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Choosing a New Boiler

Posted by boilerPRO Team
Last updated 21st November 2023
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  • There are a Huge Amount of Boilers on The Market, Here We Will Try and Narrow Down Your Search for You

    So with that in mind, If you have a gas heating system, with a gas boiler already, then you can to choose from these options below.

    • Combi-boiler (combination). Provides heat for your radiators and domestic hot water on demand. Great for a flat or small house.
    • Heat-only boiler (conventional). This will have a hot water storage cylinder and also a large cold water feed tank, usually in the loft. A good choice when you have space.
    • System boiler. Similar to the heat-only boiler, but it doesn't require the extra space you need for a cold water storage tank. Best for homes with lower water pressure.
    There are a Huge Amount of Boilers on The Market, Here We Will Try and Narrow Down Your Search for You
    • Combi Boilers

      How they work: Combi’s work as sealed systems, providing hot water for both the taps and central heating system, heating the water directly from the mains as and when it is needed — meaning there is no need for a hot water storage cylinder, or a cistern in the roof space.

      Advantages:

      • Compact
      • Quick to Install
      • Provide heat for your radiators and hot running water on demand
      • No water storage cylinder required
      • Less space used up
      • Ideal for smaller properties

      Disadvantages:

      • It’s a priority system, so it only satisfactorily deals with one heating need at a time
      • While fine for small families with one bathroom, larger families will experience poor flow rates when multiple outlets are used at once.
      • Performance is also dependant on the diameter of the pipe entering the property: if it’s less than 22mm, then a combi is a bad choice.
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    • System Boilers

      How they work: System boilers are fitted to sealed heating systems, but unlike combi’s work on the principle of storing hot water in a cylinder, so they can feed several outlets at once at mains pressure. There’s no need for a cistern in the loft and the expansion vessel is built in.

      Advantages:

      • Ideal for larger homes
      • Major components built in (i.e. expansion vessel and pump)
      • Installation is quicker, cheaper and neater
      • Flow rates are usually high as water is delivered at mains pressure
      • Hot water is instantaneous.

      Disadvantages:

      • Will run out of hot water if overused
      • Some installers claim they are more complex
      • Prone to problems more than regular boilers (such as pressure loss)
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    • Conventional Boilers

      How they work: Conventional boilers are now largely bought as replacements for homes with an open-vented system (i.e. supplied by means of a feed and expansion cistern in the roof space, which is open to the air). Like system boilers, they work on the principle of stored water and require a separate hot water cylinder.

      Advantages:

      • The water out of the taps will be at a good flow rate (not to be confused with pressure)
      • Hot water can be supplied instantaneously
      • This is the ideal setup for a ‘power’ shower, which requires a cold water feed from the cistern and a separate electric pump.

      Disadvantages:

      • They’re more expensive to install
      • Needs more components and pipework
      • Takes up more space
      • They can suffer from low pressure if the cistern is not located high enough, meaning additional shower boosters may be required
      • Hot water can run out

      Note: Sealed or Open? In a sealed circuit, the system is filled to approx 1 bar pressure and then sealed. Unlike an open-vented system, there is no cistern, so an expansion vessel handles excess water. Sealed systems are more efficient.

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  • Sizing

    Once you have determined which type of boiler you need, then choosing the right size is the next step. If you are concerned about keeping energy bills down then you will have to pick carefully.

    Boiler sizing includes these things:

    The heating and hot water capabilities of the boiler in relation to the size of your home. For example, the amount of radiators and bathrooms you have.

    The physical size of your boiler and whether it will fit in the space you have it destined for.

    This is unique to you are your home, if you are not comfortable with doing this then give us a call and we can advice you on what you need.

    01372 620 621

    Note: This is just a rough rule of thumb, we highly recommend you call one of our Gas Safety registered engineers, to discuss your options.

    Size/Type of House Number of Bedrooms Number of Bathrooms Number of Radiators Recommended Boiler Size
    Small terrace, flat or bungalow 1-2 1 Up to 10 24-27kW
    Medium terrace, bungalow or semi-detached house 3-4 1-2 Up to 15 28-34kW
    Large semi-detached or detached house* 4+ 2+ Up to 20 35-42kW

    Sizing
  • Efficiency

    It’s important to buy the most efficient boiler you can, it could save you hundreds of pounds a year. The boilers that work to the highest standard are the fan-assisted room-sealed type — i.e. it takes air from outside the building and combustion products are forced out using a fan. We recommend aiming for at least a five-year warranty.

    Check your boiler to see the older SEDBUK rating or the new ErP boiler rating, these are the authorities that rate the boilers. Older boiler will have a SEDBUK rating, but newer one will have ErP rating. They are clear in layout, with the most efficient boilers having green A+ ratings and the worst having the F’s and G’s, take a look for yourself.

    Efficiency
    • SEDBUK

      SEDBUK is no longer used as a rating because it was updated to meet a new EU Law. We still recommend checking your older boiler to see if you could be saving money on your heating. It may be time to upgrade!

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    • ERP

      Very similar to SEDBUK, but more comprehensive as a guide. Take a look below.

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  • A Few Extra Bits to Think About

    A good boiler needs a good heating distributions system. An old central heating system can get clogged up and sludge collects in the bottom of radiators, meaning it will take longer to heat your home up, costing you more money. A new boiler will be more efficient, but cleaning the system and adding cleaning agents will help and we recommend doing this in conjunction with the replacement of the boiler. This is called Powerflushing, it will prolong the life pf your appliances.

    A few brands to look out for are Worcester-Bosch, Glowworm and Vaillant. Although we recommend these boilers, we suggest you look at all your options and ask us for advice on what boiler may best suit you.

    Take a look at Powerflushing
    A Few Extra Bits to Think About
  • Not Connected to the UK Gas Network?

    There are alternatives, which include fitting an oil boiler, LPG (liquid petroleum gas) boiler, or a wood-burning stove fitted with a back boiler. There are also electric boilers, but the tend to be more expensive to maintain.

    Not Connected to the UK Gas Network?
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