The Spirax Sarco LP30 conductivity probe, when used in conjunction with the LC3000 or LC3050 level controller, provides highly accurate, self-monitoring low level alarms for steam boilers. It consists of a sensor body (with a removable cable plug) and a separate sensor probe. Under normal operating conditions, the sensor probe is partially immersed, and the resistance to earth is low. When the water level drops below the sensor probe, the resistance to earth becomes high, causing the controller to issue a low-level alarm signal. The comparator probe compensates for any earth resistance leakage caused by scale, dirt, or internal moisture, ensuring a correct low-level alarm is detected even under harsh conditions.

Features

• High-accuracy, self-monitoring low level alarm sensor.
• Suitable for pressures up to 32 bar g (239°C).
• Maintenance-free operation.
• Securely fixed sensor probe.
• Available probe lengths: 500 mm (19.7"), 1000 mm (39.4"), and 1500 mm (59").

Limiting Conditions

Parameter	Value
Design pressure conditions	PN40
Maximum boiler pressure	32 bar g (464 psi g)
Maximum temperature	239°C (462°F)
Cold hydraulic test pressure	60 bar g (870 psi g)
Maximum ambient temperature	70°C (158°F)
Maximum sensor cable length	50 metres (164 ft)
Cable plug sealing rating	IP65

Materials

No.	Part	Material	Standard
1	Sensor body	Austenitic stainless steel	BS EN 10088-3 (1.4306)
2	Cover	Austenitic stainless steel	Type 316L
3	Name-plate	Polycarbonate
4	Plug and socket	Polyamide
5	Gasket	Silicone rubber
6	Comparator probe	Austenitic stainless steel	Type 316L
7	Primary & secondary insulators	PTFE	BS 6564 Grade UA Type 1
8	Dowel pin	Austenitic stainless steel	Type 302/304
9	Probe tip	Austenitic stainless steel	Type 316L
10	Lock-nut	Austenitic stainless steel	BS 6105 A4 80

Weights (approximate, including packaging)

Probe Length	500 mm (19.7")	1000 mm (39.4")	1500 mm (59")
Sensor Weight	0.51 kg (1.1 lb)	0.63 kg (1.4 lb)	0.92 kg (2.0 lb)

Note: Sensor weight alone is 0.32 kg (0.7 lb).

Wiring Diagram

Installation

The sensor features a ½" BSP female threaded connection. A protection tube is required when installed in a boiler or a highly turbulent tank. The products have been specifically designed for use on steam or condensate which are in Group 2 of the Pressure Equipment Directive 2014/68/EU (Category 4 Safety Accessories).

WARNING

It is essential that the probe tip of the LP30 does not touch any part of the boiler. Standards require that the tip is at least 14 mm from the protection tube, and this must be checked when the probe is installed.

Probe Clearance Test

This test ensures the satisfactory installation of new systems and may also be used for fault finding on existing systems. A pair of 'checking wires' are used in conjunction with an Insulation Resistance Tester to test if there is less than 14 mm radial clearance from the tip end. This test is particularly useful for probe lengths over 800 mm. Shorter probes may be checked for alignment by visual means alone.

Test Method:

1. Drain water level to at least 50 mm below alarm level and vent boiler or vessel to atmosphere.
2. Remove probe (if installed) and fit a pair of checking wires to the end of the probe tip, 90° relative to each other and a maximum 10 mm from the tip end.
3. Carefully pass probe through screwed connection and into the protection tube. The checking wires will deflect to allow them to pass through, and then spring back.
4. Screw down probe by hand.
5. Attach the earth lead of the meter to the boiler and the live lead to pin 1 of the probe connector. Check the contact to boiler with the meter.
6. Activate meter and observe display. Slowly unscrew probe one full turn (without unduly rocking the probe).
7. If no short circuit is found, disconnect the meter leads, unscrew and withdraw the probe.
8. Remove checking wires and install probe.
9. Low alarms must be functionally tested by lowering the water level before the boiler is allowed to run unsupervised.

DANGER

It is essential to remove the checking wires from the probe before commissioning the boiler or vessel. Failure to do this could lead to the low alarms not working.

If a short circuit was found during the test, further investigation is needed. Possible reasons include:

• Probe tip bent or not attached properly.
• Protection tube and/or screwed connection out of alignment.
• Protection tube not of large enough bore and/or not deep enough (the tube should be at least 40 mm deeper internally than the end of the probe).