The Johnson Controls N2 bus protocol was revolutionary when introduced in the 1980s. Four decades later, many of those devices are still running. If your building uses N2 equipment, you face a common challenge: how do you integrate this legacy technology with modern systems?
Understanding N2
- Proprietary: Only JCI equipment speaks N2
- Slow: 9600 baud communication
- Limited: 100 devices per trunk max
- No longer developed
- Simple: Basic, reliable communication
- Proven: Enormous installed base
- Documented: Protocol well-understood
- Durable: Controllers run 25+ years
Integration Options
Metasys NAE controllers communicate directly with N2 devices, acting as translators to expose N2 points as BACnet objects.
- ✓ Native integration — JCI designed for their devices
- ✓ Single vendor technical support
- ⚠ Premium pricing
- ⚠ Vendor lock-in continues
Niagara JACE connects to N2 via serial adapter and driver, mapping N2 points to BACnet objects.
- ✓ Open platform with broad support
- ✓ Competitive service from multiple integrators
- ✓ Modern web-based interface
- ⚠ Third-party N2 driver
Option 3: Protocol Gateways
Dedicated gateway devices translate between N2 and BACnet without a full supervisory platform:
- Contemporary Controls BASgateway
- Chipkin N2 Gateway
- HMS Anybus Gateway
N2 Bus Issues: Decades-old wiring may have poor termination, incorrect topology, ground loops
Addressing Conflicts: Verify no duplicate addresses before connecting
Timing: N2 is slow — configure 10-30 second polling intervals
Practical Integration Steps
- Document your N2 system: Inventory all devices with addresses and topology
- Choose integration approach: Consider point count, budget, long-term plans
- Install integration hardware: Connect to N2 bus, verify connectivity
- Configure point mapping: Map N2 points to BACnet, configure scaling
- Test and verify: Verify reads, test writes, confirm behavior
Planning for the Future
N2 integration is typically a bridge strategy, not an endpoint. Consider gradual migration — replacing N2 devices with BACnet as they fail or during renovations.
Working with Controls NYC
At Controls NYC, we have extensive experience with N2 integration. We've connected N2 systems to Niagara, BACnet platforms, and custom solutions across many NYC buildings.
Contact us to discuss your N2 integration needs.
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