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Best Heating Control for a Granny Annexe with Its Own Boiler
A granny annexe with its own boiler needs its own control strategy. The resident should be able to set a comfortable temperature without touching the main house system, and the boiler should only fire when there is real demand. This guide covers five heating controls that suit that setup, from a full boiler control module to a budget app thermostat.
The picks split into three groups: boiler-side controls for installers and technically confident owners, app-based thermostats for everyday remote management, and line-voltage thermostats for electric heating. A quick scan of the overview table below will point most readers to the right shortlist in under a minute.
Overview of the Picks
| Product | Key Spec | Best Use | Price Tier |
|---|---|---|---|
| Tekmar 256 Boiler Control for 1-Stage Boiler | 1-stage boiler control | Boiler-side outdoor reset and staging | Premium |
| Honeywell L7224U-1002 Universal Electronic Oil Aquastat | Oil aquastat with EnviraCOM | Oil boiler temperature and limit control | Mid-to-high |
| Thermostat 1C, Programmable App Control for Boiler Heating | App control, humidity display | Budget room-by-room control | Budget |
| Remote Temperature Adjustments Smart Boiler Thermostat | Tuya app, knob control | Simple smart control for a family annexe | Mid |
| Aube Technologies TH115-A-120S Programmable Line Voltage Thermostat | 7-day programmable, line voltage | Electric heating circuits | Mid |
Tekmar 256 Boiler Control for 1-Stage Boiler
Tekmar 256 Boiler Control for 1-Stage Boiler
Type: Boiler control module
Boiler compatibility: 1-stage boiler
Function: Boiler-side temperature and staging control
Mounting: Boiler panel or nearby wall mount
Intended use: Residential hydronic heating
The Tekmar 256 is a boiler-side control rather than a room thermostat. It manages how a single-stage boiler fires and how hot the water is allowed to get, which is the piece most annexes are missing when the boiler runs too hot or short-cycles. It is built as a hard-wired module for installation near the boiler.
This is a pick for the installer or technically confident owner who wants the annexe boiler to run efficiently on its own terms. The caution is straightforward: it does not give the resident a room-level dial or app, so a separate room thermostat is still needed for day-to-day comfort control.
Trade-off: It is a professional-grade module with no resident-facing interface, so it only makes sense alongside a separate room thermostat.
Honeywell L7224U-1002 Universal Electronic Oil Aquastat with EnviraCOM Communication
Honeywell L7224U-1002 Universal Electronic Oil Aquastat with EnviraCOM Communication
Type: Electronic oil aquastat
Communication: EnviraCOM
Intended use: Oil-fired boiler control
Function: Temperature and high-limit control
Compatibility: Universal oil boiler replacement
The Honeywell L7224U-1002 is the control to reach for when the annexe runs an oil boiler. It replaces a mechanical aquastat with an electronic one, adds high-limit protection, and exposes EnviraCOM so it can talk to compatible Honeywell controls and thermostats. The universal fit is the reason it earns a place here — one part covers many older oil boiler setups.
It suits owners upgrading an ageing oil installation in an annexe, not gas or electric systems. The caution is that EnviraCOM only pays off if the rest of the control chain supports it, so a mixed-brand setup may not unlock the communication features.
Trade-off: The smart communication features are only useful with compatible Honeywell accessories, so a mixed-brand annexe system may not benefit.
Thermostat 1C, Programmable App Control for Boiler Heating, Floor Controller with Humidity Display, Lock, Remote Climate Manager
Type: Programmable boiler thermostat
Control: App control
Display: Humidity readout
Features: Programmable schedule, child lock, remote climate management
Intended use: Boiler heating and floor heating circuits
The Thermostat 1C is the budget entry point for this list and a genuinely practical one. It is a programmable boiler thermostat with app control, a humidity display, a lock function and remote climate management, which covers the basics an annexe resident actually uses. For the price tier it packs in more features than expected.
It suits a family annexe where the resident wants app scheduling without a big install budget, and the lock is useful for shared or rental setups. The caution is that budget app thermostats of this type often have thinner documentation and less polished app support than premium brands, so buyers should expect a basic setup experience.
Trade-off: At this price the app and documentation are likely to be basic, so buyers wanting a polished interface should look higher up the list.
Remote Temperature Adjustments, Scheduled Heating Periods, Precise Knob Selection, Celsius and Fahrenheit Switching Smart Boiler Thermostat with Tuya App Control, Programmable Knob for Home
Type: Smart boiler thermostat
Control: Tuya app plus physical knob
Features: Scheduled heating periods, remote temperature adjustment, C/F switching
Intended use: Home boiler and heating control
Installation: Wall-mounted, programmable
This is the middle pick and the best all-rounder for a typical annexe. The Tuya app handles remote temperature adjustments and scheduled heating periods, while the physical knob gives the resident a simple fallback that does not depend on a phone. Celsius and Fahrenheit switching is a small touch that matters in mixed-household setups.
It suits a resident who wants smart scheduling but still prefers a physical dial for everyday changes, which is common in annexe setups used by older relatives. The caution is that Tuya-based devices can be slower to set up than mainstream ecosystems, and the knob-plus-app combination takes a little learning.
Trade-off: Tuya app onboarding is less streamlined than big-brand ecosystems, so expect a slightly fiddly first setup.
Aube Technologies TH115-A-120S 7-Day Programmable Line Voltage Thermostat for Electric Heating
Aube Technologies TH115-A-120S 7-Day Programmable Line Voltage Thermostat for Electric Heating
Type: Line voltage thermostat
Programming: 7-day programmable
Intended use: Electric heating
Compatibility: Line voltage electric heating circuits
Mounting: Wall-mounted
The Aube TH115-A-120S is the pick for annexes that heat with electric circuits rather than a wet boiler — underfloor mats, baseboard heaters, or similar. It is a 7-day programmable line voltage thermostat, which means it handles the mains-level load directly rather than switching a separate relay. For an annexe with electric heating, that is the correct control type.
It suits owners fitting out a small electric-heated annexe where a programmable weekly schedule is enough. The caution is that it is not a boiler control and will not work with a hydronic system, so buyers must confirm the heating type before ordering.
Trade-off: It is strictly for electric heating and offers no app control, so it is the wrong choice for a wet boiler system.
Before You Buy
- Compatibility: Match the control type to the annexe boiler — a boiler-side module for a wet system, an aquastat for oil, a line-voltage thermostat for electric heating.
- Resident interface: Decide whether the resident needs an app, a physical dial, or both, and whether a lock function is wanted for shared or rental use.
- Room vs boiler control: A boiler control manages efficiency; a room thermostat manages comfort. Most annexes need both.
- Installation: Boiler-side controls and line-voltage thermostats are hard-wired jobs and usually need a qualified installer.
- Communication: Features like EnviraCOM or app control only pay off if the rest of the system is compatible.
- Budget: A budget app thermostat covers basic scheduling cheaply, while boiler-side controls cost more but improve efficiency.
- Documentation: Budget app devices often ship with thinner manuals, so factor in setup time.
Frequently Asked Questions
-
What is the best heating control for a granny annexe with its own boiler?
For most annexes with a wet boiler, the Remote Temperature Adjustments Smart Boiler Thermostat is the best all-rounder. For oil boilers, the Honeywell L7224U-1002 is the right boiler-side control. -
Does an annexe with its own boiler need a separate thermostat?
Yes. The annexe boiler should have its own room thermostat so the resident can control comfort independently of the main house. -
Can a boiler control replace a room thermostat?
No. A boiler control manages how the boiler fires and how hot the water gets; a room thermostat controls the actual room temperature. -
What is the difference between a line voltage thermostat and a boiler thermostat?
A line voltage thermostat switches electric heating circuits directly, while a boiler thermostat signals a boiler. They are not interchangeable. -
Can a budget app thermostat work in an annexe?
Yes, for basic scheduling and remote control. Budget models may have simpler apps and documentation than premium brands. -
Is a hard-wired boiler control a DIY job?
No. Boiler-side controls and line-voltage thermostats are usually installed by a qualified heating engineer.
Bottom Line
For most granny annexes with their own boiler, the best heating control is the Remote Temperature Adjustments Smart Boiler Thermostat: it combines Tuya app scheduling with a physical knob, which suits both tech-comfortable and older residents. Oil boiler owners should pair it with the Honeywell L7224U-1002, and electric-heated annexes should go straight to the Aube TH115-A-120S.
