L91

L91 & L41 FM Approved High Limit Controls - Protect your process with reliable, FM-approved temperature limit controls. Future Design Controls’ L91 (1/16 DIN) and L41 (1/4 DIN) high limit controllers deliver advanced safety, fast response, and full compliance for critical process applications.

Cost-Effective

High Performance Without the Price Tag!

Easy to Use

Simple Set-Up and Use

Short Lead Times

Average Days to Ship 2-3 Business Days

Why Choose the L91 & L41?

FM Approved for use in ovens, furnaces, and industrial heating systems.
Universal Input: Thermocouple & RTD with fast 5 scans/second sampling.
Flexible Outputs: Relay, SSR driver, or Triac with optional second output.
User-Friendly Operation: Clear displays, remote reset options, and straightforward configuration.
Durable & Reliable: Backed by a 3-year warranty and designed for harsh environments.

Key Features at a Glance

High-Limit Safety: Configurable latching outputs for high, low, or combination alarms.

Optional Second Output: Use as alarm silence, retransmission, or communications.

Flexible Power Options: 90–264 VAC standard; low-voltage AC/DC optional.

Event Input: Remote reset or parameter lock.

Communication Ready: RS485 Modbus with access to all parameters.

Linear Retransmission: 0–10 VDC or 4–20 mA for process/setpoint values.

L91 Display Logic (Single Display)

Normal condition: Shows current temperature, setpoint, or SAFE message.
Alarm condition: Displays temperature; outputs remain latched until reset manually or via remote input/communications.

L41 Display Logic (Dual Display)

Upper Display: Always shows process temperature.
Lower Display: Configurable for setpoint or SAFE message.
Alarm condition: Lower display defaults to setpoint; outputs latch until reset.

L91 High Limit Controller

Power: 90–264 VAC (optional low voltage AC/DC).
Input: Universal thermocouple or RTD.
Output #1: Relay, SSR driver, or Triac.
Output #2: Optional (relay, SSR driver, Triac, transmitter supply, RS485 Modbus RTU communications, remote reset, or 0–20/4–20mA, 0–5/1–5VDC, 0–10VDC retransmission).

L41 High Limit Controller

Power: 90–250 VAC (optional low voltage AC/DC).
Input: Universal thermocouple or RTD.
Output #1: Relay, SSR driver, or Triac.
Output #2: Optional (relay, SSR driver, Triac or transmitter supply).
Communications: RS485 Modbus RTU or 0–20/4–20mA, 0–5/1–5VDC, or 0–10VDC retransmission.

Applications

The L91 and L41 FM approved limit controls are ideal for:

Industrial ovens & furnaces
Food & beverage processing equipment
Heat treatment systems
Packaging machinery
General industrial process protection

Get Started Today

Ensure safety, compliance, and reliability with Future Design Controls’ L91 & L41 FM Approved High Limit Controls.

L91 Specification Review

Power Input:
- 90-264VAC
- 11-26VAC/VDC optional
Input sample rate – 5 scans/second
Input:
- Universal Thermocouple & RTD
  - Special Order linear mA/VDC [FM approval applies only to units with thermocouple or RTD input].
- Event Input – Optional: Configurable as a Remote Reset or to Lock all parameters.
Limit Control Output #1 – Latching: Configurable as High Alarm, Low Alarm or combination High-Low Alarm Setpoint with one digital output. Available Digital Outputs:
- Relay: 2A/240VAC resistive Form C [SPDT]
- SSR driver: 5VDC/30mA
- Triac: 1A/240VAC
Output #2 is available with one of the following options: Digital Output [relay, triac or SSR driver] transmitter power supply, communications and Event Input for remote reset & Lock.
- Digital Outputs are same as output #1 except relay is Form A [SPST].
- Transmitter Power Supply [Isolated]:
  - 20VDC/25mA
  - 12VDC/40mA
  - 5VDC/80mA
- Linear Retransmission:
  - Process or Setpoint Values
  - 0-5/1-5/0-10VDC, 0-20/4-20mA
- RS485 Modbus Communication with access to all parameters.
Configurable Display when not in alarm condition HSP, LSP, SP2, PV and word SAFE.
- When in Alarm display defaults to PV with output 1 annunciation energized.

L41 Specification Review

Power Input:
- 90-250VAC
- 11-26VAC/VDC optional
Input sample rate – 5 scans/second
Input:
- Universal Thermocouple & RTD
  - Special Order linear mA/VDC [FM approval applies only to units with thermocouple or RTD input].
- Event Input – Standard: Configurable as a Remote Reset or to Lock all parameters.
Limit Control Output #1 – Latching: Configurable as High Alarm, Low Alarm or combination High-Low Alarm Setpoint with one digital output. Available Digital Outputs:
- Relay: 2A/240VAC resistive Form C [SPDT]
- SSR driver: 5VDC/30mA
- Triac: 1A/240VAC
Output #2 is available with one of the following options: Digital Output [relay, triac or SSR driver] or transmitter power supply.
- Digital Outputs are same as output #1
- Transmitter Power Supply [Isolated]:
  - 20VDC/25mA
  - 12VDC/40mA
  - 5VDC/80mA
Communication Options; RS485 Modbus or Retransmission
- Linear Retransmission:
  - Process or Setpoint Values
  - 0-5/1-5/0-10VDC, 0-20/4-20mA
- RS485 Modbus Communication with access to all parameters.
Upper Display shows Process Variable (temperature).
Lower Display is configurable
- Non-alarm condition display is configurable to show the word SAFE or current Setpoint value.
- When process is in Alarm condition the lower display will show, dependent upon configuration, either SAFE or current Setpoint value
- When process goes from alarm to a non-alarm condition the lower display will revert to the configured non-alarm display; i.e. SAFE.