Finder 72 Series Monitoring Relays and Float Switches

Introduction

The Finder 72 Series offers a comprehensive range of monitoring relays and float switches designed for precise liquid level control and management in various industrial and domestic applications. This series includes level control relays for conductive liquids, priority change relays for alternating loads, and float switches for reliable fluid level regulation.

The relays operate by measuring the resistance through the liquid between electrodes. The float switches utilize a floating body that activates a switch based on the liquid level.

Applications include:

? Industrial washing machines
? Swimming pools
? Control and management of water
? Bottling plants
? Milk processing plants
⚙️ Control panels for pumps

Monitoring Relays

Level Control Relays for Conductive Liquids

These relays monitor and control liquid levels in conductive media using electrodes.

Type 72.01: Adjustable Sensitivity Level Control Relay

Features: Adjustable sensitivity (5-150 kΩ, or 5-450 kΩ), available for 400V supply, suitable for low contact loads (down to 5V, 1mA), LED indicator, reinforced insulation (6 kV), 35mm rail mounting. Can control single level or between Min./Max. limits.

Diagram Description: Shows a compact relay unit with terminals. Includes a diagram illustrating sensitivity range adjustment (5-150 kΩ) and selectable delay times (0.5s or 7s) and functions (filling/emptying).

Contact Specification	72.01/72.11
Contact Configuration	1 CO (SPDT)
Rated current/Max. peak current	16/30 A
Rated voltage/Max. switching voltage	250/400 V AC
Rated load AC1	4000 VA
Rated load AC15 (230 V AC)	750 VA
Single phase motor rating (230 V AC)	0.55 kW
Breaking capacity DC1: 24/110/220 V	16/0.3/0.12 A
Minimum switching load	500 mW (10V/5mA)
Standard contact material	AgNi

Supply Specification	72.01/72.11
Nominal voltage (UN)	24 V AC/DC, 110-125 V AC, 230-240 V AC, 400 V AC
Rated power AC/DC	2.5/1.5 VA (50 Hz)/W
Operating range	19.2-26.4 V AC (50/60 Hz), 20.4-26.4 V DC

Technical Data	72.01/72.11
Electrical life at rated load AC1	100 x 10³ cycles
Electrode voltage	4 V AC
Electrode current	0.2 mA
Run-on time	0.5 - 7 s (selectable)
Max sensitivity range	5-150 kΩ (adjustable)
Insulation between supply/contacts/electrode (1.2/50 μs)	6 kV
Ambient temperature	-20...+60 °C
Protection category	IP 20

Wiring Diagram Description: Shows connections for supply (L/N), electrodes (B1, B2, B3), and output contacts (11-14). Includes terminal designations and function selection for Filling (F) and Emptying (E).

Type 72.11: Fixed Sensitivity Level Control Relay

Features: Fixed sensitivity (150 kΩ), selectable emptying or filling functions via link, fixed 1s delay, LED indicator, reinforced insulation (6 kV), 35mm rail mounting. Can control single level or between Min./Max. limits.

Diagram Description: Similar to 72.01, showing a compact relay unit with terminals. Includes a diagram illustrating fixed sensitivity (150 kΩ) and selectable functions via link (Z1-Z2). Delay time is fixed at 1s.

(Technical specifications are largely identical to 72.01, see table above)

Wiring Diagram Description: Similar to 72.01, showing connections for supply (L/N), electrodes (B1, B2, B3), and output contacts (11-14). Includes terminal designations and function selection via link (Z1-Z2).

Type 72.51: Modular Level Control Relay

Features: 6 functions (filling, emptying, window mode), adjustable sensitivity (5-150 kΩ or 5-450 kΩ), LED indicator, internal isolating transformer (for 72.51.0.xxx.000x models), reinforced insulation (6 kV), 35mm rail mounting.

Diagram Description: Shows a modular relay unit with terminals. Includes a diagram illustrating adjustable sensitivity (5-150 kΩ or 5-450 kΩ) and selectable functions (FL, FS, ES, EL, WL, WS).

Contact Specification	72.51
Contact Configuration	1 CO (SPDT)
Rated current/Maximum peak current	6/15 A
Rated voltage/Max. switching voltage	250/400 V AC
Rated load AC1	1500 VA
Rated load AC15	250 VA
Single phase motor rating (230 V AC)	0.185 kW
Breaking capacity DC1: 24/110/220 V	3/0.35/0.2 A
Minimum switching load	500 mW (10V/5mA)
Standard contact material	AgSnO2

Supply Specification	72.51
Nominal system voltage (UN)	24 V AC/DC, 110-240 V AC/DC
Rated power	2/1 VA (50 Hz)/W
Operating range	19.2-26.4 V AC (50 Hz), 88-264 V AC

Technical Data	72.51
Electrical life at rated load AC1	100 x 10³ cycles
Switch-off delay time	0.5 - 7 s (selectable)
Power-on activation time	< 3 s
Insulation between supply and contacts (1.2/50 μs)	5 kV
Dielectric strength between open contacts	1000 V AC
Ambient temperature	-20...+60 °C
Protection category	IP 20

Wiring Diagram Description: Shows connections for supply (L/N), electrodes (B1, B2, B3), and output contacts (11-14). Includes terminal designations and function selection options.

Functions for Level Control Relays (72.01, 72.11, 72.51)

Function Codes (72.01 & 72.51):

FL: Filling, Long (7s) run-on delay.
FS: Filling, Short (0.5s) run-on delay.
ES: Emptying, Short (0.5s) run-on delay.
EL: Emptying, Long (7s) run-on delay.
WL: Window function, Long (7s) run-on delay (72.51 only).
WS: Window function, Short (0.5s) run-on delay (72.51 only).

Function Codes (72.11):

F: Filling, Z1-Z2 open, 1s run-on time.
E: Emptying, Z1-Z2 linked, 1s run-on time.

Diagram Descriptions for Functions:

Filling Control (3 electrodes): Monitors liquid between Min (B2) and Max (B1) electrodes. Switch-on occurs when liquid is below B1 or falls below B2 (after delay T). Switch-off occurs when liquid reaches B1 (after delay T).
Filling Control (2 electrodes): Monitors liquid around a single level B1. Switch-on occurs when liquid is below B1 (after delay T). Switch-off occurs when liquid reaches B1 (after delay T).
Emptying Control (3 electrodes): Monitors liquid between Max (B1) and Min (B2) electrodes. Switch-on occurs when liquid is above B2 or rises to B1 (after delay T). Switch-off occurs when liquid falls below B2 (after delay T).
Emptying Control (2 electrodes): Monitors liquid around a single level B1. Switch-on occurs when liquid is above B1 (after delay T). Switch-off occurs when liquid falls below B1 (after delay T).
Window Function (3 electrodes): Maintains liquid level between Min (B2) and Max (B1) electrodes. If liquid is over B1, output operates after delay T. If liquid falls below B1, output de-energizes after delay T. If liquid is below B2, output operates after delay T. If liquid rises over B2, output de-energizes after delay T.

Priority Change Relay

Type 72.42: Priority Change Relay

Features: Special relay for alternating loads (pumps, compressors, air conditioning, refrigeration). 2 independent NO outputs (12A), 4 functions (MI, ME, M1, M2), 2 independent control signals, insulated from supply, 110-240V and 24V AC/DC versions, modular 35mm wide housing, Cd-free contact material.

Diagram Description: Shows a modular relay unit with terminals. Includes a diagram illustrating multi-functionality (MI, ME, M2, M1) and terminal assignments.

Contact Specification	72.42
Contact Configuration	2 NO (2 DPST-NO)
Rated current/Max. peak current	12/20 A
Rated voltage/Max. switching voltage	250/400 V AC
Rated load AC1	3000 VA
Rated load AC15	1000 VA
Single phase motor rating (230 V AC)	0.55 kW
Breaking capacity DC1: 24/110/220 V	12/0.3/0.12 A
Minimum switching load	300 mW (5V/5mA)
Standard contact material	AgNi

Supply Specification	72.42
Nominal voltage (UN)	24 V AC/DC, 110-240 V AC/DC
Rated power (in stand-by)	0.12 W (24V), 0.18 W (110-240V)
Rated power (with 2 active relays)	1.1/1.7 VA (50 Hz) (24V), 1.5/3.9 VA (50 Hz) (110-240V)
Operating range	16.8-28.8 V AC (50/60 Hz), 16.8-32 V DC (24V) 90-264 V AC (50/60 Hz), 90-264 V DC (110-240V)

Technical Data	72.42
Electrical life at rated load AC1	100 x 10³ cycles
Output delay time (T on function diagrams)	0.2-20 s
Power-on activation time	≤ 0.7 s
Minimum impulse duration	50 ms
Insulation between supply and contacts (1.2/50 μs)	6 kV
Dielectric strength between open contacts	1000 V AC
Ambient temperature	-20...+50 °C
Protection category	IP 20

Functions for Type 72.42:

MI (Alternating Outputs on Supply Voltage): Outputs alternate on successive applications of supply voltage. One output closes, alternating between 11-14 and 21-24 to ensure even wear on motors. Other output can be forced closed by S1 or S2, with a delay to prevent surges.
ME (Alternating Outputs by Control Signal): Supply voltage is permanently applied. S1 closure forces one output to close, alternating between 11-14 and 21-24. S2 closure forces both outputs to close.
M2 (Output 2 only): Supply permanently applied. S1 or S2 closure activates output 2 (21-24). Used when load 1 (11-14) is out of service.
M1 (Output 1 only): Supply permanently applied. S1 or S2 closure activates output 1 (11-14). Used when load 2 (21-24) is out of service.

Diagram Descriptions: Detailed wiring diagrams and timing charts illustrate the operation of each function (MI, ME, M1, M2) for the 72.42 relay, including examples of its use with level controllers.

Application Notes for 72.01, 72.11, 72.51

General Applications: Sensing and control of conductive liquid levels via filling, emptying, or window operations. Control can be around a single level (2 electrodes) or between Min/Max levels (3 electrodes). Type 72.01 is ideal for monitoring liquid conductivity.

Positive Safety Logic: Relays use normally open output contacts. In case of supply failure, operation ceases, considered the safest option.

Overrunning of Tank on Filling: Factors to consider include pump performance, discharge rate, electrode position, and run-on time delay. Minimizing delay reduces overrun risk but increases switching rate.

Prevent Dry Running of Pump on Emptying: Similar considerations to filling apply. Minimizing run-on time delay reduces risk but increases switching rate.

Run-on Time: Short delay for small tanks/quick reaction; longer delay (7s) for larger industrial applications to avoid frequent switching.

Electrical Life of Output Contact: Enhanced by larger distance between electrodes (3-electrode control). Smaller distances or single-level control lead to more frequent switching and shorter contact life. Longer run-on time enhances life.

Pump Control: Small single-phase pumps (up to 0.55 kW, 230V AC) can be driven directly. For frequent switching, use a higher power relay or contactor. Large pumps require an interposing contactor.

Water Leakage/Condensation in Oil Lubrication Systems: Use 72.01.8.240.0002 with (5-450) kΩ sensitivity and sensor 072.11 for detecting condensed water vapor or leakage.

Floor Flooding Control: Use 72.01.8.240.0000 or 72.11.8.240.0000 with floor water sensor 072.11 to detect spills or flooding.

Electrodes and Cable Lengths: Typically 2 or 3 electrodes. Tank conductivity can substitute the common electrode (B3). Max cable length is 200m (for cable ≤ 100 nF/km). Direct electrical connection between terminals is possible without electrodes but without sensitivity setting.

Electrode Choice: Depends on the liquid. Standard electrodes (072.01.06, 072.51) are suitable for many applications. Corrosive liquids may require custom electrodes.

On-site Commissioning: Check relay sensitivity against electrode resistance. Suggested to use fill function and shortest run-on time for initial setup.

Commissioning Steps: Detailed instructions provided for 72.01, 72.11, and 72.51, involving setting sensitivity, observing LED indicators, and confirming function.

Float Switches

Finder's 72 Series Float Switches are designed for reliable fluid level regulation in various applications.

Type 72.A1: Grey Water Float Switch

Features: 1 CO (SPDT) contact, 10A resistive / 8A inductive load, cable lengths 5m, 10m, 15m, 20m. Suitable for emptying and filling. Includes counterweight (110g) and cable grip. H05 RN F cable.

Applications: Grey water pumping and drainage.

Diagram Description: Shows a float switch with a cable and counterweight. Application diagrams illustrate Emptying and Filling functions, detailing wire usage (black, brown, blue) and insulation requirements.

Technical Data	72.A1.1000.xx01 / xx02
Contact Configuration	1 CO (SPDT)
Rated current	10 A (8 A)
Rated voltage	250 V AC
Protection degree	IP 68
Max liquid temperature	+45 °C
Max pressure	10 BAR
Cable material	H05 RN F* (PET body)
Body material	Polyethylene (PET)

Type 72.B1: Black Water Float Switch

Features: 1 CO (SPDT) contact, 10A resistive / 8A inductive load, cable lengths 5m, 10m, 15m, 20m. Suitable for emptying and filling. Includes counterweight (110g) and cable grip. H05 RN F cable. ACS certified for alimentary uses.

Applications: Black water systems, drainage plants, pumping stations.

Diagram Description: Similar to 72.A1, showing the float switch and application diagrams for Emptying and Filling functions with wire usage and insulation details.

Technical Data	72.B1.1000.xx01
Contact Configuration	1 CO (SPDT)
Rated current	10 A (8 A)
Rated voltage	250 V AC
Protection degree	IP 68
Max liquid temperature	+45 °C
Max pressure	10 BAR
Cable material	H05 RN F* (PET body)
Body material	Polyethylene (PET)

Type 72.C1: Space Saving Float Switch

Features: 1 CO (SPDT) contact, 10A resistive / 8A inductive load. Space-saving version for narrow spaces. Manual switch for automatic (ON/OFF) or manual (always ON) operation. Cable length 2m. Suitable for emptying and filling. H07 RN F cable.

Diagram Description: Shows a compact float switch with a manual switch. Application examples illustrate tank filling, high level (pump starts, tank drains), and low level (pump stops) scenarios. Outline drawings provide dimensions.

Technical Data	72.C1.0000.0201
Contact Configuration	1 CO (SPDT)
Rated current	10 A (8 A)
Rated voltage	250 V AC
Minimum switching load	1200 mW (12V/100mA)
Breaking capacity DC1	6 A - 30 V DC
Protection degree	IP 68
Max liquid temperature	+50 °C
Level adjustment range	6...12 cm
Max depth	10 m
Cable material	H07 RN F*
Body material	Polypropylene

Functions:

Emptying: Black/brown wires used. Circuit opens when float is down, closes when float is up. Blue/grey wire must be insulated.
Filling: Black/blue/grey wires used. Circuit closes when float is down, opens when float is up. Brown wire must be insulated.
Grounding wire is always yellow and green.

Accessories

Finder offers a range of accessories to complement the 72 Series relays and float switches:

Suspended Electrodes: For conductive liquids, suitable for wells and reservoirs. Available in various lengths (e.g., 6m, 15m) and materials (e.g., stainless steel AISI 316L). Some are compatible with food processing applications or high chlorine/salt water.
Floor Water Sensor (072.11): Detects floor surface water for flood detection. Connects to electrode terminals (B1, B3) of 72.x1 relays in Emptying function.
Electrode Holders: Available with two or three poles. Electrodes are not included and must be ordered separately. Suitable for various tank types and materials.
Electrode Connectors: For interconnecting multiple electrodes to achieve required length.
Electrode Separators: To maintain distance between electrodes.
Adaptors for Panel Mounting: Plastic adaptors for mounting relays onto 35mm or 17.5mm wide panels.
Marker Tags & Identification Tags: For labeling relays and components.

Ordering Information

The ordering code structure allows for customization of the 72 Series products. Below is a general overview:

Monitoring Relays (72.01, 72.11, 72.42, 72.51)

Example: 72.01.8.240.0000

Series: 72
Type: 0 (Level control, adjustable sensitivity), 1 (Level control, fixed sensitivity), 4 (Priority change), 5 (Modular level control)
No. of Poles: 1 (1 CO), 2 (2 NO)
Contact Material: 0 (AgSnO2 for 72.51, AgNi standard), 5 (AgNi + Au for 72.01)
Supply Voltage: 024 (24V), 125 (110-125V), 230 (110-240V), 240 (230-240V), 400 (400V for 72.01 only)
Option: 0 (Max 150 kΩ), 2 (Sensitivity range adjustable 5-450 kΩ)
Supply Version: 0 (AC/DC), 8 (AC), 9 (DC)

Float Switches (72.A1, 72.B1, 72.C1)

Example: 72.A1.1000.05.01

Series: 72
Type: A (Grey water), B (Black water), C (Space saving)
No. of Pole: 1 (1 CO)
Versions: 0000 (72.C1), 1000 (72.A1, 72.B1)
Cable: 01 (H05 RN F / H07 RN F), 02 (EPDM)
Cable Length: 02 (2m for 72.C1), 05 (5m), 10 (10m), 15 (15m), 20 (20m)

Accessories Included: Counterweight (110g) for 72.A1, mounting bracket and clamps.

Outline Drawings and Dimensions

Dimensional information is provided for various product types:

Types 72.01/72.11 (Box Clamp): Overall dimensions approximately 35mm (width) x 54.6mm (depth) x 88.8mm (height).
Type 72.51 (Box Clamp): Overall dimensions approximately 17.5mm (width) x 56.5mm (depth) x 60.8mm (height).
Type 72.42 (Box Clamp): Overall dimensions approximately 35mm (width) x 44.8mm (depth) x 88.8mm (height).
Type 72.A1 Float Switch: Body dimensions approx. 81.2mm diameter, 146.2mm height.
Type 72.B1 Float Switch: Body dimensions approx. 81.2mm diameter, 170mm height.
Type 72.C1 Float Switch: Body dimensions approx. 69.6mm width, 136.1mm length, 46.7mm height.

Technical Data Summary

Key technical specifications across the 72 Series:

Parameter	72.01/72.11	72.42	72.51	Float Switches (General)
Insulation (Supply/Contacts)	6 kV	6 kV	5 kV	N/A (Float switches are typically IP68 rated)
EMC Standards	EN 61000-4-2, -3, -4, -5, -6; CISPR 11 (Class B)	EN 61000-4-2, -3, -4, -5, -6; CISPR 11 (Class B)	EN 61000-4-2, -3, -4, -5, -6; CISPR 11 (Class B)	N/A
Max Cable Length (Electrodes to Relay)	200 m (≤ 100 nF/km)	N/A	200 m (≤ 100 nF/km)	N/A
Ambient Temperature	-20...+60 °C	-20...+50 °C	-20...+60 °C	+45 °C (72.A1/B1), +50 °C (72.C1)
Protection Category	IP 20	IP 20	IP 20	IP 68

	Finder Serie 72 Level Control Relays and Float Level Regulators Comprehensive technical catalog for Finder Serie 72 level control relays and float level regulators, detailing types 72.01, 72.11, 72.42, 72.51, 72.A1, 72.B1, and 72.C1. Includes product specifications, applications, wiring diagrams, and accessories for industrial automation.
	Finder Serie 72 Level Control Relay Datasheet and Specifications Detailed specifications, features, and application guide for the Finder Serie 72 conductive liquid level control relay, including model numbers, operating principles, and accessories.
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