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Salus RT520RF Room Thermostat RF Programmable Boiler Plus Compliant
The Salus RT520RF is a wireless programmable room thermostat that satisfies the Boiler Plus requirements of Building Regulations Part L for gas boiler installations in England — making it the mandatory compliance solution whenever a new gas boiler is installed. Its built-in OpenTherm load compensation is one of the four recognised Boiler Plus compliance routes, and it is the most cost-effective of them: unlike weather compensation or smart connected thermostats, load compensation requires no additional hardware and satisfies the regulation on its own. The thermostat communicates wirelessly over 868 MHz RF up to 30 m to the RXRT520 receiver (included), which connects directly to the boiler. Battery-powered (2 × AA), so no 230 V wiring to the thermostat itself. Pre-paired out of the box for tool-free setup. Optimum Start, Optimum Stop, TPI control algorithm (±0.25°C accuracy), Landlord PIN, Service Mode reminder and cooling mode are all included. 5-year warranty. ErP Class V rated.
Boiler Plus
Compliant
Open Therm
Load compensation
868 MHz
RF wireless
30m
RF range
TPI ±0.25°C
Control accuracy
5 yr
Warranty
ℹ Boiler Plus — what it is and why this thermostat satisfies it: Building Regulations Part L (England, in force from April 2018) requires that when a gas boiler is installed or replaced, an additional energy efficiency measure must be fitted. Four options are recognised: flue gas heat recovery, weather compensation, a smart thermostat with automation/optimisation, or load compensation. The RT520RF’s built-in OpenTherm load compensation satisfies this requirement. Installers and homeowners in England need to provide evidence of Boiler Plus compliance to Building Control — the RT520RF is a fully documented, compliant solution.
How OpenTherm Load Compensation Works
Standard on/off thermostats signal the boiler to fire at full temperature until the room reaches the setpoint, then switch off completely. This creates temperature overshoot, cycling, and inefficiency. Load compensation via OpenTherm works differently:
Room far below setpoint
The thermostat signals the boiler to fire at a higher flow temperature. Maximum heat output drives the room temperature up quickly.
Room approaching setpoint
As the room warms, the thermostat reduces the requested flow temperature. The boiler modulates down rather than cycling on/off.
Room at setpoint
The boiler is instructed to maintain a low flow temperature that exactly matches the ongoing heat loss — the heating system runs continuously at low output with no overshoot.
The result is no temperature overshoot, no cycling, and lower return temperatures to the boiler — which is the condition in which a condensing gas boiler achieves its highest efficiency. Salus estimate typical gas savings of 7 – 12 % versus a standard on/off thermostat, depending on the property and boiler.
What’s in the Box
RT520RF Thermostat
Battery-powered wireless thermostat with large backlit LCD. 118 × 95 × 26 mm. Wall-mount bracket or free-standing desk position.
RXRT520 Receiver
Mains-powered (230 V AC) receiver unit that connects to the boiler. 96 × 96 × 27 mm. Pre-paired to the thermostat — simply mount, wire and switch on.
2 × AA Batteries
Supplied for the thermostat. Long battery life — typical use gives 1 – 2 years before replacement.
Wall Bracket + Mounting Screws
Thermostat mounting bracket and all fixings for wall installation. The thermostat can also be placed on a desk or shelf without the bracket.
Key Features
Boiler Plus Compliant via OpenTherm Load Compensation
The RT520RF satisfies Building Regulations Part L (England) Boiler Plus requirements through its on-board OpenTherm load compensation. This is the most straightforward compliance route: no additional controls hardware, no internet connectivity required, and no dependency on cloud services. The thermostat automatically detects whether the boiler supports OpenTherm and switches to load compensation mode if it does. If the boiler is not OpenTherm-compatible, the RT520RF falls back to standard volt-free relay (on/off) switching — still a programmable thermostat, but without the modulating control.
Boiler Plus compliantOpenTherm auto-detectionVolt-free fallback
OpenTherm Protocol — Two-Way Boiler Communication
OpenTherm is a two-way digital communication protocol between the thermostat and boiler. Unlike a simple on/off volt-free contact, OpenTherm allows the thermostat to tell the boiler its exact requested flow temperature, and the boiler to report back its actual flow temperature, return temperature, flame status, and fault codes. This bidirectional link enables load compensation, makes fault diagnosis easier (some boiler faults appear on the thermostat display), and gives the installer visibility of boiler operation without accessing the boiler itself. The RT520RF is compatible with all OpenTherm-capable gas boilers from manufacturers including Worcester Bosch, Vaillant, Ideal, Baxi, Viessmann and others.
Two-way OpenThermFlow temp modulationFault code visibility
TPI Algorithm — ±0.25°C Temperature Accuracy
The Time Proportional and Integral (TPI) control algorithm is a significantly more accurate method of temperature control than simple hysteresis (on/off) thermostats. A hysteresis thermostat fires the boiler at, say, 19.5°C and switches it off at 20.5°C, causing a 1°C oscillation around the setpoint. TPI calculates the proportion of time the boiler should fire in each cycle based on how far the room temperature is from the target, achieving ±0.25°C accuracy — a 4× improvement. This improves comfort, reduces temperature overshoot and eliminates the sensation of the heating system ‘hunting’.
TPI algorithm±0.25°C accuracy0.1°C display resolution
Optimum Start and Optimum Stop
These two features adapt the heating programme schedule to weather and building conditions automatically. Optimum Start calculates how early the boiler needs to begin heating in order for the room to reach the setpoint at the programmed ‘on’ time. In colder weather, it starts earlier; in mild weather, later. The result is the room is always at temperature when needed, without wasting energy by starting unnecessarily early. Optimum Stop works in reverse: it switches the boiler off before the programmed end time, using the residual heat in the building to coast the room to the end of the heating period without additional gas consumption.
Optimum StartOptimum StopWeather-adaptive scheduling
Battery-Powered Thermostat — No Wiring to the Room
The RT520RF thermostat runs on 2 × AA batteries. There is no 230 V cable to run to the thermostat location. This is the single biggest practical advantage of an RF wireless thermostat: the thermostat can be placed anywhere in the room — on an internal wall away from the radiator, on a desk or windowsill — without lifting floorboards, chasing walls, or disturbing decoration. The RXRT520 receiver is the only mains-connected component, and it mounts at the boiler or control location where wiring is already present.
Battery thermostatNo 230V wiring to roomRXRT520 receiver included
868 MHz Pre-Paired RF — Up to 30 m Range
The 868 MHz frequency band provides excellent wall penetration compared to 2.4 GHz (Wi-Fi band) devices, giving reliable connectivity through multiple floors and solid walls. The rated range of 30 m is a clear-air measurement; real-world range through walls is typically 10 – 15 m. The thermostat and receiver are factory pre-paired: no pairing procedure is required on installation. Simply mount, connect the receiver, and the system is operational. The RT520RF is also compatible with the full existing range of Salus receivers, so it can replace an older Salus wireless thermostat without changing the receiver.
868 MHz RFUp to 30m rangePre-paired out of box
Programmable 7-Day Schedule — Predefined and Customisable
The large backlit LCD provides clear access to a 7-day heating programme with multiple time/temperature periods per day. Predefined programmes are included for typical household patterns; all periods are fully customisable. A manual override allows the setpoint to be temporarily raised or lowered until the next scheduled change, without altering the underlying programme. The thermostat also includes a cooling mode for use with heat pump or air conditioning systems that provide cooling.
7-day programmeManual overrideCooling mode
Landlord PIN and Service Mode
The Landlord PIN allows a property owner or letting agent to lock certain settings and menus so tenants cannot change programmed schedules, minimum/maximum temperature limits, or operating modes. The thermostat remains usable for temperature adjustment within the permitted range but the underlying programme is protected. Service Mode enables the thermostat to be programmed with a service reminder: after a set period, a notification appears on the display alerting the occupant that a boiler service is due. For landlords managing multiple properties, this provides a simple, automated way to prompt annual boiler servicing without relying on tenants.
Landlord PIN protectionService reminder modeRental property ready
Technical Specifications
| Thermostat (RT520RF) | |
| Power supply | 2 × AA batteries |
| Dimensions (H × W × D) | 118 × 95 × 26 mm |
| RF frequency | 868 MHz |
| RF range | Up to 30 m (clear air) |
| Mounting | Wall bracket or desk/shelf (free-standing) |
| Receiver (RXRT520) | |
| Power supply | 230 V AC 50 Hz |
| Dimensions (H × W × D) | 96 × 96 × 27 mm |
| Max output load | 3(1) A |
| Control output | OpenTherm modulating or volt-free relay (COM/NO/NC) |
| Control Performance | |
| Temperature range | 5 – 33.5°C |
| Display resolution | 0.1°C or 0.5°C (selectable) |
| Control algorithm | TPI (Time Proportional & Integral) |
| TPI accuracy | ±0.25°C or ±0.5°C (selectable) |
| Adjustable hysteresis | 0.25°C – 0.5°C |
| Features | |
| Boiler Plus compliance | Yes — via OpenTherm load compensation |
| OpenTherm | Yes — auto-detected, two-way communication |
| Optimum Start / Optimum Stop | Yes |
| Programming | 7-day, predefined + fully customisable |
| Manual override | Yes (until next scheduled period) |
| Cooling mode | Yes |
| Landlord PIN | Yes |
| Service Mode reminder | Yes |
| Works with NO and NC actuators | Yes |
| Pre-paired | Yes — factory paired, no pairing required on install |
| Compatible receivers | Existing Salus RT-series receiver range |
| Certifications | |
| Boiler Plus | Compliant (Building Regulations Part L, England) |
| ErP rating | Class V |
| Warranty | |
| Warranty | 5 years |
| Support period end date | 31 December 2030 |
| Box Contents | |
| Included | RT520RF wireless thermostat, RXRT520 receiver, wall bracket, 2 × AA batteries, mounting screws |
Frequently Asked Questions
Related Products
Salus RT520 (Wired Version)
Wired version of the same thermostat — same features, no RF receiver required
Strom 14.4kW Electric Boiler (SBSP15H)
Compatible electric boiler for use with room thermostats
Grundfos UPM3 AUTO Circulator Pump
High-efficiency heating circulator to complement a controlled heating system
Intatec HPBV28 Heat Pump Ball Valve
Isolation valve for heating systems undergoing thermostat upgrades
$34.01
Original: $97.18
-65%Salus RT520RF Room Thermostat RF Programmable Boiler Plus Compliant—
$97.18
$34.01More Images
Salus RT520RF Room Thermostat RF Programmable Boiler Plus Compliant
The Salus RT520RF is a wireless programmable room thermostat that satisfies the Boiler Plus requirements of Building Regulations Part L for gas boiler installations in England — making it the mandatory compliance solution whenever a new gas boiler is installed. Its built-in OpenTherm load compensation is one of the four recognised Boiler Plus compliance routes, and it is the most cost-effective of them: unlike weather compensation or smart connected thermostats, load compensation requires no additional hardware and satisfies the regulation on its own. The thermostat communicates wirelessly over 868 MHz RF up to 30 m to the RXRT520 receiver (included), which connects directly to the boiler. Battery-powered (2 × AA), so no 230 V wiring to the thermostat itself. Pre-paired out of the box for tool-free setup. Optimum Start, Optimum Stop, TPI control algorithm (±0.25°C accuracy), Landlord PIN, Service Mode reminder and cooling mode are all included. 5-year warranty. ErP Class V rated.
Boiler Plus
Compliant
Open Therm
Load compensation
868 MHz
RF wireless
30m
RF range
TPI ±0.25°C
Control accuracy
5 yr
Warranty
ℹ Boiler Plus — what it is and why this thermostat satisfies it: Building Regulations Part L (England, in force from April 2018) requires that when a gas boiler is installed or replaced, an additional energy efficiency measure must be fitted. Four options are recognised: flue gas heat recovery, weather compensation, a smart thermostat with automation/optimisation, or load compensation. The RT520RF’s built-in OpenTherm load compensation satisfies this requirement. Installers and homeowners in England need to provide evidence of Boiler Plus compliance to Building Control — the RT520RF is a fully documented, compliant solution.
How OpenTherm Load Compensation Works
Standard on/off thermostats signal the boiler to fire at full temperature until the room reaches the setpoint, then switch off completely. This creates temperature overshoot, cycling, and inefficiency. Load compensation via OpenTherm works differently:
Room far below setpoint
The thermostat signals the boiler to fire at a higher flow temperature. Maximum heat output drives the room temperature up quickly.
Room approaching setpoint
As the room warms, the thermostat reduces the requested flow temperature. The boiler modulates down rather than cycling on/off.
Room at setpoint
The boiler is instructed to maintain a low flow temperature that exactly matches the ongoing heat loss — the heating system runs continuously at low output with no overshoot.
The result is no temperature overshoot, no cycling, and lower return temperatures to the boiler — which is the condition in which a condensing gas boiler achieves its highest efficiency. Salus estimate typical gas savings of 7 – 12 % versus a standard on/off thermostat, depending on the property and boiler.
What’s in the Box
RT520RF Thermostat
Battery-powered wireless thermostat with large backlit LCD. 118 × 95 × 26 mm. Wall-mount bracket or free-standing desk position.
RXRT520 Receiver
Mains-powered (230 V AC) receiver unit that connects to the boiler. 96 × 96 × 27 mm. Pre-paired to the thermostat — simply mount, wire and switch on.
2 × AA Batteries
Supplied for the thermostat. Long battery life — typical use gives 1 – 2 years before replacement.
Wall Bracket + Mounting Screws
Thermostat mounting bracket and all fixings for wall installation. The thermostat can also be placed on a desk or shelf without the bracket.
Key Features
Boiler Plus Compliant via OpenTherm Load Compensation
The RT520RF satisfies Building Regulations Part L (England) Boiler Plus requirements through its on-board OpenTherm load compensation. This is the most straightforward compliance route: no additional controls hardware, no internet connectivity required, and no dependency on cloud services. The thermostat automatically detects whether the boiler supports OpenTherm and switches to load compensation mode if it does. If the boiler is not OpenTherm-compatible, the RT520RF falls back to standard volt-free relay (on/off) switching — still a programmable thermostat, but without the modulating control.
Boiler Plus compliantOpenTherm auto-detectionVolt-free fallback
OpenTherm Protocol — Two-Way Boiler Communication
OpenTherm is a two-way digital communication protocol between the thermostat and boiler. Unlike a simple on/off volt-free contact, OpenTherm allows the thermostat to tell the boiler its exact requested flow temperature, and the boiler to report back its actual flow temperature, return temperature, flame status, and fault codes. This bidirectional link enables load compensation, makes fault diagnosis easier (some boiler faults appear on the thermostat display), and gives the installer visibility of boiler operation without accessing the boiler itself. The RT520RF is compatible with all OpenTherm-capable gas boilers from manufacturers including Worcester Bosch, Vaillant, Ideal, Baxi, Viessmann and others.
Two-way OpenThermFlow temp modulationFault code visibility
TPI Algorithm — ±0.25°C Temperature Accuracy
The Time Proportional and Integral (TPI) control algorithm is a significantly more accurate method of temperature control than simple hysteresis (on/off) thermostats. A hysteresis thermostat fires the boiler at, say, 19.5°C and switches it off at 20.5°C, causing a 1°C oscillation around the setpoint. TPI calculates the proportion of time the boiler should fire in each cycle based on how far the room temperature is from the target, achieving ±0.25°C accuracy — a 4× improvement. This improves comfort, reduces temperature overshoot and eliminates the sensation of the heating system ‘hunting’.
TPI algorithm±0.25°C accuracy0.1°C display resolution
Optimum Start and Optimum Stop
These two features adapt the heating programme schedule to weather and building conditions automatically. Optimum Start calculates how early the boiler needs to begin heating in order for the room to reach the setpoint at the programmed ‘on’ time. In colder weather, it starts earlier; in mild weather, later. The result is the room is always at temperature when needed, without wasting energy by starting unnecessarily early. Optimum Stop works in reverse: it switches the boiler off before the programmed end time, using the residual heat in the building to coast the room to the end of the heating period without additional gas consumption.
Optimum StartOptimum StopWeather-adaptive scheduling
Battery-Powered Thermostat — No Wiring to the Room
The RT520RF thermostat runs on 2 × AA batteries. There is no 230 V cable to run to the thermostat location. This is the single biggest practical advantage of an RF wireless thermostat: the thermostat can be placed anywhere in the room — on an internal wall away from the radiator, on a desk or windowsill — without lifting floorboards, chasing walls, or disturbing decoration. The RXRT520 receiver is the only mains-connected component, and it mounts at the boiler or control location where wiring is already present.
Battery thermostatNo 230V wiring to roomRXRT520 receiver included
868 MHz Pre-Paired RF — Up to 30 m Range
The 868 MHz frequency band provides excellent wall penetration compared to 2.4 GHz (Wi-Fi band) devices, giving reliable connectivity through multiple floors and solid walls. The rated range of 30 m is a clear-air measurement; real-world range through walls is typically 10 – 15 m. The thermostat and receiver are factory pre-paired: no pairing procedure is required on installation. Simply mount, connect the receiver, and the system is operational. The RT520RF is also compatible with the full existing range of Salus receivers, so it can replace an older Salus wireless thermostat without changing the receiver.
868 MHz RFUp to 30m rangePre-paired out of box
Programmable 7-Day Schedule — Predefined and Customisable
The large backlit LCD provides clear access to a 7-day heating programme with multiple time/temperature periods per day. Predefined programmes are included for typical household patterns; all periods are fully customisable. A manual override allows the setpoint to be temporarily raised or lowered until the next scheduled change, without altering the underlying programme. The thermostat also includes a cooling mode for use with heat pump or air conditioning systems that provide cooling.
7-day programmeManual overrideCooling mode
Landlord PIN and Service Mode
The Landlord PIN allows a property owner or letting agent to lock certain settings and menus so tenants cannot change programmed schedules, minimum/maximum temperature limits, or operating modes. The thermostat remains usable for temperature adjustment within the permitted range but the underlying programme is protected. Service Mode enables the thermostat to be programmed with a service reminder: after a set period, a notification appears on the display alerting the occupant that a boiler service is due. For landlords managing multiple properties, this provides a simple, automated way to prompt annual boiler servicing without relying on tenants.
Landlord PIN protectionService reminder modeRental property ready
Technical Specifications
| Thermostat (RT520RF) | |
| Power supply | 2 × AA batteries |
| Dimensions (H × W × D) | 118 × 95 × 26 mm |
| RF frequency | 868 MHz |
| RF range | Up to 30 m (clear air) |
| Mounting | Wall bracket or desk/shelf (free-standing) |
| Receiver (RXRT520) | |
| Power supply | 230 V AC 50 Hz |
| Dimensions (H × W × D) | 96 × 96 × 27 mm |
| Max output load | 3(1) A |
| Control output | OpenTherm modulating or volt-free relay (COM/NO/NC) |
| Control Performance | |
| Temperature range | 5 – 33.5°C |
| Display resolution | 0.1°C or 0.5°C (selectable) |
| Control algorithm | TPI (Time Proportional & Integral) |
| TPI accuracy | ±0.25°C or ±0.5°C (selectable) |
| Adjustable hysteresis | 0.25°C – 0.5°C |
| Features | |
| Boiler Plus compliance | Yes — via OpenTherm load compensation |
| OpenTherm | Yes — auto-detected, two-way communication |
| Optimum Start / Optimum Stop | Yes |
| Programming | 7-day, predefined + fully customisable |
| Manual override | Yes (until next scheduled period) |
| Cooling mode | Yes |
| Landlord PIN | Yes |
| Service Mode reminder | Yes |
| Works with NO and NC actuators | Yes |
| Pre-paired | Yes — factory paired, no pairing required on install |
| Compatible receivers | Existing Salus RT-series receiver range |
| Certifications | |
| Boiler Plus | Compliant (Building Regulations Part L, England) |
| ErP rating | Class V |
| Warranty | |
| Warranty | 5 years |
| Support period end date | 31 December 2030 |
| Box Contents | |
| Included | RT520RF wireless thermostat, RXRT520 receiver, wall bracket, 2 × AA batteries, mounting screws |
Frequently Asked Questions
Related Products
Salus RT520 (Wired Version)
Wired version of the same thermostat — same features, no RF receiver required
Strom 14.4kW Electric Boiler (SBSP15H)
Compatible electric boiler for use with room thermostats
Grundfos UPM3 AUTO Circulator Pump
High-efficiency heating circulator to complement a controlled heating system
Intatec HPBV28 Heat Pump Ball Valve
Isolation valve for heating systems undergoing thermostat upgrades
Product Information
Product Information
Shipping & Returns
Shipping & Returns
Description
The Salus RT520RF is a wireless programmable room thermostat that satisfies the Boiler Plus requirements of Building Regulations Part L for gas boiler installations in England — making it the mandatory compliance solution whenever a new gas boiler is installed. Its built-in OpenTherm load compensation is one of the four recognised Boiler Plus compliance routes, and it is the most cost-effective of them: unlike weather compensation or smart connected thermostats, load compensation requires no additional hardware and satisfies the regulation on its own. The thermostat communicates wirelessly over 868 MHz RF up to 30 m to the RXRT520 receiver (included), which connects directly to the boiler. Battery-powered (2 × AA), so no 230 V wiring to the thermostat itself. Pre-paired out of the box for tool-free setup. Optimum Start, Optimum Stop, TPI control algorithm (±0.25°C accuracy), Landlord PIN, Service Mode reminder and cooling mode are all included. 5-year warranty. ErP Class V rated.
Boiler Plus
Compliant
Open Therm
Load compensation
868 MHz
RF wireless
30m
RF range
TPI ±0.25°C
Control accuracy
5 yr
Warranty
ℹ Boiler Plus — what it is and why this thermostat satisfies it: Building Regulations Part L (England, in force from April 2018) requires that when a gas boiler is installed or replaced, an additional energy efficiency measure must be fitted. Four options are recognised: flue gas heat recovery, weather compensation, a smart thermostat with automation/optimisation, or load compensation. The RT520RF’s built-in OpenTherm load compensation satisfies this requirement. Installers and homeowners in England need to provide evidence of Boiler Plus compliance to Building Control — the RT520RF is a fully documented, compliant solution.
How OpenTherm Load Compensation Works
Standard on/off thermostats signal the boiler to fire at full temperature until the room reaches the setpoint, then switch off completely. This creates temperature overshoot, cycling, and inefficiency. Load compensation via OpenTherm works differently:
Room far below setpoint
The thermostat signals the boiler to fire at a higher flow temperature. Maximum heat output drives the room temperature up quickly.
Room approaching setpoint
As the room warms, the thermostat reduces the requested flow temperature. The boiler modulates down rather than cycling on/off.
Room at setpoint
The boiler is instructed to maintain a low flow temperature that exactly matches the ongoing heat loss — the heating system runs continuously at low output with no overshoot.
The result is no temperature overshoot, no cycling, and lower return temperatures to the boiler — which is the condition in which a condensing gas boiler achieves its highest efficiency. Salus estimate typical gas savings of 7 – 12 % versus a standard on/off thermostat, depending on the property and boiler.
What’s in the Box
RT520RF Thermostat
Battery-powered wireless thermostat with large backlit LCD. 118 × 95 × 26 mm. Wall-mount bracket or free-standing desk position.
RXRT520 Receiver
Mains-powered (230 V AC) receiver unit that connects to the boiler. 96 × 96 × 27 mm. Pre-paired to the thermostat — simply mount, wire and switch on.
2 × AA Batteries
Supplied for the thermostat. Long battery life — typical use gives 1 – 2 years before replacement.
Wall Bracket + Mounting Screws
Thermostat mounting bracket and all fixings for wall installation. The thermostat can also be placed on a desk or shelf without the bracket.
Key Features
Boiler Plus Compliant via OpenTherm Load Compensation
The RT520RF satisfies Building Regulations Part L (England) Boiler Plus requirements through its on-board OpenTherm load compensation. This is the most straightforward compliance route: no additional controls hardware, no internet connectivity required, and no dependency on cloud services. The thermostat automatically detects whether the boiler supports OpenTherm and switches to load compensation mode if it does. If the boiler is not OpenTherm-compatible, the RT520RF falls back to standard volt-free relay (on/off) switching — still a programmable thermostat, but without the modulating control.
Boiler Plus compliantOpenTherm auto-detectionVolt-free fallback
OpenTherm Protocol — Two-Way Boiler Communication
OpenTherm is a two-way digital communication protocol between the thermostat and boiler. Unlike a simple on/off volt-free contact, OpenTherm allows the thermostat to tell the boiler its exact requested flow temperature, and the boiler to report back its actual flow temperature, return temperature, flame status, and fault codes. This bidirectional link enables load compensation, makes fault diagnosis easier (some boiler faults appear on the thermostat display), and gives the installer visibility of boiler operation without accessing the boiler itself. The RT520RF is compatible with all OpenTherm-capable gas boilers from manufacturers including Worcester Bosch, Vaillant, Ideal, Baxi, Viessmann and others.
Two-way OpenThermFlow temp modulationFault code visibility
TPI Algorithm — ±0.25°C Temperature Accuracy
The Time Proportional and Integral (TPI) control algorithm is a significantly more accurate method of temperature control than simple hysteresis (on/off) thermostats. A hysteresis thermostat fires the boiler at, say, 19.5°C and switches it off at 20.5°C, causing a 1°C oscillation around the setpoint. TPI calculates the proportion of time the boiler should fire in each cycle based on how far the room temperature is from the target, achieving ±0.25°C accuracy — a 4× improvement. This improves comfort, reduces temperature overshoot and eliminates the sensation of the heating system ‘hunting’.
TPI algorithm±0.25°C accuracy0.1°C display resolution
Optimum Start and Optimum Stop
These two features adapt the heating programme schedule to weather and building conditions automatically. Optimum Start calculates how early the boiler needs to begin heating in order for the room to reach the setpoint at the programmed ‘on’ time. In colder weather, it starts earlier; in mild weather, later. The result is the room is always at temperature when needed, without wasting energy by starting unnecessarily early. Optimum Stop works in reverse: it switches the boiler off before the programmed end time, using the residual heat in the building to coast the room to the end of the heating period without additional gas consumption.
Optimum StartOptimum StopWeather-adaptive scheduling
Battery-Powered Thermostat — No Wiring to the Room
The RT520RF thermostat runs on 2 × AA batteries. There is no 230 V cable to run to the thermostat location. This is the single biggest practical advantage of an RF wireless thermostat: the thermostat can be placed anywhere in the room — on an internal wall away from the radiator, on a desk or windowsill — without lifting floorboards, chasing walls, or disturbing decoration. The RXRT520 receiver is the only mains-connected component, and it mounts at the boiler or control location where wiring is already present.
Battery thermostatNo 230V wiring to roomRXRT520 receiver included
868 MHz Pre-Paired RF — Up to 30 m Range
The 868 MHz frequency band provides excellent wall penetration compared to 2.4 GHz (Wi-Fi band) devices, giving reliable connectivity through multiple floors and solid walls. The rated range of 30 m is a clear-air measurement; real-world range through walls is typically 10 – 15 m. The thermostat and receiver are factory pre-paired: no pairing procedure is required on installation. Simply mount, connect the receiver, and the system is operational. The RT520RF is also compatible with the full existing range of Salus receivers, so it can replace an older Salus wireless thermostat without changing the receiver.
868 MHz RFUp to 30m rangePre-paired out of box
Programmable 7-Day Schedule — Predefined and Customisable
The large backlit LCD provides clear access to a 7-day heating programme with multiple time/temperature periods per day. Predefined programmes are included for typical household patterns; all periods are fully customisable. A manual override allows the setpoint to be temporarily raised or lowered until the next scheduled change, without altering the underlying programme. The thermostat also includes a cooling mode for use with heat pump or air conditioning systems that provide cooling.
7-day programmeManual overrideCooling mode
Landlord PIN and Service Mode
The Landlord PIN allows a property owner or letting agent to lock certain settings and menus so tenants cannot change programmed schedules, minimum/maximum temperature limits, or operating modes. The thermostat remains usable for temperature adjustment within the permitted range but the underlying programme is protected. Service Mode enables the thermostat to be programmed with a service reminder: after a set period, a notification appears on the display alerting the occupant that a boiler service is due. For landlords managing multiple properties, this provides a simple, automated way to prompt annual boiler servicing without relying on tenants.
Landlord PIN protectionService reminder modeRental property ready
Technical Specifications
| Thermostat (RT520RF) | |
| Power supply | 2 × AA batteries |
| Dimensions (H × W × D) | 118 × 95 × 26 mm |
| RF frequency | 868 MHz |
| RF range | Up to 30 m (clear air) |
| Mounting | Wall bracket or desk/shelf (free-standing) |
| Receiver (RXRT520) | |
| Power supply | 230 V AC 50 Hz |
| Dimensions (H × W × D) | 96 × 96 × 27 mm |
| Max output load | 3(1) A |
| Control output | OpenTherm modulating or volt-free relay (COM/NO/NC) |
| Control Performance | |
| Temperature range | 5 – 33.5°C |
| Display resolution | 0.1°C or 0.5°C (selectable) |
| Control algorithm | TPI (Time Proportional & Integral) |
| TPI accuracy | ±0.25°C or ±0.5°C (selectable) |
| Adjustable hysteresis | 0.25°C – 0.5°C |
| Features | |
| Boiler Plus compliance | Yes — via OpenTherm load compensation |
| OpenTherm | Yes — auto-detected, two-way communication |
| Optimum Start / Optimum Stop | Yes |
| Programming | 7-day, predefined + fully customisable |
| Manual override | Yes (until next scheduled period) |
| Cooling mode | Yes |
| Landlord PIN | Yes |
| Service Mode reminder | Yes |
| Works with NO and NC actuators | Yes |
| Pre-paired | Yes — factory paired, no pairing required on install |
| Compatible receivers | Existing Salus RT-series receiver range |
| Certifications | |
| Boiler Plus | Compliant (Building Regulations Part L, England) |
| ErP rating | Class V |
| Warranty | |
| Warranty | 5 years |
| Support period end date | 31 December 2030 |
| Box Contents | |
| Included | RT520RF wireless thermostat, RXRT520 receiver, wall bracket, 2 × AA batteries, mounting screws |
Frequently Asked Questions
Related Products
Salus RT520 (Wired Version)
Wired version of the same thermostat — same features, no RF receiver required
Strom 14.4kW Electric Boiler (SBSP15H)
Compatible electric boiler for use with room thermostats
Grundfos UPM3 AUTO Circulator Pump
High-efficiency heating circulator to complement a controlled heating system
Intatec HPBV28 Heat Pump Ball Valve
Isolation valve for heating systems undergoing thermostat upgrades
