Current through September 18, 2024
Authority: IC 22-13-2-13
Affected: IC 22-12; IC 22-13; IC 22-14; IC 22-15
Sec. 87.
(a) Supply
systems shall be as follows:
(1) Supply ducts
and any dampers contained therein shall be made from galvanized steel,
tinplated steel, or aluminum, or shall be listed Class 0, Class 1, Class 2 air
ducts. Class 2 air ducts shall be located at least three feet (3') from the
furnace bonnet or plenum. A duct system integral with the structure shall be of
durable construction that can be demonstrated to be equally resistant to fire
and deterioration. Ducts constructed from sheet metal shall be in accordance
with the following Table No. 4B.
TABLE NO. 4B
| Minimum Metal Thickness for Ducts* |
| Duct Type |
Diameter or Width |
| 14 inches or less |
over 14 inches |
| Round |
0.013 in. |
0.016 in. |
| Enclosed Rectangular |
0.013 in. |
0.016 in. |
| Exposed Rectangular |
0.016 in. |
0.019 in. |
*When "nominal" thickness is specified, 0.003 inch shall be
added to these "minimum" metal thicknesses.
(2) Sizing of Ducts. Ducts shall be designed
so that when a labeled forced-air furnace is installed and operated continually
at its normal input rating in the mobile structure, with all registers in full
open position, the static pressure measured in the duct plenum shall not exceed
that shown in Table No. 4B or exceed that shown on the label of the appliance.
When an air-cooler coil is installed between the furnace and the duct plenum,
the total static pressure between the furnace and the coil shall not exceed
that shown on the label of the furnace. The minimum dimension of any branch
duct shall be at least one and one-half inches (1 1/2"), and of any main duct,
two and one-half inches (2 1/2").
(3) Airtightness of Supply Duct Systems. A
supply duct system shall be considered substantially airtight when the static
pressure in the duct system, with all registers sealed and with the furnace air
circulator at high speed, is at least eighty percent (80%) of the static
pressure measured in the furnace casing, with its outlets sealed and the
furnace air circulator operating at high speed. For the purpose of this
subdivision and (b), pressures shall be measured with a water manometer or
equivalent device calibrated to read in increments not greater than one-tenth
inch (1/10") water column.
TABLE NO. 5B
| Maximum Allowable Static Pressures in
Supply Duct Systems |
| Input to Forced-Air Furnace, Btu/hr |
External Static Pressure Inches Water
Column Measured at the Furnace Outlet |
| Temperature of Outlet Air Determined by
Function of Limit Control |
|
|
Above 165°F |
165° F or Less |
| 55,000 and under |
0.10 |
0.20 |
| Over 55,000 to 80,000 |
0.10 |
0.24 |
| Over 80,000 to 100,000 |
0.15 |
0.30 |
(4)
Expandable or Multiple Mobile Structure Connections. An expandable or multiple
structure may have ducts of the heating system installed in the various units.
The points of connection must be so designed and constructed that when the
mobile structure is fully expandable or coupled, the resulting duct joint will
conform to the requirements of this section.
(5) Air supply ducts that are not located
within the heated side of the mobile structure insulation having an R factor of
at least four (4) shall be insulated.
(6) Supply ducts within the mobile structure
but not within insulation described in (a)(5) shall be insulated with rigid
insulation having a thermal insulation (R) not less than 2.5 or flexible
insulation having a thermal insulation (R) not less than three (3) with a
continuous vapor barrier having a perm rating of not more than 1.0.
(7) Supply ducts exposed directly to outside
air, such as under chassis crossover ducts, shall be insulated with material
having a thermal insulation (R) of not less than 4.0 with continuous vapor
barrier having a perm rating of not more than 1.0.
(8) Aluminum foil used as a vapor barrier
shall be at least two (2) mils in thickness.
(b) Return air systems shall be as follows:
(1) Return Air Openings. Provisions shall be
made to permit the return of circulating air from all rooms and living spaces,
except toilet room(s) and kitchen, to the circulating air supply inlet of the
furnace.
(2) Duct Material. Return
ducts and any diverting dampers contained therein shall be in accordance with
the following:
(A) Portions of return ducts
directly above the heating surfaces, or closer than two (2) feet from the outer
jacket or casing of the furnace shall be constructed of metal in accordance
with Table No. 4B of this section or shall be listed Class 0 or Class 1 air
ducts.
(B) Return ducts, except as
required by (a) above, shall be constructed of one inch (1") (nominal) wood
boards (flame spread classification of not more than 200), other suitable
material no more flammable than one inch (1") board or in accordance with
(a).
(C) The interior of
combustible ducts shall be lined with noncombustible material at points where
there might be danger from incandescent particles dropped through the register
or furnace such as directly under floor registers and the bottom of vertical
ducts or directly under furances having a bottom return.
(3) Sizing. The cross-sectional areas of the
return air duct shall not be less than two (2) square inches for each one
thousand (1,000) Btu/hour input rating of the appliance. Dampers shall not be
placed in any return air duct, except that a diverting damper may be placed in
a combination fresh air intake and return air duct so arranged that the
required cross-sectional area will not be reduced at all possible positions of
the damper.
(4) Permanent
Unclosable Opening. Areas not served by return air ducts or closed off from the
return opening of the furnace by doors, sliding partitions or other means shall
be provided with permanent unclosable openings in the doors or separating
partitions to allow circulated air to return to the furnace. Such openings may
be grilled or louvered. The net free area of each opening shall be not less
than one (1) square inch for every five (5) square feet of total living area
closed off from the furnace by the door or partition serviced by that opening.
Undercutting doors connecting the closed-off space may be used as a means of
providing return air area. However, in the event that doors are undercut, they
shall be undercut a minimum of two inches (2") and not more than two and
one-half inches (2 1/2"), and no more than one-half [sic.]
(1/2") of the free air area so provided shall be counted as return air
area.
(c) Joints and
Seams. Joints and seams of ducts shall be securely fastened and made
substantially airtight. Slip joints shall have a lap of at least one inch (1")
and shall be individually fastened. Tape or caulking compound may be used for
sealing mechanically secure joints. Where used, tape or caulking compound shall
not be subject to deterioration under long exposures to temperatures up to
200° F. and to conditions of high humidity, excessive moisture, or
mildew.
(d) Supports. Ducts shall
be securely supported.
(e)
Registers or Grills. Fittings connecting the registers or grills to the ducts
system shall be constructed of metal or material which complies with the
requirements of Class 1 or 2 ducts as stated in the Indiana Mechanical Code
([675 IAC 18-1 [675 IAC
18-1 was repealed filed Oct 28, 1988, 3:00 p.m.: 12 IR
588, eff Jan 2, 1989. See
675 IAC 18-1.3.]).
Registers or grills shall be constructed of metal or conform with the Indiana
Mechanical Code (675 IAC 18-1
[675 IAC 18-1 was repealed filed
Oct 28, 1988, 3:00 p.m.: 12 IR 588, eff Jan 2, 1989. See
675 IAC 18-1.3.]).
Floor registers or grills shall resist without structural
failure a two hundred (200) pound concentrated load on a two inch (2") diameter
disc applied to the most critical area of the exposed face of the register or
grill. For this test the register or grill is to be at a temperature of not
less than 165° F. and is to be supported in accordance with the
manufacturer's instructions.
