How to choose a pressure relief valve for boiler pressure relief

Making the correct pressure relief valve selection for your boiler is essential to maintaining the effectiveness and safety of your heating system. By releasing excess pressure when necessary, a pressure relief valve helps to maintain the ideal pressure inside your boiler.

There are a few things to take into account when choosing a pressure relief valve. These variables include your boiler type, the highest pressure it can withstand, and the particular needs of your heating system. It’s also critical to select a valve that complements the structure and design of your boiler.

Long-term savings and avoidance of expensive repairs can be achieved by comprehending the significance of a pressure relief valve and selecting the appropriate one. We’ll walk you through the process of choosing the ideal pressure relief valve for your boiler in this post, enabling you to make an informed choice that will keep your house warm and safe.

Choosing the right pressure relief valve for your boiler is crucial for safety and optimal performance. A pressure relief valve safeguards your boiler by releasing excess pressure, preventing potential hazards like explosions. When selecting a valve, consider factors such as the boiler"s maximum pressure, flow rate, and the type of boiler system you have. It"s essential to match the valve"s specifications with your boiler"s requirements to ensure effective pressure relief. Additionally, check for certifications and quality standards to guarantee the valve"s reliability and durability. Regular maintenance and inspections of the valve are also vital to ensure it functions correctly when needed. By making an informed choice and maintaining your pressure relief valve, you can ensure a safer and more efficient heating system for your home.

Operating principle

When it comes to closed water heating systems, the majority of regular users are only familiar with one kind of safety valve: the straightforward spring valve with a fixed setting that is depicted in the picture. The explanation is obvious: these components are installed everywhere on any boiler because they are all a part of the safety group, which also includes the air vent and pressure gauge.

Note: Safety features are built right into wall-mounted heat generators that run on gas or electricity. They are positioned inside the housing so that the outside cannot see them.

Let’s examine how a typical emergency valve functions, as depicted in the above diagram:

1. Under normal conditions, the diaphragm attached to the stem and supported by a spring sits tightly in the seat and seals the passage tightly.
2. If the coolant overheats, it expands and creates overpressure in a closed system, partially compensated by the expansion tank.
3. When the water pressure reaches the valve threshold (usually 3 bar), the spring is compressed and the diaphragm opens the passage. The boiling coolant is automatically discharged until the spring has enough force to close the passage cross-section again.
4. In the event of an emergency, the homeowner can perform the overpressure relief himself by turning the knob at the top of the product.

A brief note regarding the location of the safety group and relief valve in a closed heating system. It is located on the supply main section directly next to the boiler (a maximum distance of 0.5 m is advised). 5 м).

Important point. The installation of cocks, valves, and other shut-off devices is prohibited on the pipeline that runs from the heat generator to the safety elements.

The product branch pipe does not need to be connected to the sewer system; instead, puddles or damp areas will signal a triggering valve and issues with the heating network. For instance, when using a solid fuel boiler, the expansion tank may have failed or the circulation pump may have malfunctioned (possibly due to an outage of electricity). Debris between the plate and the seat frequently causes the device to start leaking. The following video provides more details on how it works:

Information clarification. Because the diaphragm explodes due to the pressure of the heating medium compressing the spring, masters and installers refer to spring-loaded relief valves as explosion valves. They are not to be confused with explosive devices that are placed on the chimneys of industrial natural gas boilers.

Types of safety valves

There are issues with the conventional blow-off design mentioned above. When boiling has begun, or when the temperature in the boiler tank reaches 100 °C or above, the spring mechanism that is triggered by excessive pressure is not accurate and may be delayed. Naturally, you can try using a screwdriver to adjust the product or adjusting the settings (some versions come with an adjustment cap), but these methods don’t always produce the desired result.

Second moment: the boiler’s safety valve guards against damage but not overheating. After all, if combustion in the furnace continues, coolant discharge cannot be used to cool the heating unit. Lastly, since the water inside them can boil without raising the pressure, these devices are completely pointless in open-type heating systems.

Prominent producers of heating fittings provide items with contemporary designs that do not have the aforementioned drawbacks—thermal relief valves. These safety features respond when the system’s temperature rises to a critical point rather than when the water head increases. These devices come in three varieties:

• resettable with remote temperature sensor;
• combined device with temperature sensor and make-up circuit;
• the same with direct installation in the pipeline.

As a point of reference. These are the names of trustworthy companies whose emergency valves are safe to purchase and install in private residences. These manufacturers are the well-known European brand Danfoss, Herz Armaturen (Austria), and ICMA and CALEFFI (Italy).

All varieties work on the same principle: a bellows filled with a temperature-sensitive liquid that expands significantly when heated activates a spring mechanism with a diaphragm (or two). When the critical temperature is reached, the thermal relief valves respond fairly accurately in this manner. We suggest going over each of them in greater detail.

Element with remote sensor

Encased in a housing featuring two spigots for connecting to the supply mains and discharging to the sewerage system, the product is the identical spring mechanism. Mechas (2 groups – main and reserve) move the rod that opens the plate and the path to the heat carrier. They are compressed by the temperature-sensitive liquid that emerges from the sensor bulb via the capillary tube when the water overheats (from 95 to 100 ° C). The figure depicts the safety element’s design:

There are three ways in which the solid fuel boiler’s strapping incorporates the temperature valve:

• with cooling through the water circuit of the heat generator;
• same, through a special emergency heat exchanger;
• coolant discharge with automatic make-up.

The first plan, which is displayed below, is utilized to heat water for DHW in double-circuit heating systems. The hot water from the circuit is drained into the sewer and replaced with cold water from the water supply when a sensor positioned beneath the surface of the TT boiler triggers the mechanism. Such a flow system will promptly cool the boiler jacket and avert the consequences, regardless of the accident’s cause.

Note: The publication uses schemes from the CALEFFI brand that were obtained from the manufacturer’s official resource.

Heat generators with an integrated emergency heat exchanger for cooling in the event of overheating are connected to the second circuit. European brands like Atmos and Di Dietrich are among those that manufacture these units.

Watch the video to see an example of how to connect the discharge element using a typical heat exchanger:

Because the valve releases coolant rather than cooling water, the final scheme can only be implemented in tandem with an automatic make-up system.

Exercise caution. Using automatic make-up on wood heaters with cast iron fuel boxes is not advised. The latter is susceptible to cracking when exposed to excessively cold water in the return because it is frightened of temperature changes.

Combination valves with system make-up

This brilliant symbol of the emergency fittings serves three purposes simultaneously and is conceptually comparable to bypass valves:

1. Discharge of the overheated coolant from the boiler tank on the signal of a remote sensor.
2. Efficient cooling of the heat generator.
3. Automatic cold water make-up of the heating system.

The product’s design is depicted in the above image, where you can see that a single stem has two plates on it that open two passageways at once: the first one releases boiling coolant, and the second one replenishes losses by carrying water in the opposite direction. This is how the wiring diagram for the solid fuel boiler and combined bypass valve is displayed:

Note: The flow must be arranged through an open expansion tank or an indirect heating boiler if using such a device is required to cool a TT-boiler with a cast iron heat exchanger.

The by-pass valve with triple outlet is integrated into the coolant supply pipe close to the heating unit, but it operates on the same general principle as the combined valve. The body part inserted into the pipe contains the bellows. The two upper pipes are connected to the water supply and make-up line, while the bottom pipe is used for discharge. These products are utilized in boiler rooms that are cramped for space.

How to choose a relief valve

Naturally, a standard blow-off valve will be less expensive to buy and install than temperature sensors. Because they almost instantly stop heating in the event of an accident, closed heating systems connected to gas, diesel, or electric boilers will be easily protected. An additional item is a heat generator that runs on coal or wood and cannot be switched off right away.

Please use the following advice to choose a thermal relief or overpressure valve with success:

1. When using any energy carriers, except solid fuel, safely buy a conventional blasting device.
2. Study the documentation of your heat source or boiler (depending on what needs to be protected) and select the safety valve according to the maximum allowable pressure stated therein. Most of the heating equipment is designed for a limit of 3 Bar, although there are exceptions – Lithuanian boilers Stropuva withstand only 2 Bar, and some Russian units (of inexpensive) – 1.5 bar.
3. For effective cooling of wood-fired heat generators in case of emergency, it is better to put one of the thermal relief valves. Their maximum working pressure is 10 bar.
4. In open systems with TT boilers, pressure relief is useless. Select a safety product that operates at a fluid temperature of 95-100 °C, suitable for your unit and make-up method.

Advice: Don’t purchase inexpensive safety valves made in China. It is not only untrustworthy, but it starts to leak after the initial explosion.

There are also valves with adjustable settings available, in addition to models with fixed settings. There is no particular need to purchase them if you are not an expert in the field of heating.

Selecting the appropriate pressure relief valve for your boiler is essential to keeping your heating system effective and safe. The main purpose of the valve is to relieve the boiler of excess pressure, averting potential dangers like explosions or damage to the apparatus.

Take into account the boiler’s size, fuel type, and operating pressure when choosing a pressure relief valve. The pressure requirements of different boilers vary, so it’s critical to select a valve that can meet your system’s unique requirements.

To make sure they are dependable and long-lasting, search for valves that also adhere to industry certification requirements and standards. Speaking with an expert heating technician is also a smart idea if you want recommendations specific to the requirements of your boiler.

To guarantee proper operation, the pressure relief valve requires routine maintenance and inspection. Valve wear and malfunction can occur over time, jeopardizing your heating system’s safety. If necessary, replace the valve and schedule routine checks to ensure your boiler is operating safely and smoothly.

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