Zentium Pro

The Zentium Pro Thermostat is a dual zone thermostat that allows control over heating and cooling via its simple digital crown. The thermostat can be stand alone or combine with intelligent lighting control keypads such as the Lutron Palladiom or Crestron Horizon. The product from Polar Bear, leverages from years of experience working with Building Management Systems (BMS) and lighting control systems.

There shouldn’t be a learning curve to use a thermostat…

The refinements of the Zentium has come from working closely with leading BMS & AV system integrators. Zentium merges both commercial features with the design aesthetics, high end installations demand.

  • Dual Zone (Two Rooms completly independantly)
  • Air Conditioning Control, including,
    • Heat Boost
    • Fan speed control & auto
    • Temperature sync
  • Towel Radiator control
  • Hot Water Control
  • Operation Mode
  • Eco Modes
  • Built in Timer / Scheduler
  • Intergrate with Leading Lighting Control Keypads
  • Huge range of custom & bespoke finishes
  • Heating Modulation

Direct Air Conditioning Control

The new Zentium ACM has a built in connection so it can be directly connected to an air conditioning unit. Just connect the Zentium to you chosen AC manufacturers indoor unit, select the driver from the Zentiums menu and our thermostat now fully controls and manages the temperature, fan speed and can even activate heat boost if available

Heat Boost

When the Zentium is configured with other heat sources it will automatically control these to provide methods of heat boost to accelerate the heaitng within a space. This could be automatically switching the AC unit into heating mode or triggering a relay to drive a trench heater or other electric heat source.

Lighting Control Intergration

The many faces of the Zentium Pro Thermostat, shown integrated with leading lighting keypad manufacturers.

Digital Crown

The digital crown is the perfect user interface for controlling temperature. It is simple and it’s universally understood. Another unique aspect of the digital crown interface is that when features are disabled from the device, you haven’t got buttons that don’t do anything, that only lead to more user confusion.

The digital crown controls the temperature of the zone by turning it up and down. Feedback to the user in addition to the colour screen is via a soft glowing halo within the digital crown. Pressing the crown selects different pages to give the user access to fan speed a second zone or custom* pages. These can be disabled by the installer if these features are not suitable for the area the product is installed in.

Virtual Temperatures

In addition to the five remote probes and the internal temperature sensors, the Zentium thermostat can receive a DISPLAY temperature from a third-party device within the BMS system and use it as if it was its own built in temperature reading.

This is ideal for installations with VRF indoor units that have their own room temperature sensors (sometime called return air temperature). By passing the temperature from the VRF to the Zentium, it creates a much more accurate and robust control loop between the wall thermostat and the VRF indoor units.

Once the thermostat’s zone is set to use the virtual temperature, values can be passed to the thermostat. These values will then be used as its display temperature and also be applied to its internal logic used to determine demand status.

Heating Modulation

Achieving a stable room temperature with minimal use of dead band is the goal of many BMS engineers. Polar Bear Design adds a new tool to the engineers list by allowing the heating system to be modulated and giving a third state to the normal On & Off of an underfloor actuator.

This feature allows the engineer to slow down the heating of the floor in the last 1 °C period of heating. This reduces the residual heat within the floor so as to dramatically reduce overshoot of the room’s temperature. Overshooting the rooms temperature can lead to flip flopping between heating and cooling. Normally this is contained by increasing the dead band zone, but that tends to only lead to a wider fluctuation of temperature for the user.

Heating modulation combats this and allows for smaller dead band settings and tighter overall control over comfort.

Enabling Heating Only or Cooling Only

The Zentium thermostat is traditionally a Heating and Cooling controller. However, it can be configured to a ’Cooling only’ or ’Heating only’ product. When these changes are set, any display symbols or pages relevant to those features are removed from the user’s interface, eliminating confusion.

Dual Zone

Zentium is a dual zone thermostat allowing two rooms to be monitored and controlled independently. This is achieved by using a number of remote probes wired into the system. If the thermostat is installed in a single zone environment, then zone 2 can be disabled. When disabling zone 2 any symbols or pages are removed from the user’s interface.

Towel Radiators

The Zentium allows you to set a period of time you want a towel radiator to come on for. This feature like the others is simple to use using the digital crown. The Zentium can control up to two independent towel radiators and each can be disabled if not required, so they are removed from the users interface. See this video for a quick how to.

Product Parts

Digital CrownFace PlateMid PlateZentium Base Unit



Room Temperature SensorCentigrade or Fahrenheit
With configurable display resolutions of 0.1, 0.5 & 1.0 °C/°F
Accuracy ±0.5°C ±1°F
Includes Virtual Temperature Support
Dead band support0 – 8°C (in half degree increments) for heating
0 – 8°C (in half degree increments) for cooling
Total dead band width 16 °C
Floor TemperatureConfigurable Maximum Floor Temperature (for zone 1 & 2) Configurable Minimum Floor Temperature (for zone 1 & 2)
Zone Support
Zone 1:
Internal temperature probe & Humidity Sensor
3no. 10k3 remote probe inputs (2 x Wall & 1x Floor)
Zone 2:
2no. 10k3 remote probe inputs (1 x Wall & 1x Floor)
Zone 2 can be enabled or disabled

Heating Mode
Heating support can be enabled or disabled (per zone)
Includes Heating Modulation Support

Heat Boost Modes3 stage heating option
Stage 1: Primary heating source (Wet, Electric or Air)
Stage 2: (boost) Secondary heating (Wet, Electric)
Stage 3: (boost) Third Stage Heating (Warm Air)
Each stage configurable with temperature separation
Cooling Mode
Cooling support can be enabled or disabled (per zone)

Towel Rail Control
Optional Control over Towel Radiator Demand, via direct override and/or Timer
up to two towel radiator control (1per zone)
Hot Water Control
Optional Control over Hot Water Demand, via direct override and/or Timer
Operation Modes (opMode)Each zone (room) has an independent opMode (OFF, AUTO, Away, Heating Only, Cooling Only)
AWAY includes a configurable frost protection setback temperature.
Eco ModesEach Zone has independent Eco Mode that control the deadbands of the heating and cooling
There are four ecoModes avaible for each zone (OFF, Low, Medium & High) each eco mode has configurable threshold levels.
Humidity Support
Between 15% & 85% RH humidity readings
Accuracy ±2% RH

Setpoint Range
Adjustable setpoint between 5 & 36°C in 0.5 & 1.0 °C increments
Allows for installer configurable setpoint limits

Scheduling / TimeclockBuilt in RTC
7 x Room Pre-sets / profiles
Zone:1 5/2 day timer with 4/4 timers
Zone:2 5/2 day timer with 4/4 timers
Towel Rail Timer 2 per day
Hot Water Timer 2 per day
18 – 28 V DC – 80mA (used for power supply & volt drop calculations)
DC Power supplies used must have short circuit and overload protection

Typical Power Consumption
40mA / 1.0 W @ 24v DC
Test conditions: All features enabled, with external probes fitted. Screen in dim mode.

IP20 Rating, indoor use only

Ambient operating temperature: -5 °C to 45 °C, (23 °F to 113 °F)
0% to 85% non-condensing relative humidity. Indoor use only.

SELV/PELV/NEC® Class 2 wiring connects thermostats to other devices on the Modbus link.
Mode: RTU Framing (JBUS)
Baud Rate: 9600, 19200, 57600 & 115200
Byte Format: 8N1
Modbus ID: 1 – 32 (range)

Air-Conditioner control
(only on “ACM” Models)
For control of individual Air-Conditioner indoor units without a BMS
Secondary Modbus: as above, but MASTER mode @ 9600bps
Contact Polar Bear Design for the latest compatibility

SELV/PELV/NEC® Class 2 wiring connects thermostats to other devices on the Modbus link.
Mode: RTU Framing (JBUS)
Baud Rate: 9600, 19200, 57600 & 115200
Byte Format: 8N1
Modbus ID: 1 – 32 (range)

ESD Protection
Meets IEC 801-2. To withstand 15 kV electrostatic discharge without damage or memory loss.

Internal EEPROM is rated for 100,000 writes (non-volatile configuration only)

Power Failure
Features marked as non-volatile are saved to internal EEPROM memory and will be restored after power is returned.

See mounting details


DC Power Terminal (x2pin) accepts 24AWG to 12 AWG wires
Modbus Terminal (x3pin) accepts 28AWG to 16AWG wires
Remote probes Terminal (x10pin) accepts 28AWG to 16AWG wires

2.4 inch IPS TFT Screen 36.72(W) x 48.96 (H) mm
(262K) / Transmissive / Normally Black
Life Time 50,000 hrs (@ 25 °C)

Zentium Accessories

UMC Controller

8 way underfloor heating manifold controller

1g - Single gang, Metal backbox

The Zentium requires our specific J-box style back box to ensure correct fixings, enough cables space and correct alignment. The double gang back box is a special back box that ensure alignment of the lighting keypad and thermostat. If a Polar Bear Design back box is not used it is the responsibility of the installer to confirm their suitability, prior to design and ordering.

Floor Sensor

10K3 Floor sensor. Part available with a high quality thermistor element or platinum element. The sensor is housed in a plastic cap.

Pipe Strap On Sensor

10K3 Strap on pipe sensor, for obtaining temperatures of pipes

Thimble Wall Sensor

10k3 wall sensor avaialbe in Aluminium, Stainless Steel, Brass and white plastic

Button Wall Sensor

10K3 button wall sensor, used for remote temperature sensing and also room temperature averaging

What lighting keypads can be combined with the Zentium Thermostat ?

  • Lutron Palladiom
  • Lutron SeeTouch (US)
  • Lutron SeeTouch (International)
  • Lutron Pico / RA2 Select
  • Crestron Horizon

We are also investigating custom combinations such as Control 4

What is the standard finish ?

Our standard finish is Brushed Satin Nickel. The digital crown is bright nickel has a carbon fibre ring.

Can the Zentium be interfaced to a Control 4 system ?

Yes, the Zentium uses a standard RS485 Modbus communications protocol. The control 4 has a standard modbus module which allows the Zentium to be configured into your control 4 environmet.

Can the Zentium be interfaced to a Crestron system ?

Yes, the Crestron sytem has a number of methods to interface with the Zentium thermostat.

Creston Home

We have a gateway product that allows the Crestron & Crestron Home control systems to comunicate with the Polar Bear Design HVAC solution via BACnet IP.

Product Model Types & Variations

Model Numbers
ZEN-TH2-MB4-STD-NONESingle gang, base unit only (Face plate kit required)
ZEN-TH2-MB4-ACM-NONESingle gang, base unit only - with Air Conditioning Interface
Face Plate Kits


Single gang complete unit (2 Zone) Modbus Thermostat


Single gang, base unit only (Face plate kit required)


Single gang, base unit only - with 4 digital inputs


Single gang, base unit only - with Air Conditioning Interface


Zentium Lutron Pico Plate Kit including digital crown


Zentium Crestron Horizon Face Plate Kit including digital crown

We have produced a number of video clips for the Zentium. These are convienently added to youtube play lists

New Features


How To

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