Differential pressure regulator

PREMASREG® differential pressure monitors are used to measure positive, negative or differential pressures in clean air. The pressure transmitters are used in clean room, medical and filter technology, in ventilation and air conditioning ducts, in spray booths and commercial kitchens, for filter monitoring and level measurement or for controlling frequency converters.

Guide and useful information about differential pressure regulator

Differential pressure controllers for ventilation, air technology, and building automation

Brief explanation:
Anyone who works in building automation or ventilation technology is familiar with the problem: a ventilation system may be perfectly designed on paper, but its performance still gradually deteriorates in everyday use. This is often not due to “too little air,” but to pressure losses that accumulate over weeks or months: filters become clogged, ducts become dirty, volume flows drift, dampers no longer work properly, or fans run outside their optimal range.

This is exactly where differential pressure controllers come into play. They measure the pressure difference between two points (e.g., before and after a filter or between a duct and the reference pressure) and convert this into clear information: Is the air flow still at the target level, or is the system currently losing efficiency and operational reliability?

In practice, differential pressure controllers are particularly often used to:

Reliably monitor filter conditions
Maintain defined underpressure/overpressure ranges (pressure zones)
Stabilize pressure conditions in air ducts (e.g., with variable loads)
Transfer measured values cleanly to GLT/building automation systems

Content

Why is a differential pressure regulator useful in the ventilation system? Differential pressure in air and ventilation: What is actually being regulated? Typical applications in building automation & BMS Which signals & interfaces are relevant in practice? Selection guide: What should you look for in a differential pressure regulator? Now select differential pressure controller for ventilation

Why is a differential pressure controller useful in ventilation systems?

When you take a closer look at ventilation and air conditioning systems, differential pressure is one of the most important parameters of all—because it not only “measures” something, but also indirectly reflects the actual condition of the system.

This is because air is transported through the system, and every component in the air flow causes a pressure loss. This is normal from a design perspective. Problems arise when these pressure losses change – for example, due to contamination or dynamic operating conditions.

Typical causes include:

increasing filter contamination (the most common case),
changes in air volume/volume flow,
damper positions, fan control, or unfavorable flow conditions,
contaminated ducts or components, and changing operating conditions (e.g., day/night operation, partial load, load jumps).

A correctly installed differential pressure controller makes such changes visible – before the system starts to run noticeably worse. This is relevant for operators because it has a direct influence on:

Energy consumption
Air quality/comfort
Maintenance costs
System availability

Differential pressure in air and ventilation: What is actually being regulated?

A differential pressure controller always considers two pressure points and calculates the following:

Δp = p1 – p2

Typical measurement/control tasks in ventilation:
1) Filter monitoring
As the filter becomes more heavily loaded, the pressure loss at the filter increases. A differential pressure controller helps to detect this condition at an early stage and make maintenance planning easier.
Advantages:

Avoids unnecessary filter changes (too early)
Prevents inefficient ventilation (too late)
Stable air volumes in controlled systems
Reduced operating costs through optimized maintenance

2) Pressure maintenance in the ventilation duct
In HVAC systems, differential pressure can be used to stabilize air flows – especially with variable volume flows (VAV).

3) Underpressure/overpressure areas (pressure zones)
A defined pressure difference is crucial in sensitive areas:

Clean rooms & laboratory areas
Technical rooms / switch rooms
Stairwells (smoke protection pressure systems – depending on the system)
Isolation rooms (hospitals)

Typical applications in building automation & BMS

From a building automation perspective, a differential pressure controller is more than just a sensor: it provides an operating status that flows directly into trends, alarms and service processes.
In practice, differential pressure regulators are often used in the following applications:

Filter monitoring in HVAC systems
Monitoring supply and exhaust air filters in air handling units
Differential pressure measurement in ventilation ducts
Monitoring of air ducts and fans (e.g. indirect "running / not running")
Pressure zone control in clean rooms or sensitive areas
BMS alarm in the event of limit value violations (e.g. "Filter closed", "Unstable air flow")

This is a real advantage, especially for larger buildings or industrial plants, because operators can not only react, but also carry out targeted preventive maintenance.

Which signals & interfaces are relevant in practice?

Many users look first at the measuring range or accuracy when making a purchase - that is absolutely right. However, the question is at least as important in building automation:
How well can the device be integrated into the existing automation and BMS structure?

Depending on the system environment, these are typically used:

Analog outputs (e.g. 0-10 V / 4-20 mA depending on device)
Limit value/switching signals (e.g. for filter alarm)
Digital communication in BMS structures (depending on system requirements)

An important aspect here is the choice of communication protocol. Modbus a widely used bus system, enables differential pressure switches to be seamlessly integrated into existing systems. Whether via classic wired Modbus connections or wireless solutions such as Wireless Modbus - Both offer a high degree of flexibility and reliable communication in building automation. The crucial point: differential pressure values should not "just be there somewhere", but should actually be usable in the BMS - for trend recording, alarming and diagnostics.

Selection guide: What should you look for in a differential pressure regulator?

If a differential pressure controller is to operate reliably in the ventilation duct over the long term, the selection is not just a matter of the data sheet. In practice, the combination of measuring range, installation, medium, and operating conditions is often the deciding factor.

The following points are particularly relevant:

Measuring range suitable for ventilation technology
In ventilation, pressure differences at the filter or in the duct are often significantly smaller than in other media. Therefore, a suitably selected range is crucial for stable and meaningful values.

Mounting & installation location
Whether in a control cabinet, wall-mounted, or installed close to the duct – this influences installation, service, and measurement quality.

Medium: Air / non-aggressive gases vs. liquids
For ventilation units and HVAC systems, differential pressure is usually measured in air (e.g., at the filter or in the duct) . Small pressure differences in the range of a few pascals up to typical filter pressure losses are decisive here.

However, as soon as differential pressure is to be measured in liquid media, conditions such as pressure level, connection types, media compatibility, and sealing and housing design change. In these cases, specially designed differential pressure sensors are used.

You can find suitable solutions for liquid media here: Discover differential pressure sensors for liquid media

Stability in dynamic operating conditions
Modern systems rarely operate statically. Good measurement results must remain plausible even under load changes and flow influences.

Parameterization & serviceability
A device only provides real benefits if limit values can be set logically and service personnel receive clear information in the building management system.

Now select differential pressure controller for ventilation

In many projects, differential pressure only appears on the agenda when filters are constantly clogged, air volumes are no longer adequate, or the building management system is constantly reporting faults. However, this can be avoided at an early stage with clean differential pressure monitoring—without adding unnecessary complexity to the system.

At S+S Regeltechnik, we have the right field devices for this very purpose. Our differential pressure controllers for ventilation and air technology are designed to reliably cover typical measurement tasks in the HVAC environment – from filter monitoring to pressure zone monitoring – and can be neatly integrated into building automation systems. This provides you with clear measured values, traceable trends, and a reliable basis for maintenance and control.

Note: In building automation, in addition to air applications, there are also cases where differential pressure in liquid media needs to be measured – e.g., in hydraulic systems or cooling circuits. This requires different measuring ranges and connection concepts than in ventilation technology. You can find suitable pressure transmitters for liquids here:
Pressure transmitters / differential pressure sensors for liquid media

Select differential pressure regulator

FAQ

What does a differential pressure regulator do in a ventilation system?

It monitors and/or regulates the pressure difference between two points, e.g., before/after a filter in the ventilation duct, in order to map the filter status or pressure maintenance.

Is a differential pressure regulator the same as a differential pressure sensor?

In everyday language, terms are often mixed up. Technically, a sensor can only measure, while a controller (depending on the device) also supports limit values, switching logic, or control functions.

What are the advantages of differential pressure controllers in ventilation systems?

A differential pressure controller offers advantages in terms of operation, energy, and maintenance:

Early detection of dirty filters
Stable air flow thanks to reliable pressure monitoring
Optimized maintenance intervals (condition monitoring)
Increased operational reliability in HVAC systems
Greater transparency in building management systems (BMS)
Ideal for retrofitting and modernizing existing systems

Why is differential pressure needed for filters?

The differential pressure increases as the filter becomes more contaminated. This allows filter replacement to be planned as needed and keeps the air flow of the system stable.

Can differential pressure be evaluated in the building management system?

Yes, differential pressure is a typical GLT value. It is ideal for trend recording, alarms (limit values), and condition monitoring.

We also manufacture individually

Do you have special requirements? As a manufacturer with our own production in Germany, we are always able to produce outside the standard range.

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Differential pressure regulator