Chromalox PK407-4, PK407-3 General, Mounting, Fahrenheit, Sensing Bulb, Capillary Tube

Figure 2

GENERAL

NOTICE: Type AR Thermostats are designed for temperature control service only. Because they do not fail safe, they should not be used for temperature limiting duty.

The system designer is responsible for the safety of this equipment and should install adequate back-up controls and safety devices with their electric heat- ing equipment. Where the consequences of failure could result in personal injury or property damage, back-up controls are essential.

Principle of Operation — Control action of these thermostats is provided through the principle of liquid volume change. With a variation in temperature, the liquid in the sensing bulb expands or contracts, causing a bellows to actuate the switching mechanism.

Housing — The control housing and cover assembly is of heavy- gauge electrical grade plastic.

FIRE/ELECTRIC SHOCK HAZARD. Use AC supply only. Thermostat is not DC rated.

Control Range — The following temperature ranges are available:

Fahrenheit

60° to 250° 200° to 550°

Process Temperature Differential — is variation in controlled process temperature between maximum, when thermostat turns OFF and minimum, when thermostat turns ON. This spread in temperature may be minimized by —

1.Making sure control is mounted to vertical surface (see Step 1, MOUNTING section).

2.Avoiding excess heating capacity (oversized heaters).

3.Locating control sensing bulb in optimum position between heat source and work.

In general, it is difficult to predict the actual operating differ- ential of a given process. Temperature differential may be as low as 4°F for low range controls to as high as 17°F for higher range controls since the differential is a percentage function of the dial range.

Packing Glands — If a sealed or leak-proof connection is required at the point where the capillary enters the oven, tank, pipe or simi- lar equipment, an appropriate packing gland is available as an optional part. (Model CCF-25A, CCF-25D or CCF-25E)

FIRE/EXPLOSION HAZARD. This thermostat 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.

MOUNTING

Note: Do not mount thermostat where it will be subject to vibra- tion, shock, grease, dust, lint or corrosive vapors. Do not mount adjacent to a large magnetic contactor, as vibration and shock will cause thermostat to interact erratically — resulting in chattering of the contactor.

The air temperature in and around the thermostat enclosure should be kept as near to normal room temperature as possible...

never above 150°F.

1. Thermostat must be mount- ed in a vertical position only.

2.Use sheet metal or wood screws through the four 7/32” diameter mounting holes in baseplate to mount control (see Figure 2).

3.For controlling platen or die temperatures, insert entire sensing bulb into drilled holes selected for snug slip fit.

The longer, more sensi- tive Style 9 bulbs should be used for controlling air tem- peratures or pipe line heating.

4.NOTICE:

A.Bending or deforming sensing bulb will alter

control calibration —

requiring recalibration after installation. See CALIBRA- TION section, page 3. If necessary, Style 9 bulbs can be coiled to 1” I.D. (see Figure 3).

B.Do not kink capillary tube. The resulting constrictions in fluid flow can destroy control function or broaden temper- ature differential. Minimum capillary tube bending diame- ter is 1/2” I.D. (see Figure 4).

C.Any deformations of bulb or capillary that result in leakage of fluid from control renders control inoperative.

1”

Figure 3

(Sensing Bulb)

Do Not Bend or

Kink Crimped End

1/2” Rod

Figure 4

(Capillary Tube)

D.Avoid passing control capillary tube through zones whose temperature is in excess of controlled process temperature. Erratic control or destruction of control function may result.