What Size and Type of Mounting Do I Need for My Number of Collectors

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What size and type of mounting do I need for my number of collectors?

One of the most common customer questions we deal with when designing solar systems goes like this: "I'm interested in two, or maybe three, collectors – what exactly do I need for a mounting bracket and what dimensions matter?" What seems like a simple matter turns out in practice to be a combination of several interrelated decisions: roof pitch and material, orientation, distance between anchor points, total wind-exposed area and, of course, the number and type of collectors. That's why we decided to cover this topic in depth – so that after reading the article you'll know exactly what to order, without unnecessary back-and-forth.

If you're interested in which type of mounting to choose based on roof type (flat vs. pitched), also check out the article How to choose the right mounting for a solar collector – flat roof vs. pitched roof in our Knowledge Center. Here we'll focus purely on sizing and quantity – i.e., how many pieces, what dimensions, and what else you need to buy.

Basic logic: a mounting bracket is not just steel on the roof

Many customers think that a mounting bracket is just a kind of scaffolding onto which the collector is "hung." In reality, the mounting bracket is a structural element that must withstand a combination of static load (weight of collectors + fluid + snow) and dynamic load (wind force, thermal expansion, possible vibrations). An undersized mounting bracket can bend under snow, lose its pitch, or – in the worse case – be torn off entirely by a storm.

For standard flat thermal collectors with a frame of 2,000 × 1,000 mm (the most common format in Central European practice), the weight of one collector typically ranges between 35 and 50 kg (depending on the thickness of the absorber and the frame profile). Add to that the volume of liquid in the collector (usually 1.5 – 2 liters) and a possible layer of wet snow (up to 80 kg/m² in extreme conditions), and you easily reach 120 – 150 kg of load per collector under unfavorable conditions.

This leads to the first rule: the mounting bracket must be designed for the maximum possible load, not just the weight of the collector on a sunny day.

Standard collector size ranges and what they mean for the mounting bracket

Before we deal with the mounting bracket itself, we need to know what collector we're working with. In terms of size, thermal solar collectors are divided in practice into two main groups:

Flat collectors in the 2,000 × 1,000 mm format (or 2,100 × 1,000 mm): This is by far the most common format for family houses. The absorber area ranges from 1.8 to 2.1 m². With this size, the mounting bracket is dimensioned in modules of 1,000 mm (width) × 2,000 – 2,100 mm (height in tilted installation) or vice versa for horizontally oriented installation.
Larger collectors in the 2,000 × 1,250 mm or even 2,500 × 1,200 mm format: These appear in semi-commercial and commercial installations, where roof space is limited and we want to get more power from fewer anchor points. For the mounting bracket, this means increased demands on the length of horizontal profiles.

For our product portfolio and for a typical family house, let's continue with a collector sized 2,000 × 1,000 mm as our reference example. All dimensions and quantities listed below refer to this format.

Mounting for two collectors – the basic module for a family house

A two-collector setup is the most common solution for domestic hot water (DHW) heating for a 4-person family. It covers 4 – 5 kW of peak solar output and usually works with a 200 – 300 liter tank. This setup uses the Mounting for installing two collectors, which is essentially a complete set of profiles, clips, and anchoring elements for a paired installation.

In terms of dimensions, for two 2,000 × 1,000 mm collectors placed side by side, the following applies:

Total width of the assembly: 2 × 1,000 mm = 2,000 mm (plus a few cm for the end clips and installation clearance – in practice, count on an area of approx. 2,100 – 2,150 mm)
Height on the roof (at a pitch of 35 – 45°): corresponds to the length of the collector, i.e., approx. 2,000 – 2,100 mm from the bottom anchor to the top profile
Weight of the whole assembly (two collectors + mounting): typically 90 – 120 kg – standard M10/M12 hooks anchored into rafters via a purlin handle this easily
Minimum roof span (pitched roof, collectors in portrait orientation): you need a continuous, unshaded area of at least 2.2 m wide × 2.3 m high

Anchoring the mounting for two collectors is typically done at 4 anchor points (2 at the bottom, 2 at the top), with the distance between the left and right anchor hooks corresponding to the width of the collectors (approx. 1,900 mm on center). These hooks must go into the rafters or into a steel substructure – never just into the roofing material or thermal insulation.

Expansion to three or more collectors – mounting for an additional collector

When a customer comes with a request for larger heating capacity – for example a combination of DHW and heating support, or a larger family, or a garden pool – they usually need three to four collectors. This is where the Mounting for installing an additional collector comes in. This product is an expansion module: it connects to the basic pair and allows you to add another collector without having to replace or redesign the whole structure.

This is an important point from a planning perspective: if you know that in two years you'll want to expand the system, it's much smarter to choose a mounting that allows this from the start. It also pays off financially – expanding the mounting later is cheaper than a complete replacement of the whole structure, including new anchoring.

In terms of dimensions, for three collectors the following applies:

Total width of the assembly: 3 × 1,000 mm = 3,000 mm of actual collector footprint + approx. 100 mm reserve for clips = approx. 3,100 – 3,150 mm
Number of anchor points: 6 (2 on each outer side and 1 in the middle for the center collector – for systems with a continuous horizontal profile) or 8 (for systems with individual anchoring of each collector)
Load per anchor point: with three collectors, 35 kg + reserve for snow = actually up to 50 – 60 kg per anchor point, which is why we choose anchoring of at least M12 into a rafter or M10 into concrete with a chemical anchor

For four collectors, the basic unit (mounting for two) is combined with two expansion modules, or special "double-wide" mountings for 4 collectors side by side are used. The total width of this assembly reaches approx. 4,100 – 4,200 mm, which is usually the limit of available space on a typical south-facing pitched family house roof.

Collector orientation: portrait or landscape?

This is a question that's often overlooked, but it has a direct impact on the mounting size and available roof space. Collectors in the 2,000 × 1,000 mm format can be installed in two ways:

Portrait (vertical): The collector is oriented so that the long axis (2,000 mm) runs along the roof slope. Installed this way, the collector takes up a height dimension of 2,000 mm and a width of 1,000 mm. Advantage: less frost buildup, better drainage of water and condensate, less shading in low sun. Disadvantage: you need more roof height (at least 2,500 mm from the eave to the ridge at the installation location).
Landscape (horizontal): The long axis runs horizontally. The collector takes up a width of 2,000 mm and a height of 1,000 mm. Advantage: lower requirement for roof height. Disadvantage: with multiple collectors side by side, the total width increases significantly and the mounting must be adapted to this orientation (otherwise the placement of anchor points changes).

Most available mounting systems are primarily designed for portrait installation, which is also the recommended position from a hydraulic point of view. Before ordering a mounting, always check what orientation it's structurally designed for – especially the position of the grooves for attaching the collector frame.

Connecting collectors: accessories that are often forgotten

Having the right mounting isn't enough. The collectors also need to be hydraulically connected to each other. This is what the Connecting collectors together – accessories is for. These accessories include short connecting hoses or stainless steel elbows with sealing, which connect the outlet of one collector to the inlet of the next.

Before ordering connecting accessories, check:

Connection method: series or parallel? (more on this in the article Series vs. parallel connection of solar collectors – which to choose in our Knowledge Center)
Diameter of the collector connection: standard 3/4" or 1" external thread
Sealing ring material: must be resistant to temperatures up to 200 °C and to antifreeze (EPDM or PTFE – not ordinary rubber)
Distance between connections: depends on the arrangement of the collectors and how closely they're positioned to each other

A mistake we see quite often: the customer orders a mounting and collectors, but forgets the connecting accessories. The result is that the installer arrives on the roof and discovers that the small item without which the system can't be connected is missing. Order comprehensively and according to the collector's technical documentation.

Tilt angles, azimuths, and their influence on choosing a mounting

A mounting for a pitched roof differs from one for a flat roof not just in anchoring, but also in the ability to adjust the tilt angle. On a pitched roof, it's usually not necessary to address the tilt at all – the collector is installed parallel to the roof and that's it. The optimal tilt angle for Slovakia is 30 – 50° from horizontal (for year-round operation, we recommend 35 – 40°).

If the roof pitch is outside this range, there are two solutions:

Adjustable mounting with angle correction: Allows the collector to be tilted relative to the plane of the roof. Used on flat roofs (0 – 5°) or on excessively steep roofs (above 55°). Note: adjustable mountings are significantly larger and heavier, and create a larger surface area exposed to wind.
Accepting a compromise: In practice, the loss of output at a 25° tilt compared to 38° does not exceed 5 – 8% annually, which is acceptable for a family house. There's no need to over-engineer the structure because of this.

Azimuth (orientation relative to compass directions) is secondary for choosing the mounting size, but it does affect the calculation of the number of collectors. A system oriented southwest (225°) instead of due south (180°) needs 10 – 15% more collector area to achieve the same annual output.

Distribution and collection manifold for a larger number of collectors

When the number of collectors exceeds three (or when the collectors are arranged in multiple rows), series connection stops being hydraulically advantageous. This is where the distribution/collection manifold comes in – a hydraulic component that evenly distributes the flow of antifreeze to all collectors in parallel.

For larger systems (4 or more collectors, commercial installations), we recommend taking a look at the Industrial stainless steel distribution/collection manifold set with ball valves – 6/4"×1"; 2-way. This product is suitable for systems with two parallel branches, where each branch can have, for example, 3 – 4 collectors in series. Ball valves allow one branch to be shut off without affecting the rest of the system – practical for maintenance or replacing a collector.

We cover the topic of distribution and collection manifolds in more detail in the article Distribution and collection manifold in a solar system – what it's for and when you need it in our Knowledge Center.

Practical scenarios: how many collectors, what mounting?

Over the years, we've dealt with dozens of different situations. Here are the most common ones, with specific recommendations:

Scenario 1: Family house, 4 people, DHW only, south-facing pitched roof, 38° pitch

This is the classic case. We recommend 2 flat collectors 2,000 × 1,000 mm, a 250 – 300 liter tank. Mounting: basic Mounting for installing two collectors, portrait installation, anchoring into 4 rafters with an M10 hook at least 160 mm long. Anchoring into rafters every 900 mm – i.e., at a distance corresponding to the standard rafter spacing. Total width of the assembly: 2,100 mm, height: 2,200 mm. No complications.

Scenario 2: Family house, 5 people, DHW + solar heating support, southwest-facing pitched roof, 32° pitch

The lower pitch and azimuth deviation require a larger collector area. We recommend 3 collectors, a 400 – 500 liter tank. Mounting: Mounting for two collectors + Mounting for an additional collector as an extension. Total width: 3,100 mm. Number of anchor points: 6. Connecting the collectors: series (2+1) or parallel using accessories. A 32° pitch is at the edge of optimal, but the annual loss of output compared to 38° is only about 4% – it's not worth addressing with a tilt correction.

Scenario 3: Cottage, pool + DHW, flat roof, limited load-bearing space due to the roof covering

Here the situation is more complex. A flat roof requires a tilting mounting with ballast weight, or anchoring through the roof covering into a concrete slab. For 2 – 3 collectors on a flat roof, a ballast system with a tilt of 25 – 35° is most often chosen. These mountings are larger in size – the base width is approximately 1.5 times the collector width for stability. For 2 collectors on a flat roof: a footprint of at least 2,500 mm × 2,800 mm including the ballast base is needed. Watch out for shading – on a flat roof you must maintain a minimum distance between rows of collectors so the rows don't shade each other (rule: distance = 3× shadow height at the winter solstice).

Scenario 4: Apartment building, 8 housing units, commercial installation, 8 collectors in two rows

Here different thinking is needed. 8 collectors in a single row would take up approx. 8,200 mm of width, which is unrealistic on a typical roof. Solution: 2 rows of 4 collectors each, each row with its own branch connected to a common distribution/collection manifold. Mounting: a separate assembly for each row (mounting for 2 collectors × 2 + 2 × extension for an additional collector). Hydraulics: parallel connection of both rows via the distribution/collection manifold. Tank: 1,500 – 2,000 liter industrial, or a battery of tanks.

Backup electric heating – when the sun isn't enough

Even the best-sized solar system isn't enough to cover 100% of DHW needs in winter. That's why it's standard to install a backup electric heating element in the tank. This is used for example the 2 kW electric heating element for OKC tanks, which is screwed into the tank via a standard threaded opening and connected to a thermostat. A 2 kW output is suitable for tanks up to 300 liters – heating 200 liters by 30 °C takes about 3.5 hours. For larger tanks, a 3 – 4 kW element or a dual element is recommended.

The topic of sensors and their installation (at the tank and on the collector) is covered in the article Installing a temperature sensor for a solar collector – placement and connection in the Knowledge Center.

Mounting material and corrosion protection

The roof is an aggressive environment: UV radiation, temperature swings from -25 °C in winter to +80 °C on an overheated collector in summer, acid rain, salt fog in suburban areas. That's why the mounting material is essential.

Galvanized steel: The cheapest option. The zinc coating provides protection for about 10 – 15 years, after which corrosion begins. On a roof used for 20+ years, the structure may need replacing before the collectors themselves. Suitable for lower budgets and less aggressive environments.
Aluminum (Al): The golden mean. Lightweight, doesn't corrode, good strength properties. Most of the quality mid-range mountings are aluminum. Lifespan of 25 – 30 years without maintenance.
Stainless steel: The most expensive, most durable. Ideal for coastal locations or industrial zones where the air is aggressive. For an ordinary family house, stainless steel is unnecessarily expensive – aluminum is sufficient.

Beware of combining materials: an aluminum mounting with zinc-coated screws can cause galvanic corrosion. Always use screws and clips made of the same material or with a matching surface (nylon washer as an insulator).

Procedure for choosing a mounting – step by step

To sum it up in a clear procedure, here's a guide on how to approach choosing a mounting systematically:

Determine the number of collectors based on the number of people, DHW needs, and any heating support required.
Measure the available roof area – width and height of the unshaded area, orientation (azimuth), and pitch.
Choose the collector orientation – portrait or landscape – based on the available height and width.
Choose the basic mounting – for 2 collectors, the basic assembly; for 3+, add an expansion module.
Verify the anchoring – what material will the hooks go into? Wooden rafters, concrete, steel? Adjust the type and size of screws/anchors accordingly.
Add connecting accessories – collector connections, or a distribution/collection manifold for larger numbers.
Don't forget backup heating – an electric heating element in the tank for the winter months.
Check the structural load – for a larger number of collectors (4+), we recommend consulting a structural engineer.

You'll find a detailed procedure for the physical installation itself in the article Installing a solar collector mounting step by step in our Knowledge Center.

Common mistakes when choosing and installing a mounting

To conclude the technical part, here are the most common mistakes we encounter in customer projects:

Underestimating snow load: In Slovakia, snow cover can reach up to 80 kg/m² during prolonged extreme conditions. Size the mounting for this load, not just for the weight of the collectors.
Incorrect distance between anchor hooks: Hooks placed at the wrong distance mean the mounting profiles don't fit into the grooves. Always measure according to the mounting's technical drawing, not by eye.
Omitting sealing washers under the hooks: Every hole in the roof covering is a potential leak point. Every hook must have a rubber sealing washer fitted under the roofing.
Series connection of more than 3 collectors: With 4 or more collectors in series, the pressure difference increases and the first collector is significantly hotter than the last – the system operates inefficiently. Switch to a parallel connection.
Omitting the expansion gap: Aluminum profiles expand by about 2 mm per meter of length with a 100 °C temperature difference (summer/winter). For a 3-collector assembly (3 m), that's 6 mm – without an expansion gap, the profile will deform the entire structure.
Wrong orientation of connections in landscape installation: Collectors mounted horizontally have connections on the shorter side – these must not be at the bottom (condensate would block the venting).

Frequently Asked Questions (FAQ)

Can I install just one collector on a mounting designed for two?

Yes, you can – the mounting is structurally sized for two collectors, but it can easily handle one. However, from an aesthetic and hydraulic point of view, it's better to install collectors in pairs, or to leave preparation for a second collector (blind caps on the connections) and add it later. In that case, we recommend buying the Mounting for an additional collector right away as a spare, while it's on sale.

What tilt angle should a mounting on a flat roof have?

For Slovakia, the optimal tilt angle is 35 – 40° from horizontal. On a flat roof, this means the tilting mounting must have adjustable legs for the appropriate angle. A 25° tilt is an acceptable compromise (5 – 8% output loss) and reduces wind load. A tilt below 15° is not recommended – there's a risk of dirt and condensate accumulating in the absorber, which shortens its lifespan.

Do all collectors in one assembly have to be at the same height on the roof?

Ideally, yes – the same height ensures uniform hydraulic conditions (the same hydrostatic pressure in each collector). If the roof doesn't allow this, it's possible to place collectors in two rows one above the other, but the hydraulic scheme must be parallel with a balancing valve. More on this in the article Series vs. parallel connection of solar collectors in our Knowledge Center.

How many anchor points do I need for 4 collectors?

For four collectors, we recommend at least 8 anchor points (2 for each collector – top and bottom). With mountings featuring continuous horizontal profiles, 6 points may be sufficient if the profile span is adequately stiffened. Each point carries 50 – 70 kg during extreme snowfall – choose M12 hooks at least 200 mm long for wooden rafters, or M10 chemical anchors into concrete (minimum depth 80 mm).

What if I have collectors from a different manufacturer – can the mounting be combined with the collector?

The mounting is usually compatible with different collector manufacturers, since it clamps onto the collector frame using T-nuts and adjustable clips. The critical dimension is the width of the frame profile groove (typically 8 or 10 mm) – make sure the mounting's clips match the collector's groove. If in doubt, send us the technical drawing of the collector frame and we'll advise you.

How long does a mounting last, and does it need any maintenance?

A properly installed aluminum mounting lasts 20 – 30 years without intervention. We recommend checking the tightness of the anchor screws once every 3 – 5 years (thermal expansion can loosen them) and visually inspecting the condition of the sealing under the hooks. For details, see the article Common faults in solar system accessories and how to fix them in our Knowledge Center.

Conclusion: mounting size is not a matter of intuition, but of calculation

Choosing the right mounting for solar collectors is not a matter of chance or "eyeballing it." It's a combination of specific decisions: the number and size of collectors, available roof area, orientation and pitch, roof structure material, anchoring method, expected snow and wind load, planned future system expansion, and last but not least, the hydraulic connection scheme. Each of these parameters affects what mounting and in what quantity you order.

The good news is that a clear, proven formula applies to most family houses: two collectors = basic mounting assembly for a paired installation, each additional collector = one expansion module. You complete the hydraulics with connecting accessories, and for a larger number of collectors, with a distribution/collection manifold. Backup heating is provided by an electric heating element. This trio – mounting, connection, backup – forms the basis of a reliable solar system that will work without problems for decades.

If you're not sure about your choice, also check out the article Frequently asked questions about solar collector accessories in our Knowledge Center, or browse the entire accessories category – there you'll also find more detailed technical parameters for every product mentioned in this article.

Do you have a question about this topic?

Can't decide, or dealing with a specific situation in your household? Write to us - we're happy to help.