fbpx
  • home
  • Blog
  • Types of Boilers Explained: Combi, System, and Heat-Only

Updated: October 14, 2024

Choosing the right boiler is essential for efficient heating and hot water in your home. With several types of boilers available, understanding the differences between them will help you make an informed decision. In this article, we’ll break down the three main types of boilers: Combi, System, and Heat-Only (also known as Regular or Conventional boilers), and provide insights into their pros and cons.

1. Combi Boilers

Overview:
A combi boiler, short for “combination boiler,” provides both heating and hot water directly from a single unit. This design eliminates the need for separate water storage tanks, making it a space-saving option for many households.

How it works:
Combi boilers heat water on demand through a heat exchanger. When you turn on a hot water tap or your heating, the combi boiler instantly heats the water by burning fuel (usually gas). Unlike traditional boilers, there’s no need for a separate hot water tank because the water is heated as required.

Pros of Combi Boilers:

  • Space-saving: Since there’s no need for a separate hot water tank or cold-water storage, a combi boiler is compact and ideal for smaller homes or apartments.
  • Energy-efficient: Combi boilers only heat water when needed, reducing waste and energy costs.
  • Instant hot water: You won’t need to wait for the water to heat up since the system heats water as soon as you need it.

Cons of Combi Boilers:

  • Limited flow rate: If you have multiple taps or showers running at the same time, the flow of hot water may decrease.
  • Not ideal for large homes: For properties with several bathrooms or high water demand, a combi boiler may not provide adequate performance.
  • Dependent on mains pressure: Combi boilers rely on good mains water pressure to function effectively. If the water pressure is low, the boiler’s performance will suffer.

Combi Boiler Key Points:

  • Best for smaller homes with low to moderate hot water needs.
  • No need for a water storage cylinder or tank.
  • May struggle with water flow when multiple outlets are used simultaneously.
Boiler Installation in Aberdeen

2. Heat-Only (Regular) Boilers

Overview:
Heat-only boilers, also known as regular or conventional boilers, are the traditional type of boilers. These systems consist of three main components: the boiler itself, a hot water storage cylinder, and a cold-water storage tank.

Keston Boilers in London

How it works:
Heat-only boilers heat water and store it in a hot water cylinder for later use. The cold water is supplied to the system through a cold-water tank (usually located in the attic), and gravity helps deliver the water to the boiler. This design is well-suited for homes with multiple bathrooms and high water demand.

Pros of Heat-Only Boilers:

  • High water flow rates: Since water is stored in a cylinder, heat-only boilers can supply hot water to multiple outlets simultaneously without losing pressure.
  • Good for older heating systems: If you have an older central heating system that may not tolerate the high pressure of newer boilers, a heat-only system is a safer choice.
  • Low mains pressure-friendly: If your home suffers from low mains water pressure, a heat-only boiler is a better option because it relies on gravity rather than mains pressure.

Cons of Heat-Only Boilers:

  • Space requirements: You’ll need enough room for both a hot water cylinder and a cold-water storage tank. This setup can be difficult for smaller properties.
  • Slower hot water delivery: Unlike combi boilers, which provide instant hot water, heat-only systems require time for the water to heat up in the cylinder.
  • Cold-water cistern: The cold-water cistern in the attic can freeze during winter and may be prone to leaks.

Heat-Only Boiler Key Points:

  • Suitable for large homes with multiple bathrooms.
  • Requires space for both a hot water cylinder and a cold-water tank.
  • Great for areas with low mains pressure or homes with older heating systems.

3. System Boilers

Overview:
System boilers are similar to heat-only boilers but are a more modern and compact solution. While they still use a hot water cylinder to store heated water, system boilers don’t require a cold-water storage tank, as the water is supplied directly from the mains.

How it works:
Like heat-only boilers, system boilers heat water and store it in a cylinder for later use. However, system boilers contain all the necessary components (such as the pump and expansion vessel) within the boiler unit itself, simplifying installation and saving space.

Boiler Installation in Penarth

Pros of System Boilers:

  • High hot water capacity: System boilers can meet high hot water demand in homes with multiple bathrooms.
  • Space-efficient: Since there’s no need for a cold-water tank, system boilers require less space compared to regular boilers.
  • Quick and easy installation: All major components are integrated into the unit, making system boilers easier to install.

Cons of System Boilers:

  • Dependent on mains pressure: Like combi boilers, system boilers rely on mains pressure. If the pressure is low, the hot water flow rate will be affected.
  • Requires hot water storage: You still need space for a hot water cylinder, which may be an issue for smaller homes.
  • Less suitable for older heating systems: The high pressure of a system boiler may not be ideal for older heating systems, which are more accustomed to lower pressure systems.

System Boiler Key Points:

  • Ideal for homes with high hot water demand.
  • Does not require a cold-water cistern.
  • Easier installation due to integrated components.
  • Not suitable for areas with low mains pressure.
Central Heating Services In Rhoose

Boiler Type Comparison

Boiler TypeSpace RequirementSuitable for Large HomesInstant Hot WaterMultiple Hot Water OutletsReliant on Mains Pressure
Combi BoilerCompactNoYesNoYes
Heat-Only BoilerLarge (needs tank and cylinder)YesNoYesNo
System BoilerMedium (needs cylinder)YesNoYesYes

Boiler Type FAQ

What is a condensing boiler?
A condensing boiler is a type of boiler that’s highly energy-efficient. By law, all new boilers must be condensing boilers. They work by capturing and reusing some of the heat that would otherwise be lost, making them up to 90% efficient. Both combi, heat-only, and system boilers can be condensing.

What size boiler do I need?
The size of your boiler refers to its power output, measured in kilowatts (kW). Your installer will assess your home’s heating and hot water needs based on the number of radiators, bathrooms, and occupants to determine the correct size. Generally, larger homes need boilers with a higher kW output.

Final Thoughts

Choosing the right boiler depends on your home’s size, water demand, and existing system. Combi boilers are compact and energy-efficient, ideal for small to medium-sized homes with low hot water demand. Heat-only boilers are best for larger homes with high water demand, especially if you have multiple bathrooms. System boilers offer a balance, providing high water capacity without the need for a cold-water tank, making them suitable for homes with high hot water demand and limited space.

No matter which type you choose, it’s essential to consult with a qualified heating engineer to ensure the boiler fits your specific needs.

Read about: Baxi Boiler Prices

Also read: Genuine Vaillant Boilers Review In Uk