Herschel Thermostats and Infrared Heating Controls

A Herschel thermostat is the room control for a Herschel infrared heating system: it measures the temperature in the space and switches the panels on and off to hold the level you set. In that it does what any room thermostat does, and the general case is well put by Smart Energy GB: a smart thermostat "controls heating" and "helps you manage how your central heating is set and adjusted"¹. What makes Herschel controls distinctive is that most Herschel panels have no usable control of their own. The Herschel Krystal infrared panel heater, for example, is controlled "via hard wiring to one of Herschel's iQ range of thermostats (purchased separately)"², so the thermostat is not an accessory but the thing that makes the heater a heating system rather than a hot metal plate on a wall.

Not every Herschel heater is in that position. The Select Portable Infrared Heater 500W "has an in-built thermostat to provide simple temperature control making it fully compliant with European energy saving regulation (Lot 20)"³, and many outdoor heaters come with built-in on/off switches and remote control options⁴. But for the wall and ceiling panels that make up most Herschel installations, a separate thermostat is how the room gets a setpoint, a schedule and the Lot 20 energy-saving features the regulations expect. Herschel's own wiring rule for Select XLS panels is that they are "installed on individual fused spurs and a single XLS Thermostat can be placed in the room"⁵.

Why Herschel panels need a separate control

Infrared panels heat people and surfaces directly rather than warming the air, so a panel left switched on simply keeps radiating at full output. A thermostat turns that output into a controlled system: it reads the room, cuts the power when the setpoint is reached and brings the panels back as the room cools. Home Energy Scotland's summary of what heating controls do applies directly here: they "allow you to set and maintain the temperature in your home and make sure it's warm for the times of day that you're at home and switched off to save electricity when you're not"¹².

The control also carries the regulatory weight. Herschel states that its range of thermostats "incorporate Lot 20 compliant Energy-Saving features such as Open Window technology and Adaptive Start", along with full app control, geofencing and motion sensors¹⁰. Open Window technology drops the heat when a sudden temperature fall suggests a window has been opened; Adaptive Start brings the room up to temperature in time for the schedule rather than at it. Without a thermostat, a fixed-wattage panel has neither, which is why Herschel sells the controls as a required part of the installation rather than an upgrade. Herschel also states 240v as the rated voltage limit of its single-phase heaters⁴, and the thermostat is where that load is switched.

The iQ MD2 wired thermostat: 16 amps, 3.6kW

The MD2 is Herschel's wired room thermostat and the higher-capacity of the two iQ controls. It is a "16 Amp wired thermostat" enabling "up to 3.6 kW of Herschel heaters to be connected"⁶, which is roughly double what the wireless option can switch on one circuit. It communicates on the 2.4GHz wifi band for app control⁶, and it is installed differently from the wireless options: "MD2 is wired directly to the mains circuit and to the heaters and requires recessing into the wall"⁶. That makes it a job for an electrician, and it makes the wall part of the installation.

Herschel positions the MD2 as "suitable for commercial applications such as hotels, care homes, student accommodation and let properties"⁷, which fits its capacity: a single MD2 can run several panels in one large space. The price is £69.00⁷. One limit matters before ordering: "the MD2 thermostat is not compatible with Remote models"⁶. The Summit 2600 outdoor heater illustrates the split, since the non-remote model "can be used with external thermostat controllers, such as the Herschel iQ MD2, allowing thermostatic and App control"¹³.

The iQ T2 wireless thermostat: £69 with a receiver

The T2 is the wireless route, sold as a set of two parts: "The T-T2 pack incorporates one T2 thermostat and one R2 Receiver"⁸. The battery-powered thermostat talks to the receiver over a 433 MHz radio link, and the receiver is the piece wired into the heater circuit⁸. The set "will control up to 2kW (at 230V supply) of Herschel Infrared heaters on one electrical circuit"⁸, so a room with more than 2kW of panels needs either a second circuit and receiver or the wired MD2. The setpoint range is 5 to 35 degrees C "with temperature increments 0.5 °C"⁸, and the T2 carries the Open Window and Adaptive Start energy-saving features⁸.

The price is £69.00⁹, the same figure as the MD2, with the R2 receiver also listed at £54.00 on its own⁹. The R2's own listing confirms the setpoint range of 5 to 35 degrees C and its use "with T2 thermostat"⁹. Wifi for app control is "enabled via R2 receiver"⁸, which is worth understanding: the thermostat itself is a radio device, and the internet connection lives at the receiver.

Choosing between cabled and cable free setups for your home

The practical difference is where the wiring goes. A wireless thermostat "usually sends a signal to a receiver connected to the boiler, which then tells the boiler when to turn the heating on or off, without a direct wired connection between thermostat and boiler"¹; in Herschel's case the receiver sits on the heater circuit instead. Netatmo's guidance on wireless thermostats is that they involve "no complex installation" and are "installed more flexibly than a wired thermostat"¹⁴, which is the T2's advantage: it can sit where the room is best measured, not where a cable can reach, and it needs no chasing into the wall.

The MD2 trades that flexibility for capacity and permanence: 3.6kW against 2kW, and a fixed control that cannot be lost or have its batteries run flat. Herschel notes that its battery-powered thermostats, the T-BT and T2, "should give you a full heating season's operation on a fresh set of 1.5V alkaline batteries", though poor radio contact can raise consumption up to four times normal⁵.

Two wifi caveats apply whichever you choose. Herschel states that "you cannot manage a wireless thermostat on a network extender (where attached devices are just 'guests')": the thermostat and app must be paired and operated on the main network¹⁵. And app features need "good 2.4GHz wifi signal" and a router without too many simultaneous connections¹⁶. Offline, nothing stops working: Herschel's range headline is "No WiFi? No Problem. All Our Thermostats Can Operate Without WiFi"¹¹. The wider trade-offs are set out in wired vs wireless room thermostats.

Managing your heating by phone, speech and the SmartLife App

Herschel's app is Smart Life, and it is the route to scheduling, remote control and voice. The T2 set lists Smartlife app control and voice control that "Works with Alexa and Google Assistant when paired with the SmartLife App"⁸. The iQ R3 controller, which works with the Comfort and Inspire ranges, is the most app-dependent of the lot: it connects on 2.4GHz wifi, and its programming is "Only via Smart Life App", with voice control through "Alexa or Google Assistant via Smart Life App"¹⁷. The plugin T-PL thermostat adds the same app and voice pairing¹³, and Herschel's portable heaters are also app-controlled, with all models connectable to home or office wifi for "precise App control using the Smart Life App"¹⁸.

Pairing is where most problems land. Herschel's support article on the subject states that "the root cause of App pairing problems lies in the phone and the thermostat failing to connect successfully to the same" 2.4GHz local wifi network¹⁵. Once paired, voice control does not need a smart speaker in the house: Herschel confirms "you do not need a local Alexa or Google device (e.g. like an Echo Dot or Google Home Hub) to run the commands for you"¹⁶. One model is excluded from app control entirely: the T-BT "is not Wifi Enabled and therefore cannot pair"⁵.

A PIR motion sensor can be added to app-enabled thermostats, but only as an accessory: "The PIR sensor must be used in conjunction with a Herscher Thermostat, it will not control your heating just on its own"¹⁹. The wider picture of what app control does and does not buy a household is in smart thermostats and heating controls and energy independence.

What compatibility restrictions mean for your guarantee

The single most important line on every Herschel control product page is the same: "Herschel iQ controls will only work with Herschel heaters"¹⁰. The restriction goes further on some models. The T-PL "will only work with Herschel XLS heaters. It is not possible to operate the T-PL with any other brand of infrared heater"¹³, the T-BT is likewise exclusive to Herschel XLS heaters with the built-in SMART-R receiver²⁰, and the T-MTLED SmartLED thermostat cannot be operated "with any other brand of infrared heater"²¹.

The warranty follows the compatibility. Across the iQ MD2, T2 set, R3, T-MKS, T-BT and T-MTLED, Herschel's condition is identical: "Attempted use with any other heater brand will invalidate the warranty"⁶. The controls carry a 2 year warranty⁹.

Within the Herschel range, the pairing rules are generous. Herschel advises one controller per room, with each controller able to run one or multiple panels; multiple R2 receivers can be paired with a single T2, and multiple panels pair to a single XLS thermostat⁵. The battery and plugin thermostats can each be paired to more than one heater so that everything in a room follows one setting²⁰.

Installation, and what owning Herschel controls means

Installation weight differs sharply by model. The MD2 is "wired directly to the mains circuit and to the heaters and requires recessing into the wall"⁶, which is electrician work and a permanent alteration to the building. The T2's receiver still needs wiring into the heater circuit, but the thermostat itself mounts anywhere in radio range. Herschel's Comfort ceiling tile heaters are described as "easy to install and control using Herschel's iQ thermostats or existing building management controls"²², and the Select XLS LED front-lit panel offers "Independent light only control"²³, so lighting and heating can be separated.

Regulation is on the side of fitting proper controls. Approved Document L requires that in new dwellings, and when a heat generator is replaced in an existing one, "each room should be provided with thermostatic room controls"²⁴. Planning Portal sustainability guidance for self-build homes goes further and advises households to "install smart systems that control lighting, heating, and cooling based on occupancy and time of day"²⁵. Uswitch's guidance on electric heaters notes that standalone heaters "tend to be more energy efficient if they have thermostatic controls" that switch off at a set temperature²⁶. Herschel states that its heaters and control products "are certified to national safety standards" and that its thermostats are tested to be free of radio interference⁵.

On independence, the honest position is mixed. A Herschel infrared system removes the household's dependence on gas: the fuel is electricity, which can come from the household's own supply arrangement or a solar array. What replaces the gas dependence is a dependence on the manufacturer. The controls only work with Herschel heaters, the app only works with Herschel's Smart Life platform, diagnosis and spare parts run through one company, and the warranty depends on staying inside that ecosystem. Local control at the thermostat continues without wifi¹¹, but scheduling, energy monitoring and voice all run through the app and the maker's servers. The general pattern is examined in heating controls and energy independence.

How the thermostat changes infrared running costs

The thermostat is where an infrared system earns or wastes its money, because a panel without one runs at full wattage whenever it is switched on. Herschel's own guidance on running costs makes the point: with thermostat control, "it is likely you will actually require 5 hours running a day or less, especially if you have two 600 Watt heaters", and Herschel claims its infrared is cheaper to run than storage heaters²⁷. That claim is a maker's, and the independent view is more measured: the Energy Saving Trust states that "a well-controlled infrared system will probably cost less to run than standard electric panel heaters", and that infrared "might also be cheaper to run than storage heaters or electric underfloor heating, depending on how they're controlled, but there's little research available to confirm this"²⁸. Control is the variable in both halves of that sentence.

The cost of the control itself is modest against the panels: £69.00 for either the MD2 or the T2 set⁷, with the plugin T-PL at £79.00 and the SmartLED T-MTLED at £102.00¹³. Smart Energy GB adds a general caution about smart controls of any brand: "They can be expensive and have an installation cost. And having one means you are only tracking your heating. So you can't keep an eye on your electricity and gas usage"²⁹. For a Herschel household the arithmetic is therefore simple in shape: the thermostat is a small one-off cost that determines whether multi-kilowatt panels run for five hours a day or all day. Whether the resulting bills beat the alternatives depends on the tariff, the insulation and the control discipline, and on that the independent evidence is genuinely thin²⁸. More on the general question is in do smart heating controls actually save money?.