Most Common Mistakes When Choosing a Cabinet

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Most Common Mistakes When Choosing a Manifold Cabinet

A manifold cabinet seems like a trivial thing at first glance - a metal or plastic box that hides an underfloor heating or heating-circuit manifold. The reality for installation companies and ordinary builders alike is different, though: a wrongly chosen cabinet can cause problems that only show up years later, when they're far more expensive and unpleasant to fix. In practice, when selling and advising on manifold cabinets, we keep seeing the same mistakes - which is exactly why we decided to put them together clearly in one place, along with specific recommendations on how to avoid them.

This article follows on from the basic guide How to Choose a Manifold Cabinet and covers specific, recurring errors we see in real projects - from underestimating size, to mixing up the cabinet type, to forgetting about servicing accessibility. If you're currently planning to buy a cabinet for an underfloor or radiator heating manifold, we recommend going through all the points - most of them can be fixed in a few minutes at the ordering stage, but only with great difficulty once it's built into a wall or partition.

Why it's worth paying attention to choosing a cabinet

A manifold cabinet isn't just a decorative cover. It performs three practically equally important functions: it protects the manifold and fittings from mechanical damage and dust, it allows comfortable access for bleeding, flow adjustment or servicing, and last but not least it determines how much space you actually have available for the manifold itself, including all connected circuits, the pump group, the mixing valve, and future expansion. If any of these three functions is underestimated, the result is either an aesthetic compromise (the cabinet sticks out from the plaster, the door won't close fully), or an operational problem (the technician can't reach the fittings, water from the air-vent valve doesn't flow where it should, or a further circuit can't be added later).

From experience with installation companies and end customers, we know the vast majority of complaints and later adjustments have nothing to do with the quality of the cabinet itself, but with the wrong choice of size, type, or location before installation. So let's go through the specific mistakes one by one.

Mistake #1: Underestimating size and no spare margin

The most common mistake we see is choosing a cabinet exactly "to fit" the current number of circuits, with no margin at all. An underfloor heating manifold is often ordered or installed before the final decision on room layout is made (especially for new builds, where partitions can still change during shell construction), and just as often a bathroom radiator, garage heating, a conservatory, or an extension gets added later. If the cabinet is tight, sized exactly for the current number of circuits, any future expansion means either unsightly additional pipework outside the cabinet, or a complete replacement with a larger one - which, for a built-in recessed version, means work on the wall.

In practice we recommend allowing for at least one spare position, ideally a margin of 2-3 circuits for family houses, where finishing an attic, garage or extension can reasonably be expected in the future. For the three commonly available manifold cabinet widths - 385 mm, 485 mm and 615 mm - a simple rule applies: the wider the cabinet, the more room for circuits, fittings and any pump or mixing group. As a rough guide, the 385 mm cabinet suits smaller flats or individual rooms with fewer circuits, the 485 mm covers an ordinary medium-sized family house, and the 615 mm makes sense where there are more circuits, extra equipment (circulation pump, mixing valve), or exactly the future margin mentioned above.

Below is a simple comparison of the three most commonly sold cabinet widths, to show at a glance how much extra space you get moving between sizes.

A practical tip from the field: if you're not sure how many circuits you'll need in the future, it's better to choose a cabinet one size class larger. The price difference between the 385 mm and 615 mm variants is usually lower than the cost of later replacing a built-in cabinet after construction is finished.

Mistake #2: Mixing up recessed and surface-mounted cabinets

The second very common mistake happens already at the ordering stage - a customer, or even a less experienced installer, mixes up the recessed and surface-mounted versions. These two types can't be substituted for each other without changing the building preparation: a recessed cabinet is installed into a pre-prepared niche in the masonry or a plasterboard partition, and its frame sits flush with the plaster surface, while a surface-mounted cabinet is installed onto a finished, flat wall surface and protrudes entirely from it.

If this mix-up is only discovered at the installation stage - that is, once the niche in the wall is already prepared, or conversely once the wall isn't meant to be worked on any further - it means either additional masonry work, or a compromise solution that doesn't look good and can also complicate fitting the door afterwards. We cover the detailed differences between the two types, including when each variant is worth it, in a separate article, Recessed vs. Surface-Mounted Cabinet.

A rule we recommend following without exception: the cabinet type (recessed/surface-mounted) has to be decided before any masonry or plasterboard work starts at its installation location - not only once the manifold physically needs hanging.

A real-world example

A common scenario we come across: the investor orders a surface-mounted cabinet, since it's usually a bit cheaper and simpler to install, but the construction company has meanwhile already prepared a niche for the recessed variant during shell construction (often out of old habit, or based on project documentation for a different type). The result is either having to brick up the niche afterwards, or ordering a different type of cabinet - either way it's a loss of time and money that could have been avoided with one check question before ordering.

Mistake #3: Misjudging the space depth and location

The third recurring mistake relates to the depth of the space the cabinet is meant to go into - especially for the recessed version. A manifold with fittings, shut-off ball valves and any pump group needs real depth, not just width and height. If preparing the niche in a partition only allows for the thickness of the cabinet itself, with no margin for protruding fittings and future pipework connections, the manifold simply won't fit into the prepared space, or the door won't close fully.

A related problem is the cabinet's location within the layout of the flat or house itself - too low, behind a door, in a corner behind furniture, or somewhere that can't be comfortably reached for future servicing. The recommended mounting height and suitable locations in various types of spaces (hallway, utility room, closet) are covered in detail in the article Cabinet Placement in an Apartment or House.

The diagram below sums up the recommended sequence that should precede the actual installation - from surveying the space to the final installation - in exactly the order that helps prevent most of the mistakes mentioned above.

Mistake #4: Forgetting about servicing accessibility

The cabinet gets opened from time to time - when bleeding the system at the start of the heating season, when adjusting the flow on individual circuits, when replacing batteries in wireless heads, or during routine servicing. If the cabinet is placed somewhere the door can't open to its full width (for example right next to a door that opens the same direction, or directly at floor level with no room to kneel), every service visit becomes needlessly complicated.

We recommend testing before installation whether the door really does open to its full angle and whether enough free space remains in front of the cabinet - in practice, allowing at least 60-70 cm of free space in front of the cabinet has proven reliable, enough to work comfortably with tools while crouching. We cover this topic in more detail, including specific examples of unsuitable placements, in the article Cabinet Accessibility for Servicing.

Mistake #5: Unsuitable material and surface finish for the environment

The fifth mistake concerns choosing the cabinet's material and surface finish relative to the environment it will be installed in. A cabinet located in a damper environment (for example near a laundry, a bathroom, or in an unheated garage) needs a more durable surface finish than one in a dry living room. It's also true that a cabinet visible in a representative part of the flat (hallway, living room) should be chosen with the door and frame's appearance in mind too, not just the technical function.

A detailed overview of the materials used (steel sheet with a powder-coated finish is the most common variant) and recommendations by environment type can be found in the article Materials and Surface Finish of Cabinets. In simplified terms: in a dry indoor environment, a standard painted steel cabinet is perfectly sufficient and also the most economical choice, while in a damper or more industrial environment it's worth discussing more durable surface finishes directly with the supplier.

Mistake #6: Ignoring the door and frame accessories

The sixth mistake seems minor, but in practice causes a surprising number of additional orders: forgetting that on recessed cabinets, the door and masking frame are often a separate item that has to be ordered separately, or at least deliberately checked as being included in the package. With surface-mounted cabinets this situation is simpler, since the door is usually part of the complete set, but even here it's worth checking the exact package contents before ordering.

If a customer orders just the cabinet body without a door or frame and only realises it at installation time, it means further waiting for the missing part to be delivered, and often a halt to the building work too. A complete overview of the available accessories and what to watch out for when ordering is covered in the article Accessories - Doors and Frames.

Mistake #7: Choosing by price regardless of actual need

The last common mistake is the opposite extreme of the first - trying to save money by choosing the cheapest available cabinet regardless of whether it actually suits the number of circuits and future needs. The price difference between the individual sizes of manifold cabinets is actually relatively small compared to the total cost of the heating system, yet the impact of a wrong choice on the comfort of future use and servicing is disproportionately larger.

For a better picture, here are the real, approximate prices of three commonly sold surface-mounted manifold cabinets of different widths:

So the difference between the smallest (385 mm, €63.10) and the largest (615 mm, €75.15) surface-mounted cabinet is only around €12. If there's even a small chance you'll add a circuit in the future, or need room for a pump group, it's worth paying that difference upfront - especially compared to the cost of later work on an already finished wall.

Specific recommended cabinets

If you're currently deciding which size of surface-mounted cabinet to choose, here's a brief overview of the three best-selling variants, with a note on who each suits best.

Manifold cabinet 385 mm - surface-mounted - the smallest and also the cheapest variant, suitable where you're certain the number of circuits will stay low even in the future (a smaller flat, one heating zone). Price from €63.10.

Manifold cabinet 485 mm - surface-mounted - the most versatile choice for an ordinary family house, offering a reasonable margin without unnecessarily large dimensions. Price from €67.53.

Manifold cabinet 615 mm - surface-mounted - the largest variant, ideal for a higher number of circuits, a planned pump or mixing group, or if you want a solid margin for years ahead. Price from €75.15.

Summary: overview of mistakes and how to avoid them

The diagram below sums up all the mistakes covered side by side, so you can quickly check before ordering whether you've missed any of them.

What to do if you're not sure

If you're not sure which size or type of cabinet is right for your case, we recommend the following simple approach: first, check the planned number of circuits with your designer or installer, including any that might be added in later construction stages (attic, extension, bathroom radiator). Then measure the actual space where the cabinet is to go - including depth, not just width and height - and only then decide on the type (recessed/surface-mounted) based on whether it's a finished wall or a wall still under construction.

When in doubt, it's always better to choose a cabinet one size class larger than to rely on a precise estimate - as shown above, the price difference between sizes is minimal compared to the cost of a later adjustment. And finally, always check before the final order whether the door and frame are included in the package, to avoid extra waiting for a missing part right before installation.

Frequently Asked Questions

Can an already built-in recessed cabinet be enlarged later?

Practically not, without work on the masonry or partition - the niche is prepared exactly to the dimensions of the original cabinet. If there's a risk you'll need more room in the future, it's far simpler to choose a larger cabinet from the start than to replace it later.

Is the price difference between the individual cabinet sizes really that small?

Yes, for the surface-mounted models compared here, the difference between the 385 mm (€63.10) and 615 mm (€75.15) variant is around €12. Given how much simpler it is to have a sufficient margin from the start than to make a later replacement, it's often worth choosing the larger variant even with only mild doubts about future needs.

Do I need to sort out the door and frame separately when ordering a cabinet?

For recessed cabinets, this is a common situation that needs checking before ordering - the door and frame aren't always automatically included in the package. For surface-mounted cabinets, the door is usually part of the complete set, but even here we recommend confirming the exact package contents at the time of ordering.

What margin for future circuits do you recommend when choosing cabinet size?

From experience, we recommend at least one spare position; for family houses with planned finishing work (attic, extension, garage), a margin of 2-3 extra circuits is preferable. This margin translates directly into the choice of cabinet width - 385, 485 or 615 mm.

How do I know if I have enough space in front of the cabinet for servicing?

Check that the door can open to its full angle without hitting other doors or furniture, and that at least 60-70 cm of free space remains in front of the cabinet for comfortable work with tools while crouching or kneeling.

Is it worth thinking about the cabinet's material and surface finish, or is it just aesthetics?

It's not just aesthetics. In a damper environment (near a laundry, an unheated garage), choosing a more durable surface finish has a direct impact on the cabinet's lifespan. In a dry indoor environment, a standard painted version is perfectly sufficient.

Have a question about this topic?

Not sure what to choose, or dealing with a specific situation in your home? Write to us - we're happy to help.