Wireless GRMS Retrofit for Hotels Using the HX Series

For most hotel operators, the idea of upgrading to a Guest Room Management System (GRMS) triggers an immediate concern: the disruption. Rewiring a 200-room property means opening walls, relocating guests, coordinating with contractors for months, and absorbing costs that can run into the millions. For many properties — particularly mid-scale hotels, heritage buildings, and properties in dense urban locations — that level of disruption is simply not viable.

Smart G4's HX Series was designed specifically to remove that barrier. It is a fully wireless GRMS platform that delivers the same room automation capabilities as a wired system — HVAC control, lighting, curtains, DND/MUR, occupancy detection, energy management, and PMS integration — without requiring any new wiring infrastructure. Existing cabling stays in place. Rooms remain operational throughout the upgrade. And the total installed cost is a fraction of a conventional wired retrofit.

This article explains how the HX Series works, what it can do, and how hotel operators should evaluate it against a conventional wired GRMS upgrade.

Why Retrofit Is the Dominant GRMS Use Case

The global hotel stock is overwhelmingly existing inventory. New-build hotels represent a small fraction of annual room additions — the vast majority of properties were built before smart room automation was commercially available, and many are operating with legacy HVAC controls, manual lighting, and no occupancy-based energy management at all.

For these properties, the business case for GRMS is clear:

• Energy savings: Occupancy-based HVAC setback in vacant rooms consistently delivers 30-40% reductions in guest room energy consumption.
• Guest experience: Automated welcome scenes, pre-conditioning, and DND/MUR integration improve satisfaction scores and reduce front desk calls.
• Operational efficiency: Real-time room status visibility for housekeeping and engineering reduces labour costs and response times.
• PMS integration: Connecting room status to the PMS enables pre-arrival conditioning, VIP room preparation, and automated housekeeping workflows.

The obstacle has always been installation cost and disruption. The HX Series removes both.

How the HX Series Works

The HX Series uses a mesh wireless protocol operating in the sub-GHz frequency band, chosen for its superior penetration through concrete and steel — the materials that dominate hotel construction. Each HX device communicates directly with the HX central controller and with neighbouring devices, creating a self-healing mesh network that maintains connectivity even if individual nodes lose signal.

Core HX Devices

HornetX Room Controller The HornetX is the central intelligence of each guest room. It connects to the room's existing HVAC system via a standard 0-10V or relay interface, manages up to four lighting circuits, and communicates wirelessly with all other HX devices in the room. Installation requires only a power connection — no data cabling.

HX Wireless Panels Bedside panels, door bell units, service requester panels, and bathroom panels all communicate wirelessly with the HornetX. They are battery-powered or use energy harvesting, eliminating the need for power runs to panel locations. The panels use the same touch interface and design language as Smart G4's wired GRMS series, so guests experience no difference in usability.

HX Energy Saver Units The HX energy saver connects to the room's main circuit breaker and manages the room's total energy load based on occupancy. When the room is vacant, non-essential circuits (decorative lighting, entertainment systems, bathroom heating) are cut to a standby setpoint. The 40A heavy-duty variant handles rooms with high-load HVAC systems.

HX Wireless Sensors Occupancy detection uses a combination of door/window magnetic contacts, PIR motion sensors, and — for premium deployments — the HX breathing sensor, which detects human presence through micro-movement even when a guest is sleeping. This eliminates the false-vacant readings that cause HVAC setback to activate while a guest is in the room.

HX Wireless Curtain Motors Battery-powered and solar-rechargeable curtain motors integrate directly into the HX mesh, enabling automated curtain control as part of welcome scenes, wake-up routines, and energy management sequences. No motor wiring is required.

HX System Architecture

Each floor or zone is served by an HX floor controller, which aggregates room data and communicates with the property-level HX server over the hotel's existing IP network. The HX server provides:

• Real-time room status dashboard for engineering and housekeeping
• PMS integration (Opera, Mews, Cloudbeds, and others via the sBUSPro interface)
• Energy consumption reporting per room, per floor, and per property
• Remote configuration and firmware updates for all HX devices
• Fault alerting and diagnostic tools

The HX server runs on a standard rack-mounted appliance installed in the hotel's server room. No cloud dependency is required — the system operates fully on-premises, with optional cloud monitoring available.

HX Series vs Wired GRMS Retrofit

Factor	HX Wireless Retrofit	Wired GRMS Retrofit
New cabling required	None	Extensive (data + power)
Room disruption	Minimal (hours per room)	Significant (days per room)
Guest relocation needed	No	Often yes
Installation timeline (200 rooms)	3-4 weeks	3-6 months
Installed cost vs wired	40-60% lower	Baseline
HVAC control	Full (0-10V / relay)	Full
Lighting control	Up to 4 circuits	Up to 8 circuits
Curtain automation	Yes (wireless motors)	Yes (wired motors)
Occupancy detection	PIR + door + breathing sensor	PIR + door + key card
PMS integration	Yes (sBUSPro)	Yes (sBUSPro)
Energy management	Full (per-room)	Full (per-room)
DND/MUR	Yes	Yes
Scalability	Add devices without rewiring	Requires cabling for additions

Installation Process

A typical HX Series retrofit in a 200-room hotel follows this sequence:

Phase 1: Survey and Design (Week 1)

The Smart G4 installation team conducts a wireless site survey to map signal propagation through the building's structure. The survey identifies any areas requiring signal repeaters and produces a device placement plan for each room type. The HX server and floor controllers are specified based on the property's network topology.

Phase 2: Infrastructure Installation (Week 1-2)

The HX server and floor controllers are installed in the server room and comms cupboards. This work is confined to back-of-house areas and has no impact on guest rooms or operations.

Phase 3: Room Installation (Weeks 2-4)

Room installation proceeds floor by floor, typically at a rate of 15-20 rooms per day with a two-person team. Each room installation involves:

• Mounting the HornetX controller and connecting to HVAC and lighting circuits (typically 2-3 hours per room)
• Installing wireless panels at bedside, door, and bathroom locations (30-45 minutes per location)
• Installing HX energy saver unit at the distribution board (30 minutes per room)
• Commissioning and testing all room functions (45 minutes per room)

Rooms are returned to service the same day. No guest relocation is required.

Phase 4: PMS Integration and Commissioning (Week 4)

The HX server is connected to the hotel's PMS, room status mapping is configured, and the full property is commissioned as a system. Engineering and housekeeping staff are trained on the management dashboard.

Energy ROI Calculation

For a 200-room hotel with average room energy consumption of 8 kWh per day and an average occupancy rate of 70%:

• Rooms vacant per day: 60 rooms
• Energy wasted in vacant rooms (without GRMS): 60 rooms × 8 kWh × 365 days = 175,200 kWh/year
• HX Series setback efficiency: 35% reduction in vacant room energy
• Annual energy saving: 61,320 kWh/year
• At $0.12/kWh: $7,358/year in direct energy savings
• Typical HX Series installed cost (200 rooms): $180,000-$220,000
• Simple payback period: 24-30 months

This calculation excludes additional savings from occupied-room optimisation (pre-checkout setback, pre-arrival conditioning efficiency) and operational savings from reduced housekeeping labour and maintenance response times, which typically add 15-25% to the total benefit.

Suitability Assessment

The HX Series is the right choice for:

• Existing hotels undergoing soft refurbishment where opening walls is not part of the scope
• Heritage and listed buildings where structural modifications are restricted
• Phased upgrades where the operator wants to start with one floor or wing and expand over time
• Budget and mid-scale properties where the cost of a wired retrofit is not justified by room rates
• Properties with high occupancy where extended room downtime during installation is not acceptable

A wired GRMS installation remains the preferred choice for:

• New-build hotels where cabling is installed during construction at minimal incremental cost
• Full gut-renovation projects where walls are already open
• Ultra-luxury properties requiring the maximum number of lighting circuits and the highest level of panel customisation

For properties that fall between these categories, Smart G4's engineering team can specify a hybrid approach: wired GRMS in new-build wings or fully renovated floors, HX wireless in existing wings where disruption must be minimised.

Comparing HX to Competitor Wireless Offerings

Honeywell INNCOM and INTEREL both offer wireless GRMS options, but these are typically positioned as entry-level or limited-function systems rather than full-featured replacements for their wired platforms. Key differences:

• Protocol openness: HX operates on sBUSPro, an open protocol with published documentation. INNCOM and INTEREL wireless systems use proprietary protocols that lock the property into single-vendor maintenance and upgrades.
• Sensor capability: The HX breathing sensor has no equivalent in INNCOM or INTEREL wireless product lines. This matters for energy management accuracy — a system that cannot detect a sleeping guest will either leave the HVAC running (wasting energy) or set it back (creating a complaint).
• PMS integration depth: HX's sBUSPro interface supports bidirectional PMS integration with the same feature set as the wired platform. Competitor wireless systems often offer read-only or limited PMS connectivity.
• Scalability: HX devices can be added to an existing installation without any infrastructure changes. Adding devices to INNCOM or INTEREL wireless systems typically requires reconfiguration of the central controller.

Explore Smart G4 HX Series and Hotel GRMS Solutions

Contact the Smart G4 team to request a wireless site survey and HX Series proposal for your property.