Viconics R842 - Manual (Page 2)

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Description (Cont’d)
The R842 has several advantages over traditional
electromechanical baseboard relays. The latter use
the principle of thermal expansion to make or break
the high voltage circuit. This operation typically takes
45 seconds and adds inaccuracy to the temperature
control loop. The R842, with enhanced electronic
circuitry, substantially reduces this long time delay
and is not affected by ambient temperature
conditions.
Due to its compact design, the R842 easily fits into
most electric baseboard enclosures and can replace
most competitive models. For junction box mounting,
a standard ½” male screwed fitting is available. In
addition, a high intensity LED is provided to indicate
operation and simplify troubleshooting. Silent
operation will ensure that each installation is trouble
free.
R842 Relay Models
Model No.
Voltage
(Vac)
Amperage
(A)
R842-120 120 22
R842-208 208 22
R842-240 240 22
R842-277 277 19
R842-347 347 18
R842-600 600 10
T186 Electronic PI Thermostat
The microprocessor-based design of the R842
permits the use of T186 electronic room sensor with
setpoint as an alternative to electromechanical
thermostats. The T186 transmits the actual
temperature and setpoint to the R842. The resulting
solid state PI control loop is much more accurate
than that offered by conventional thermostats and
eliminates wasted energy caused by on/off cycling
with these types of thermostats (see Fig. 2).
The T186 can also be used as lower cost alternative
to the use of solid state relays and pulse width
modulated thermostats, sometimes used to control
electric heat baseboards.
Fig.2 - On/Off mechanical control vs PI electronic control
T186 Sensor Models
Model No. Scale Range
T186C-01 5 °C to 30 °C
T186F-01 40 °F to 90 °F
Fig.3 - T186 electronic PI room sensor with setpoint
Typical Guide Specification
The relay shall be a microcomputer-based with PI, time
proportioning control capability. It should have an
average life of greater than 500,000 cycles and include
a built-in transformer. Relays shall be compatible with
all of the following control signals: Viconics T186
electronic room sensor with setpoint permitting PI
control with an accuracy of +/-0.3ºC and standard 24
Vac thermostats. Relay shall have a constant 10 second
time delay and shall not be affected by ambient
temperatures. The relays shall be equipped with a
status LED to confirm operation. Required quality: R842
electronic baseboard relay from Viconics.
Setpoint (comfort temperature)
T186 PI control
Electromechanical thermostat
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