Chromalox PG421-1 Operation, Before energizing this heater, Maximum Ambient Temperatures

8.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.

9.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.

Wrong Right

Radiant

Heaters

L1

L2

Figure 6

L1

L2

3 Conductors

in 1 Conduit

A	B C D	E	F	Radiant
				Heaters

L1

L2

L3

3Conductors in 1 Conduit

Figure 7

OPERATION

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 terminal box cover has been properly replaced, and that secondary insulation bushings have not been omitted.

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 magnetic contactors. See Chromalox Radiant Heater Manual for further information regarding Input Controllers and Contactors.

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.

Maximum Ambient Temperatures —

Chromalox Radiant Heaters are not recommended for applica- tions in ambient temperatures exceeding 450°F. Higher ambient 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 gener- al principle of Radiant Heater application that 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 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.