ComGas fits and upgrades heating controls for homes across Farnham, Guildford and the surrounding area — from a straightforward programmer and thermostat through to zoned systems and smart, learning thermostats. Controls are chosen to suit the boiler and wiring already in place, not fitted regardless of compatibility.
The right control depends on what's already wired in, not just what looks good on the wall.
Heating controls range from a basic timer and thermostat through to zoned systems with independent room control and smart thermostats that learn a household's routine. Each layer does a genuinely different job, and adding one doesn't automatically replace the need for another — a smart thermostat doesn't zone a system, and TRVs don't replace a programmer.
Before recommending an upgrade, we check what the boiler and existing wiring actually support. Some smart thermostats need a specific type of boiler control signal to work properly; some systems have no wiring centre or zone valves to build on. Getting this right first avoids fitting a control that can't do what it's expected to.
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How we approach heating controls
From a simple programmer to a fully zoned, smart-controlled system.
Controls are specified against the boiler type, existing wiring and how the household actually wants to manage its heating, rather than fitted as a standard package.
Programmers, Thermostats and Room Sensors
Every heating system needs a baseline of time and temperature control — when it comes on, and what temperature it's aiming for — before anything more sophisticated is added on top.
A programmer sets when the heating and hot water switch on and off through the day and week
A room thermostat provides a single reference temperature the system heats towards
TRVs fitted to individual radiators allow each room to run at its own comfortable temperature within that schedule
Replacing a failed or very old programmer or thermostat is often straightforward, provided the wiring behind it is in reasonable condition
A smart thermostat adds remote control, scheduling flexibility and, on some models, usage learning — but which one will actually work depends on how your boiler is wired for control.
Compatible thermostat models depend on the boiler's control wiring — simple on/off, OpenTherm modulating, or a proprietary system
Learning thermostats adjust the schedule over time based on observed usage patterns
App control and geofencing let the heating respond to whether anyone is home, rather than running to a fixed clock
A smart thermostat with weather compensation can moderate the system's flow temperature against the outside temperature automatically
Zoning splits a heating system into independently controlled sections — typically heating and hot water, or upstairs and downstairs — and depends on the valve and wiring arrangement already in place.
S-plan systems use separate motorised zone valves for heating and hot water, each independently controlled
Y-plan systems use a single mid-position valve serving both heating and hot water from one wiring arrangement
A wiring centre coordinates the signals between zone valves, thermostats and the boiler's demand for heat
Adding zoning to an existing system depends on whether suitable valves and wiring routes already exist, or can practically be added
Boiler Plus Compliance and Weather/Load Compensation
Boiler Plus sets a minimum control standard for combi boiler replacements in England, and weather and load compensation are two of the ways a system can meet it while also running more efficiently.
Boiler Plus applies when a combi boiler is replaced, requiring time and temperature control plus one further efficiency measure
Weather compensation adjusts the boiler's flow temperature automatically against the outside temperature
Load compensation adjusts flow temperature based on how close the room is to its target, rather than running at a fixed setting
Both approaches help a condensing boiler run in its most efficient condensing range more of the time
Weather and load compensation are what actually keep a condensing boiler condensing.
A condensing boiler is only genuinely condensing — and therefore running at its efficient best — when the water returning to it is cool enough to extract the extra heat from the flue gases. A boiler left on a fixed high flow temperature all winter can spend a lot of its time running hotter than it needs to, particularly in milder weather, which reduces the condensing effect and wastes fuel.
Weather compensation and load compensation both address this by adjusting the flow temperature automatically — weather compensation against the outside temperature, load compensation against how close the room already is to its target — rather than leaving the installer's commissioning setting in place indefinitely. For a Boiler Plus compliant combi replacement, one of these (or an equivalent smart thermostat) is required in any case, so it's worth specifying the one that will genuinely suit how the household uses its heating.
A condensing boiler is most efficient when return water is cool enough to trigger condensing
Weather compensation adjusts flow temperature against outside temperature automatically
Load compensation adjusts flow temperature against how close the room is to target
One of these, or an equivalent smart control, is required for Boiler Plus compliance on a combi replacement
Reviews from real ComGas customers, shown as submitted through Google.
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Lucie Victoria
15 May 2025
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Excellent service, highly recommend
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James Mowat
30 April 2025
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Incredible service — problems fixed perfectly once again.
Lee, Paul and the team at COMGAS are fantastic. They arrived on time and got straight to work, quickly identifying the root cause of the plumbing and heating issues I was experiencing.
The problems were diagnosed swiftly, I was kept fully informed throughout, and both issues were fixed with impressive speed and precision.
Having worked in the industry for nearly 20 years, I know how rare it is to find reliable, trustworthy, and genuinely skilled professionals — let alone a team this good.
I joked about it at the time, but it’s true: I had the best shower I’ve ever had in this house after they finished the job — and I’ve lived here for 10 years!
I honestly couldn’t ask for more and can’t recommend COMGAS highly enough.
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Faz
31 March 2025
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ComGas replaced my boiler and water tank at short notice. So glad i used them. Thank you
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Laura Andrews
26 March 2025
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Lee came out to the school I work in to look at a problem with our heating, he diagnosed the issue and was able to fix it on the spot in a neat and tidy manor. Would highly recommend
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Chloe
26 March 2025
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I recently used Comgas for a gas and heating service, and I couldn't be more impressed! From start to finish, their team was professional, friendly, and highly knowledgeable. They quickly identified the issue with my heating system and explained everything in detail, offering both short- and long-term solutions.
The technician was punctual and took extra care to ensure everything was running smoothly. I really appreciated their attention to detail and how they made sure to clean up after the work was completed. My home is now warm and cozy, all thanks to their expert service. I highly recommend Comgas for anyone looking for reliable, efficient, and trustworthy gas and heating professionals!
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Bec Newey
8 July 2024
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Messaged Lee on a Sunday evening with request. Instant reply that evening and engineer came next day. Polite, professional and helpful. Thorough investigation and speedy resolution to a leak with sink in wc. Happy customer.
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P Duffy
2 April 2024
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Scott and the team have served me well over several years. Skilled craftsmen. Dependable careful and very cosy-effective. I highly recommend them.
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Cilla Trout
22 March 2024
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Definitely recommend friendly reliable service
Scott was helpful and reassuring regarding our boiler answered our concerns and explained the problem and best course of action thank you for your advice
Heating controls questions
Frequently asked questions.
If you're planning a controls upgrade alongside a new boiler, or want more control over an existing system, get in touch and we'll confirm what your system supports.
What's the difference between a room thermostat and a programmer?
A programmer sets when the heating comes on and off. A room thermostat sets the temperature it's aiming for while it's on. Most systems need both — a programmer alone doesn't tell the system how warm to get, and a thermostat alone doesn't control when it runs.
Do I need a smart thermostat to comply with Building Regulations?
Not necessarily a smart thermostat specifically — Boiler Plus requires time and temperature control plus one further measure, which could be weather compensation or load compensation instead. A smart thermostat is one way to meet the requirement, not the only one.
What is Boiler Plus and does it apply to me?
Boiler Plus is a Building Regulations requirement that applies when a combi boiler is replaced in England. It sets a minimum control standard beyond a basic thermostat and programmer, met by adding weather compensation, load compensation, a compatible smart thermostat, or flue gas heat recovery.
Can a smart thermostat control my hot water as well as heating?
Many can, provided your system has a separate hot water control circuit for it to switch, such as an S-plan system. On some simpler systems, hot water and heating share the same control and can't be separated without further work.
What's the difference between S-plan and Y-plan?
S-plan uses two separate motorised valves — one for heating, one for hot water — each controlled independently. Y-plan uses a single mid-position valve serving both from shared wiring. S-plan generally allows more independent zoning; Y-plan is a simpler, more compact arrangement.
Will a smart thermostat work with my existing boiler?
It depends on how your boiler is wired for control. Some smart thermostats need a modulating (OpenTherm-type) connection to get the full benefit; others work with a simple on/off signal. We check this before recommending a specific model.
What is weather compensation and is it worth having?
It's a control that automatically adjusts your boiler's flow temperature against the outside temperature, so the system doesn't run hotter than the weather requires. It genuinely helps efficiency, particularly on systems that would otherwise sit on a fixed high setting all winter.
Can I add TRVs to an existing system without other changes?
Usually yes, provided at least one radiator is left without a TRV to act as the reference point for the main room thermostat. We check the existing valve types and pipework before fitting TRVs to confirm this.
