Fenwal Temperature Control

Electromechanical Temperature Controls

Fenwal controls manufactures mechanical temperature control devices. The switches are bi-metal switches that use expansion and contraction to cause the switching. This type of mechanism can be extremely accurate but lacks in displaying the temperature. In todays computerized/automated world this type of control tends to be used for over temperature control or alarm as opposed to the process control point.

The FENWAL THERMOSWITCH was invented in the 1930's to control fish tanks, irons and other simple applications, but it was soon realied that they could be used for industrial, commercial and process applications. They're durability, reliability and accuracy are the strong points for THERMOSWITCHES.

THERMOSWITCH® Temperature Controllers are tubular devices featuring an outer shell made of high-expanding metal and internal struts made of low-expanding metal, with a pair of electrical contacts between them.

When the temperature of the media being measured changes, a corresponding change in the spacing of the contacts provides instant on/of

f control with a small differential, resulting in +1°F precision, depending upon the application.

Series 17000, 18000

PROBE TYPE, SPDT

Series Features:

Fast Response - outer shell is the active sensing member

Precise Control - substantially reduces overshoot & undershoot

Extreme Sensitivity - slow make and break contacts, resolution 0.1°F (0.05°C)

Vibration Resistance - best possible control under difficult physical conditions

Cost-effective, Compact, Simple-In-Operation

Numerous Mounting Configurations

Specifications:

Overlapping ranges from -100°F to 600°F (-73° to 316°C)

1200 Watt resistive load at 120/240 VAC

5/8" diameter THERMOSWITCH® models available

Agency Approvals:

UL and CSA

Applications:

Food service equipment

Packaging equipment

Laminating presses

Agricultural equipment

Fenwal's snap action liquid filled THERMOSWITCH® controllers, the expandable liquid surrounding the bellows is in direct contact with the temperature sensing outer shell providing a fast response for accurate temperature sensing.  The 20000 series switches are no longer available.  Sords Electric has a few left, email us with a part number.

Series 20000, 21000, 22000

PROBE TYPE, SPST

Series Features:

Individually field adjustable micro-switches

One or two micro-switches

Specifications:

Overlapping ranges from 0° to 300°F (-18° to 148°C)

Ratings to 15 A at 120/250 VAC

Factory preset temperatures available

NEMA 4 enclosure available

Agency Approvals:

UL, CSA

Applications:

Food service equipment

Medical vaporizers

Commercial dishwashers

Based on the differential expansion of metals principle, an increase in temperature causes the stainless steel outer case of the Surface Mounting THERMOSWITCH® controller to expand at a greater rate than the internal bridge assembly.

Because the case is in direct contact with the heated surface, a temperature change is sensed almost instantaneously.

Series 30000

SURFACE MOUNT TYPE, SPST

Series Features:

Fully adjustable

Narrow temperature differential

Compact size

Economical

Factory preset temperatures

NEMA 4 enclosure

Specifications:

Overlapping ranges from 50° to 600°F (10° to 315°C)

1200 Watt resistive load at 120/240 VAC

Minimum contact rating of 100,000 cycle

Options:

Cross mounting bracket

Slotted and extended adjusting screw lengths

Factory preset temperature

Special range calibration

Agency Approvals:

UL

Applications:

Plastic laminating presses

Food warming trays

Popcorn machines

Domestic appliances

Industrial steam cleaners

Sords Electric and Control

Heat Trace Cable - Heating Cable

Heating Cable

As winter is upon us, it is time to think of freeze protection and keeping pipes warm. Heating Cable is one way to do this, we sell electric heat trace. All heat tracing requires INSULATION. It will not work without it.

There are two main types of heating cable; self regulating and constant wattage.

Self-regulating cable
Self Regulating Heating Cable has two parallel conductors or bus wires extruded in a polymer core. The core's resistance changes porportionally with temperature.

The key to understanding Self-regulating cable is the output adjusts proportionally to the cable sheath temperature not the temperature of the pipe heated.

There is no direct feed back for the pipe temperature. Most self-regulating cables are designed to give their rated wattage at 50 degrees F. The wattage output willexceed the rated wattage when the cable temperature is below 50 degrees and the lower the cable temperature the larger this wattage i.e. amperage is. INRUSH!! A high start up current is the result. Tight temperature control is also more difficult with self-regulating cable, because the wattage output is always changing seeking 50 degrees F on the cable not the pipe or fluid in the pipe.

Self-regulating cable works quite well for freeze protection applications. Freeze protection and low temperature applications that do not require very tight control. The inrush can be considered on the design of wiring and breakers, and there are some other cost savings to consider. A thermostat is recommended for most applications. However, when there are several very short runs or several pipe size changes one ambient thermostat can save on a job.

The semi-conductive core contains a graphite network, which allows electricity to flow from one bus wire to the other. When the core is dense and colder, there are many paths for electricity to take through the graphite network, producing more heat.

Since the core material expands as it heats, the graphite network is elongated, disrupting some of the paths. More and more paths are disrupted as heating continues until the system reaches self-controlled thermal stability. When the core material cools it contracts, reconnecting some of the electrical paths in the graphite network, and more equivalent heat is produced.

This temperature response occurs independently at each point along the heater. If an externally produced high temperature occurs next to a low temperature in the cable, each section of heating cable will adjust its own heat output in relation to its own local requirements.

Advantages:

Cut to fit in the field.

Possible lower operating cost.

Possible lower installation cost.

Wide variety of wattages

Most tolerant to overlapping

Low Cost

Disadvantages:

High start-up currents

Difficult to precisely control temperature

Not well suited for procsss control

Low design temperatures

Constant Wattage Cable is made up with two parallel conductors or wires. These wires have a heater wire wrapped around and connected in approximately 2-foot intervals in parallel. This design provides constant wattage output or a uniform output all along its length. The heater wires are designed such that if any section of cable should fail the rest of the heater would continue to operate without change.

Constant wattage cable should NOT be overlaped. The effect of double the wattage where the cable crosses will cause high temp failures.

The constant wattage output makes maintaining higher and more accurate process temperatures easier. This cable is well suited for freeze protection and many low temp process control applications.

This cable can be cut in the field. When terminated the last 2-foot heater section becomes a cold sections "unheated". This provides an unheated section of cable to penetrate the insulation, enter the junction box and make up power connections. Constant Wattage Cable needs a thermostat on each pipe and each pipe size in order to maintain accurate temperature control.

Advantages:

Cut to fit in the field.

Easily controlled

Built in cold length at every power connection

Wide variety of wattage outputs

Low cost

480 Volt Cable available

Design Temperatures up to 500° F

Disadvantages:

Requires pipe sensing thermostats

CANNOT be overlaped