Bulletin 30-034.009
Page 5
Copyright © 2022 Unico Inc.
All furnaces are suitable for zero clearance between the
duct and combustible material. For servicing the control
box, allow enough room (“L”) to swing the cover open
and to service the blower module (Figure 5).
The hinge
is located on the electric furnace control box closest to
the discharge end of the electric furnace.
"L"
Service clearance for horizontal installations
(Top view)
IL00493.cvx
Electric Furnace
Main Plenum
Blower module
Airflow
Models
"L"
WON0202, WON0502
13.0
WON0752, WON1002
16.0
WON1502, WON0504,
WON0754, WON1004,
WON1504
21.0
WON2002
24.0
Figure 5. Service clearance for horizontal
installations
For round metal plenum systems, use the correct
diameter metal pipe adapter for your plenum size. For
example, the 1218 and 2430 systems typically use 7-
inch (178mm), the 3642 system uses 9-inch (228.6-
mm), and the 4860 systems use 10-inch (254mm)
diameter pipe. Figure 6 shows the installation of the
Plenum adapter (10-inch round plenum adapter is
already attached).
IL00381a.cvx
Electric
Furnace
Plenum
Adapter
Figure 6. Start Collar Installation
Always allow a minimum of 24 inches (610 mm) of
straight duct between the discharge side of the electric
furnace and any tee or elbow as shown in figure 7.
IL00068a.CVX
Dimensions inches [mm]
24"
[610mm]
minimum
Electric
Furnace
Elbow or
Tee
Air Handler
Figure 7. Minimum distance from duct to furnace
The furnace also includes a 9½ × 9½-inch (241 × 241-
mm) square plenum adapter. If the plenum is smaller,
then use a reducer fitting. Fiberglass reducers are
available to reduce the 9½-inch (241mm) square duct to
8½-inch (216-mm) or 6½-inch (165mm) square duct as
shown in table 7. Alternately, the reducer can be
eliminated if you use the metal plenum adapter shown
in table 6.
The plenum adapters are designed to fit inside the
square duct and are secured with sheet metal screws and
washers. The joint must be sealed per UL-181A-M or
UL-181A-P as seen in figure 8 to ensure an airtight
system.
Note: All metal connections must be mechanically
fastened with sheet metal screws and the joints and
seams must be taped with UL-181A-P foil faced tape or
sealed with UL-181A-M duct mastic.
IL00377a.cvx
Electric
Furnace
Plenum
Adaptor
Square
Fiberglass
Reducer
1 1/2" (38mm) flat head sheet
metal screws and 1" (25mm)
O.D. washers
Fiberglass
Reducer
Plenum
Adapter
UL 181A-M
Mastic Closure
Figure 8. Square Duct Installation (Furnace shown
with optional square plenum adapter)