Watlow WATROD Duct Heater - Manual (Page 8)

WATLOW IND.
WATROD Duct Heater Installation & Maintenance Manual
I&M NUMBER: 316-42-6-1 Page: 8
Date:6/11/2008 Rev: 3.00
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WATLOW IND.n # 6 INDUSTRIAL LOOP RD. n HANNIBAL MO, 63401n PHONE 573-221-2816 n FAX 573-221-3723
When installed horizontally the user must determine whether the duct wall has sufficient strength to
support the unit by the flange only. A frame may be necessary to support the unit in the duct. This frame
can have tapped holes or captive nuts to receive mounting bolts. An access panel in the duct can
facilitate installation.
DANGER: HAZARD OF FIRE. Electric heaters are capable of developing high temperatures so extreme
care should be taken to locate heaters in safe environments. Mounting heaters in atmospheres
containing combustible gases and vapors should be avoided. According to article 501 of the NEC, the
maximum surface temperature of the heater shall not exceed 80 % of the auto-ignition of the surrounding
atmosphere when the heater is continuously energized. Care should also be taken to keep combustible
materials far enough away to be free of the effects of high temperatures.
9. Mounting Holes / Bolts
Standard mounting holes are
3/8” (9.53 mm) diameter with a tolerance of 0.005” (0.13 mm). The center
line to center line spacing on the mounting holes of the flange have a tolerance of 0.015” (.38 mm),
therefore the mounting holes on the duct should also have a center line to center line tolerance of 0.015”
(0.38 mm).
For duct heaters with Carbon Steel Flanges 5/16” – 16 UNC-2B Grade 5, SAE J429 (M8 x 1.25 x length
ASTM A449) bolts should be used. For 304 Stainless Steel Flanges 5/16” – 16 UNC-2B Grade B8,
ASTM A320 (M8 x 1.25 x length ASTM A320) bolts should be used. Recommended washers are 5/16”
(7.94 mm) spring type in the corresponding material. For other flange materials consult the factory. The
thread engagement on the bolts should be equal to or exceed the cross section diameter of the bolt.
It is important when tightening the bolts that enough torque is used to seat the gasket. A minimum
torque of 50 ft/lbs is recommended to seat a 1/8” (3.18 mm) thick gasket of the materials recommended
in Section 6.
Consult the factory for proper mounting bolt size if mounting hole size is not 3/8” (9.53 mm) diameter.
10. Wiring
WARNING; HAZARD OF ELECTRIC SHOCK. Any installation involving electric heaters must be
grounded to earth to eliminate shock hazard.
Electrical wiring to the heaters must be installed in accordance with the National Electric Code and any
state and local electrical code by qualified personnel.
Consult wiring diagram supplied with the unit for correct feeder wires connections. If one is not supplied,
the factory should be consulted for the appropriate wiring diagram. Feeder wire should be properly
selected based on amperage, electrical power rating, ambient temperature, and type of environment.
Feeder wire should also be housed in either rigid or flexible conduit which carries the same classification
as the heater enclosure. It is the users responsibility to properly size and install feeder wire.
Feeder wire line connections may be made directly to stud terminals or box type compression fittings.
Box type compression fittings will accept a #4 AWG maximum wire while stud terminals will accept a
#10 ring connector(T&B, Amp, etc.). It is essential that these connections be tight. Stud terminals should
be tightened to a maximum torque of 20 in-lbs while the bottom nut is supported. Ground connection
(color coded "green") is supplied inside the housing for ground wire.
Line voltage must be equal to or less than rating stamped on the heater assembly.