What is a monobloc heat pump and what are their pros and ...

Exactly what is a monobloc heat pump? With so many types of heat pumps available (and more being developed all the time), it can be hard to understand which models offer what and make a decision on the products that are best suited to your project. 

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When you are researching heat pumps you will very quickly learn that there are a number of different types and versions. Initially you'll probably come across ground source and air source heat pumps and, as you dig deeper, you'll realise that there are different types of air source heat pumps as well. 

Not only are there versions that deliver heat to air (often referred to as air conditioning) but also those that deliver heat to water, as commonly used in our homes to deliver heat to the central heating system and hot water cylinder. Then we dig deeper and find different types of air to water heat pumps.

Monobloc heat pumps are one of the air to water heat pump options to choose from. And in this handy guide, renewables and ventilation installer David Hilton explains what monobloc heat pumps are and what they can offer homeowners.

What is a monobloc heat pump?

So, how do heat pumps work? Monobloc heat pumps have all the refrigerant components housed in the outdoor case. The refrigerant pipes are all factory assembled and factory sealed. This is often referred to as 'hermitically sealed'. 

There are two different types of monobloc heat pump: one with the pump, expansion and control components all built into the outside case, and the other with the pump, expansion and controls components fitted in the home.

The first type has the advantage that for a very simple installation less space is taken up inside the home, but that means that there is more wiring that needs to be installed to the outside unit and you are also limited by the pumps and sensors in that unit. 

The pipework on all monobloc units is, however, outside of the heated envelope of the home so in many cases the heat pump will protect itself by ensuring there is a minimum amount of heat in the water, even if the home does not require any heat.

The Aircal King Heat Series heat pump is high COP DC Inverter (variable-speed) heat pump for heating and cooling.

(Image credit: Aircal)

Are monobloc heat pumps a good option in the UK?

With monobloc heat pumps, the only connections to the outside unit are the electrical wiring and two water pipes meaning that this setup is very well suited to the UK climate, which is generally wet, rather than cold. 

In colder climates, such as those experienced in mainland Europe, a split system (see explanation of what this is below) is often better due to the refrigerant not freezing up in cold weather. If a monobloc is plumbed in a cold area there is a risk that the water in the pipes could freeze and damage the system, unless the water is either treated with anti-freeze (Glycol) or antifreeze valves are fitted to protect the heat pump. 

There are two main types of glycol: Ethylene Glycol (which is poisonous) and propylene glycol, which is the most commonly used of the two. Glycol protects the water from freezing and a mix of around 25% glycol in the water will offer protection against freezing down to around -10C. However, when glycol is added to water the solution is less able to hold heat and the 25% mix in the water will lower the heat carrying capacity by around 10%. It is crucial therefore to make sure that you have larger pipework plumbed in the central heating system or it may not be able to deliver enough heat. Anti-freeze valves overcome this issue but they release water when it gets really cold. 

This is not really an issue as most heat pumps maintain a minimum of around 20C in the water at all times. It is in times of a power failure and ambient temperatures outside of around 3C, or less, that the valves would release water. The installer should be able to show you how to top up the water if this does happen.

How are monobloc heat pumps different to split heat pumps?

Split systems are made up of two parts. Half the heat pump is outside the building and half is inside, with refrigerant pipes connecting them together. These can be more useful in colder climates or where the outside fan unit needs to be further away from the building.  A monobloc heat pump does not need a refrigeration engineer to install it so the whole installation can be done by a plumber and electrician. This makes the installation simpler and therefore a bit less expensive than split heat pumps. 

Monobloc heat pumps can also be less expensive than split heat pumps. Due to all the heat pump components being in the heat pump housing outside of the home there is less space required inside the home too.

The Samsung 8kw R32 Monobloc Air Source Heat Pump from The Heat Pump Warehouse and costs £1,992.94.

(Image credit: The Heat Pump Warehouse)

What are the disadvantages of monobloc heat pumps?

While there are many advantages to monobloc heat pumps, it is important to understand their limitations and downsides in order to be able to make an informed decision. Read my Mitsubishi Ecodan 11.2kW heat pump review, the model I have in my home, to find out more.

The main disadvantage to be aware of is the way in which they can, in certain cases, use energy unnecessarily. 

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In a highly efficient home, such as those built to Passive House standards, it may be the case that the heat pump uses additional energy to keep itself warm when the home does not need it. In these cases special design considerations, such as glycol or split systems, need to be adopted to optimise the efficiency.

So you&#;ve decided that an air source heat pump is right for you (rather than their ground source heat pump counterparts), and you were hoping that would be the end of the decision-making, right? Not just yet. But don&#;t worry, even though the different air source heat pump types can feel like you&#;ve opened another can of worms, it isn&#;t so complicated, especially when experts like us here at Heat Pumps UK are guiding you through it all. 

When it comes to air source heat pumps, there are two main types. Here we outline monobloc v split system heat pump types, including what each does, how they differ, plus their pros and cons, so you can make an informed choice of which is best for your home. 

What Are Monobloc Heat Pumps? 

Monobloc heat pumps work like all other air to water heat pumps in that they draw on the heat from the ambient temperatures of the outside air to heat a home, and expel that heat when cooling a home. But the reason a monobloc heat pump system gets its name is how the system does its job. 

A monobloc air source heat pump is a complete package in a single unit that is stored outside of the property. The compressor, heat exchanger and water are all contained in this single outdoor unit and connects directly to the home&#;s central heating system which can be controlled with a thermostat indoors. 

What Are Split System Heat Pumps? 

A split system heat pump system &#; as you might have already guessed &#; does exactly the same job, but across more than one unit. The system is effectively split between separate units, hence the name. Here, a condenser collects the heat from the air outdoors, before sending heated gas to an indoor unit inside the home, where the water is then heated and the radiators or underfloor heating heat up, too. 

Monobloc v Split System Heat Pumps: How They Differ 

So, the main difference is the way the system actually works. The end result will be the same: a warmer home using renewable green energy, rather than fossil fuels. But the journey is the difference. 

With a monobloc system everything happens in the same unit and the water is heated outdoors before moving inside your house to heat it. With split heat pumps the process is split in two, where the heat from the air is separated and sent indoors where it will then heat the water for your heating system. 

Pros & Cons Of Monobloc Heat Pumps

Pros 

There are many positives with monobloc heat pumps, which is part of the reason they are so popular. 

Don&#;t Take Up Indoor Space Space inside the home often comes at a premium, so any heating system that doesn&#;t require indoor units will already be appealing to many. The fact that a monobloc heat pump only requires one unit, and that unit is installed outdoors, is a huge benefit over split systems or even conventional heating systems. One Unit Maintenance An all-in-one unit will always be easier to maintain and troubleshoot than a system that&#;s split across multiple units &#; that&#;s just basic engineering. If something goes wrong with your heat pump, with a monobloc system it usually will be fixed much sooner than a split heat pump system. Quick InstallationSelf-contained monobloc units are much quicker to install because of their all-in-one nature. They don&#;t connect at multiple points &#; just a simple installation to work with your current central heating system. Because they are so easy to install, it takes less time for a heat pump installer to get the system up and running, and therefore they&#;re even cheaper to install.

Cons

There are, of course, some drawbacks to monobloc heat pumps too.

Unique Installation Requirements Since monobloc systems connect directly to your current central heating system, the single unit needs to be installed at a specific place on the outside of your property where it can be connected easily. There is practically zero flexibility here, too, meaning if you don&#;t have the space outdoors to install it where it needs to be, then you simply can&#;t have a monobloc heat pump system installed. Size Of The System Whilst an all-in-one system has many benefits, one thing that can&#;t be changed is the sheer size of the unit. So much technology has to fit into the single unit, making it much larger than split systems which consist of two much smaller units. These larger systems then need to fit in your outdoor space, taking up a significant amount of room, and monobloc heat pumps need additional space around the unit for it to work efficiently. Louder OperationA monobloc heat pump has all of its technology inside one large unit, and because of that, they usually make more noise than a split system heat pump. If your system is going to be installed in a place where the noise won&#;t bother you, then it&#;s less of a concern, but it&#;s certainly worth bearing in mind. 

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Pros & Cons Of Split System Heat Pumps 

Pros 

Split heat pumps also have their benefits.

Integrated Domestic Hot Water Plenty of split system air source heat pumps come with an integrated hot water storage tank included (notice we said plenty not all). This means that you can get hot running water for your home as standard, but most monobloc systems will need a separate hot water cylinder in order to provide you with domestic hot water as well as heat. Having a water tank incorporated saves on space, whilst also being much more convenient for you. More Flexible Installation Unlike monobloc heat pump systems, there is much greater flexibility when it comes to where the units can actually be installed. It&#;s only the indoor unit that actually connects to the central heating system, but the outdoor unit can go almost wherever you like. That means less noise and greater flexibility, so you can place it somewhere that&#;s truly convenient for you. Smaller UnitsSplitting the system allows for two much smaller units than a monobloc system can have. And whilst, yes, that does mean you need to find space for two units rather than one, they&#;re much smaller and more convenient to house &#; both indoors and outdoors. Their smaller sizes also contribute to their quiet operation, too.

Cons

As with anything, split heat pumps also have a number of drawbacks that must be considered before purchasing. 

Requires An Indoor UnitWhilst we&#;ve already highlighted the benefits of installing two smaller systems, there&#;s no denying that having to find space for a unit inside can be frustrating. Thankfully, most split system heat pumps can have their indoor unit installed where your old boiler once was. The problem comes if your split system heat pumps don&#;t have an integrated water tank (not all of them do). When this happens, you&#;ll need to find additional storage for a water tank inside your home, creating a bit of a headache if your home is already limited on space. More Time Consuming Installation Split system heat pumps are slightly more complicated to install because of the separate units which will need your installer&#;s attention. Because of the added complexities, the installation will also take longer than a monobloc heat pump system, which will then push costs up a little more. Higher Upfront CostsSpeaking of costs, split system heat pumps are also just inherently more expensive than monobloc systems too. Their technology is a little more complex and therefore a little more expensive. With upfront and installation costs adding up, you can expect to pay more for a split system heat pump than a monobloc heat pump.

Which Heat Pump System Is Right For Me?

Choosing the right heat pump is important &#; get it right and you&#;ll be benefiting from a greener heating system in your home for years to come. When it comes to monobloc or split system heat pumps, it isn&#;t really you that gets to decide: it&#;s your house and its suitability for a specific type of heat pump. 

As we&#;ve already mentioned, both have installation requirements attached to them, meaning if you don&#;t have the outdoor space at a specific point on your exterior wall, then a monobloc system won&#;t work for you. Likewise, if you don&#;t have the interior space because you&#;ve opted for a split system heat pump without an integrated water storage tank, then it won&#;t be appropriate for you either. 

Your property ultimately determines the type of heat pump that is suitable for your home. If you&#;re unsure, contact a heat pump installer to carry out a home assessment to determine which heat pump system is best for you.

Trust Heat Pumps UK to put you in touch with the best heat pump installers in your area today. We can help you find out about available funding opportunities under the Boiler Upgrade Scheme plus finance options.  

Monobloc v Split System Heat Pumps: Final Verdict

Ultimately, neither system is necessarily better than the other. Both heat pumps will provide you with better air quality in your home, better regulated temperatures, improved energy efficiency, and all that whilst saving you money and reducing your carbon footprint.

By filling out your details with us today, we can put you in touch with heat pump installers in your area with the best deals. A quick inspection (usually free) from the installer you choose will tell you whether a monobloc or split system heat pump is best suited to your home, too, giving you added peace of mind that you&#;re making the right choice when installing a hot water heat pump at home!

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You don't need to be claiming benefits!

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