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4.5 Timed Sampling Mode
Used in small to medium sized boilers where the blowdown requirements are less than 5000 lbs/hr. A boiler this size or
smaller cannot be sampled continuously because the volume of water (blowdown) lost to sampling would prevent the
conductivity from rising above the set point.
The controller utilizes an internal timing circuit to open a blowdown valve at periodic intervals.When the valve opens,
the unit reads the conductivity. The controller reacts to the conductivity reading only while this valve is open. If the
conductivity is above the preset level, dened as set point including differential, the system will continue to blowdown
until the conductivity drops below the preset level.
There is a ‘Trap Sample’ programming menu option provided for under the timed boiler sampling. This option allows a
boiler water sample to be temporarily trapped near the probe so that any ashed steam can settle out and be recompressed.
This prevents erratic conductivity readings from occurring.
If ‘Trap Sample’ is selected as ‘N’ or ‘no’ then this option is not enabled and conductivity will be read at the end of the
sample duration time.
If ‘Y’ or ‘yes’ is selected, then this option is enabled and the blow down valve will be temporarily closed for the amount
of programmed ‘Trap Time’. The boiler water sample will settle out during this time. At the end of the ‘Trap Time’ the
conductivity will be read and reacted on. If the conductivity is below the set point, the controller will start another ‘Off
Time’ cycle. If the conductivity is above the set point, the controller will conduct another blow down or ‘Duration’
cycle time.
4.6 Continuous Sampling
For large boilers with a blowdown requirement in excess of 5000 lbs/hr. The controller constantly monitors system
conductivity with the sample going to drain.
When the conductivity exceeds preset limits, dened as set point including differential, the controller activates a mo-
torized or solenoid valve on an auxiliary blowdown line. When the conductivity drops below the set point (including
differential), the valve closes.
4.7 Boiler Installation Notes
LMI provides the controller, an optional sampling probe, and probe mounting cross. The conductivity electrode provided
can be installed to temperatures of up to 400° F (205° C) and pressures of 250 psi (17.3 Bar). Temperatures and pres-
sures exceeding these extremes will require the use of a sample cooler and/or other probes. Check that all other valves
installed to complete this installation have a high enough pressure and temperature rating.
Additional equipment required to complete installation for a TIMED sample method of control:
1. Fully ported shut off valve for blowdown line. Allows the electrode to be removed from the system
while the boiler is on.
2. Adjustable ow control valve or orice union and various sized plates. Controls blowdown rate and
insures back pressure at the electrode.
3. Motorized or solenoid operated valve, normally closed. Controls the opening and closing of the
blowdown line.
4. One quarter (1/4) turn mechanical ball valve. For ushing the probe line.
.
(866) 433-6682 • (281) 359-8538 • sales@novatech-usa.com • www.novatech-usa.com
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