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CoolAutomation GS-SMT-HOA underfloor heating controller, 8 zones, Modbus RTU
✗
UL Listed
This product has not been certified by an NRTL (UL, ETL, CSA or
equivalent). Installation in USA projects may require a Field Evaluation
by a recognized laboratory. Consult your local AHJ before specifying.
⚡
Mains Voltage · No US Cert
This device operates with or switches mains voltage (120/240VAC) and
has not been certified by an NRTL. USA installation requires a Field
Evaluation by a recognized laboratory and explicit AHJ approval.
Regular price
$873.00 USD
Regular price
-10%
$970.00 USD
Sale price
$873.00 USD
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The CoolAutomation GS-SMT-HOA is an 8-zone controller for hydronic and electric underfloor (radiant floor) heating. Each zone has its own 10K temperature sensor input, setpoint and relay output, and every zone appears as a separate unit in home automation, BMS and the CoolAutomation apps when the board is connected to a CoolMaster, CoolMasterPro, CoolMaster EDGE or CooLinkBridge.
Relays are dry contacts rated 5 A up to 230 V AC, so they can drive zone valves, actuators or contactors directly, and each has an On / Off / Auto override switch for commissioning and service. A general output closes whenever any zone calls for heat, ready to start the boiler or pump. Communication is Modbus RTU over RS485.
Key Features
- 8 independent zones, each with 10K temperature sensor input, setpoint and relay output
- Dry-contact relays, 5 A, up to 230 V AC, with On / Off / Auto override switch per relay
- General heat-demand output, active when at least one zone is on
- 2 × 0–10 V DC analog outputs
- Modbus RTU over RS485; DIP-switch address and end-of-line resistor
- Up to 4 boards (32 zones) per CoolMaster or CooLinkBridge, 8 boards (64 zones) per CoolMaster EDGE, 10 boards (80 zones) per CoolMasterPro
Typical Applications
Homes, hotels and spas with hydronic radiant floors or electric floor heating, where floor zones and VRF/split air conditioning are controlled from the same KNX, BMS or home automation system.
Technical Specifications
| Power supply | 24 V DC |
| Power consumption | 0.5 A |
| Zone inputs | 8 × 10K type 2 temperature sensor (or binary input) |
| Zone outputs | 8 × relay, dry contact, 5 A, up to 230 V AC |
| Analog outputs | 2 × 0–10 V DC |
| Communication | RS485, Modbus RTU; 2-wire shielded polarized twisted pair, 20–24 AWG |
| Max bus wiring length | 800 m (2600 ft) |
| Dimensions (H × W × D) | 19 × 210 × 120 mm (0.75 × 7.8 × 4.72 in) |
| Weight | 0.12 kg (0.26 lb) |
| Operating temperature | -10 °C to +50 °C (14 °F to 122 °F), 0–80 % RH |
| Certifications | Not UL/NRTL listed |
| Manufacturer part no. | GS-SMT-HOA |
Related Products
CoolMaster, CoolMasterPro, CoolMaster EDGE, and their KNX versions for bringing underfloor heating zones into KNX alongside VRF.
Not UL/NRTL listed — relay outputs can switch line-voltage loads; installation by a licensed electrician to local code. Verify local code requirements before specifying in US installations.
Datasheet (PDF) · Wiring details (PDF) · Available to order.
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