Combi Boiler Pressure Gauges & Thermomanometers | Cewal

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What Are Pressure Gauges? Why Are They a Critical Component in a Combi Boiler?

A pressure gauge (manometer) is a mechanical or electronic indicator that measures the pressure of a liquid or gas in a closed system. In combi boiler systems, pressure gauges show in real time whether the water pressure in the heating installation stays within the safe range (usually 1.0 - 1.5 bar). If the pressure drops, the radiators do not heat up; if the pressure rises, the safety relief valve opens and the boiler discharges water. For this reason, the pressure gauge is regarded as the boiler's "blood pressure monitor" and is the first step in fault diagnosis.

A pressure gauge is one of the first spare parts a combi boiler technician should carry before going out on site. This is because a pressure gauge with a stuck needle, a shifted zero point or a fogged glass pushes the customer to add water again and again in needless panic, which leads to corrosion in the radiators and scaling in the heat exchanger. Yedepa.com keeps Cewal and OEM-brand pressure gauges in stock, made in the same molds as the boiler manufacturers' original parts.

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Working Principle and Technical Details of Pressure Gauges

Combi boiler pressure gauges generally work on the Bourdon tube principle. The pressure of the water passing through it tries to straighten a coiled copper or brass tube; the tip of the tube moves a mechanical gear lever, and this lever moves the gauge needle. Thermomanometers, in addition to this mechanism, contain a bimetallic spring or a capillary-tube thermometer, so both pressure and temperature are read from a single gauge.

The most widely used technical standard in the combi boiler market is the Cewal Ø40 mm body. This diameter is preferred because it fits as standard into almost all European-made combi boiler panels (Vaillant, Baxi, Ferroli, Baymak, Beretta, Ariston). The measuring range is usually 0-4 bar, with the optimum operating zone marked in green and the danger zone in red.

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Feature	Value
Body diameter	Ø40 mm (standard)
Pressure range	0 - 4 bar
Temperature range (thermomanometer)	30 - 120 °C
Connection	1/4" or capillary hose
Body material	ABS plastic / brass fitting
Operating principle	Bourdon tube + bimetal

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Pressure Gauge Types and Models

There are three main groups of pressure gauges in the spare parts market, and each group is designed for different combi boiler models:

Plain Pressure Gauge: Shows only the water pressure. It is usually positioned in a small round window on the front panel. It is frequently used in Beretta, Riello, Ferroli and Viessmann models.
Thermomanometer: Shows both the pressure and the flow water temperature at the same time. It is produced with two needles (dual scale). This type is factory-fitted in most Vaillant, Baxi Luna, Eca, Ariston and Biasi models.
Capillary (Long-Hose) Pressure Gauge: When the gauge is on the panel and the pressure sensing element is on the hydraulic block, the thin copper hose connecting the two is called a "capillary". These models are standard especially in the Vaillant VUW, VCK and Susler series.

In terms of brands, Cewal is of Italian origin and is the original equipment supplier for almost all European combi boilers. The pressure gauges we offer in the OEM category are quality-controlled equivalent products that comply exactly with the boiler manufacturer's technical specifications.

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Which Model to Choose? A Decision Guide by Brand and Boiler

When choosing a pressure gauge, you must pay attention to three things: (1) connection type (capillary or direct threaded), (2) body diameter (Ø40 mm is the most common), (3) whether it is single-scale or dual-scale (thermomanometer). If the wrong model is bought, it either does not fit the panel or leaks at the hydraulic block.

Vaillant VUW series: Valliant Vuw Combi Boiler Thermomanometer or the Cewal Ø40 Vaillant VUW Compatible 101271 pressure gauge is fully compatible.
Vaillant VCK / Susler: Valliant Vck & Susler Combi Boiler Thermomanometer is the only correct choice; its capillary hose is factory length.
Baymak Luna 3 / Baxi Luna / Falke: Baymak & Baxi Luna Combi Boiler Thermomanometer or the Cewal Ø40 JJJ008922460 plain pressure gauge fits.
Eca and Ariston: Eca & Ariston Combi Boiler Thermomanometer is a common part for both brands.
Biasi series: Biasi Combi Boiler Thermomanometer fits directly into the original panel.
Ferroli: Cewal Ø40 Ferroli Compatible 40030560 is the original code in the manufacturer's spare parts catalog.
Viessmann WH1D: Viessmann Wh1d Combi Boiler Pressure Gauge is a plain type that fits into the front panel clip.
Beretta / Riello: The OEM-quality Beretta Riello Combi Boiler Pressure Gauge is sold as an exact equivalent.

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Pressure Gauge Types Available at Yedepa.com

The main pressure gauge models in our stock that we can ship the same day are:

Biasi Combi Boiler Thermomanometer - Cewal, 9 USD
Valliant Vck & Susler Combi Boiler Thermomanometer - Cewal, 9 USD
Baymak & Baxi Luna Combi Boiler Thermomanometer - Cewal, 8 USD
Valliant Vuw Combi Boiler Thermomanometer - Cewal, 8 USD
Eca & Ariston Combi Boiler Thermomanometer - Cewal, 8 USD
Cewal Ø40 JJJ008922460 - Baymak Luna 3 / Falke / Baxi Compatible - 5 USD
Cewal Ø40 Ferroli Compatible 40030560 - 5 USD
Cewal Ø40 Vaillant VUW Compatible 101271 - 5 USD
Viessmann Wh1d Combi Boiler Pressure Gauge - Cewal, 5 USD
Beretta Riello Combi Boiler Pressure Gauge - OEM, 5 USD

All products are shipped boxed and labeled. Yedepa.com lets you add products to your cart and place an order with a single click, even while your technician is on site.

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Professional Selection Criteria (Technician Checklist)

When replacing a pressure gauge, it is not enough just to say "it fits the panel". These are the criteria the technician should check to confirm the job has been done correctly:

Zero-point calibration: When the boiler is switched off and the system pressure is fully released, the needle must be exactly at "0". Otherwise a false pressure is read.
Needle flutter: Constant fluttering of the needle while the pump is running indicates that air is leaking into the Bourdon tube; this is a manufacturing defect in the product, and it should be returned.
Glass fogging: In thermomanometers, condensation forming inside the glass indicates a fault in the temperature sensor.
Capillary hose length: On Vaillant and Baxi models, a hose shorter than the factory length gets pulled and bursts when the panel is closed.
Gasket check: When fitting a pressure gauge, sealing must always be ensured with a new fiber washer or PTFE tape.
Bar scale: Fitting a pressure gauge outside the 0-4 bar range recommended by the boiler manufacturer (e.g. 0-10 bar) reduces accuracy and misleads the customer.

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Use and Maintenance Recommendations

Although a combi boiler pressure gauge looks like a passive indicator, there are precautions that need to be taken across the system for it to have a long service life. The maintenance list below applies to both technicians and informed end users:

Protect against overpressure: Open the filling valve slowly. Fast filling suddenly strains the gauge's Bourdon tube and permanently shifts the needle.
Safety relief valve check: At pressures above 3 bar, the safety relief valve should discharge water. If it does not, the fault is in the valve, not the pressure gauge.
Seasonal setting: In summer, around 0.8 bar is normal in a closed system; in winter, with the boiler in operation, it should be kept between 1.2-1.5 bar. Above 2 bar, drain water from the system.
Scale and sediment: In capillary-connected models, sediment clogs the channel over time; the hose end should be cleaned during annual maintenance.
Temperature shocks: When the boiler rises to 80 °C at full load, the bimetallic spring of the thermomanometer fatigues; replacement every 5-7 years on average is recommended.
Frost protection: In unused summer houses, if the boiler has not been fully drained, the water remaining inside freezes and bursts the pressure gauge. This counts as a natural disaster and is not covered by the warranty.

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Pressure Gauge Fault Symptoms and Quick Diagnosis

The pressure gauge-related complaints technicians most often encounter in the field, with diagnostic tips:

Needle stuck at zero: The Bourdon tube is fatigued or the gear lever is broken. Complete replacement is required.
Pressure appears high but the radiator does not heat up: The pressure gauge is giving a false reading. Compare it with a test pump.
Water droplets inside the glass: The tube has cracked inside; the leak will spread to the panel over time. Replace urgently.
Thermo needle constantly at 120 °C: Bimetallic sensor fault; replace it before it short-circuits the panel.

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Frequently Asked Questions (FAQ)

Question 1: What pressure in bar should a combi boiler pressure gauge show?
\\ Answer: When the boiler is cold, 1.0 - 1.2 bar; when running, 1.2 - 1.5 bar is the ideal range. If it rises above 2 bar, water should be drained from the system.

Question 2: Is the Cewal brand original or an equivalent?
\\ Answer: Cewal is of Italian origin and is the original equipment supplier that manufactures the factory-fitted pressure gauges of major brands such as Vaillant, Baxi, Ferroli and Beretta. In other words, it is not an "original equivalent"; it is directly original.

Question 3: What is the difference between an OEM pressure gauge and a Cewal pressure gauge?
\\ Answer: OEM products are quality-controlled equivalents that comply exactly with the boiler manufacturer's technical specifications. Cewal, on the other hand, is the direct manufacturer for many brands. Both can be used with confidence; the price difference usually comes from brand prestige.

Question 4: Is it necessary to drain the boiler water completely when replacing the pressure gauge?
\\ Answer: No. It is enough to close the valves around the hydraulic block and drain locally. Draining completely creates unnecessary work and causes air venting problems.

Question 5: Can I use a thermomanometer and a plain pressure gauge interchangeably?
\\ Answer: If it physically fits, you can, but when the panel cutout is different a gap remains and spoils the appearance. You also lose the thermo temperature reading; the boiler's electronic board does not read this information, it only shows it to the user.

Question 6: How long is the warranty on a pressure gauge I buy from Yedepa.com?
\\ Answer: All our Cewal and OEM-brand pressure gauges are under warranty for 2 years against manufacturing defects. Faults caused by incorrect installation, freezing and overpressure are not covered by the warranty.

Question 7: Should I use PTFE tape or a fiber washer when fitting a pressure gauge?
\\ Answer: PTFE tape should be preferred for threaded connections, and a fiber washer for flat-seating ones without a capillary. When wrapping PTFE tape on the gauge end, leaving the last two threads bare prevents excess tape from getting inside and clogging the mechanism.

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Conclusion: The Right Pressure Gauge, a Healthy Boiler

The pressure gauge is the health indicator of the combi boiler system. Because of a pressure gauge giving false readings, your customer may call you again and again saying "my boiler is broken", when the problem is actually in a small gauge. That is why stocking quality, correctly calibrated and brand-compatible pressure gauges, for technicians and technical service companies alike, prevents the loss of both time and trust.

Yedepa.com adds Cewal and OEM-brand pressure gauges to its stock, each individually tested, especially for its B2B technician and service network. You can search using ready card numbers for Vaillant VUW, VCK Susler, Baymak Luna 3, Baxi, Ferroli, Beretta, Riello, Viessmann WH1D, Biasi, Eca and Ariston models and place an order with a single click, even while your technician is on site. Thanks to our Cantaş-integrated pricing infrastructure, you see up-to-date prices instantly and make invoiced purchases using our payment term surcharge table.

Yedepa Advantages:

Cewal original supplier parts
OEM quality assurance and 2-year warranty
B2B payment term options exclusive to technicians and service companies
Secure shipping across Turkey
Detailed compatibility filter by card code, boiler model and brand
Technical support line: matching the right part to the right boiler

Sourcing the right pressure gauge for every combi boiler model you encounter in the field from a single address is now very easy: Yedepa.com - Pressure Gauges category, the technician's true spare parts warehouse.