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I:\OFFICE\Web Site\distiller pdf\100CSCE.wpd
SECTION 3
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OPERATION
3.1 BEFORE YOU START
The flow switch trip point adjustment requires qualified service personnel to access inside the enclosure (see
Sections 2.2). Make sure the trip point has been properly adjusted prior to start of operation.
3.2 SWITCH SETTINGS
Typically Rheotherm flow switches come from the factory set up for a 10 to 1 flow rate range, and with the
trip level set approximately as requested by the customer.
When power is first turned on, the flow switch may indicate a high flow rate, even if there is no flow
occurring. Correct indication of flow level will result after an initial period, which can extend to about forty
(40) seconds and depends on where the trip adjust is set.
For standard flow switches, the relay operates as stated below. For nonstandard units, the operation is
described in SPECIAL INSTRUCTIONS (SECTION 6).
Low Flow Switch — The relay is energized (N.O. contact is
closed
) and the LED is
green
when the
flow rate is
above
the trip level. Therefore, the alarm condition (relay de-energizes) occurs when the
flow rate drops below the trip level or there is a loss of power to the sensor (N.O. contact is
open
) and
LED color becomes
red.
High Flow Switch — The relay operation is exactly as described above. When used as a high flow
switch, the alarm condition is considered to be when the relay is energized (N.O. contact is
closed).
3.3 GENERAL INFORMATION
The Rheotherm instrument is compensated for a wide range of both ambient and flowing media temperatures.
However, abrupt changes in the temperature of the flowing material can cause the instrument to read the flow
rate improperly, which could lead to an inappropriate tripping of the relay or a delay in reading loss of flow.
A proper reading is obtained only when the transducer is in thermal equilibrium with the material. Typically,
a 20°F abrupt change in temperature may require 40 seconds to stabilize.
In general, the heater used in the transducer does not develop enough power to cause damage to the system
in the absence of flow. This includes those used in liquids even if the line becomes empty and filled with air.
Special cases will be discussed in the section entitled SPECIAL INSTRUCTIONS (SECTION 6).
3.4 USE AS A LEVEL SWITCH (Insertion Probes only)
The probe switch design can be used to provide one point level switch indication. When the probe tips
are submerged in liquid, the relay is energized and the LED is
green
. When the liquid level drops below
the probes and they are surrounded by air or vapor, the relay de-energizes and the LED turns
red
.
