Step-by-step installation of a manifold and manifold cabinet

Installation of the manifold and manifold cabinet step by step

The manifold for floor or radiator heating is the heart of the entire distribution system - it distributes the heating water to individual circuits and also collects it back from them into the boiler. Even the highest quality manifold with accurate flow meters and quality valves will cause problems if it is installed incorrectly - poorly balanced, without air venting, in a cabinet with unsuitable dimensions, or with piping laid without step insulation. In this article, we will go through the entire installation process from preparation, through the installation of the cabinet, the installation of the manifold itself, connecting the circuits, to pressure testing and commissioning. The goal is to provide you with a real working procedure that installation companies use in hundreds of apartments and family homes every year.

If you are still choosing the manifold itself or deciding how many circuits you need, we recommend first reading the articles "How to choose a manifold for floor heating" and "How many circuits and outlets do I need on the manifold" - this text follows on from having already made a decision on the type and size of the manifold and focuses exclusively on the physical installation.

Preparation before installation - what you need to clarify in advance

Before you start drilling holes in the wall, you should have the following points resolved. A mistake in this phase is very difficult to correct in practice - it often means cutting a new groove or replacing an already embedded cabinet.

• Exact position of the manifold relative to the floor circuits - ideally in the center of the layout, so that the lengths of individual floor heating circuits are as balanced as possible (a difference of max. 15-20 % between the longest and shortest loop is recommended).
• Height of cabinet installation - in floor heating, the bottom edge of the cabinet is usually placed about 150-250 mm above the level of the rough floor, so that the piping from the floor has sufficient arch to slope into the cabinet without bending.
• Type of cabinet - built-in (recessed into the partition) or surface-mounted (on the wall surface). In masonry partitions of thickness 100-150 mm, built-in cabinets are more common, while in drywall or thin partitions, surface-mounted cabinets are often used.
• Number and dimensions of circuits - this determines the width of the manifold and thus also the minimum internal width of the cabinet.
• Supply and return from the heat source - direction of connection (left/right, top/bottom) according to the layout of the mechanical room or technical room.

Measuring and determining the cabinet dimensions

A practical rule is: the width of the manifold plus a minimum reserve of 100-150 mm on both sides for handling with wrenches, service valves and possible future expansion with an additional circuit. In apartments up to about 70 m² with 6-8 circuits, a cabinet of about 450-600 mm width is commonly used, while in larger family homes with 10-14 circuits, cabinets over 1000 mm are used. In our range, we commonly include for example Wall-mounted manifold cabinet N-MAX 1 - 450mm for smaller apartments with one small manifold, for more demanding connections with multiple circuits we recommend Wall-mounted manifold cabinet N-MAX 5 - 1200mm. As an alternative to the N-MAX range, we also offer Wall-mounted manifold cabinet N-KLASIK 2 - 535mm, which is suitable for apartments with a medium number of circuits. A detailed guide on selecting the exact dimensions and placement can be found in the article "How to choose a manifold cabinet - dimensions and placement."

Installation of the manifold cabinet step by step

1. Marking and installing the built-in cabinet

In masonry partitions, the outline of the cabinet including the frame, which will be visible after plastering, is first marked on the wall. Then a groove is cut or cut into the partition - for brick and aerated concrete partitions, a diamond saw with subsequent chiseling of the core with a hammer and chisel has proven effective, while for gas silicate partitions, a hand saw for aerated concrete is often sufficient. The depth of the cut must take into account the thickness of the cabinet plus a reserve of about 15-20 mm for plastering, so that after the final finishing, the cabinet frame is in line with the wall surface.

The cabinet is placed into the cut on a level (we check the vertical and horizontal plane), fixed with plaster, mounting foam or mortar in the corners so that it does not shift during hardening. It is important to check during fixing that the side and top edges are parallel to the wall - a cabinet installed at an angle will show an uneven gap when installing the doors.

2. Installation of the surface-mounted cabinet

In surface mounting (typically on drywall partitions or where it is not possible to cut masonry), the cabinet is anchored directly to the wall surface through mounting holes in the back wall of the cabinet body. In drywall, suitable anchors for hollow materials (e.g. toggle or screw anchors with a load capacity corresponding to the weight of the filled cabinet with the manifold - calculate 8-15 kg depending on the size) are used. In solid masonry, standard plastic anchors 8-10 mm are sufficient.

3. Pipe transition into the cabinet

The piping from the floor (or from the wall in a riser distribution) must enter the cabinet through prepared cutouts in the lower, or side wall of the cabinet body. The cutouts are made according to the diameter of the pipes used (most commonly 16, 17 or 20 mm) with a slight reserve, so that the pipe does not get stuck on a sharp edge of metal or plastic during thermal expansion. It is recommended to install a rubber grommet or at least a protective sleeve in the transition - this will prevent the pipe insulation from being abraded by metal.

Installation of the manifold itself into the cabinet

4. Mounting the manifold on brackets

Most manifolds are delivered with brackets (supports), which are attached either directly to the back wall of the cabinet or to pre-prepared mounting rails inside the cabinet body. The axial distance between the supply and return branches of the manifold is standardized (most commonly 210 mm or 220 mm according to the manufacturer) and the brackets in the cabinet must be prepared for this - therefore it is important to know the type of manifold before buying the cabinet, or to buy the cabinet and manifold as a verified combination.

The manifold is inserted so that the supply branch (with flow meters or control valves) is on top and the return branch (with thermostatic heads or closing valves for actuators) is at the bottom - this is a common standard for the vast majority of manufacturers, although there are also opposite configurations, so always check the documentation for the specific model.

5. Connecting the supply and return from the heat source

The main supply and return are connected to the manifold face, usually via ball valves with a thermometer or directly via the mixing system valves (in floor heating almost always via a mixing unit with a three-way or four-way valve, which reduces the return water temperature from the boiler to a temperature suitable for the floor circuits, typically 35-45 °C on the supply to the manifold).

The connecting material is selected according to the type of pipe supplying to the manifold - most often copper or steel pipe with threaded or crimped connection, or alternatively multi-layer (PEX-AL-PEX) pipe with compression or crimp fittings. All connections must be sealed during installation either with Teflon tape, hemp with sealant, or use sealing O-rings according to the type of fitting.

6. Connecting individual floor heating loops

Each loop is connected separately to its own pair of outlets (supply + return). The order of connection is not technically critical, but in practice it is advisable to follow a logical order corresponding to the room layout - this will simplify later identification of loops during balancing and in case of a fault. We recommend making a simple diagram directly during installation or at least labeling the loops with tags (room + approximate loop length).

Walking isolation - why not skip it when connecting to the manifold

Most often, a transition from insulated pipe embedded in the floor (wrapped with walking isolation) to an uninsulated section feeding directly to the fittings is made directly at the pipe entrance into the manifold cabinet. Walking isolation is laid on the pipe along the entire length of the loop laid in the floor - its main task is not thermal insulation in the sense of preventing heat loss (this is the responsibility of the system insulation board), but damping of footstep noise and partially also compensation of pipe expansion in the screed.

In our range you will find two common length variants - Walking Isolation 1.5m, 6mm, 75m pack for larger projects with longer loops and Walking Isolation 1.0m, 6mm, 12.5m pack rather for smaller coverage or repairs. A thickness of 6 mm is the standard choice, which suits most apartment and family projects. Details on correct laying can be found in a separate article Walking Isolation - what it is for and how to lay it correctly.

Practical note from realizations: walking isolation is laid directly before the pipe enters the cabinet up to the place where the pipe bends upwards towards the fittings - the last 15-20 cm before the fitting is usually not insulated, because there the pipe passes through a fixed transition in the cabinet sheet metal.

Pressure test before foaming and covering

After connecting all loops and before the final pouring of the floor with screed (or before closing the cabinet and starting painting), it is necessary to perform a pressure test. Standard procedure:

• The system is filled with water and thoroughly vented through the vent valves on the manifold (usually on the front of the supply and return branch).
• The pressure is increased to 1.5-2 times the operating pressure, in practice 4-6 bar is commonly used for floor heating (the exact value is determined by the project documentation or the standard according to which the system is implemented).
• The pressure is monitored for at least 24 hours and recorded in a pressure test protocol (date, pressure value at the beginning and end, temperature).
• A pressure drop indicates a leak - all connections on the manifold and transitions in the floor should be checked before pouring the screed.

The pressure test is always carried out before pouring the pipe into the concrete screed - a subsequent repair of a leak in the poured floor means cutting the screed and in practice it is one of the most expensive mistakes that can be easily avoided by following the procedure during installation.

Depressurization and balancing after installation

After a successful pressure test and before the final commissioning of the system, a fine depressurization of individual loops follows (one after another, with the main supply open) and then balancing of flows on flow meters or using adjustable valves according to the designed values for each room. This topic is covered in detail in the article Depressurization and Balancing of the Floor Heating Manifold - we recommend reading it before the first start of the system, because an incorrectly balanced manifold is one of the most common causes of uneven heating of individual rooms.

Closing the cabinet and final finishing

After verifying the tightness and setting the system, the cabinet is closed with a cover frame and doors. In the case of in-wall installation, the plaster around the cabinet frame is first leveled, then the frame is installed so that it aligns with the wall surface, and only then are the doors mounted - usually white, lockable or with magnetic snap closure depending on the cabinet model. Care must be taken to ensure that the doors, when closed, do not create pressure on the protruding elements of the manifold (actuators, heads) - if it seems that the space is too tight, it is better to reconsider before final embedding whether a larger cabinet would not be more suitable.

An important practical detail: when installing cabinets where electric servomotors and room thermostats with a control unit will be mounted later, it is necessary to plan for the electrical installation (low voltage from thermostats, possibly 230V power supply for the control unit) during the cabinet installation - it is advisable to leave a cable gland in the wall before plastering.

Most common installation errors we encounter in practice

• Undersized cabinet - the distributor fits into it, but there is no space for servomotors or for future expansion with a circuit. The solution is to always plan for at least one extra circuit as a reserve.
• Incorrect installation height - a cabinet installed too low causes a sharp bend in the pipe at the entrance from the floor, which increases the risk of pipe damage.
• Missing floor insulation at the cabinet entrance - leads to the transfer of noise and vibrations from the pump and water flow into the building structure.
• Missing or incomplete pressure test - the problem appears only after the screed is poured, when the repair is many times more expensive.
• Supply and return pipe swapped - the system works, but the regulation (thermostatic heads, servomotors) does not work as expected, because they are mounted on the wrong branch.
• Inappropriate cabinet anchoring in drywall - using standard toggle anchors instead of swivel anchors leads to gradual loosening and sagging of the entire cabinet with the distributor.

More about typical problems that appear already during operation (not only during installation) can be found in the article Common distributor faults and their solutions, and about regular maintenance in the article Maintenance and servicing of the heating system distributor.

Difference between EK distributor installation and distributor with flow meters

From the perspective of the physical installation into the cabinet, there is no significant difference between a simple EK distributor (without flow meters, with regulating valves) and a distributor with flow meters - the procedure for mounting on consoles, connecting circuits and pressure testing is identical. The difference appears only during the adjustment: with an EK distributor, the flow is set by estimating the number of turns of the regulating valve and then corrected according to the room temperature, while with a distributor with flow meters you can see the current flow in l/min directly on the scale and can precisely set it according to the design values. A detailed comparison of both types can be found in the article EK distributors vs. distributors with flow meters - differences.

Practical example from implementation - 3-bedroom apartment, 6 circuits

As an illustration, we present a typical procedure commonly used in an apartment with floor heating in the living room, kitchen, two bedrooms, bathroom and hallway (total of 6 separate circuits):

• A distributor with 6 outlets and flow meters was mounted in a cabinet with an internal width of about 600 mm, to leave space for future installation of servomotors.
• The cabinet was placed in the hallway, about 200 mm above the level of the rough floor, near the riser with the supply from the boiler in the basement.
• All floor heating circuits were equipped with 6 mm floor insulation on a section of about 1.2 m before entering the cabinet, to eliminate noise transfer from water flow just under the floor in the hallway.
• The pressure test at 4.5 bar lasted 24 hours without pressure drop, after which the floor was poured with anhydrite screed.
• After the screed hardened (about 21 days), the system was gradually heated according to the standard procedure for starting anhydrite floors and then the final flow adjustment was performed according to the area of individual rooms.

This procedure is representative for most apartment implementations in Slovakia and can be used with minor modifications (different number of circuits, different cabinet size) also in single-family homes.

Connection of mixing unit and placement of circulation pump

In most floor heating systems, the distributor is not connected directly to the boiler circuit, but through a mixing unit, which reduces the temperature of the return water from the boiler (often 60-70 °C) to a temperature suitable for floor heating. During installation, it is important to know exactly where the unit belongs in the assembly and why - a common mistake in DIY installation is placing the pump on the wrong side or omitting the check valve, which prevents gravitational water flow when the circulation is off.

The mixing valve (three-way or four-way) works on the principle of mixing the cooled return water from the distributor with the hot water from the boiler so that the temperature at the inlet to the distributor supply branch is always within a safe range for the floor pipe. The circulation pump is always installed after the mixing valve, in the direction of flow to the distributor - never before the valve, because that would disrupt the correct mixing function.

In practice, we also encounter compact mixing units that are delivered as a complete unit (valve, pump, thermometers, check valve) ready for direct screwing onto the distributor - this significantly simplifies installation compared to assembling individual components separately and reduces the risk of error in the flow direction connection. When choosing between individual components and a compact unit, it is also worth considering the space in the cabinet - compact units are more expensive, but take up less space and installation takes a fraction of the time compared to assembling on site.

Common questions about distributor and cabinet installation

Must the distributor cabinet be exactly in the center of the apartment layout?

It is not a necessity, but it is a recommended procedure, as it minimizes differences in the lengths of individual circuits and thus simplifies the hydraulic balancing of the entire system. If the layout does not allow it, the imbalance can be compensated through the setting of flow meters, although with a slightly higher pressure loss on longer circuits.

Can the manifold be installed without a cabinet, just openly on the wall?

Technically yes, but it is almost never used in residential spaces for aesthetic and safety reasons - an open manifold is more susceptible to mechanical damage and does not provide protection against possible water leakage into the room. In technical rooms, boiler rooms or cellars, open mounting without a cabinet is commonly used.

How long does the installation of a manifold and cabinet take in practice?

For a standard apartment with 6-8 circuits, the actual installation of the cabinet, manifold and connection of the circuits takes an experienced plumber approximately 4-6 hours. This does not include the time required for cutting a groove in the wall (if it is a built-in version) or the time for the pressure test, which lasts at least 24 hours without the need for physical presence.

Is step insulation also necessary for an above-floor cabinet?

Yes, step insulation is laid on the pipe in the floor regardless of the cabinet type - its purpose (noise damping, expansion) does not relate to the cabinet itself, but to the placement of the pipes in the screed. The difference is only that with an above-floor cabinet, the pipe exits the floor directly onto the wall surface, and the transition from insulated to non-insulated section is more visible.

What to do if the manifold no longer fits into the original cabinet after years of operation during replacement?

This situation occurs quite often during modernizations, when the original simple manifold is replaced by a model with flow meters and servomotors, which is physically larger. The solution is either to replace the entire cabinet with a larger model (if the space in the wall allows it), or to switch from built-in to above-floor mounting, which is not limited by the thickness of the wall.

Must the pressure test be documented in writing?

For privately funded residential projects, this is not a legal requirement, but it is strongly recommended to prepare at least a simple protocol (date, measured pressure at the beginning and end, signature) - it serves as proof of a properly performed test in case of a complaint or a dispute with the supplier of the screed or floor covering.

Summary

The installation of a manifold and its cabinet is not a complicated operation, provided a logical procedure is followed - correctly determining the location and size of the cabinet, firmly and evenly mounting it into or onto the wall, properly connecting the supply, return and individual circuits, using step insulation at the pipe inlet, thoroughly pressure testing before covering, and finally professional air venting and balancing. Each of these steps has its pitfalls, which can be easily avoided by giving sufficient attention to them already in the preparation phase. In our range you will find cabinets of various sizes and accessories including step insulation, and in subsequent articles of the Knowledge Center we also cover related topics such as the selection of a manifold, number of circuits, differences between EK and flow meter versions, air venting, balancing and service - we recommend reading them before the actual implementation, so that you have a complete picture of the entire process from design to long-term trouble-free operation.

Do you have a question on this topic?

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