When does a boiler need replacing? – Ten signs to look for

One of the questions we are asked most often as heating engineers, is ‘when does a boiler need replacing?’. On the surface, this is an easy question, but in reality, there are a huge number of variables that can decide on the correct answer.

Ten signs that show your boiler may need replacing.

  1. Age
  2. Efficiency
  3. Rising Energy Costs
  4. Breakdown frequency and reliability
  5. Leaks
  6. Strange Noises
  7. Obsolete parts
  8. Incomplete Combustion
  9. Newer Technology
  10. Remaining in control

So let’s explain what each of these indicators means in more detail.

1. Age of the boiler

A condensing boiler is designed to last up to 15-20 years. They are still a relatively new technology, so some may last longer. There’s no doubt that at this age and beyond, they will start to show signs of wear and tear.

Many commercial boilers were built from cast iron and speaking to the service engineers on-site here at Kimpton, they have sometimes been called out to maintain and repair cast iron boilers that are over 30 years old and still running.

Much depends on how well they have been serviced during their lifetime. Those that have been regularly maintained should obviously last longer as the system will have been running at its peak efficiency for most of its operating life.

But generally, if your boiler is 15-20 years or older, it may well need replacing soon. If it’s not imminent, it would be prudent to at least budget for replacement in the coming few years.

2. Efficiency

An old cast iron boiler can last many, many years. As we said above, we often get called out to boilers that are approaching 30 years old. This is great for consistency, but very poor for efficiency.

The technological advances that have been made in that 30+ years are huge. These older cast iron boilers can operate with efficiencies as low as 50%.

A 15 year old boiler will, on average be around 70% efficient. A brand new stainless steel commercial boiler can operate at efficiencies of 98%.

To explain boiler efficiency simply.

With an old boiler at 70% efficiency, if you put 100kW of energy into it, you will get 70kW out, with a brand new super-efficient boiler, 100kW in will produce 98kW out.

This is a 40% saving, just through increased efficiency and it offers the potential to save you 40p in the £1 for everything you spend on heating costs.

Coupled with long warranties available on most new commercial boilers and the maths begins to swing heavily in favour of making the switch to a more efficient boiler, sooner rather than later.

3. Rising Energy Costs

As any system gets older, it becomes less efficient. Even with regular maintenance, parts begin to wear and the whole system becomes less efficient. It may be only by a few percent per year, but over time, this slow degeneration compounds into an overall, inefficient system.

This happens most regularly within the heat transfer surfaces. These can operate with very fine tolerances and a build-up of scale or coating can begin to erode this efficiency. We also sometimes see corrosion within the boiler or heat exchanger. This can be caused by the build-up of solids or tiny metal parts that build up and can cause galvanic corrosion and just a build-up of dirt that may not have been caught by the filtration system.

All of this adds up to a less efficient operation and rising fuels bills. The calculation on when is the right time to replace the boiler comes down to how much MORE efficient a new system would be compared to this increasingly inefficient existing system. There’s no set time scale but it does tend to be at around 15-20 years or older when the cost of replacement starts to look like a more cost-effective option.

4. Breakdown frequency and reliability

No-one wants a breakdown of their boiler. There’s never a right time for it to happen and it invariably breaks down when it’s under most stress in the middle of winter – just when you need it most. A cold office or building causes you issues with unhappy staff.

Routine maintenance should highlight areas for concern going forward and give you an early indication that replacement may be necessary, but if breakdowns become more frequent, then that time may need to be now. As a rule of thumb, one breakdown within a year is unfortunate, two maybe seriously unlucky, but three is probably preventable as the second one should have been taken as a sign that it’s probably time for replacement.

Add to this the cost of these “out of warranty” repairs and the business case begins to stack up too. Most commercial boilers, installed by Kimpton, come with a five-year warranty or sometimes even longer and as long as it’s regularly and properly maintained, there should be very few surprise costs that you face during this warranty period.

If the repair costs of your boiler are starting to stack up, then it’s time to give serious consideration to a replacement boiler.

5. Leaks

An older commercial boiler can be at risk of developing leaks.

Cracks within the body of the boiler, seals that become dried or perished over time and heat build-up due to scale or dirt within the system are all obvious risk factors.

Galvanic corrosion again presents a risk where a small piece of copper from within the system can literally burn its way through an aluminium heat exchanger if the conditions are right and it’s left unchecked.

But the risk from leaks is more than just the damage to the boiler, it’s the risk to property or business that presents a greater financial risk. A boiler with leaks can fail catastrophically at any time and cause untold water damage to the areas around it.

The cost of the business interruption is often far more than the cost of repair or replacement of a boiler that’s showing signs of failure. What’s more, if you choose your replacement time, you can minimise that interruption and keep unexpected costs to an absolute minimum.

6. Strange Noises 

Hardly the most technical description, but boiler systems, as they age, often begin to make strange noises, from bubbling to crashes and bangs. Their causes are varied and many.

They can be caused again by pressure build-up, blockages within the system or wear within bearings. Noise within the system can travel too, so it isn’t always obvious where it’s coming from. It could be from the pipes, the pump, from deep within the heating system, or even the boiler itself.

Low water pressure is also an issue as this can cause cavitation (air bubbles) and force the pump to work too hard and create noises.

Again, any of these can sometimes be a symptom of imminent failure or at least a sign that a system has issues.

Many of these issues are preventable and/or repairable by a suitably experienced heating engineer. Our engineers are regularly called out to systems where they just need bleeding or topping up. On the surface, these can be simple remedies and the causes can be a simple leak or failure of an expansion vessel within the system.

So, any noises, however loud or unusual can be an early warning that shouldn’t be ignored. Speak to an engineer. If the symptoms are caught early, often a boiler system can be given a new lease of life through simple repair, without the need for main component replacement.

7. Obsolete parts

Parts becoming obsolete is something that pleases no-one, but is a simple fact of life. As a boiler model becomes older they are replaced with newer, more efficient models.

There is normally a five-year window after a model is discontinued, where parts are still available, but after this, replacement and service parts for the older boilers stop being produced and eventually become almost impossible to obtain.

The same is true in almost any industry, from electronics to the motor industry.

This almost forced obsolescence can be responsible for a boiler replacement, where it is running fine, but just wants for a routine service part that is no longer available.

But, whilst it may feel like a forced choice, if parts become unavailable, it may be time to upgrade to a newer boiler. The savings in running costs will almost certainly make it worth the investment and take away any risk of business interruption for many years to come.

8. Incomplete or inefficient Combustion

This is perhaps the single biggest reason that you must get your boiler regularly serviced.

It’s not about us trying to drum up work, it’s about risk of life.

Incomplete or inefficient combustion has the potential to be the biggest single risk with an ageing commercial boiler. A system where incomplete combustion is becoming an issue WILL produce Carbon Monoxide (CO).

This is often known as the silent killer as it has no smell or taste. If it enters your bloodstream for prolonged periods, it stops your blood from carrying enough oxygen and can kill you. The big risk to life is that as it is virtually undetectable without a specific Carbon Monoxide detection system and it can be days, months or even years before its effects take hold.

The symptom of incomplete combustion can be as simple as the colour of the flame. This is shown as a yellow flame, rather than the normal blue. This is normally caused by dirt or soot preventing the correct mix of gas and air from entering the combustion chamber and the combustion being compromised. It is another very good reason for regular servicing of your commercial boiler as this dirt and soot build-up will be regularly removed and even more importantly, CO leakage WILL be detected by the engineer

To compound the risk, older boilers were not designed to prevent Carbon Monoxide leakage and as such, present a risk to life if they are not operating efficiently. According to the NHS in England, every year there are around 25 deaths from accidental carbon monoxide poisoning in England and Wales.

Many or most of these are avoidable through planned and preventative maintenance.

9. Newer Technology

Innovation in boiler design is happening all of the time. Some innovations are small steps and others, great leaps in design and efficiency.

This new technology is providing more efficient boilers, but also other benefits, such as a smaller footprint, or more flexible fuelling arrangements. These may free up valuable space within your building.

Newer boiler controls can also provide better close control of your system and more visibility of what your boiler and system are doing remotely.

10. Remaining in control

Perhaps the most compelling reason to plan to replace your existing commercial boiler is to remain in control. If it is getting older, there is no doubt for ALL of the reasons above that it will fail at some point in the future. Whilst it’s still running – even if it is inefficient or noisy, you can choose when you want to get it done.

Logic says that summer is the best time to do it as it’s when you need your heating the least. More importantly, perhaps it’s when you would have the lowest level of potential business disruption. When it’s freezing outside, you need your heating and that’s the worst possible time to lose it.

Many of the emergency call-outs our engineers attend could have been preventable, as the signs were there that the system was failing ahead of this emergency call-out.

Invariably, failures happen when the system is working hardest – which is normally in the middle of winter when you need it most. Whilst we can bring in emergency heating solutions, it’s an expensive route that is probably best avoided.

So, the time to replace an ageing boiler is when it’s showing signs of failure, not when it’s already broken and you’re desperately in need of heat.

So after all this, does your boiler really need replacing?

You need to be able to trust your service engineer.

We have all heard tales of engineers on-site looking for short term work by inventing issues. At Kimpton, we aim for life long relationships. We will advise you honestly, so you can budget for replacement – even if it’s three or four years in the future – to establish a sensible programme for planned and preventative maintenance.

Kimpton – The team you can trust

We specialise in commercial boilers, heat pumps and HVAC of all kinds and have done since 1963. We work across the North West, North Wales, Wirral and Liverpool. We service and replace heating systems.

If your commercial boiler is ticking any or all of the above boxes, call us now for an honest assessment of what the real issue is and to plan a sensible route forward.

You can reach the Kimpton Team on 0151 343 1963


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