District Heating Leakage Protection

System LMI-F

system LMI-F


Small institutions

  • Forward and return flow meters
  • Cutoff and non-return valves
  • Control Unit

Monitoring Functions

Forward and Return flows are monitored continuously, compensating for volume and meter differences. If a preset flow difference limit is exceeded, leakage alarm is issued and the installation is cut off.

Seepage: OptiTight®
The patented OptiTight® mechanism employs individual control of the cut-off valves to test the installation tightness one or more times daily, whereby even minute seepage may be detected.

System Error:
The system checks the flow meters against each other, whereby meter blocks and occurring defects are immediately discovered.
Whenever a valve is closed - manually or by alarm - the system checks its tightness.
In case of component failure, System Alarm is issued. The installation is cut off by meter errors.

Supply Error:
The system monitors the mains supply and all internal supplies. If either of these fail, a Supply Alarm is issued. This may not cause a cutoff of the heating supply.

Alarm Functions

On leakage and meter errors, system LMI-F will cut off the installation, issue visual and audible alarms, and activate the alarm relay.
Supply errors are reported via the alarm relay, and possibly also visibly and audibly.
Meter errors are signalled visibly.


Controls and Indicators:
Operation, and alarm indicators, buzzer.
Button for buzzer mute and alarm acknowledge.

Leakage Monitor:
Base measuring period 210 sec.
Truncation at high flow rates.

Activation: 1, 2, 3 or 4 times daily.
Base time 02:00 + 24 / 2*12 / 3*8 or 4*6 hours. Delay up to 1 hour if consumption is high.
Duration: 7.5, 15, 30 or 60 minutes.
Sensitivity up to 1 litre/hour.

Mains Connection
230V 50Hz L/N/PE via external key switch.
Power consumption max 20VA.


Liquid Sensor Attachment:
System LMI-F accomodates via interface ILS-C up to two liquid sensors type LS-X, whereby the system offers point protection of paricularly sensitive ares so that the installation may be cut off on Liquid Sensor alarm if desired.

By attachment of an external SMS-alarm to the alarm relay output, system LMI-F can ship a text message to a selected mobile phone number.

system diagram LMI-F OptiTight
1: Control Unit
3: Forward Flow Meter
5: Return Cutoff Valve
2: Forward Cutoff Valve
4: Return Flow Meter
6: Non-return Valve
System Capacity and pressure drop Dimensions
Nom. Cap.
Qn (m³/h)
 ΣΔp@Qn Equivalent
Kvs (m³/h)
(mvs) (kPa) Flow meter Cutoff valve Non-return valve
LMI-F1,5 1,5 6,7 67 1,8 ½" x 110/190 mm ½" x 55 mm ½" x 47 mm
LMI-F2,5 2,5 6,3 63 3,2 ¾" x 130/228 mm ¾" x 76 mm ¾" x 56 mm
LMI-F3,5 3,5 5,9 59 4,6 1" x 260/375 mm 1" x 90 mm 1" x 65 mm
LMI-F6 6 5,7 57 8,0 1¼" x 260/375 mm 1¼" x 95 mm 1¼" x 73 mm

EAN/UPC ordering codes here

Download System LMI-F datasheet in pdf-format