FUJI NB3-P34-AC Replacement/Upgrade Solution for PXR Series

Product Overview

FUJI NB3-P34-AC Replacement/Upgrade Solution for PXR Series: Smooth Transition from Legacy PID Controllers

The FUJI NB3-P34-AC is a 1/16 DIN PID Process Controller from FUJI Electric’s PXR Series, designed for precision temperature and process variable control in industrial automation environments. As legacy PID controllers reach end-of-life or become increasingly difficult to source, facilities running older FUJI PXR-series panels face mounting pressure to modernize without disrupting production. This product page is specifically structured to support engineers and procurement teams planning a controlled migration from discontinued or aging process controllers to the NB3-P34-AC — a direct-fit replacement that preserves wiring topology, panel cutout dimensions, and control logic compatibility.

Whether your existing installation relies on an older FUJI PXR3, PXR4, or PXR5 controller, or you are replacing a third-party 1/16 DIN unit from Omron, Yokogawa, or RKC Instrument, the NB3-P34-AC offers a well-documented upgrade path that minimizes re-engineering effort and reduces commissioning time on the plant floor.

Compatibility Comparison Table

Seamless Upgrade Solutions

A successful migration to the FUJI NB3-P34-AC rarely involves the controller alone. In most retrofit scenarios, the surrounding system components must be evaluated and, where necessary, updated to ensure full compatibility and reliable long-term operation.

For installations where the existing thermocouple wiring uses older shielded extension cables or where the signal conditioner has degraded, replacing the input signal path with a dedicated signal isolator — such as a DIN-rail-mounted analog signal isolator — eliminates ground loop interference that can cause erratic PID behavior after controller swap. Similarly, if the legacy controller was driving a solid-state relay (SSR) module directly from its control output, the NB3-P34-AC’s relay output can be wired to the same SSR trigger input without modification, preserving the existing heater circuit and power wiring.

In panel environments where the NB3-P34-AC is installed alongside a FUJI PXR5 or FUJI PXR4 on a shared DIN rail, the controllers can share a common 24 VDC auxiliary power supply or operate independently from the panel’s 100–240 VAC bus. If the panel also houses a FUJI FRENIC-Mini or FUJI FRENIC-Ace variable frequency drive (VFD) for motor speed control, the NB3-P34-AC’s analog retransmission output (where fitted) can feed a 4–20 mA setpoint signal directly to the VFD’s analog input terminal, enabling closed-loop process control without additional signal converters.

For facilities upgrading from a legacy distributed control system (DCS) that used hardwired I/O to individual loop controllers, the NB3-P34-AC’s optional RS-485 Modbus RTU port allows integration into a modern SCADA or PLC-based supervisory layer. A FUJI SPB or compatible Modbus-to-Ethernet gateway can bridge the RS-485 segment to an Ethernet network, enabling remote setpoint adjustment and process variable monitoring from a central HMI — such as a FUJI V9 series HMI or any Modbus-compatible operator panel — without rewiring the field instruments.

When multiple NB3-P34-AC units are installed in a single control cabinet, proper power distribution is critical. A dedicated 24 VDC DIN-rail power supply module rated at sufficient amperage for the total controller load, combined with individual fuse terminals on a Phoenix Contact or Weidmüller terminal block rail, provides the clean, stable power that PID controllers require for accurate analog input readings. Terminal marking sleeves and cable duct accessories should be updated during the retrofit to reflect the new wiring diagram, reducing future maintenance time.

If the retrofit also involves replacing a legacy programmable logic controller (PLC) — for example, migrating from a FUJI MICREX-SX or an older Mitsubishi MELSEC FX series — the NB3-P34-AC can operate as a standalone loop controller independent of the PLC scan cycle, offloading temperature control tasks from the PLC CPU and improving overall system response time. The PLC retains supervisory control via Modbus commands, while the NB3-P34-AC handles the fast PID loop locally.

Retrofit Guidance FAQ

Q: Can I reuse the existing thermocouple wiring when replacing my old PXR3 with the NB3-P34-AC?
A: Yes. The NB3-P34-AC accepts the same thermocouple types (K, J, T, E, R, S, B, N) as the PXR3 and PXR4. The input terminal assignment is compatible, so existing compensating cable runs do not need to be replaced. Verify the input type setting in the NB3-P34-AC parameter menu matches your thermocouple type before powering up.

Q: Will my existing PID tuning parameters transfer directly?
A: PID parameters (P, I, D values) from the legacy controller can be used as a starting point, but due to differences in internal sampling rates and algorithm implementation, we recommend running the NB3-P34-AC’s auto-tuning function during initial commissioning to generate optimized parameters for your specific process. This typically takes one to two complete process cycles.

Q: Is the panel cutout the same as the PXR3 and PXR4?
A: Yes. The NB3-P34-AC uses the standard 1/16 DIN 48×48 mm panel cutout. No panel modification is required when replacing a PXR3, PXR4, or any other standard 1/16 DIN controller. The mounting clip system is also compatible with standard panel thicknesses of 1–8 mm.

Q: Can the NB3-P34-AC communicate with my existing SCADA system via Modbus?
A: The NB3-P34-AC supports RS-485 Modbus RTU communication on its optional communication port. If your SCADA system already polls other FUJI PXR controllers on the same RS-485 bus, the NB3-P34-AC can be added to the same network segment by assigning a unique station address. No changes to the SCADA driver or communication cable are required.

Q: What is the installation depth, and will it fit in my existing shallow panel?
A: The NB3-P34-AC requires approximately 60 mm of depth behind the panel face. If your existing panel was designed for a controller with greater depth, a panel spacer or rear-mount bracket can be used. For very shallow enclosures, verify clearance before ordering.

Q: How do I handle the relay output wiring if my old controller used an SSR drive output?
A: The NB3-P34-AC’s relay output (SPDT, rated for resistive loads) can be wired to trigger an external SSR in the same way as a voltage pulse output. Connect the relay NO contact and common to the SSR’s control input terminals. Ensure the SSR’s control input voltage range is compatible with the relay’s switching voltage in your circuit.

Warranty Assurance

Every FUJI NB3-P34-AC unit shipped by TOPNLMS is covered by a 12-month warranty from the date of delivery. Prior to shipment, each unit undergoes functional verification including power-on testing, input signal response check, and output relay operation confirmation. Units are packaged in anti-static protective packaging with original manufacturer labeling where available.

In the event of a confirmed defect within the warranty period, TOPNLMS provides a replacement unit or full refund based on the customer’s preference and stock availability. Our after-sales response target is within 24 hours on business days. For time-critical production environments, we recommend discussing priority stock reservation at the time of order to ensure a spare unit is available for immediate dispatch if needed.

All units are sourced through verified supply channels. Documentation including test records and shipping manifests is available upon request for quality audit purposes. We support procurement teams requiring supplier qualification documentation, CE declarations, or product datasheets as part of their vendor approval process.

For volume orders, OEM replacement programs, or standing purchase agreements for ongoing maintenance stock, please contact our sales team directly to discuss pricing, lead times, and consignment options.