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Frequently asked questions about combi boilers

Here are the answers to some of the most commonly asked questions about combi boilers.

What are combi boilers?

A combi boiler provides central heating and hot water. It heats water instantaneously when a hot tap or shower is turned on.

Will I still need a separate hot water cylinder?

No, because a combi boiler provides heat for central heating and heats water for your taps on demand, there is no need for tanks in the loft or a hot water storage cylinder.

Do combi boilers provide good water pressure?

The water is fed from the mains so the water pressure is generally good. However, depending on heat output, the flow can be limited if other taps are running at the same time. If you have more than one bathroom, a system boiler might be a better option. Try our title="Find the perfect boiler for you with our product selector tool">Find a boiler tool to find out.

How can I prevent the hot water supply from my combi boiler from fluctuating?

Turning on more than one tap will reduce the flow of hot water. If the water is not hot enough you may need to turn the tap down in order to reduce the flow and increase the temperature.

Do all types of shower work with a combination boiler?

Most standard shower fittings are compatible with a combi boiler, but if you have a modern multi-jet shower the water demand may exceed that provided. Pump assisted power showers can only be installed with tank fed systems.

Are combi boilers economical to run?

Yes, because they only produce hot water when it is needed. Wide modulation ranges ensure smooth operation, fewer ignitions, greater reliability and lower fuel bills.

What sizes do gas combi boilers come in?

Baxi combi boilers are available in a range of outputs of 24-40 kW so they can meet hot water requirements for different property sizes. Your Gas Safe registered installer can determine the output you need by doing a site survey.

Can I get a combination boiler if I have LPG?

Yes, the Baxi Duo-tec Combi 28 is available as a dedicated LPG model.

What is SEDBUK?

SEDBUK is the national standard for energy performance for heating appliances.  SEDBUK stands for 'Seasonal Efficiency of a Domestic Boiler in the UK', and is designed to provide a fair comparison of the energy performance of different boilers.

SEDBUK 2005 ratings are shown on labels as A-G, similar to those found on refrigerators and washing machines, where A is at least 90% efficient. This method was superseded by SEDBUK 2009, where the boiler efficiency is shown as a percentage.

All boilers installed in the UK from 6th April 2011 must be greater than 88% SEDBUK (2009) or greater than 90% SEDBUK (2005). 

Can combi boilers be made even more efficient?

Linking a new Baxi combi boiler to a Multifit GasSaver will further increase fuel savings as it recovers the heat from the flue gases which would otherwise be wasted. This reduces annual consumption of gas used to heat hot water by up to 37%* compared to a standard SEDBUK 2005 90% A rated high efficiency boiler.

* Test conducted by independent scientific test house, TNO. Calculation based on an average householder's consumption of 100 litres of hot water per day.

How much does a combi boiler cost?

Every installation is different so we recommend you obtain a quote from several Gas Safe registered installers when thinking about replacing your boiler.  You can find a local Gas Safe registered installer by using Find an Installer.

Who can install a new combi boiler?

All gas work carried out in your home should be done by a Gas Safe registered engineer. The Gas Safe Register is the official list of gas engineers who are registered to work safely and legally on boilers, cookers, fires and all other gas appliances.
Gas work includes:

  • installing, repairing or servicing a gas boiler
  • installing or repairing a gas fire, gas cooker or hob

You can find a local Gas Safe registered installer by using Find an Installer.

How often should I get my combi boiler serviced?

Your boiler should be serviced annually by a Gas Safe registered installer in order to check that it is operating safely and at peak efficiency. An annual service is also a requirement of your boiler's warranty.
heateam can provide servicing and support for all of our heating products, whether the product is in or out of warranty.

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