As with any mechanical equipment, personal injury
can result from contact with sharp sheet metal
edges. Be careful when you handle this equipment.
CAUTION
3 − Heaters should be located so that they are
protected from damage from aircraft or other
appliances needed for servicing of aircraft. Refer
to requirements of the enforcing authorities.
In a confined area, the heater must be installed in
accordance with the current edition of CSA-B149
installation compliance codes. Be sure to check with
local codes and ordinances for additional requirements.
Additional Requirements
The Commonwealth of Massachusetts stipulates the
following additional requirements:
1 − Gas furnaces shall be installed by a licensed
plumber or gas fitter only.
2 − The gas cock must be T handle" type.
Duct Heater Installation
Connect the return air and supply air ducts to unit. The
unit must be installed on the positive pressure side of the
circulating air blower. The CFM through the unit must be
adjusted within the range listed on the unit rating plate.
The air flow pattern must be reasonable and even.
Failure to comply with these adjustments may void
the warranty.
The connecting duct to the unit shall
have removable access panels on both upstream and
downstream sides of the duct heater. These openings
shall be accessible when the furnace is installed in
service and shall be of such size that smoke or
reflected light may be observed inside the casing to
indicate the presence of leaks in the heat exchanger.
The cover for the openings shall be attached in such a
manner as to prevent leaks.
A duct furnace shall be installed with an inlet duct
which will provide air distribution equivalent to a
straight run of duct having the same cross-sectional
area as the inlet connection and not less than 2
equivalent diameters in length. See figure 1.
SINGLE BLOWER APPLICATION
(Top View)
155
TRANSITION
HED UNIT
BLOWER
AIR FLOW
DUCT
LENGTH “L"
The formula for computing duct length L" is:
4WH
W = WidthH = Height (Inlet)
W + H
Duct length L" is computed as shown by the formula, and
rounded to the nearest whole number.
MODEL
INLET DUCT −− in. (mm)
DUCT
NO.
WIDTH
HEIGHT
LENGTH “L"
HED−75
15
13−3/8
29
(381)
(340)
(737)
HED−100, −125
15−5/8
15−3/8
31
(397)
(391)
(788)
HED−150
17−1/8
15−3/8
33
(435)
(391)
(839)
HED−200,−25O,
35−1/16
15−3/8
43
−300
(891)
(391)
(1093)
FIGURE 1
NOTE
− The appliance may be installed downstream
from refrigerated units supplying air below the dew
point of the ambient air surrounding the appliance. A
¼” barbed connection under the burner box is provided
for condensate drainage.
The duct connection from the blower to the unit must be
a smooth transition. Any side of the transition shall not
taper more than 15°. Where elbows or turns are used,
proper air distribution can be obtained by the use of
properly designed air turns.
NOTE
− Do not install heater in explosive or flammable
atmosphere, laden with grain dust, sawdust, or similar
airborn materials. Do not install heater where direct
contact with water may occur.
Install the unit in the desired location as governed by
clearances, vent connection, air direction, gas supply,
electrical supply and service accessibility.
Improper installation, adjustment, alteration, service
or maintenance can cause property damage,
personal injury or loss of life. Installation and
service must be performed by a licensed
professional installer (or equivalent), service agency
or the gas supplier.
IMPORTANT
In these conditions, condensate will form in the duct
heater. A condensate drain connection is provided
on the duct heater for condensate removal. Installer
must make adequate provisions to route
condensate from this drain connection. The
condensate drain should be checked periodically
and cleaned as required.
CAUTION
4
