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107
HF Series Open Coil Element Duct Heater
General
1. Provide open coil, electric duct heaters, as manufactured and as listed in the schedule.
2. Power voltage and phase, control voltage, wattage, duct size, number of steps to be as per schedule.
3. Heaters to be either Slip-in or Flanged type as called for.
4. Three phase heaters shall have balanced three phase steps unless specified otherwise.
5. All heaters to be ETL listed for zero clearance to combustible surfaces and bear the ETL label.
6. All heaters shall meet the requirements of the latest National Electric Code.
7. Standard terminal box, recessed terminal box, standard control cabinet, remote control cabinet as well as element
housing and racks all to be made of heavy gauge galvanized steel. (Aluminized steel optional).
8. All heating coils to be made of high grade Nickel/Chromium resistance wire and terminated by means of a loop
of wire being sandwiched between stainless steel or Nickel plated washers and terminal hardware. All terminal
hardware to be insulated from the heater by a two piece ceramic bushing.
Element Assembly
1.
To be of “Module” design with each module independently and easily removable
from the terminal box or control cabinet.
2.
Each module to contain no more than 2 layers of element coils so that any one
coil may be replaced without disturbing others.
3.
Element coils of each module to be on staggered spacing so that all coils per
module will be in the air stream, and shadowing (overheating) and/or blank
areas eliminated.
Element Housing
1.
To be of No. 18 gauge galvanized (aluminized) steel and to be of roll-formed
construction with multiple brakes and ribs for stiffness and rigidity.
Element Rack
1.
To be constructed of No. 20 gauge galvanized (aluminized) steel and formed with
multiple brakes and ribs for stiffness and rigidity.
2.
Ceramic coil supports to be floating, but contained and easily replaceable.
3.
Ceramic coil insulators to be on staggered spacing per rack to eliminate blank
areas in the air pattern thru the heaters, and provide uniform heating over the
entire cross section of the element.
4.
Racks to support element coils on no more than 3 1/2” centers.
Terminal Box or Control Cabinet
1.
Shall be constructed of heavy gauge galvanized steel (aluminized optional)
and in sizes up to 18” X 18” shall be No. 20 gauge and over to be No. 18 gauge.
All boxes to have a solid cover, of the same gauge, complete with a piano type
hinge on the longest side, approved tool operated latch and pull ring. Covers
over 48” long to be provided with two latches and pull rings.
2.
Insulation consisting of 1/2” high density fiberglass will be provided, attached
to the cabinet, between the cabinet and the heating section.
3.
Recessed terminal boxes used when ducts are internally insulated, or in air handling
units, to be of the same general construction as item 1 above.
Airflow Direction
Heaters will be interchangeable for mounting in a horizontal or vertical duct except when
position sensitive Mercury contactors, SCR’s or capillary type limit controls are built-in. In
these cases, airflow direction is as specified.
Safety Controls
1.
Primary over temperature protection shall be provided by built in disc type
automatic reset thermal cutouts for duct heaters up to 10’ in width. Heaters over
40” high require two cutouts. Capillary type automatic reset thermal cutouts are
required for any heater 10’ wide or over. Capillary type controls to be UL listed
and of the “fail safe” type.
2.
Secondary over temperature protection shall consist of a sufficient number of
load carrying replaceable disc controls to de-energize the elements if the
primary system fails.
3.
Fuse link type heat limiters shall not be acceptable. All manual safety devices
shall be resetable thru the terminal box without removing the heater from the
duct.
Wiring Diagrams
1. A separate, complete and specific wiring diagram shall be permanently attached to each heater. Typical wiring
diagrams are not acceptable.
2. Control and line terminals in each heater shall be marked identical to the wiring diagram.
Heater Controls
1. All heater controls shall be factory mounted and wired.
2. Contactors shall be definite purpose type. No application type relays will be acceptable.
3. All controls shall be furnished as specified.
Product Specifications
MINIMUM DUCT
SIZE 8” X 6”
MAX KW 20 KW
PER SQ. FT.
Note:
Duct Heaters are available
up to 1000KW. KW and stages
shown above are limited example
of available models.
LINE
VOLTS KILOWATTS STAGE
120
208
240
0.5-2.5
1
2.6-5.0
5.1-8.0
8.1-11.0
11.1-15.0
15.1-19.0
2
19.1-24.0
24.1-28.0
28.1-30.0
30.1-34.0
3
34.1-38.0
38.1-42.0
42.1-46.0
46.1-51.6
51.7-55.0
4
55.1-60.0
277
0.5-2.5
1
2.6-5.0
5.1-8.0
8.1-11.0
2
11.1-15.0
480
600
0.5-2.5
1
2.6-5.0
5.1-8.0
8.1-11.1
11.2-15.0
2
15.1-19.0
19.1-24.0
24.1-28.0
3
28.1-30.0
30.1-34.0
34.0-39.9
40.0-44.0
44.1-48.0
48.1-53.0
53.1-56.0
56.1-60.0