Boiler house Level controls
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Local regulations may restrict the use of this product to below the conditions quoted. In the interests of development and improvement of the product, we reserve the right to change the specification without notice. © Copyright 2021
AI-P693-31 EMM Issue 1
Tank Level Control (On/Off or Modulating) using Capacitance Probes
Description The system comprises a Spirax Sarco LP21 level probe and PA420 preamplifier together with either an LCR2250 or LCR2251 controller, associated valves and fittings, depending on the application. Separate literature is available which explains the individual equipment in detail.
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Typical arrangements The system provides the following options:-
Applications Spirax Sarco capacitance probe based systems can be used to monitor and control the level of a wide range of conductive liquids. The controllers may be used in a variety of configurations for many different filling or emptying applications. For modulating level control, Spirax Sarco supply a control valve with an electric actuator, the controller uses the valve travel time to determine its position The controllers must be mounted in an enclosure or panel to provide environmental protection. They are DIN rail mounting. If the tank or vessel contents are turbulent the probe should be mounted in a protection tube.
Modulating fill control with high alarm Modulating fill control with low alarm Modulating empty control with high alarm Modulating empty control with low alarm
Using the LCR2250 controller
On/off fill control with high alarm On/off fill control with low alarm
Using the LCR2251 controller
On/off empty control with high alarm (with pump contactor) On/off empty control with low alarm (with pump contactor)
Examples of the many level control duties possible
LCR2251 controller
LCR2250 controller
Control valve
LP21 probe/ PA420 preamplifier
LP21 probe/ PA420 preamplifier
Make-up water
High level alarm
Pump on
Valve modulates to maintain water level within this band
Pump contactor
Pump off
Low level alarm
Condensate return to boiler house
Pump
Fig. 1 Boiler feedtank make-up with modulating control and low level alarm
Fig. 2 Condensate return tank on/off emptying control with high level alarm
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