Boiler house Level controls
2
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 2020
TI-P693-15 EMM Issue 1
LP21 Capacitance Level Probe
Description The Spirax Sarco LP21 is a capacitance probe designed for modulating level control in conductive liquids, in conjunction with a PA420 preamplifier, which is supplied separately. It can also be used for adjustable on/off control. The LP21 may be used with one or more controllers or transmitters to provide level control, level alarms, and/or outputs to a building management system. The probe is normally installed in a steam boiler or metal tank where it is earthed through the ½ " BSP screwed connection, the boiler or tank forming the earth return path. It may be used in a non-conductive tank (e.g. plastic or concrete) if an earth rod is provided. The PA420 preamplifier (described in separate literature), is screwed to the top of the probe and hand tightened, enabling easy removal without the need to disturb the probe. Caution: The probe is not suitable for outside installation without additional environmental protection. Available probe lengths (approximate) in mm 370, 470, 550, 600, 650, 750, 800, 900, 950, 1 050, 1 200, 1 350 or 1 500. Note: Probe length includes the 25 mm 'dead' length at its tip. The probe must not be cut to length. Pressure/temperature limits Nominal pressure rating PN40 Maximum pressure 32 bar g Maximum temperature 239 ° C
PA420 Preamplifier connector
2.3 21
5
6
2
1
70 ° C
Maximum
3
Ambient temperature
5 ° C
Minimum
Designed for a maximum cold hydraulic test pressure of
60 bar g
Technical data Sensing depth
4
Probe length minus 25 mm
Minimum conductivity
5 µS/cm or 5 ppm
Degree of protection
IP54
Materials No.
Description
Material
1 2 3 4 5 6
Probe body
Austenitic stainless steel
BS EN 10088-3 (1.4306)
Cover assembly
Austenitic stainless steel
Type 316L
Probe (sheathed)
Stainless steel tube
ASTM A269 Gr. 316L
Probe sheathing
PTFE
BS 6564 Grade UA Type 1
'O' ring
Nitrile rubber
Name-plate
Polycarbonate
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