What thread does the programmable head need – M30x1.5 and adapters

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What thread does the programmable head need – M30×1.5 and adapters

When a customer orders a programmable head, they almost always ask the same question: "Will it fit my radiator?" The answer is usually yes – not because all valves are the same, but because there are several well-established standards and corresponding adapters. Problems arise when the customer is not familiar with these standards, forces the head on, and damages the seal or the valve thread. That is why we are addressing this topic in detail – from the basics of thread geometry to specific adapter solutions for different valve manufacturers.

If you are looking for a specific installation guide, see the article Installation of a programmable head on a radiator step by step in this Knowledge Center. Here we focus exclusively on the mechanical connection – that is, what you need to know before you reach for the wrench.

What is M30×1.5 and why is it important

The abbreviation M30×1.5 describes a metric thread with an outer diameter of 30 mm and a pitch of 1.5 mm. It is the connecting element between the body of the thermostatic valve and the head (manual or programmable). This dimension has effectively dominated the European market for radiator valves and is today used by almost all manufacturers of valves sold in Slovakia and throughout the EU.

Why exactly M30×1.5? It is a historical compromise agreed upon by European valve manufacturers – primarily Danfoss, Heimeier, Oventrop and others – and later adopted by most Asian manufacturers. The result is that if you have a relatively new valve (say, not older than 20–25 years) from a typical European manufacturer, there is a high probability that you have M30×1.5 and most programmable heads will fit on it without an adapter.

It is important to know where the external and internal threads are. The valve has an external thread (i.e., a thread "bulging" outward), the head has an internal thread (nut). The head is therefore slipped onto the valve and tightened or secured with a bayonet ring, depending on the design. Most modern programmable heads have a quick-connect mechanism for M30×1.5 – it is enough to slide and turn the ring by about 90°, not to tighten the entire thread. This simplifies installation and reduces the risk of mechanical damage.

Overview of thread standards found on Slovak radiators

Although M30×1.5 dominates, there are other standards – especially in older installations, in industrial buildings, or with imported goods. Here is a practical overview of what you may encounter:

M30×1.5 – European standard, most widespread. Danfoss RA/RAS, Heimeier, Oventrop, IMI Hydronic, Herz and dozens of others.
M28×1.5 – older Danfoss (RAVL series), also some older Czech and Slovak products. Diameter 2 mm smaller, thread not interchangeable with M30.
M32×1.5 – less common, some industrial valves, occasionally Herz or Oventrop in special versions.
Giacomini** (G 3/4") – BSP (British) thread, found in Italian installations, sometimes in bathroom towel radiators.

Caleffi** – Italian manufacturer, proprietary adapter, not always compatible with M30.

Vaillant/Buderus** – selected panel radiators have their own bayonet or adapter.

Old Slovak/Czech valves** – e.g., Annibale, Meibes, ČSN-standard types, sometimes metric thread M26×1.5 or another non-standard dimension.

From practice: during renovations of panel buildings from the 70s–80s, you often encounter valves without any international standard – either non-adjustable (fixed conical tap without a thread for a head), or with a non-standard thread. In such cases, the best solution is to replace the entire valve, not to look for an adapter that does not exist.

How to determine what thread you have on the radiator – without a caliper

Theoretically, you should measure the diameter with a caliper. In practice, however, most people do not have a caliper at home and measuring on an installed valve is complicated anyway. A much faster approach is a visual and identification method:

Look at the manufacturer's label – modern valves have the type engraved or stuck on the body. Look for a combination of letters and numbers like "RA", "RAS", "RAVL", "RTL", "FK", "FHV", "Oventrop E", "Heimeier V-exact", etc.

Search online for the model – with the manufacturer and type, the technical sheet will reveal the thread in 60 seconds.

Ask the head seller – a serious seller (even on atria.sk) will advise you based on a photo or description of the valve.

Try to fit a plastic M30 nut – most heads include a nut in the package; if it can be fitted without problems, you have M30×1.5.

Coarse visual estimate – M30 looks like a "standard" nut on a radiator valve with a diameter of about 3 cm. If the valve seems significantly smaller or larger, consider M28 or M32.

From practice: the most common mistake is misplaced trust – the customer says "I have Danfoss" and automatically assumes M30. But the old Danfoss RAVL (white-gray plastic cover) is M28×1.5 and without an adapter, the standard programmable head does not fit. The new Danfoss RA/RAS is M30×1.5. This one letter in the designation makes the difference between a functional and a non-functional installation.

Adapters – when and which ones you need

An adapter is a brass or plastic intermediate piece that on one side fits the valve body (e.g., M28 external thread) and on the other side provides an M30×1.5 external thread, thus allowing a standard head to be mounted. Some manufacturers call them "reductions" or "intermediate adapters".

When you need an adapter and when you don't:

You don't need an adapter: The valve has M30×1.5 (most new installations), the head is a standard European one.

You need an adapter: The valve is M28×1.5 (old Danfoss), M32×1.5, or another non-standard dimension.

You need a manufacturer-specific adapter: Some valves (Giacomini, Caleffi, Vaillant, Comap) have proprietary threads or bayonets and require an original or certified adapter from the manufacturer.

Adapter for Danfoss RAVL (M28 → M30)

This is by far the most popular adapter on the Slovak market. The Danfoss RAVL valve was massively installed in panel buildings in the 80s and 90s – it is estimated that tens of percent of households in older residential buildings still have it. The adapter has an external thread of M28×1.5 (screws into the valve) and provides an external thread of M30×1.5 (for the head). It usually comes with a sealing ring. After fitting the adapter, you can fit any standard M30 head.

Adapter for Heimeier, Oventrop, IMI (direct M30 – no adapter needed)

These valves are directly M30×1.5 and any standard head can be fitted directly. Heimeier V-exact II, Oventrop E and Uni LH, IMI Hydronic TA-Clim – all M30×1.5. The only exception are older Heimeier types with an external thread of M30 but a different lifting pin – in case of doubts, we recommend checking the lifting pin, see the section below.
Adapter for Herz

Herz, as an Austrian manufacturer, has most of its products on M30×1.5, but some older or special types (e.g., Herz RL-1) use a different thread. It is safe to verify the type before ordering.

Adapter for Giacomini and Italian valves

Giacomini uses a G 3/4" BSP thread (British pipe), which is a completely different geometry from the metric M30. Special adapters exist for this type, but they are less common and sometimes need to be ordered directly through the Giacomini distributor. From practice: if you have a Giacomini R470 or similar valve in a bathroom towel radiator, be prepared that finding a suitable adapter may take time.

Lifting pin of the valve – the second dimension that matters

The thread is only the first half of the problem. The second, less discussed, is the lift – that is, how many millimeters the head must lift or press the valve pin to fully open or close the valve.

Most European valves have a lifting pin with a diameter of 3 mm and a lift of 3.5–4.5 mm. This is the standard to which programmable heads are calibrated. Exceptions include:

Danfoss RTL – a valve for floor heating, with a different lift and a stiffer mechanism, not compatible with a standard programmable head.

Certain Heimeier types – the lifting pin may be recessed (deeper embedded), which causes the head to not close the valve sufficiently. Solution: a special extended version of the adapter or another type of head.

Industrial valves with a large lift – the head simply does not have enough lift and the valve never fully closes. Here, a pneumatic or motor drive is needed, not a standard TRV head.

From practice: a customer had a new Oventrop valve with a programmable head installed on it, which heated the room perfectly, but in summer (when the head wanted to close), the valve remained slightly open and some heat was always coming from the radiator. Cause: the lifting pin was 0.8 mm longer than standard, the head physically could not press it into the fully closed position. Solution: replacement with another type of valve with a shorter pin lift.

Specific programmable heads and their thread compatibility

Let's now look at specific products available in the category programmable heads on atria.sk, and check their thread parameters:

Elektrobock HD10 and HD20

Elektrobock HD10 is a basic weekly thermostat with manual control. It has a standard thread of M30×1.5 with a quick-connect mechanism. The package includes adapters for Danfoss RA (M30) and an adapter for Danfoss RAVL (M28). Thus, it directly solves 95% of installations without the need to buy anything else.

Elektrobock HD20 is a more powerful model with an LCD and several weekly programs. The thread is also M30×1.5, with a set of adapters for Danfoss RA and RAVL. It also includes an adapter for Heimeier, which expands compatibility to older installations.

For both Elektrobock models, the quick-connect plastic ring with the M30 nut is part of the head body – it is not a separate nut, but an integrated bayonet. This requires less care during installation: there is no need to tighten with force, it is enough to slide and turn until it clicks.

Elektrobock EMF-1

Elektrobock EMF-1 is a room thermostat with an external sensor – not a classic programmable head in the traditional sense, but an electric motor-driven valve actuator controlled by an external regulator. The thread connection is the same M30×1.5, but the drive mechanism is different: instead of a bimetallic or paraffin element, it has an electric motor. The advantage is a higher lifting torque, making it suitable for valves with a stiffer lift.

SALUS PH 55 and PH 60

SALUS PH 55 is a compact programmable head with a weekly program, compatible with the SALUS Smart Home system. Thread M30×1.5, an adapter for Danfoss RA and RAVL is included in the package. SALUS differs from Elektrobock in that it also includes an adapter for Junkers/Bosch – which is an advantage in areas where this system is common.

SALUS PH 60 is an advanced version with Bluetooth and app control. The thread is still M30×1.5. What is important for PH 60: the bayonet mechanism is more rigid and requires more precise centering before turning – customers who are used to the looser ring of Elektrobock sometimes report that the head "cannot be mounted", but the problem is only incorrect angling. See the article Installation of a programmable head on a radiator step by step for the correct procedure.

What is in the package – when you don't need to buy anything extra

Most modern programmable heads include a set of 2–4 adapters in the package, which usually cover:

Direct M30×1.5 nut (for standard valves, usually integrated in the head body)

Adapter for Danfoss RAVL (M28×1.5)

Adapter for Danfoss RA (sometimes combined with the previous one)

Adapter for Heimeier (some models)

Adapter for Junkers/Bosch or COMAP (depending on the head manufacturer)

If you have an Oventrop, IMI Hydronic, TA-Hydronics or another less common but still M30×1.5 valve – direct mounting without an adapter. If you have an old Danfoss RAVL – use the included adapter. If you have something more exotic, you either order a special adapter or (which is cheaper and a cleaner solution) replace the valve body.

Important note: never install an adapter without a seal. Each adapter should be accompanied by a rubber O-ring or flat gasket. Without it, water leakage is a risk. If you are not sure, an O-ring with an inner diameter of 22 mm and a width of 2 mm is a safe choice for M30 connections.

Typical installation errors – from customer practice

Over the years of practice, the same installation errors with programmable heads keep repeating. Here is their list so you can avoid them:

Use of brute force – the customer tries to force the head on because they think "it's holding a bit". Result: damaged valve thread, need to replace the valve body. Correct: if it doesn't go easily, stop and find out why.

Forgotten seal – the O-ring fell out of the adapter and the customer didn't notice. After starting heating, the area around the valve got wet.

Old head not unscrewed before adapter installation – it sounds absurd, but it happens: the customer installs an adapter on an old manual head, not directly on the valve.

Not performing calibration after installation – a programmable head needs an adaptation (lift test) after the first start, during which it automatically determines the valve's movement range. If the customer skips this, the head does not regulate correctly. See the article Calibration and adaptation of a programmable head after installation for more information.

Installation on a valve in a closed system under pressure – when replacing a head, you need to close the supply and properly bleed the system. Otherwise, flooding the space during the removal of the old head is a risk.

What to do if no adapter fits

If you encounter a non-standard valve, where none of the included or commonly available adapters fit, you have three realistic options:

Replace the valve body – the cleanest solution. Buy a new M30×1.5 valve (e.g., Heimeier, Oventrop, Danfoss RA) and have it installed. The cost of the valve is 10–25 €, installation another 20–50 €. Result: a modern valve with guaranteed compatibility with all M30 heads.

Order a manufacturer-specific adapter – e.g., directly from Giacomini, Caleffi or through a technical distributor. It may take a week, cost 5–15 €.

Contact the technical support of the head manufacturer – manufacturers like SALUS or Elektrobock have technical departments that can advise in atypical situations.

In no case do we recommend improvised solutions – twisted wire, tape, sealant. A valve is a pressure vessel and any non-tight or mechanically unstable solution can end in flooding the space.

Adapters for special systems (floor heating, remote control)

A special chapter is the distribution systems for floor heating. There, the heads (or actuators) are mounted on the distributor and the thread is not M30×1.5, but M28×1.5 (for actuators) or M30 with a different thread length. Programmable heads (as we know them from radiators) are not commonly used on floor heating distributors – for that, special actuators controlled by a central thermostat or regulator are used. If you are dealing with floor heating regulation, see other products and a different type of regulation.

For remote-controlled systems (e.g., SALUS Smart Home or Elektrobock RF systems), the same thread logic applies – the mechanical connection is always M30×1.5, only the electrical or radio communication differs. The thread is a thread, the protocol is a protocol – one has nothing to do with the other.

Common questions (FAQ)

Do I need to order an adapter separately, or is it included in the package of the programmable head?

It depends on the manufacturer and model. Most common heads – including Elektrobock HD10, HD20, SALUS PH 55 and PH 60 – include a set of adapters for Danfoss RA and RAVL in the package. Adapters for Giacomini, Caleffi and some other manufacturer-specific types are usually not included in the package and must be purchased separately. Always check the package contents in the product description.

How do I know that my valve is M30×1.5 and not M28×1.5?

The most reliable way is to determine the valve type from the manufacturer's label or model and check the technical sheet. Visually: M28 looks a bit slimmer, M30 "more robust". If you have an old Danfoss with a gray or white plastic cover labeled "RAVL", it is M28. A new Danfoss with a black or chrome plastic cover "RA" or "RAS" is M30×1.5. In case of doubt, try to fit a M30 nut without screwing – if it fits freely by hand, you have M30.

Can I use an adapter repeatedly (move it from valve to valve)?

Technically yes, if it is not damaged and the seal is in good condition. We recommend, however, to replace the O-ring/flat gasket with each disassembly. Adapters are cheap (1–5 €) and the risk of water leakage due to a worn seal is not worth saving.

Is there a difference in which programmable head you use on a given type of valve from the perspective of the thread?

From the perspective of the thread – no – if it is M30×1.5 on both sides, it is compatible. But be careful with the lift range: most programmable heads are designed for a valve lift of 3.5–4.5 mm. Valves with a larger lift (e.g., some industrial types) are not compatible and the head will not be able to fully close the valve. Before purchase, check the valve's lift range as well as the thread.

What if water drips from the connection between the adapter and the valve after mounting the head?

Most likely, the seal (O-ring) is missing or shifted. Immediately close the supply to the radiator (shut-off valve on the supply or the entire branch), dry the area, remove the adapter, check the seal and re-tighten. If the seal looks okay, check the valve thread – it may be damaged. Never leave a leaky spot "for later", the leak can damage the neighbor's ceiling.

Can I replace a programmable head with another one without replacing the valve?

Yes, and that is exactly the advantage of the M30×1.5 system. If you already have a compatible valve (M30×1.5), you can replace the heads as needed – manual, programmable, smart with WiFi, drive for central regulation. The valve remains, only the upper part changes. That is why it is reasonable to invest in a quality valve body at the beginning.

Conclusion – practical framework for the correct choice

The M30×1.5 thread is today the de facto European standard and if you have relatively new radiators and valves from common manufacturers, you will most likely get by without an adapter or with the included adapter for Danfoss. Problems arise with older installations, Italian valve systems or non-standard industrial valves.

Before ordering a programmable head, therefore, do three simple steps: identify the manufacturer and type of the valve, check the thread (M28/M30/other) and determine the lift range. With these three pieces of information, you are 100% sure that the head you choose will fit correctly and regulate as it should.

If you are still deciding which programmable head is right for you, see the article How to choose a programmable head for a radiator and the comparison Elektrobock vs. SALUS – comparison of programmable heads in this Knowledge Center – there you will find answers to choosing based on features, not just based on the thread.

Do you have a question about this topic?

Can't decide or are you dealing with a specific situation in your home? Write to us - we'll be happy to help.

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