas
flues penetrating the roof?
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(A) Yes. Alteration of the vent will require a permit. Ref: (102.1/GS 87-21/GS 153-327
Admin. Code), (102.9 2012 MC). A letter is on the Meckpermit.com web site under the
Mechanical Section click on “news and updates” there is a link on that page for the reroof permit requirements.
2) (Q) Unitary equipment is being installed in a hotel room. E.g. ptac unit in a hotel. Are
permits required for this installation?
(A) If this is a like for like change out permits are not required. If it is a new installation it
should have permits and inspections if it has a hidden drain/ electrical connection.
Ref: 106.1 Administrative codes.
3) (Q) What types of installations do not apply to a refrigeration trade or business and are not
required to be installed by a refrigeration contractor?
(A) House Bill 1105 was recently passed by the General Assembly and signed into law by
Governor Perdue. Changes to the law are summarized as follows:
Section 1 provides that “refrigeration trade or business” does not apply to the following: (1)
The installation of self-contained commercial refrigeration units equipped with an original
equipment manufacturer (OEM) molded plug that does not require the opening of service
valves; (2) the replacement of lamps, fuses and door gaskets; and (3) the installation and
servicing of domestic house-hold self-contained refrigeration appliances equipped with an
OEM molded plug connected to suitable receptacles which have been permanently installed
and do not require the opening of service valves.
4) Situation per Designer: A couple of weeks ago we discussed an old (approx. 35 years)
building (approx. 15,000 sq. ft.) utilizing the original hallway for the return. The ceiling is
extremely tight and there is no real room or access or practical method for adding a return
duct. It is served now by a couple of self-contained single zone units utilizing boiler hot water
and condenser water. We want to replace the ancient units with split systems with the AHU
installed in the same mechanical rooms, with condensing units on the roof and utilizing the
same single zones – no changes to ductwork. There is really no other practical/efficient/cost
effective way to replace the ancient units and get rid of the ancient boilers and cooling
towers. We know we need to submit the mechanical, electrical, and structural but really
need to know about the hallway return before we spend a lot of effort and money. When we
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talked before you indicated that this hallway return could be grandfathered since it is very
close to being like-for-like and there is no work other than replacing the central unit.
(Q) Can we still utilize the hallways for returns?
(A) Yes. Since you are doing away with an ancient cooling tower and boiler you we will
need a split system with a condenser on the roof. There will be no changes outside of
the mechanical room and roof. The installation will be allowed per the conditions
specified. 105.3, 2012 MC
5) (Q) What are the current requirements for installing Carbon Monoxide detectors in
residential single family dwellings, duplexes and townhomes? Is the requirement
the same for commercial construction?
(A) In general, a change out of fossil fuel equipment in a residence will require the addition
of a Carbon Monoxide Detector per GS. CO2 detectors are currently required adjacent
to each sleeping area per BCC rules. An all electric residence is exempt unless
they currently have an existing attached garage or are adding a new attached garage
or have or are adding a fireplace. If these conditions are present Carbon Monoxide
Detectors are required even if they do not have fossil fuel equipment. Fossil fuel fired
equipment such as a hot water heaters in a hut attached to the house are exempt from
the CO2 detector requirements, however, a gas pack or other appliance that is
communicating with the inside of the house is not exempt. The “special exemptions”
only apply to single family dwellings, duplexes and townhomes. Not required
for commercial occupancies. If a “plug in type or table model” Carbon Monoxide
detector will be used the inspector shall have ready access to the detector on the
premises. It must be in the box and readily accessible for the inspector. Having an
empty box for the inspector or taping a box to the inside of a window is not acceptable.
6) (Q) What are the plan review requirements for compliance with the new energy code
when a plan is submitted for an addition to a single family home to RTAC? The
contractor is submitting plans for an addition. The plans show extending the existing
duct and using the existing HVAC system.
(A) RTAC will not be checking the plans for energy code requirements.
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7) (Q) What tools are currently available to help inspectors with Energy Code field
compliance? (Ref. Dept. of Energy information below, will discuss DOI information
under training information later on the agenda)
(A) Per the meeting on energy code on Friday May 18th at the Dept of energy site has both
a residential and commercial checklist for the IECC codes. See the link below.
http://www.energycodes.gov/arra/compliance_checklists.stm
8) (Q) (1) Would the 2012 Energy Code require the inspector to witness a duct leakage test for
a single family dwelling? (2) Is a whole house or partial blower door test
required to be witnessed by the inspector?
(A) (1) No. 402.4.2 EC (2) Yes. 4032.2 EC
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