common manometer faults and how to fix them

A manometer in a central heating system is not only an indicator but also an essential safety component that directly affects the stability and lifespan of the entire device. Frequent malfunctions of this device often lead to incorrect pressure readings, which can cause premature boiler failures or radiator damage.

Causes of loss of accuracy and mechanical damage

The most common problem with manometers in professional heating is the gradual loss of calibration caused by vibrations and thermal shocks, which manifest as a needle shift away from zero even when the system is at rest. Mechanical damage to the internal mechanism occurs mainly due to impacts or overloading beyond the upper measuring range, when the spring deforms permanently and stops returning to the zero value.

Removing this fault requires either replacing it with a new unit or an expert inspection and adjustment of the zero position, if the mechanism is only slightly damaged. When choosing a new device, it is crucial to look for models with a robust construction solution, such as the axial manometer 0 - 10 bar, 63 mm, which is designed for more demanding conditions and has higher resistance to impact vibrations.

Influence of condensate and corrosion on pump performance

Condensate in the pipes and in the filling medium of the manometer causes corrosion of internal parts, leading to the needle jamming or complete failure of the Bourdon tube. This phenomenon is typical especially in older installations, where proper drainage is missing or the manometer is placed too close to a source of moisture without a protective space.

• Use manometers with silicone filling, which prevents moisture from entering the mechanism.
• Install a shut-off valve between the manometer and the system for easy replacement and maintenance.
• Regularly check the condition of the filling and replace it if turbidity or sediment appears.
• Avoid installation in places where condensation of steam occurs directly on the surface of the device.

A solution is often the installation of an axial thermomanometer, which combines pressure and temperature measurement and often comes with better sealing against moisture. If corrosion is already advanced, the only option is immediate replacement, as repairing the internal tube is neither technically possible nor economically justified.

Incorrect measuring range and its consequences on accuracy

One of the most common human errors in operation is the use of a manometer with an incorrect range, which leads to the operating pressure being in the lower third of the scale, where accuracy is the lowest. If your system operates at 1.5 bar and you use a manometer with a range of 0 to 10 bar, a small deviation becomes unnoticeable, while using a range of 0 to 4 bar will make every change visible and the measurement accurate.

For typical home heating systems, the ideal range is 0 to 4 bar or 0 to 6 bar, which allows for accurate pressure monitoring in the operating mode. For larger industrial systems or high-pressure boilers, it is recommended to use an axial manometer 0 - 6 bar, 63 mm, which provides sufficient reserve without compromising accuracy. Choosing the correct range is critical to prevent false alarms and for accurate leak diagnosis.

Connection and fitting problems

A non-hermetic connection between the manometer and the pipe is a common cause of gas or liquid leakage, which can lead to dangerous situations and pressure loss in the system. It often happens that the user, when replacing the manometer, does not use the correct sealing material or does not tighten it enough, which causes the gasket to crack or the threads to be damaged.

• Always use special sealing tapes or pastes designed for high temperatures and pressures.
• Check the condition of the threads on both sides before installation and clean them.
• Tighten the connection with a wrench, but not with excessive force to avoid damaging the material.
• Use radial or axial manometers according to the available space, as axial ones often have a better arrangement for sealing.

It is also important to pay attention to the correct type of fitting, whether it is G 1/2 or G 1/4, and ensure that the manometer is firmly mounted to prevent rotation under pressure. When installing an axial thermometer, special attention should be paid to the shape of the fitting, as the larger 100 mm diameter requires a firm and stable mounting.

Protection against frost and extreme temperatures

Manometers installed in unheated areas or on outdoor pipelines are exposed to the risk of freezing of the filling, which can cause the glass face to crack or internal parts to deform. In such cases, the measurement stops completely or a random value appears that does not correspond to the actual state of the system.

To protect against these phenomena, the installation of manometers with silicone filling, which has a lower freezing point, or the use of thermal insulation around the device is recommended. If the manometer is located in a risky zone, it is advisable to consider moving it to a heated area or installing a heater near the device. It is always better to prevent the problem by proper localization than to repair the consequences of freezing.

Maintenance and calibration in professional practice

Professional installers should regularly check the accuracy of manometers, as long-term exposure to pressure and temperature cycles causes them to gradually deviate from the truth. Calibration is performed by comparing with a reference standard and if the error is greater than 2 % of the full scale, the device must be replaced or repaired.

• Checking the manometer at least once a year using a calibrated tester.
• Checking the mobility of the pointer and its return to the zero position after pressure is removed.
• Replacing the manometer during every intervention in the system where it has been removed or damaged.
• Recording the calibration results for the purposes of the building's maintenance plan.

Regular maintenance and calibration of manometers in professional heating is essential for the safety and efficiency of the entire system. Ignoring these steps can lead to serious accidents and high repair costs for damaged equipment. Therefore, it is important to follow the procedures outlined in the manufacturer's manual and always choose quality products from verified suppliers.

The effect of pressure shocks on the Bourdon tube

Rapid pressure changes when starting a pump or opening valves create shock waves that can fatigue the metal over time and cause microcracks in the Bourdon tube.

Common questions

Why does the manometer show zero even though there is pressure in the system?

This condition most often indicates a blockage of the input channel by impurities or a complete failure of the Bourdon tube, which has stopped responding to pressure.

How to choose the correct range of the manometer for the heating system?

It is recommended to choose a range whose maximum value is approximately 1.5 to 2 times the operating pressure to achieve the best accuracy in the working range.

Should the manometer have a thermometer or is a separate thermometer better?

A separate thermometer provides more accurate temperature measurement, but a combined thermomanometer saves space and installation time if a rough orientation is sufficient.

Proper manometer function is key to the safe and efficient operation of your heating system, so it is important to regularly check its condition and promptly eliminate any emerging faults. An investment in a quality device and correct installation always pays off in the form of a longer boiler lifespan and lower maintenance costs.

Do you have a question about this topic?

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