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ComGas Services UK Ltd
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Central Heating

Central Heating

A central heating system is more than the boiler that heats it — pipework, radiators, valves, zoning and controls all have to be sized and set up together. We design and install complete heating systems, and upgrade existing ones, across Farnham, Guildford, Godalming, Farnborough, Fleet and Camberley.

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System design, not just the boiler

This page covers everything around the boiler, not the boiler itself.

This page covers the central heating system as a whole — the pipework, radiators, valves, zoning and controls that move heat around a property and let you set it independently by room or time. Boiler selection itself is covered separately on Boiler Installation & Replacement; whether a new boiler is being chosen or an existing one kept, this is where the rest of the system is designed, installed, upgraded or converted.

Central heating work is rarely started from nothing. It tends to follow a property extension that adds rooms the existing system was never sized to heat, a renovation, radiators and pipework reaching the end of their working life, a system with no proper zoning or thermostatic control, or an older open-vented system being converted to sealed.

ComGas Services UK Ltd
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How we design and install

A system designed as a whole, not specified room by room at random.

Pipework, radiators, valves, zoning and controls all affect how a heating system performs together. Here's what's involved in getting the whole system right, whether it's new, upgraded or converted.

System Design & Sizing

Every heating system starts with sizing the demand room by room, not estimating from floor area, so pipework, radiators and controls are all specified to match.

  • Heat loss calculated room by room, not estimated from floor area
  • Pipework routed and sized for the flow rates the system needs
  • Radiator type and output matched to each room's heat loss
  • Zoning designed around how the property is actually used
  • Controls specified to suit the system, from a single thermostat to full zone control
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S-Plan & Y-Plan Systems

For systems with a hot water cylinder, heating and hot water are controlled through one of two standard valve arrangements. We specify whichever suits the property rather than defaulting to one as standard.

  • S-plan uses separate two-port zone valves for heating and hot water
  • Y-plan uses a single three-port mid-position valve to direct flow
  • Choice depends on existing pipework and cylinder type
  • Independent zone control available with an S-plan arrangement
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TRVs, Zoning & Controls

Thermostatic radiator valves and correct zoning are what make a heating system responsive room by room, rather than simply on or off.

  • TRVs let each radiator be set independently
  • Zoning separates areas such as bedrooms and living rooms onto different schedules
  • Thermostat placed where it reads a representative temperature
  • Smart controls sit on top of the same valve and zoning arrangement
  • Smart controls cannot substitute for a system correctly zoned and balanced
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System Cleanliness

Sludge, corrosion debris and limescale are common causes of cold spots and reduced efficiency. We treat cleaning the system as a maintenance step, not an optional extra.

  • System flushed to clear existing debris
  • Magnetic filter fitted to capture ongoing sludge before it reaches the boiler
  • Correct inhibitor dosed to slow corrosion
  • Carried out on new installs and significant system changes
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Open-Vented to Sealed Conversion

Converting an older open-vented system to sealed removes the loft cistern and typically simplifies pipework, but the whole system needs assessing first.

  • Feed-and-expansion cistern removed and replaced with a pressure vessel and filling loop
  • Pipework, radiator condition and heat demand assessed before conversion
  • Usually required if the boiler is changing to a sealed-system model
  • Removes a source of air ingress and corrosion
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Extending a property changes the heating load

Adding rooms without reviewing the system is a common cause of underperformance.

New radiators add demand that the existing pump, pipework and boiler may not have spare capacity for, and pipework runs to new rooms need sizing on their own merits, not extended from the nearest existing pipe.

We assess the whole system's capacity against the extended property, not just the new rooms in isolation, before recommending what needs to change.

  • Existing pump, pipework and boiler capacity checked against the extended property
  • New pipework runs sized on their own merits, not extended from the nearest pipe
  • Whole-system assessment before recommending changes
  • Applies whether the boiler is being kept or replaced as part of the works
Discuss Your Central Heating Project
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Central heating questions

Frequently asked questions.

If you're unsure whether your existing system needs upgrading, converting, or simply adding to, get in touch and we'll assess it against the property.

Call 01252 214120
Is this the same as buying a new boiler?

No. This page covers the pipework, radiators, valves, zoning and controls that make up the rest of the heating system. Choosing or replacing the boiler itself is covered on our Boiler Installation & Replacement page — the two are usually specified together, but they're different decisions.

Do I need a full system replacement, or can my existing pipework and radiators be reused?

It depends on their condition and whether they were correctly sized in the first place. Sound copper pipework and radiators in reasonable condition can often be retained and reintegrated into an upgraded system; we assess this rather than assuming a full strip-out is needed.

What's the difference between an S-plan and a Y-plan system?

Both control heating and hot water from a boiler with a cylinder, but an S-plan uses separate zone valves for heating and hot water, while a Y-plan uses a single mid-position valve to direct flow to one, the other, or both. The right choice depends on your existing pipework and cylinder arrangement, and whether you want fully independent zone control.

Why does my system need a magnetic filter if it's already working?

A magnetic filter catches sludge and debris before it reaches the boiler's heat exchanger and pump, protecting components that are expensive to replace. It's a preventative measure, most valuable when fitted as part of a flush and system upgrade, and it's not a sign anything is currently wrong.

Can I add smart heating controls to my existing system?

Usually, provided the system is correctly zoned and the wiring supports it. Smart controls improve scheduling and monitoring, but they work through the same valves and zoning already in the system — they don't replace the need for a properly balanced system underneath.

What does converting from open-vented to sealed actually involve?

It removes the feed-and-expansion cistern in the loft and replaces it with a pressure vessel and filling loop at the boiler. We assess the whole system, including pipework and radiator condition, before confirming the conversion — it's often carried out alongside a boiler change.

I've extended my house — does my existing central heating need upgrading?

Often, yes, at least in part. New rooms add heat demand that the existing pump, pipework and boiler may not have spare capacity for. We assess the whole system against the extended property before recommending what needs to change, rather than simply adding radiators to the existing setup.

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Planning a new central heating system, or upgrading what's there?

Tell us about the property, what's changed, and what isn't working, and we'll advise on the right system design.

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