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All Temperature Control
applications must consider the desired degree of accuracy
and repeatability required, voltage and wattage of the
heater load to be controlled, whether indication is required,
where the control is to be mounted, and appropriate terminal
enclosure.
Call
ASB Heating Elements Limited for Technical Assistance:
1-800-265-9699
 Microprocessor
Based Temperature Controls and Controllers
Temperature control is
essential for the best productive use of your electric
heaters. One of the biggest advantages of electric heat
is the ability to precisely control the heater output
to match the work demand
There are 3 basic temperature
control devices, and each of these devices has a wide
range of features and options:
- bulb and capillary -
mechanical action
- surface mount - differential
expansion
- electronic, microprocessor
based controls
Bulb and Capillary
Bulb and Capillary Controllers
have a sensing bulb at the end of a small capillary tube.
A liquid expands and contracts with temperature change
in the sensing bulb. The capillary tube transmits the
force created by the liquid volume change to a bellows
assembly. The set point determines the amount of force
required to make the mechanical contact snap from and
open, or closed, position to the opposite position. He
amount of force required to make the action happen determines
the controls differential. The differential is typically
+ -5% of the scale range.
These controls are rugged,
durable, and come with high current carrying capacity.
Typical temperature ranges and currant ratings are:
Temperature Ranges
- -16 to 40°C (0-100°F)
- 10 to120°C (50-250°F)
- 70 to 280°C (160-540°F)
- 160 to 370°C (320-700°F)
Power Ratings
- up to 240 volts, 25-amp
single pole, single throw (SPST)
- up to 240 volts, 25-amp
double pole, single throw (DPST)
- up to 600 volts, 15-amp
triple pole, single throw (TPST)
Surface Mount
The B-1200 temperature
control is a small, but sensitive temperature control.
The slow make and break action of the bi-metal strut assembly
gives you excellent repeatability. Once set this device
will precisely maintain your temperature.
Electronic - Microprocessor
Based Controls
Electronic controllers
offer the widest range of temperature controller available.
From open circuit board, non-indication, on-off units
to full scale, dual indication fully programmable PID
units. Combining these controllers with mercury contactors,
solid state relays, (SSR's), or silicone controlled rectifiers
(SCR's) allow you to have precise temperature control,
regardless to the number of kilowatts used to heat your
process.
Common Control Nomenclature
for Bulb and Capillary, and surface mount controls:
- opens on temperature
rise - the contacts are non powered and mechanical force
opens and closed the contacts, used to control heating
loads
"
- closes on temperature
rise - the contacts are non powered and mechanical force
opens and closed the contacts, used to control cooling
loads, or energize an over temperature alarm
- differential - number
of degrees required to make contacts change position
- remote mounted -can
only be remotely mounted to the length of the capillary
tube, usually 7 feet
Common Control Nomenclature
for Electronic temperature controls:
- PID -proportional, integral,
derivative - matched the rate of heat output to the
system demands and reduces the amount of initial overshoot
- NO contact -normally
open contact, energy required to close it and keep it
closed
- NC contact - normally
closed contact, energy required to open it and keep
it open
- J, K, R, S. T -Instrument
Society of America (ISA) thermocouple designations
RTD - resistance temperature detector
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