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11. Delta Connections — When heaters occur in multiples of
three, they may be connected to, and balanced across, three-
phase lines. The most commonly used connection is the delta
connection illustrated in Fig. 5. Three phase Delta connections
to minimize inductive effect in conduits are made per this dia-
gram. The rule: run all 3 three-phase conductors in the same
conduit as far as possible. For single-phase, run only two con-
ductors and follow the same rule.
FIRE/EXPOSION HAZARD. This heater is not
intended for use in hazardous atmospheres where
flammable vapors, gases, liquids or other com-
bustible atmospheres are present as defined in the
National Electrical Code.Failure to comply can
result in personal injury or property damage.
Before energizing this heater:
1. Be sure all electrical connections are tightly made. Hold ter-
minal with pliers when tightening screw.
2. Be sure that all conductors are properly insulated.
3. Be sure that all element assemblies have been properly
replaced, and that secondary insulation bushings have not been
omitted.
A. Controlling Radiant Intensity
Standard Radiant heaters are built to operate at 40 watts per sq.
inch on the element sheath. When it is desired to reduce radiant
intensity, one or more of the following methods may be used.
1. INPUT CONTROLLERS. These motor-driven cycling
devices can be used to vary heater output capacity from 4 to
100%. They are usually connected in holding coil circuit of
controlling magnetic contactors. See Chromalox Radiant
Heater Manual for further information regarding Input
Controllers and Contactors.
ELECTRIC SHOCK HAZARD. Disconnect all power
before installing or servicing heater. Failure to do
so could result in personal injury or property dam-
age. Heater must be installed or serviced by a
qualified person in accordance with the National
Electrical Code, NFPA 70.
A. To Remove Heating Element
1. Remove terminal cover screws and terminal cover.
2. Disconnect heating element from electrical leads at both ends.
3. Remove screws from porcelain terminal blocks.
4. Remove element support clips and secondary insulating bushings.
5. Lift out elements.
B. To Install Element
Observe instructions for removing elements and proceed in
reverse fashion. Be sure to replace secondary insulating bushings.
WIRING (cont'd.)
OPERATION
2. SOLID STATE THYRISTOR POWER CONTROLLERS.
For best non-contact control of radiant heat, a Series #6
Chromalox Thyristor Power Controller with manual poten-
tiometer setting is recommended. Truly proportional output of
from 0 — 100% can be easily dialed-in to suit the particular
product or process requirements. The Series #6 panels are pre-
engineered, pre-packaged assemblies in an enclosure with cir-
cuit disconnect provided and ready for installation.
B. Maximum Ambient Temperatures
Chromalox Radiant Heaters are not recommended for applica-
tions in ambient temperatures exceeding 450°F. Higher ambi-
ent temperatures mean shorter heater life.
Maximum work temperature in a given time depends on sever-
al factors: Reflectivity of work, specific heat of work, mass of
work, kW input and losses from oven, and time of exposure. As
work temperature increases, the work loses heat by radiation
and by convection to the surrounding ambient. Although it is a
general principle of Radiant Heater application that work tem-
perature conventionally exceeds ambient temperature, in cases
where extremely high work temperatures are desired, it is nec-
essary to enclose the heaters in order to increase the ambient.
If evaporation of a liquid is desired as a result of increasing
work temperature, it is necessary to provide ventilation air in
order to carry away the evaporated liquid. Under carefully
engineered circumstances, a maximum work temperature of
600°F may be attained.
MAINTENANCE
C. Care of Reflectors
Reflectors should be cleaned periodically. A mild soap and
water solution or fine cleaning powder is best although more
drastic means may be required if reflectors are badly soiled by
chemical or other deposits. The reflector is aluminum. DO
NOT use alkali cleaners since alkalies will dull reflector. Mild
non-alkaline cleaners, such as used for scouring kitchen sinks,
may be used. Reflectors are replaceable and may be purchased
from Chromalox.
D. Because of the high temperatures involved, periodically check
and retighten heater terminal connections. This practice will
help to avoid "hot terminals" and the resulting damage to wire
insulation.
E. Because of the fire hazards resulting from a process malfunc-
tion, the related safety control used in the system should be
periodically checked to ensure its proper operation.
-3-
Figure 5
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