How to Customise the BEM502IRN with FL301 for Precise Engine Protection

The BEM502IRN has been a trusted irrigation engine monitor for many years. It offers
compact, easy-to-install protection for diesel engines driving pumps, generators and agricultural
machinery. Out of the box, it monitors key shutdown inputs such as oil pressure, high engine
temperature, alternator failure and coolant level.

What many people don’t realise is that the BEM502IRN can be customised on request.
By adding our FL301 Multifunction Alarm module, we can turn a standard system into a
flexible solution that lets you set your own trip point based on an analogue sender.

Why Customising the BEM502IRN Matters

In real-world operation, every installation is slightly different:

• Different engines and pump curves
• Different operating temperatures and pressures
• Different site conditions and safety margins

A simple ON/OFF switch sender is sometimes not enough. Many customers want to decide:

• Exactly what temperature is “too hot” for their engine
• Exactly what oil pressure is “too low” during load
• At what fuel or coolant level they want an alarm

By adding an FL301 to the BEM502IRN system, we can use a variable resistance sender
(such as many common automotive/industrial gauges) and convert that into a
clean, adjustable alarm or shutdown signal.

What the BEM502IRN Does

The BEM502IRN is a compact electronic engine monitor designed for:

• Diesel irrigation engines
• Stationary pumps
• Agricultural machinery and industrial engines

It provides:

• Six dedicated inputs (oil pressure, high temperature, alternator/charge, coolant level, belt, pump)
• Front panel LED indication of the first fault
• Audible alarm and shutdown relay output
• Start-up bypass delay so the engine can start before protection becomes active
• Fault memory recall so you can review previous shutdown causes

In the standard configuration, most inputs are designed for switch-type senders that
change from open to closed at a fixed pressure or temperature.

What the FL301 Multifunction Alarm Adds

The FL301 Multifunction Alarm is a small module that watches the voltage from a
variable resistance sender (for example, an oil pressure or temperature sender feeding a gauge)
and trips a relay when the signal passes a set point.

Key features of the FL301 include:

• Works with 12 V or 24 V DC systems
• Accepts an input from a variable resistance sender / gauge circuit
• 25-turn adjustment pot for fine tuning the alarm point across the full gauge range
• Selectable rising-voltage or falling-voltage trigger
• Optional slosh delay to avoid nuisance alarms
• Volt-free relay contacts (30 V DC, 1 A resistive) for alarm or shutdown

In other words, the FL301 turns an analogue sender into a precise, adjustable trip point.

Combining BEM502IRN and FL301: How It Works

When we combine the BEM502IRN with the FL301, we effectively add a new “virtual sender”
that trips at the exact level you choose. A typical configuration looks like this:

1. The sender (e.g. temperature or oil pressure) feeds the existing gauge.
2. The same sender signal is piggy-backed into the FL301 SENDER input.
3. The FL301 is configured for either rising or falling voltage depending on the type of sender.
4. Using the 25-turn pot, we set the exact point on the gauge scale where we want an alarm or shutdown.
5. The FL301 relay output is wired into a spare shutdown/alarm input on the BEM502IRN.
6. When the sender passes that point, the FL301 closes its relay and the BEM502IRN reacts (alarm and/or shutdown).

No major internal modification to the BEM502IRN is required — the FL301 sits alongside it as
an add-on module, and we configure the internal DIP switch and wiring to suit your installation.

Example: Custom High Temperature Shutdown

Imagine an irrigation engine that normally runs comfortably around 85 °C, but you want
to shut it down if the temperature ever climbs above 98 °C.

With a standard ON/OFF temperature switch, you are locked into whatever temperature the
switch manufacturer chose. With the FL301 and a matching temperature sender and gauge:

1. Install the temperature sender and gauge as normal.
2. Connect the gauge sender line to the FL301 SENDER terminal.
3. Connect the FL301 relay output to a suitable shutdown input on the BEM502IRN.
4. Run the engine up to your desired trip temperature (for example, 98 °C).
5. Adjust the FL301 set point until its LED just changes state and the relay operates at that temperature.

From that point on, whenever the gauge climbs to that same point, the FL301 will trigger and the
BEM502IRN will log and act on the fault.

Other Practical Applications

The same approach can be used for:

• Low oil pressure alarm or shutdown at a user-defined pressure
• Low fuel level alarm using a fuel sender and gauge
• Low coolant level alarm on a tank with a resistive level sender
• Gearbox or hydraulic oil over-temperature protection

This is particularly valuable in:

• Large irrigation pump installations
• Agricultural harvesters and tractors
• Industrial engines running 24/7
• Any site where unexpected downtime is expensive

Why This Custom Combination Is Different

Many engine monitors only support simple ON/OFF switch senders. The customised
BEM502IRN + FL301 combination offers:

• Fine control over the exact alarm/shutdown point
• Flexible integration with existing gauges and analogue senders
• Proven hardware with years of field use in harsh environments
• Cost-effective upgrades to existing engines without a full panel redesign

For customers who already trust the BEM502IRN, this custom option lets them “tune” the
protection system to their engine and application instead of accepting a one-size-fits-all trip point.

Custom Builds and OEM Options

Because the FL301 is a universal module, Bolec can offer:

• Customised BEM502IRN + FL301 kits for irrigation and industrial OEMs
• Pre-configured trip points matched to your engine’s recommended limits
• Panel builds that integrate gauge, monitor, alarm and wiring in one package

If you’re an OEM, engine dealer or pump installer, this approach can give you a unique selling
point: a compact, robust protection system that is tailored to your specific equipment.

Need a Custom BEM502IRN + FL301 Solution?

We can help you design and supply a customised BEM502IRN system with FL301 so that your
engine protection matches your real-world operating conditions.

Request a BEM502IRN + FL301 Custom Quote

Tell us about your engine, sender type, normal operating range and the protection level you want,
and we’ll recommend a configuration that suits your application.