0 mechanical (cont'd), 3 duct furnace airflow (cont'd) – Reznor EEDU Unit Installation Manual User Manual

Page 16

Form I-EEDU, Page 16

6.0 Mechanical

(cont'd)

3/4

(19)

3/4 (19)

(457)

FIGURE 14 -

Duct

Connection

Dimensions -

inches (mm)

NOTE: If the furnace is equipped with a

unit-mounted ductstat (Option AG3), the

sensing bulb must be removed from the

mounting bracket (save the retainer clip)

before the ductwork can be attached.

See instructions in Paragraph 8.4.3 for

re-mounting the sensor.

Size

75, 100 12-1/2"

318mm

125, 140 15-1/4"

387mm

170

18"

457mm

200

20-3/4"

527mm

225

23-1/2"

597mm

250

26-1/4"

641mm

300

31-3/4"

806mm

350

37-1/4"

946mm

400

42-3/4"

1086mm

6.3.4 Duct Connections

6.3 Duct Furnace

Airflow (cont'd)

• Type of Ductwork - The type of duct installation to

be used depends in part on the type of construction

of the roof (whether wood joist, steelbar joist, steel

truss, pre-cast concrete) and the ceiling (whether

hung, flush, etc.).

• Ductwork Material - Rectangular duct should be

constructed of not lighter than No. 26 U.S. gauge

galvanized iron or No. 24 B & S gauge aluminum.

• Ductwork Structure - All duct sections 24 inches

(610mm) or wider, and over 48 inches (1219mm) in

length, should be cross broken on top and bottom

and should have standing seams or angle-iron

braces. Joints should be S and drive strip, or locked.

• Through Masonry Walls - No warm air duct should

come in contact with masonry walls. Insulate around

all air duct through masonry walls with not less than

1/2" (1" is recommended) of insulation.

• Through Unheated Space - Insulate all exposed

warm air ducts passing through an unheated space

with at least 1/2" (1" is recommended) of insulation.

• Duct Supports - Suspend all ducts securely from

adjacent buildings members. Do not support ducts

from unit duct connections.

• Duct Sizing - Proper sizing of the supply air

ductwork is necessary to ensure a satisfactory

heating installation. The recognized authority for

such information is the Air Conditioning Contractors

Association, 2800 Shirlington Road, Suite 300,

Arlington, VA 22206 (www.acca.org). A manual

covering duct sizing in detail may be purchased

directly from them.

• Removable Panels - The ducts should have

removable access panels on both upstream and

downstream sides of the furnace. These openings

must be accessible when the furnace is in service

and should be a minimum of 6" x 10" in size so

smoke or reflected light may be observed inside the

casing to indicate the presence of leaks in the heat

exchanger. The covers for the openings must be

attached in such a manner as to prevent leakage.

See

FIGURE 15A.

• Supply Air Duct/Furnace Horizontal Connection

- The seal between the furnace and the duct must

be mechanical. Duct connection should be made

with "U" type flanges on the top and bottom of the

connecting duct. Slide the duct over the flanges of the

heater giving an airtight fit. Provide "U" type channels

for the other side flanges to ensure tight joints. Use

sheetmetal screws to fasten ducts and "U" channels

to the furnace flange. See

FIGURES 15B and 15C.

CAUTION: Joints where ducts attach to furnace must be sealed securely to prevent air leakage into

burner rack area. Leakage can cause poor combustion, pilot problems, shorten heat exchanger life

and cause poor performance. See Hazard Levels, page 2.

2) Subtract the allowable CFM from the actual CFM of the installation to determine

how much air must be diverted through the bypass duct.

Example: Blower CFM 3000

Allowable CFM -1790

Bypass CFM 1210

3) Go to the column in the Bypass CFM Chart that is closest to the pressure drop

through the heater. Move down in that column until you find the larger CFM

closest to the answer in Step 2).

Example: Go to P.D. Column .35; move down to Bypass CFM 1520

4) Move to the left column to find out the required size of the bypass duct.

Example: Bypass Duct Size is 5"

Locate the bypass duct on the side of the furnace opposite the controls and 2" from the

heat exchanger side panel. Extend the bypass duct 18" (457mm) beyond the furnace

on both the inlet and outlet ends.

NOTE: Not all capacities

are covered in the

bypass duct chart. If your

installation is not covered,

consult your Reznor

representative or the factory

to determine the appropriate

size of the bypass duct.

Directions for Sizing Bypass Duct (cont'd)

Requirements and Suggestions for Connecting and Installing Ducts