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Boiler FAQs

Whether you’re thinking about getting a new boiler, or have questions about your current one, the topic of boilers can be a confusing one. That’s why The Heating People have put together this list of commonly asked questions about boilers. We hope you find it helpful!

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A confused woman.Perplexed by heating jargon? If so, you should read these Boiler FAQs!

Whether you’re thinking about getting a new boiler; or have questions about your current one; the topic of boilers can be a confusing one.

So we’ve put together this list of commonly asked questions about boilers. We hope you find it helpful.

For tailored advice on improving your heating system, contact The Heating People to book your free survey.

What Different Types of Boilers Are Available?

Although there are many different makes and models of boiler, they all fall into three basic types:

  1. Heat-only or ‘conventional’ boilers;
  2. Combination or ‘combi’ boilers; and
  3. System boilers.

You might like to read our related blog: Your options with a boiler replacement.

Heat-only or conventional boilers

Heat-only or conventional boilers are often thought of as the traditional way of heating a home. They’re designed to provide both heating and hot-water with the use of an additional cold-water tank and hot-water cylinder.

Combination or ‘combi’ boilers

‘Combi’ is short for ‘combination’ boiler because it provides both your heating and hot water from one compact unit; without the need for additional tanks or hot water storage cylinders. Combi boilers deliver instantaneous hot water and are the most popular boiler type currently installed in the UK. 

System boilers

System boilers feature aspects of both a heat-only boiler and a combi.

Like a heat-only boiler; a system boiler needs a hot water storage cylinder to heat and store hot water for your taps. But it doesn’t need a tank in the attic; because like a combi, it takes its water supply directly from the mains.

You can read about the pros and cons of system boilers here.

What’s the difference between a condensing and a non-condensing boiler?

There’s a common misconception that a ‘condensing boiler’ is a type of boiler, when in fact, it isn’t.

The terms ‘condensing boilers’ and ‘non-condensing boilers’ are misleading. Because they describe the technology within the boiler itself, rather than what sort of boiler it is.

A condensing boiler works by recycling the wasted exhaust gas that is created during a boiler’s normal operation.

By re-using the exhausted gas; water vapour; and steam; back through the system, some of the heat and water is retained making the boiler’s operation more efficient.

But you won’t have to choose between condensing and non-condensing technology. Because it’s now law (Boiler Plus Regulations) for all new boilers to use condensing technology as standard. So whatever type of heating system you opt for, it will be condensing.

This is because condensing boilers are more energy efficient than their non-condensing counterparts. And can typically extract 90-92% of heat from fuel, compared to 50-80% that a non-condensing boiler can.

Which type of boiler is best for my home?

A man looking at different doors.This is a difficult question to answer because it depends on your lifestyle; your heating and hot water needs; and what’s most important to you from your heating system.

The Heating People pride ourselves on finding the perfect boiler to fit your needs and budget.

For us to help you; it’s a good idea to arm yourself with some key information. This will help us to find the perfect heating solution for you.

You should ask yourself the following questions:

  • Are you connected to the UK’s gas network?
  • How many people live in your house?
  • How many bathrooms do you have?
  • Do you have free space, such as a loft or airing cupboard available?
  • How many radiators do you have?
  • How important is energy efficiency to you in a boiler?
  • Are you satisfied with the performance of your current system? For instance, are you getting enough hot water?
  • Are you thinking of replacing like for like or are you interested in a new type of boiler?

Your expert engineer will ask you about what you’re hoping to achieve with your heating system. And will conduct heat loss calculations to determine what size boiler you need.

Can I change to a different type of boiler?

A man holding a question mark.Yes you can!

Whether you want to replace like for like; or whether you want to take the opportunity to change to a different type of boiler system; depends on your individual situation.

If you’re generally happy with what your old boiler offered when it was working well; then a replacement boiler similar to your old one could be a good option.

A replacement boiler is a different (and more up-to-date) version of the model you already have; which means you’ll already have a lot of the necessary parts in place.

Your other option is to change to a different type of boiler.

For example, you may want to swap from your heat-only system to a combi boiler. If so, you’ll need all-new infrastructure installed along with the boiler itself.

This will obviously be more expensive than swapping out like for like because you’ll be starting from scratch.

On the flip-side, getting either a new boiler or a replacement boiler will mean that you’re likely to save money on your bills over time.

What size of boiler do I need?

Boiler size doesn’t refer to the physical dimensions of the boiler itself. But rather how much energy is output by the boiler in terms of heat, which is measured in kilowatts (kW).

A kilowatt is equal to 1,000 watts. This unit helps us to measure the power your boiler can provide to your heating system.

For example, a 25kW boiler uses 25,000 watts (25 kW) of power per hour; to heat the water for your central heating.

Generally, the more heat and hot water you require for your home, the higher the kW boiler you will need. But the type of boiler you have will affect this.

If you have a heat-only or a system boiler; the boiler size will be based on the heat requirements of your property.

For combi boilers, the size of the boiler you need looks ‘bigger’; because it produces instantaneous hot water on demand, rather than storing it.

How are boilers sized?

You’ll need to choose a boiler that can cope with the heating demands of your home. But unfortunately, a lot of people fall into the trap of choosing a much bigger boiler than they need; ‘just in case’. But this is a mistake.

Oversizing your boiler is inefficient; costly; and can generate more power than your central heating system can handle, which will take its toll on your boiler.

But don’t worry – The Heating People will find the prefect size for your home and lifestyle after conducting a heat loss calculation. But here is a very rough size guide:

  • 24 – 30 kW Combi

Suitable to provide heating and hot water to a home with one bathroom. If you have an en suite with an electric shower, this size of boiler will still be suitable.

  • 30-36 kW Combi

Suitable for homes with two bathrooms. 

  • For larger homes with more than two bathrooms, a storage combination boiler or stored hot water should be considered. Although larger Combi boilers are available, they’re often not the best solution.

Contact us today to arrange a heat-loss calculation to determine the perfect boiler for you.

Which boiler manufacturer is best?

Lots of different boilers.With so many different boiler manufacturers available; each offering their own large range of models; choosing a boiler can be a daunting task.

We often get asked: ‘which brand is best?’ by people looking for a new boiler.

This is totally understandable, because a boiler is a big investment. And not the sort of purchase you make every day.

People will often seek out the big brands when it comes to buying mobile phones and other gadgets; and want to know whether this is a tactic they should use when getting a new boiler.

But just as there’s no ‘one-size-fits-all’ boiler for everybody, there’s no ‘right’ boiler brand either.

Each brand (and individual model within the brand) has their own pros and cons; which need to be weighed up for your particular needs.

But it’s definitely a good idea to do a bit of research into what options are available; so that you can make an informed choice. After all, your boiler will be the hardest working appliance in your home for at least the next decade!

Which are our favourite manufacturers?

The Heating People can work with all manufacturers of boiler, but we have our personal favourites!

Our favourite heat-only boilers are Worcester Bosch and ATAG.

For combi boilers, we like the Vaillant ecoTEC Exclusive with Green iQ; and the ATAG iC Economiser. Because they have built in flue gas heat recovery making them more efficient than standard boilers.

In terms of system boilers, we rate ATAG due to the advanced control options available; high build quality; and relatively low cost.

You might like our related blog: The best combi boilers 2022.

How much will a new boiler cost?

The price of replacing a boiler costs less than you might think.

It obviously depends on what you are changing from, and what you are changing to.

But as a rough guide, at The Heating People a boiler replacement costs between £1,800-£3,000.

If you’re thinking that it might be time to say goodbye to the old; and hello to the new; contact one of our specialist advisers, who will be happy to advise you on your specific options.

How long will it take to replace my boiler?

How long a boiler replacement will take, will vary depending on what work is needed; if your boiler is moving location; or if you have a like-for-like boiler. As a guide, it usually takes between 1-3 days.

What happens during a new boiler installation?

Although all homes and heating systems are different; this is a rough guide to the work included in the cost of a boiler installation with The Heating People:

Before installation

  • Survey – your engineer will talk to you about your needs and will take technical measurements to find you the perfect boiler for your home.
  • Quotation – we will send you a fixed price quotation based on the survey.
  • Booking – we will arrange a convenient time to complete the work.
  • Arrival of the engineer at your home – your engineer will discuss the planned work with you and check that you’re happy with everything.


  • Protecting your home – your engineer will put down floor coverings to protect your carpets. 
  • Draining your old system – your engineer may need to turn your water off for a short period if your old system needs draining down.
  • Test the gas for leaks – your engineer will complete a let by and gas tightness test.
  • Removal of the old boiler- your engineer will remove your old boiler and any old redundant equipment.
  • Flush and clean – depending on what we have discussed during the quotation stage, your engineer will use the flushing method agreed upon, to ensure that your heating system is clean for your new boiler.
  • Upgrade and change pipework if required – to fit your new boiler properly, your engineer may need to alter or upgrade pipework. The Heating People use only copper or professional press fit systems; we do not use DIY style push-fit systems.
  • Making good – where your new boiler’s flue is in a new position, your engineer will make good the existing flue hole, with bricks that are of a close match to your home.
  • Fitting the boiler – your engineer will then install your new boiler, the boiler flue, and make all the pipework connections.
  • Controls – your engineer will fit controls and accessories as agreed, such as: temperature sensors; thermostats; timers; system filters; and filling loops.
  • Commissioning of the system – your engineer will then fill; test; set to work; and commission your system; filling out all commissioning test results in your benchmark log book.

After installation

  • An engineer advising a customer.Handover – your engineer will then complete a handover with you when all of the work is complete. This ensures that you are as informed as possible on how to operate the boiler, how to use all of the controls, and how to get the best efficiency from your system.
  • Register the boiler – we will then register your boiler with the manufacturers to activate its guarantee and we will notify your local building control via the Gas Safe Register.

If you have any questions about boiler installations, please contact one of our team at The Heating People.

Does my boiler need to be replaced because it’s old?

When considering a boiler replacement, it’s a good idea to start by considering your boiler’s age.

A new boiler is unlikely to need to be replaced, but what’s considered an ‘old’ boiler?

There isn’t an easy answer to this question, because just like with us, age really is just a number!

There’s a common misconception that when a boiler reaches a certain age, it needs to be replaced. But this isn’t true.

With regular servicing by a Gas Safe engineer; some reliable old boilers will keep ticking over, without ever giving much of a grumble. However, others will start to deteriorate, and may start breaking down, and needing more frequent repairs.

So, if your boiler is old; and you notice any of the other warning signs that it might be on its last legs; contact The Heating People, to get some expert advice on your options.

How do I know if I need to replace my boiler?

Unfortunately, boilers don’t last forever.

If you’re wondering whether it’s time to upgrade your boiler; you might like to read our related blogs: Does my boiler need replacing? and 6 signs you need a new boiler.

But here are a few warning signs that your current boiler might be on its last legs:

  • It’s in its ‘golden years’;
  • It keeps breaking down;
  • It’s noisy;
  • It’s leaking water;
  • Your energy bills have crept up without explanation;
  • Replacement parts are hard to find because of the age of your boiler;
  • Your heating system isn’t working like it used to;
  • You never have enough hot water;
  • Your boiler is not working at all.

How do I know if my boiler needs repairing or replacing?

If your boiler is playing up; it might be a fault with a simple fix, but it could be a more serious issue.

The best option is to consult The Heating People who will be able to assess whether your boiler is safe to continue using after a fix or whether it can be repaired at all.

What is boiler efficiency?

This is a very important question. So we’ve dedicated a whole blog to it; which you can read here: What is an efficient boiler and why should I want one?

But at its simplest; an efficient boiler needs to use the least amount of energy to keep your house warm, and your water hot.

Because efficient boilers use less energy, they will cost you less on your energy bills.

You might like our related blog: How to choose an energy efficient boiler.

How is boiler efficiency measured?

All modern boilers are rated for efficiency under the European energy label introduced in September 2015. ErP stands for ‘Energy-related Products’.

Under this scale, boilers are rated from A-G, with A being the most efficient, and G being the least efficient.

To put this into context, a G-rated boiler with 73% efficiency will use 73% of the supplied energy for heating your home. But the remaining 27% of energy will be lost. So, this means that for every £1 you spend on heating your home, 27p is wasted.

What is Boiler Plus?

If you’ve done some research on boilers; you might have come across the phrase ‘Boiler Plus’ and be wondering what it means.

Boiler Plus is a new(ish) set of rules on energy efficiency; designed to improve the way you use energy in your home.

From April 6th 2018, all boilers must now have a minimum ErP (Energy related Products) rating of 92% and all gas and oil boilers must have appropriate time and temperature controls fitted.

In addition, when installed, combi boilers must have one of four of the following requirements fitted:

Rest assured that all boilers installed by The Heating People comply with all the legal requirements under Boiler Plus.

What are the benefits of replacing my boiler?

If you’re wondering what you stand to gain from a boiler replacement (aside from a boiler that actually works!) Here are some of the key advantages:

  • A warmer, more comfortable home
  • More reliable hot water
  • Quieter boiler operation
  • Space saving
  • Reduced energy bills
  • Better for the environment
  • More control
  • Peace of mind
  • Manufacturer’s guarantee
  • Reduced repair costs
  • More convenient location
  • Make your home more attractive to future buyers

Will a new boiler save me money on my bills?

With gas prices skyrocketing this year; we’re willing to bet you’re wondering whether you can cut your bills with a more efficient boiler.

Heating accounts for about half of what you spend in a year on energy bills. So an efficient boiler can make a big difference to your bills. 

The Energy Saving Trust estimates that you could save as much as £340 a year on your gas bill; by trading in an old-style G-rated non-condensing boiler for a new condensing one.

But obviously, the savings won’t be as significant if your boiler wasn’t non-condensing to start with.

And just because your boiler is A-rated out of the box; doesn’t mean it will be in your home if it’s the wrong size; has sub-standard controls; or isn’t installed right.

In these situations, your new boiler will run well below its A-label efficiency rating. Therefore, you need a skilled installer to maximise the efficiency of your heating system.

The Heating People are proud to be Heat Geek Accredited installers. Because the installer is the number one contributor to heating system efficiency.

Will I get a guarantee with my new boiler?

ATAG iC boiler.All boilers supplied by The Heating people come with a guarantee of up to 14 years.

This means that should your boiler breakdown; all labour and materials required to get the boiler back to working order are covered.

You’ll need to have your boiler serviced annually to maintain your boiler’s guarantee.

Will I receive anything in writing when I have a new boiler installed?

Once The Heating People have installed your new boiler; we register it with the manufacturers to activate its guarantee; and we’ll notify your local building control via the Gas Safe Register.

You will receive a Building Regulations Compliance Certificate in the post within 28 days of a new appliance being installed.

How often should I get my boiler serviced?

To keep your boiler running safely and smoothly, you should have it serviced once a year.

This is a legal requirement for landlords. And The Heating People will supply landlords with a Gas Safety Record on completion of the service.

How long does a boiler service take?

A boiler service usually takes less than an hour. But this depends on what sort of appliance you have, and what condition it’s in.

Why do boilers need servicing?

It’s vital that you book in for an annual service, and here are some of the reasons why:

  • A service will keep you and your family safe from risks of fire, explosions, gas leaks and carbon monoxide poisoning.
  • Regular servicing will help you to avoid a breakdown when you need your boiler most; by clearing any dirt and debris from the component parts.
  • Regular servicing will maximise the lifespan of your boiler by ensuring that it’s running as smoothly and efficiently as possible.
  • Annual servicing is essential to maintain your boiler’s guarantee, whichever manufacturer you choose to go with.
  • Annual servicing is a legal requirement for landlords.

Are there any warning signs that a boiler is in a dangerous condition?

With regular servicing, your boiler will remain safe. But as with all gas appliances, gas boilers pose risk to life if improperly maintained.

Contact a Gas Safe engineer immediately if you notice any of the following warning signs:

  • The flame in your boiler is yellow
  • The flame in your boiler is irregular
  • You’ve spotted new stains or smoke marks on walls or nearby appliances
  • There is a hissing noise coming from the boiler
  • There is a leak
  • It’s been more than a year since your last service

What happens during a boiler service?

An engineer conducting a boiler service.When servicing your boiler, The Heating people will conduct the following tests (where applicable to your boiler):

  • Visual Inspection of boiler and flue – to ensure that your boiler still meets current standards.
  • Removal of the boiler casing – to check the functioning of the main component parts, such as the burner; heat exchanger; main injector; and spark/sensor probe.
  • Flue check – to ensure that the flue is not obstructed in any way and the flue components are sealed correctly to make sure that there are no unsafe emissions being released.
  • Gas checks – a gas pressure check will ensure that your boiler is operating at the right gas pressure. The gas valve will be adjusted to check the burner is combusing efficiently and correctly (using a flue gas analyser). A gas tightness test will be conducted to ensure there are no leaks.
  • Combustion analysis – using a flue gas analyser, the products of combustion will be tested to ensure that there are not high levels of carbon monoxide and to make sure the boiler is burning as the manufacturer intended it to.
  • Cleaning – the condensate trap will be cleaned, and if the tests have indicated that it is necessary, the burner; heat exchanger; electrodes; and magnetic system filter; will also be cleaned.
  • Check the expansion vessel – to ensure that it still has water pressure to the manufacturer’s requirements. This will be topped up if required.
  • Documentation – The Heating People will provide you with a service report/checklist which includes all of the information about the safety of your boiler. Our installers will also fill in the service record in your boiler’s manual, which is important to maintain the validity of your boiler guarantee.

What is power flushing, and would it improve my heating system?

Before and after a power flush.A power flush is a cleansing process which cleans your entire central heating system, removing rust; dirt and debris; which collects in your pipes, boiler and radiators over time.

Unless it’s dealt with, this sludge will play havoc with the efficiency of your heating system; causing corrosion; blockages; and reduced efficiency.

This means that your heating system can’t perform like it used to. And you might start to notice your radiators getting colder.

It can also damage individual parts of your heating system; leading to breakdowns. And can eventually lead to the need for a full boiler replacement in the most severe cases.

If you’ve noticed that your radiators aren’t heating up properly and they don’t need to be bled; you should ask your heating engineer whether this would help.

A power flush may also be a good idea to cleanse your pipes and radiators before installing a new boiler.

Final thoughts…

We hope that you’ve found the answers to some of our most frequently asked questions helpful. If you still need advice on a boiler issue, contact The Heating People today.

Useful Links:

The Gas Safe Register

Government fact sheet on Boiler Plus

Energy Saving Trust article on boilers