ComGas installs and services domestic air conditioning for homes across Farnham, Guildford and the surrounding area — split and multi-split systems sized room by room, with indoor and outdoor units sited correctly for performance, condensate drainage and noise. We manage the F-Gas obligations that come with the refrigerant inside every system.
A system sized and sited correctly performs quietly and efficiently for years — one that isn't, rarely does.
Domestic air conditioning ranges from a single indoor unit cooling one room to a multi-split system serving several rooms from one outdoor unit. Whichever scale is right for your home, the two decisions that matter most are getting the sizing right room by room, and siting the indoor and outdoor units so the system can actually perform to specification.
We calculate cooling load from each room's own characteristics rather than a generic size chart, and consider condensate drainage, pipe run limits and noise at the same time as unit position — because a system that's the right capacity on paper can still disappoint if it's sited without regard to these constraints.
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How we approach domestic air conditioning
Sizing, siting, compliance and servicing — considered together, not separately.
Every installation is sized to the rooms it serves and sited with condensate, pipe runs and noise in mind, with F-Gas obligations and servicing built in from the outset.
Split and Multi-Split Systems
The choice between a single split system and a multi-split system depends on how many rooms need cooling and how independently you want to control them.
A single split system pairs one outdoor condenser with one indoor unit, suited to cooling one room or an open-plan area
A multi-split system pairs one outdoor unit with two or more indoor units, each independently controlled, avoiding multiple outdoor units
Indoor unit style — wall-mounted, ceiling cassette or ducted — is chosen for the room's layout and how visible the unit can be
A multi-split system has a fixed combined capacity, so the mix of indoor units needs planning together rather than adding rooms one at a time
Each room's cooling load is calculated individually, because two rooms of the same floor area can need genuinely different capacity depending on glazing and orientation.
Cooling load calculated from floor area, glazing, orientation and insulation, not read from a generic "rooms up to X sqm" chart
An undersized unit runs continuously and still struggles to keep up on the hottest days
An oversized unit cools too quickly, cycles on and off more than it should, and dehumidifies the room less effectively
A room with substantial west-facing glazing needs a different specification to a similarly sized room facing north
Where the units go affects performance, condensate drainage and noise just as much as the equipment specification itself, so siting is planned before the pipe run is fixed.
Outdoor unit position balances refrigerant pipe run, noise to neighbours, and a level, ventilated base with adequate clearance from walls and openings
Condensate — the water produced as air is cooled — needs a route to drain safely, either by gravity fall or a small condensate pump where a gravity fall isn't available
Refrigerant pipe runs have a maximum length and height difference between indoor and outdoor units that affects performance
Domestic air conditioning can usually be installed under permitted development, though unit position, size and any conservation area or listed building status can affect what's allowed
Every system holds a refrigerant that carries its own regulatory obligations, and how it's used and maintained afterwards has a real effect on running costs.
Systems holding a set quantity of F-Gas refrigerant are subject to periodic leak-check obligations, which we manage as part of servicing
Regular filter cleaning maintains airflow and efficiency, and is something homeowners can do themselves between professional services
Most domestic systems also provide a heating mode, which can be efficient supplementary heat for the room it serves, though it isn't a replacement for the home's main heating system
Running costs depend on the unit's efficiency rating, how well it's sized to the room, and how it's used — a steady target temperature is generally more efficient than repeatedly switching on to catch up
Sizing errors are the most common reason a domestic air conditioning installation disappoints.
It's a common assumption that a bigger unit is a safer choice, but oversizing causes its own problems. An oversized unit cools the air quickly, satisfies the thermostat, and switches off again before it's had time to properly remove humidity from the room — leaving the space feeling cold but still slightly clammy. It also cycles on and off more frequently, which is harder on the compressor over the system's working life than running for longer, steadier periods.
Undersizing has the opposite problem: the unit runs continuously, particularly on the hottest days, and never quite brings the room down to the set temperature. Both outcomes trace back to the same cause — sizing decided from a generic guide rather than a proper calculation of that specific room's heat gain, taking into account its glazing, orientation and construction. On a multi-split system, this matters even more, because the indoor units share a fixed total capacity from the outdoor unit, so sizing has to work for the whole layout, not just one room.
Oversized units cool quickly but dehumidify poorly and cycle on and off more than they should
Undersized units run continuously and still struggle on the hottest days
Correct sizing depends on the room's actual heat gain, not a generic size chart
Multi-split systems need sizing to work across the whole layout, since capacity is shared from one outdoor unit
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
Air conditioning questions
Frequently asked questions.
If you're considering air conditioning for one room or several, get in touch and we'll size and site the system properly before recommending equipment.
What's the difference between a single split and multi-split system?
A single split pairs one outdoor unit with one indoor unit. A multi-split pairs one outdoor unit with two or more indoor units, each independently controlled, so several rooms can be cooled without multiple outdoor units.
Can one outdoor unit run air conditioning in several rooms?
Yes, with a multi-split system, provided the combined capacity of all the indoor units is planned together against the outdoor unit's output from the outset.
Where does the condensate water go?
It drains away either by gravity, via a small pipe run with an adequate fall, or via a small condensate pump where a gravity fall to a suitable outlet isn't available. This is planned as part of the installation, not an afterthought.
How far can the indoor and outdoor units be from each other?
Refrigerant pipe runs have a maximum length and a maximum height difference between the indoor and outdoor units, which varies by system. We check this when deciding on unit positions rather than after the equipment is chosen.
Do I need planning permission for air conditioning at home?
Most domestic installations fall under permitted development, but this can be affected by the unit's size, position, and whether the property is listed or in a conservation area. We can talk through what applies to your specific property.
How often does a domestic system need servicing?
Typically annually, covering the F-Gas leak-check obligation where applicable, filter condition, and general performance. Filters themselves benefit from cleaning by the homeowner between services.
Can air conditioning be used to heat a room as well as cool it?
Most domestic systems include a heating mode and can provide efficient supplementary heat for the room they serve, but this isn't a substitute for the home's main heating system.
Why is my air conditioning unit not cooling the room properly even though it's the right size on paper?
This is often down to siting rather than sizing — a restricted refrigerant pipe run, poor airflow around the outdoor unit, or a blocked filter can all reduce performance below what the specification suggests. We'd check these before assuming the unit itself is undersized.
