Intek 100FS - Manual (Page 9)

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SECTION 3 ! OPERATION
3.1 START UP
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. SECTION 6 shows whether the unit is
factory set as a low flow switch or as a high flow switch (see 1 or 2 below as appropriate). The trip level
can be adjusted using the instructions in SECTION 3.3.
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 level adjust is set.
For standard flow switches, the relay operates as stated below. See SECTION 6 for the type of flow
switch you have. For nonstandard units, the relay operation is also described in SECTION 6.
1. Low Flow Switch The relay is energized (N.O. contact is made) when the flow rate is
above the trip level. Therefore, an 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.C. contact is made).
2. High Flow Switch The relay is energized (N.O. contact is made) when the flow rate is
below the trip level. Therefore, an alarm condition (relay de-energizes) occurs when the flow
rate is higher than the trip level, or there is a loss of power to the sensor (N.C. contact is
made).
For operation as a level switch, see SPECIAL INSTRUCTIONS (SECTION 6.3).
3.2 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. During long shutdowns, it is recommended that the power to the unit be turned off. (This
does not apply to units for which "no flow" is the standard condition.)