Chromalox S-RAD-2 - Manual (Page 2)

WIRING
Hazard of Fire. In the case of solvents of an explo-
sive nature, ventilation air must be in sufficient vol-
ume to dilute the solvent vapor so that explosive
mixtures cannot occur. In order to comply with the
standards of safety required by the insurance com-
panies, ventilation protection and other facilities
must be in accordance with National Fire Protection
Association Bulletin No. 86, entitled “Standard for
Class A Ovens and Furnaces”. This bulletin may be
obtained from the Association at 1 Batterymarch
Park, Quincy, MA 02269.
Before energizing this heater:
1. Be sure all electrical connections are tightly made.
2. Be sure that all conductors are properly insulated, and that they
will not chafe at the heater wire entrance due to expansion and
contraction of the heating element.
3. Be sure that all terminal covers 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 usualy connected in holding coil circuit of
magnetic contactors. See Chromalox Radiant Heater
Manual for further information regarding Input Controllers
and Contactors.
2. SOLID STATE THYRISTOR POWER CON-
TROLLERS — For best non-contact control of radiant
heat, a Series #6 Chromalox Thyristor Power Controller
with manual potentiometer 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 assem-
blies in an enclosure with circuit disconnect provided and
ready for installation.
B. Maximum Ambient Temperatures —
Chromalox Radiant Heaters are not recommended for applica-
tions in ambient temperatures exceeding 450
O 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 radia-
tion and by convection to the surrounding ambient. Although it
is a general principle of Radiant Heater application, the work
temperature conventionally exceeds ambient temperature, in
cases where extremely high work temperatures are desired, it is
necessary to enclose the heaters in order to increase the ambi-
ent. If evaporation of a liquid is desired as a result of increas-
ing 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
O F may be attained.
OPERATION
ELECTRIC SHOCK HAZARD. Any installation involv-
ing electric heaters must be performed by a quali-
fied person and must be effectively grounded in
accordance with the National Electrical Code to
eliminate shock hazard.
1. Electrical connection to the Radiant Heater is made through
one opening tapped for 1 /
2
” connector. Opening is in the top of
the extruded heater housing, near the terminal end.
2. Wiring should be run in flexible or rigid metal conduit and
must be installed in accordance with local codes and the
National Electrical Code by a qualified person.
CAUTION: High temperatures will oxidize cop-
per. Do not use copper wire in connecting this
heater. Insulated, nickel-plated copper wire is
recommended.
3. Access to Radiant Heater terminals is obtained by removing
the two screws in the terminal cover.
4. A sufficient length of this wire (not less than 12”) should be
used to extend from each heater terminal into a connection box
location where the temperature does not exceed 300
O F.
5. Assemble terminal, screw and wire as shown in Figure 5.
6. Tighten the terminal screws securely with a screwdriver.
Note: Where circuit wiring is installed in locations of high
ambient temperature, conductors should be insulated in accor-
dance with requirements for temperature and voltage.
7. SERIES CONNECTION of Radiant Heaters of equal volt
and watt rating is permitted in all line voltages up to 600 volts.
In making such series connections it is necessary to observe the
“right” (series-parallel) connection rather than the “wrong”
(parallel-series) connection both shown in Figure 6. If heaters
are connected according to the “wrong” illustration, failure of
any heater will cause progressive failure of other heaters still
operating.
8. 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 Figure 7.
Three phase Delta connections to minimize inductive effect in
conduits are made per this diagram. The rule: run all 3 three-phase
conductors in the same conduit as far as possible. For single-phase,
run only two conductors and follow the same rule.
Figure 6 — Series Connection
Figure 7 — Delta Connection
Figure 5 — Tightening Terminal Screws
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