VRF gateway selection
Centralized vs single-indoor-unit VRF gateways
Choose a gateway architecture before choosing the interface. A centralized gateway reaches multiple indoor units through a supported HVAC system bus. A single-indoor-unit gateway is installed for each indoor unit. B19 serves the centralized route; B27 and B25L serve the one-gateway-per-indoor-unit route. Choose the topology first, then the housing, wiring and host configuration.
B19, B27 or B25L: which architecture fits your project?
| Selection point | B19 centralized gateway | B27 compact gateway | B25L indoor-unit gateway |
|---|---|---|---|
| Gateway allocation | One for multiple indoor units on a supported system bus | One per indoor unit | One per indoor unit |
| Connection | Matched indoor or outdoor communication bus | Matched indoor-unit connection | Matched indoor-unit connection |
| Dimensions | 106 × 96 × 57 mm | 51 × 53 × 17 mm | 85 × 85 × 28 mm |
| Installation planning | Accessible control box or suitable DIN-rail location | Suitable back box or indoor-unit service space | Indoor-unit service opening or indoor smart-control box |
| Power | DC 12 V, 2.0 W | Compatible indoor-unit supply, average 0.5 W | Compatible indoor-unit supply, average 0.5 W |
| Integration selection | Manual describes Aqara Zigbee through a compatible hub; request project-specific BMS documentation | Select the ordered interface and host platform | RS485; UART for optional third-party wireless modules. Confirm host protocol. |
B27 vs B25L: which housing suits the installation?
Both gateways use one module for each indoor unit and support WeChat Bluetooth firmware adaptation. B27 measures 51 × 53 × 17 mm and suits tighter service spaces or a suitable wall back box. B25L measures 85 × 85 × 28 mm and is intended for an indoor-unit service opening or indoor smart-control box. Measure cable-bend clearance and maintenance access as well as the enclosure.
Use each model’s own connection table. The B25L manual specifies a DC 8.5 V auxiliary panel output with a maximum 0.7 W budget before built-in wireless-module consumption; the B27 manual specifies its own output range. Matching dimensions or HVAC brand names does not make their terminal assignments interchangeable.
Check B27 specifications · Check B25L specifications and 36 wiring routes.
How many gateways do you need?
For one outdoor unit and eight indoor units on a supported shared bus, one B19 may provide centralized control after system matching. For the same eight indoor units using B27 or B25L, allocate eight gateways. Multiple outdoor systems or separate communication networks require a topology review before the B19 quantity can be confirmed.
The B19 manual lists up to 64 air-conditioning devices, subject to the supported system architecture. A host address or wired centralized-control option does not change the one-gateway-per-indoor-unit allocation of B27 or B25L.
Check the HVAC interface before the automation protocol
Collect complete equipment model numbers and terminal photographs. A brand name or a VRF label is not enough to establish compatibility. Confirm the bus connection, polarity where applicable, required addressing and whether the existing wired controller can remain connected.
For a Modbus or other BMS project, request the matching protocol documentation and supported control points for the exact ordered version. RS485 terminals alone do not establish Modbus support. Do not assume BACnet, KNX, WiFi and Zigbee are all available together.
Consider installation and commissioning access
B19 does not require an additional thermostat for its supported direct-bus control route. Its Aqara integration still requires a compatible hub. Choose a location with access to power, the appropriate bus and future service.
B27 reduces enclosure size at each indoor unit. Check back-box space and separation from mains wiring. B27 and B25L use a WeChat mini-program brand-adaptation route that requires the matching firmware and connection; confirm commissioning access with the installing team before shipment.
Validate the first installation before repeating it
- Record indoor/outdoor models, topology, unit count and existing controller models.
- Confirm gateway version, host platform, destination region and required control points.
- Install a sample using the approved model-specific wiring.
- Check device discovery, commands, feedback and original-controller coexistence where supported.
- Test restart behavior and document the accepted configuration for the rollout.
Send a project schedule for gateway selection
Include destination country, equipment models, terminal photos, indoor/outdoor quantities, target platform, sample quantity and expected rollout. ACMELEC can discuss the matching configuration and project quotation.
Product details: B19 centralized VRF gateway · B27 compact indoor-unit gateway · B25L indoor-unit gateway · Compare all five AcmeLink gateways
Installation references: B19 English manual · B27 English manual · B25L English manual.