Frequently Asked Questions About Manifold Cabinets

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A manifold cabinet is one of those things most people only think about the moment they're standing in front of open pipework in a hallway or storage room, wondering what to do with it. Over the years we've been selling heating equipment on atria.sk, practically the same questions keep coming up in our advice service and in product discussions - what size to choose, whether to recess it into the wall or mount it on the surface, what height to install it at, how the installation works, and what to do later if the number of circuits changes. In this article we've gathered the most common questions in one place and answer them practically, the way we'd explain it to a customer on the phone.

A manifold cabinet isn't just a decorative cover. It's a component that determines how comfortably the manifold can be operated, serviced and bled throughout the whole life of the heating system - quite possibly 20-30 years. That's why it deserves the same attention when choosing it as the manifold or the boiler itself.

We understand why this topic seems simple at first glance - after all, it's "just a box on the wall". In reality, though, the cabinet is exactly where most of the small but unnecessary mistakes happen: the wrong size that has to be broken out and replaced two years later, an unsuitable height that forces you to bend down or reach up every time you bleed the system, or a location too close to a corner where the door can't open properly. None of this is expensive to fix when planned in advance, but it's unpleasant and sometimes costly to fix afterwards, once everything is built in and painted. That's exactly why it's worth going through these questions before the installer arrives with a drill.

What's the difference between a surface-mounted and a recessed cabinet

This is clearly the most common question customers ask us before they've even looked at a specific size. The difference is where the cabinet's body sits relative to the wall surface.

A surface-mounted cabinet is installed entirely on the wall surface - it requires no breaking out or chiselling, the cabinet simply hangs on the wall similarly to, say, an electrical distribution board. It's the faster solution, suited especially to renovating a finished space where you don't want to disturb the masonry, or to plasterboard partitions where recessing would be complicated. The downside is that the cabinet physically protrudes from the wall (typically by 12-15 cm), so it can be somewhat in the way in a narrow hallway or storage room.

A recessed cabinet, by contrast, is set into a chiselled-out or pre-prepared opening in the masonry, so once finished only the frame with the door is visible, flush with the wall or only slightly proud of it. It looks tidier and doesn't take up room space, but it requires rough building preparation in advance - chiselling out or fitting into the wall already at the shell-construction stage, which is often unrealistic or unnecessarily laborious when renovating a finished flat.

In practice it works like this: for a new build or a full renovation where the walls are being chiselled into anyway for the pipework, it makes sense to go straight for a recessed version. For an add-on installation into a finished flat, garage, or where a manifold needs to be added or replaced without disturbing the masonry, a surface-mounted cabinet is clearly the more practical and faster choice.

What cabinet size to choose based on the number of circuits

The second most common question is size - and here we should be honest, there's no universal table of "this many circuits = this size", because it also depends on the type and width of the specific manifold, the number of additional components (circulation pump, mixing unit, filter, shut-off ball valves with air vent), and the margin you want to leave for the future. Even so, there's a rough rule that has proven reliable in practice.

Smaller cabinets around 385 mm wide tend to suit smaller manifolds with 2 to 4 circuits - typically a smaller flat, or just part of the underfloor heating in a bathroom and one other room. Medium sizes around 485 mm comfortably fit a manifold with 4 to 6 circuits including room for a circulation pump. Larger cabinets from 615 mm up are worth it where the house or flat has 6 or more circuits, or where the cabinet also houses a mixing unit for underfloor heating combined with a radiator circuit.

An important tip we give almost every customer: if you're torn between two sizes, go for the larger one. A tight cabinet is awkward to operate, hard to bleed even wearing a glove, and any future expansion (for example finishing an attic room or garage) will force you to replace the whole cabinet - unnecessary extra work and cost.

A practical example from everyday installation

A common situation we deal with in our advice service: a family house, underfloor heating on the ground floor (4 circuits) and a plan to finish one more room in the attic later (estimated +1 to 2 circuits). In such a case we recommend not buying a cabinet sized exactly for 4 circuits, but going straight for a size that also covers that planned margin - in this specific case, rather 485 mm or even 615 mm if there's enough space on the wall. The price difference between the individual sizes (a matter of a few euros) is negligible compared to what it would cost to break out and fit a larger cabinet a year or two later.

Manifold cabinet 385 mm - surface-mounted - the most compact size in our range, ideal for a smaller flat or a manifold with 2 to 4 circuits, where there's no room for a larger cabinet. Price from €63.10.

Manifold cabinet 485 mm - surface-mounted - the most versatile, best-selling size, which comfortably covers current circuits plus a small margin for the future in most ordinary households. Price from €67.53.

What if I'm not sure about the future number of circuits

This is mostly asked by people building or renovating a house in stages - for example dealing with the ground floor now, while the attic or basement will come a year or two later. The recommended approach is simple: count the circuits you'll definitely need now, add an estimate for the stages you're planning within the next 3 to 5 years, and choose the cabinet size based on that total. If you're genuinely unsure, it's better to leave one or two blanked-off spare connections on the manifold - they cost only a fraction of the price of a full cabinet replacement, and in the future they can simply be opened and connected to a new circuit without any breaking out.

The second common situation is a flat in an apartment building, where the number of circuits doesn't change, but the owner later decides, for example, to replace radiators with underfloor heating in one room. The same recommendation applies here too - a slightly larger cabinet now saves work later.

Where to place the cabinet and at what height

The third most common question isn't about size but about placement. A manifold cabinet should always be located where the manifold itself is - that is, generally at the point where the distribution pipes arrive from the boiler room or heat source into the individual rooms. This is most often a hallway, a storage room, a utility room, or a shaft next to a staircase.

For installation height, we follow a simple practical rule: the bottom edge of the cabinet should be around 30 to 40 cm above the floor - low enough for the pipework coming from under the floor to fit in below, but not so low that you have to crawl on the ground every time you bleed the system. The top edge, on the other hand, shouldn't exceed the height you can comfortably reach without a ladder - roughly up to 160 cm from the floor. If the manifold is taller and the cabinet would exceed this range, it's better to choose a wider cabinet and turn or rearrange the manifold inside it, rather than having to mount it too high.

Besides height, you also need to leave free working space in front of the cabinet - realistically at least 40 to 50 cm, so the door can open fully and you can comfortably reach all the valves and air-vent screws. We've seen cabinets crammed right under a suspended ceiling or boxed in by furniture many times in practice, and it always ends with the furniture having to be moved or dismantled at service time.

How cabinet installation works, step by step

Installing a surface-mounted cabinet is half a day's work for one experienced installer; installing a recessed cabinet takes a bit longer because of the building preparation. In both cases the procedure consists of the same steps, only the extent of wall preparation differs.

In the first step, the exact position is determined with regard to the route of the incoming pipework and the height according to the rules above. In the second step, the wall is prepared - for the surface-mounted version this is just drilling holes for the anchor plugs, while for the recessed version it means chiselling out and fitting the building sleeve, including bricking it in or fixing it with plaster. In the third step, the cabinet body is fixed, the manifold is fitted into it, and the pipework is connected from all sides - supply and return, plus the individual underfloor or radiator heating circuits. The fourth step, the pressure test, is the most important in terms of future problems - the system is pressurised and monitored for several hours (ideally overnight) to see if the pressure drops, which would signal a leaking joint. Only after a successful test is the door fitted and the final finishing done around the frame.

Manifold cabinet 615 mm - surface-mounted - the largest size in the range, suitable for manifolds with 6 or more circuits, or where the cabinet also houses a circulation pump or mixing unit besides the manifold. Price from €75.15.

Material, surface finish and door

Another group of questions concerns the finish of the cabinet itself. Standard manifold cabinets are made from galvanised or painted steel sheet, most often in white (a shade similar to RAL 9016 or 9010) that visually matches a white wall and a white radiator. The door is either plain (simple white sheet) or has a decorative frame that looks a bit more presentable - suitable for example for a hallway, where the cabinet is permanently visible rather than hidden in a storage room.

Some customers ask whether the cabinet can be repainted a colour other than white - with painted sheet this is possible in most cases, you just need a suitable metal primer and should expect that the coating can get scratched around the hinges and lock during future servicing. If you're planning to repaint the cabinet, we recommend doing it before installation, while it's freely accessible from all sides.

Lock and ventilation

Most cabinets have a simple square or triangular key on the door (the same type used, for example, on electrical distribution boards or mailboxes) - so it's not a security lock against burglary, but a safeguard against a small child accidentally opening the door, or against unqualified interference with the manifold. There's no real science to ventilating the cabinet - the manifold and pipework are a closed system that doesn't lose enough heat to require active ventilation; any light perforation of the door is more about letting moisture out in case of a small water leak during bleeding.

Servicing, maintenance and future accessibility

The last major group of questions relates to what happens after installation - that is, what living with the cabinet is like over years of operation. Bleeding the underfloor heating circuits is usually done once a year, most often in autumn before the heating season starts, or any time you notice a room heating less well than before. That's exactly why it's important to be able to reach the cabinet comfortably without having to move furniture or remove tiling - a point we already mentioned under placement.

When the heating system is changed or extended in the future - for example finishing an attic, replacing the manifold with a larger one, or adding thermostatic control of individual circuits - it's practically always easier if the cabinet had adequate spare room from the start. Replacing the whole cabinet because a new, larger manifold doesn't fit inside means extra breaking out, reconnecting the pipework, and extra time, all of which can be avoided by choosing the right size from the start, as described above.

If you're dealing with servicing an older cabinet that no longer has a replacement door available from the original manufacturer, in many cases a door from a different manufacturer with a similar outer size can be used - manifold cabinets, in the vast majority of cases, follow similar, practically standardised size ranges (385, 485, 615 mm and so on), so replacing just the frame or door is solvable in the vast majority of cases without replacing the whole cabinet body.

Most common mistakes we see in practice

Over the years of selling heating equipment, a few mistakes keep recurring in our advice service and when dealing with complaints and service questions - mistakes that are fairly easy to avoid if you know about them in advance.

Cabinet size too tight. A customer orders a cabinet sized exactly for the current number of circuits with no margin at all. The manifold does fit inside, but the gaps between it and the cabinet walls are so small that the air-vent valves and shut-off taps can't be reached comfortably. The result is that the manifold has to be unscrewed and pulled out of the cabinet at every service visit, turning routine maintenance from 15 minutes into an hour.

Cabinet placed too high or too low. We mentioned this above too - when the bottom edge of the cabinet ends up right at floor level, or conversely right under the ceiling, operating it becomes uncomfortable for years to come. This mistake can also be spotted and fixed before installation - it just needs to be measured.

Forgetting the pressure test before covering up. We mentioned this in the installation steps, but it's worth repeating here too - it's one of the most common causes of later complaints, where a small leak only shows up after the walls have been built in or tiled, and the repair then requires opening up the structure again.

Wrong estimate of future circuits. As described in the previous section, underestimating future expansion of the system (a new room, a change in heating) is one of the most frequently repeated situations customers come to us with, asking how to solve the lack of space in an already finished, too-small cabinet.

Missing working space in front of the cabinet. Furniture, shelves or a door placed too close to the cabinet prevent it from opening fully. When planning the interior around the cabinet's location, it's good to allow free space in front of it at least as wide and deep as the open door.

Frequently Asked Questions

Do I need a cabinet that's an exact fit, or is the next size up enough?
The next size up is enough. Extra free space in the cabinet doesn't hurt - on the contrary, it makes both installation and later operation easier. Only atypical or very large manifolds with more than 10-12 circuits are handled with a custom fit, and these usually use separate distribution cabinets instead of standard manifold cabinets.

Can a surface-mounted cabinet be recessed into the wall later?
Not directly - surface-mounted and recessed versions have a different body construction (the recessed version has a separate building sleeve for bricking in). If you want to switch from a surface-mounted to a recessed solution, it's practically always a replacement with a new product, not a modification of the existing one.

Is a pressure test necessary, or can it be skipped for a small renovation?
We never recommend skipping the pressure test, regardless of the scale of the work. A hidden leak behind a bricked-in or covered door often only shows up weeks or months later, when the repair is significantly more complicated and expensive than if it had been caught right away during the test.

Can I install the cabinet myself, or is a professional necessary?
Fixing the cabinet body to the wall itself (especially for the surface-mounted version) is manageable for a competent DIYer. We always recommend leaving the pipework connection to the manifold, especially if it involves working on an existing heating system, to a heating engineer or plumber - it's a pressurised system, and a faulty joint can result in water leaking into the structure.

What's the price difference between the individual cabinet sizes?
The difference between the smallest size, 385 mm (€63.10), and the largest, 615 mm (€75.15), in our range is only about 12 euros, which is negligible compared to the cost of a later replacement with a larger size. That's why, when in doubt, we recommend going for the larger size.

Can the cabinet be used for a combination of a radiator and underfloor circuit in one room?
Yes, that's a common configuration. In that case, besides the underfloor heating manifold, the cabinet often also houses a mixing unit that lowers the water temperature for the underfloor circuits compared to the higher temperature used for radiators. It's precisely because of this extra component that a larger cabinet size, for example 615 mm, is usually recommended for such solutions.

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.