General Assist Technical Training
VR-II Indoor Unit Training
Technical and sales overview
Indoor unit range, controller wiring, external outputs, EEV protection, options and system compatibility
The AIRSTAGE VR-II indoor unit platform was developed for the VR-II heat recovery system. It retains a broad range of indoor-unit formats while introducing updated controller wiring, external-output specifications and additional EEV fault protection.
Important: Do not mix polar 3-wire and non-polar 2-wire remote-controller wiring on the same indoor-unit control system. Confirm controller, accessory and software compatibility before installation or replacement.
1. Product lineup
The VR-II indoor-unit range comprises 12 unit types and 55 models, with nominal capacities from 2.2 kW to 25.0 kW. This is the same overall capacity range as the V-II series.
| Indoor-unit category | Typical model series | Typical application |
|---|---|---|
| Compact cassette / cassette | AUXB, AUXD, AUXA | Offices, meeting rooms and retail spaces |
| Compact, slim and low-static duct | ARXB, ARXD, ARXA | Hotels, apartments and partitioned rooms |
| High-static-pressure duct | ARXC | Large commercial areas and longer duct systems |
| Floor / ceiling and ceiling | AB*A | Classrooms, shops and spaces with limited ceiling access |
| Compact wall-mounted / wall-mounted | AS*A, AS*E | Smaller rooms and applications requiring straightforward installation |
2. Technical changes
2.1 Non-polar 2-wire remote-controller wiring
VR-II indoor units use a non-polar 2-wire connection for new-generation wired remote controllers. This simplifies field wiring and reduces the likelihood of polarity-related installation errors.
- New controller families include UTY-RNR*, UTY-RNH*, UTY-RSK* and UTY-RHK*.
- Some previous remote controllers remain compatible, but new-controller functions may not be available.
- Mixed installation of polar 3-wire and non-polar 2-wire controller systems is not permitted.
2.2 External-output specification
The external-output circuit was revised to support a broader DC 12-24 V interface range and longer field wiring, depending on the applicable indoor-unit specification.
| Item | V-II reference | VR-II reference |
|---|---|---|
| Coil voltage | DC 12 V | DC 12-24 V |
| Output current | Up to approximately 50 mA | Approximately 5-10 mA, subject to model specification |
| Indicative wiring distance | Up to approximately 25 m | Up to approximately 150 m, subject to design conditions |
DC 24 V interfaces: Where the connected control device uses a DC 24 V supply, use a suitable field-supplied DC/DC relay and confirm coil and contact ratings before connection.
2.3 EEV connection-error protection
A dedicated detection circuit identifies a connection fault at the indoor-unit electronic expansion valve coil. When an EEV connection error is detected, the outdoor unit stops to protect the compressor and refrigerant circuit.
- Improves fault detection during commissioning and service.
- Reduces the risk of compressor damage associated with incorrect EEV operation.
- Provides a clearer diagnostic path for indoor-unit connection faults.
3. Optional parts and accessories
Many optional parts are common with V-II and J-II indoor units. Always verify the exact accessory against the indoor-unit model and current technical documentation.
| Accessory group | Examples | Purpose |
|---|---|---|
| Panels and airflow accessories | UTG-UF*C-W, UTG-UG*A-W, UTR-YDZB/C | Finishing, airflow control and outlet blanking |
| Fresh-air and insulation kits | UTZ-VXAA, UTZ-VXGA, UTZ-KXGA/B/C | Fresh-air introduction and high-humidity insulation |
| Remote sensing and receivers | UTD-RS100, UTB-YWC, UTB-TWC, UTY-LRH*B1 | Remote temperature sensing and wireless control |
| Duct accessories | UTD-GXSA/B/C-W, UTD-RF204, UTD-SF045T, UTD-LF25NA, UTD-LF60KA | Auto louvre, flanges and filtration |
| Drain and EEV accessories | UTZ-PX1BBA/MBA/NBA, UTZ-DPB24T, UTR-EV09XB, UTR-EV14XB | Condensate management and external EEV installation |
Auto louvre grille for slim duct units
The optional auto louvre grille can be operated in coordination with the indoor-unit remote controller. The moving louvre improves horizontal air distribution and can support more even room-temperature distribution during heating and cooling.
4. Compatibility overview
| Equipment category | VR-II | V-II | J-II | Notes |
|---|---|---|---|---|
| Central controllers | Compatible | Compatible | Compatible | Includes UTY-APGX, UTY-PEGX, UTY-DTG*, UTY-DCG* and UTY-CGG*. Minimum software versions apply to some products. |
| Network converters and gateways | Compatible | Compatible | Compatible | Includes UTY-VGGXZ1, UTY-VLGX, UTY-ABGX and UTY-VSGXZ1. |
| Service and monitoring tools | Compatible | Compatible | Compatible | UTY-ASGX and UTY-AMGX require the applicable software version. |
| VR-II RB units | Compatible | Not available | Not available | UTP-RX01AH, UTP-RX01BH and UTP-RX04AH are specific to VR-II. |
| Three-pipe separation tubes, branch kits and headers | New VR-II components | Not interchangeable | Not interchangeable | Use only the specified heat-recovery piping components. |
Compatibility limitation: Some indoor/outdoor combinations carry model-specific restrictions. The original compatibility material notes that ARXC72 and ARXC90 units cannot be connected in certain combinations. Confirm the current design and technical manual before selection.
5. Key training points
- Controller wiring: Confirm whether the installation uses non-polar 2-wire or legacy polar 3-wire control. Never mix the two systems.
- External outputs: Verify voltage, current, relay type and wiring distance before connecting a BMS, PLC, fan or indicator.
- EEV diagnostics: Investigate EEV connection errors immediately because the protection function can stop the outdoor unit.
- Service tools: Use UTY-ASGX or the applicable monitoring tool to support commissioning, operational checks and fault isolation.
- Accessory selection: Common V-II and J-II accessories can reduce stock complexity, but exact model compatibility must still be confirmed.
- Heat-recovery piping: VR-II RB units and three-pipe branch components are system-specific and must not be substituted with two-pipe components.
6. Sales summary
The VR-II indoor-unit range supports a wide variety of commercial building applications while retaining familiar unit formats and many common accessories. The principal value points are:
- Simplified remote-controller wiring.
- Broader external-control integration capability.
- Improved EEV fault detection and compressor protection.
- Wide indoor-unit selection from 2.2 kW to 25.0 kW.
- Compatibility with established central controls, gateways and service tools.
- Dedicated heat-recovery piping and RB-unit solutions for simultaneous heating and cooling applications.
Document note: This training overview is based on preliminary Fujitsu General engineering-support material issued in 2012. Product availability, software versions, accessory codes and compatibility may have changed. Always refer to the current technical manual, design documentation and local product information before specifying or servicing equipment.