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Gas valves for condensing boilers: The crucial link

In condensing boilers, the gas valve is a key compo­nent for combus­tion control. It ensures safe, reli­able oper­a­tion and is crucial for providing the optimum combus­tion mixture. The gas valve range from ebm-papst offers the ideal solu­tion for both pneu­matic and elec­tronic networks.

If there were only one type of gas in the world, life would be much easier for heater manu­fac­turers. They would need to configure their combus­tion system just once to provide the optimum gas and air mixture ratio, after which the condensing boiler would provide heat equally effi­ciently in all parts of the world – leaving aside ambient para­me­ters such as temper­a­ture or air pres­sure for now.

However, natural gas is produced by a natural process, and it has a different heating value depending on where it comes from. In the Nether­lands and Germany, for example, L-gas is tradi­tion­ally used. Its name reflects the fact that it is low-calorific (L = low). This contrasts with H-gas from Russia, which has a higher methane and thus energy content, making it high-calorific (H = high). Since sources are running dry and the market is changing, there are also new fuels such as lique­fied gas from the USA, as well as synthetic gas or hydrogen from power-to-gas plants. There­fore, finely balanced systems are required to set the optimum combus­tion mixture.

Fig. 1a: The inter­ac­tion between all compo­nents is a deci­sive factor for both elec­tronic and pneu­matic networks. The gas valve plays an impor­tant role here in ensuring the correct combus­tion mixture. (Graphic | ebm-papst)

Key role within the network

In prac­tice, pneu­matic combus­tion control has proven its worth in this regard for many years. As a result of fluc­tu­a­tions in gas quality, elec­tronic combus­tion control is gaining in impor­tance as an alter­na­tive. ebm-papst offers both vari­ants as a complete solu­tion under the names CleanEco (pneu­matic, Fig. 1a) and Clean­Vario (elec­tronic, Fig. 1b).

Within these systems, the gas valve plays a key role. Firstly, it prevents the gas from flowing out in an uncon­trolled manner, and secondly, it only allows the exact quan­tity that needs to be mixed with the air to flow through. The impor­tant thing is to ensure a coor­di­nated approach with the blower, venturi, and control unit. That works best when all compo­nents come from a single source. This is why ebm-papst has also included gas valves in its range since 2011 and is contin­u­ously expanding and refining the range, such that four power classes (Fig. 2 and 3) in the range 1.5 – 762 kW can now be offered.

Fig. 1b: The inter­ac­tion between all compo­nents is a deci­sive factor for both elec­tronic and pneu­matic networks. The gas valve plays an impor­tant role here in ensuring the correct combus­tion mixture. (Graphic | ebm-papst)

The classic solu­tion: the D01 valve

Mechan­ical valves are used in pneu­matic networks. Their oper­ating prin­ciple is that if the ther­mo­stat in the home switches on or if someone turns on the hot water faucet, the boiler starts working. The blower rotates as per the required power, the gas valve is opened, and the taper in the venturi causes a vacuum that draws in the gas. In simple terms, the faster the blower rotates, the more gas is taken in. This must not happen in an uncon­trolled manner. There­fore, the valve should only open until it allows the exact quan­tity for the combus­tion mixture to pass through.

How does this work? A look at the inte­rior of valve D01 from ebm-papst provides the answer (Fig. 4). There are two safety valves on the gas inlet side. If one fails, the other can still prevent an uncon­trolled supply of gas. The safety valves are lifted by way of elec­tro­mag­netic coils and the gas can flow in. The oper­ating valve is located on the outlet side, which is connected to the venturi. The vacuum gener­ated by the blower exerts a force via a working diaphragm. This force mechan­i­cally lifts the oper­ating valve.

Two adjusting screws can be used to regu­late the extent of this action: the offset and main flow throttle setting. The offset (shifting the zero point) can be set on the servo controller. The offset pres­sure is always regu­lated to zero, regard­less of the suction pres­sure gener­ated by the premixing blower. This also enables pres­sure fluc­tu­a­tions in the supply network to be compen­sated. The throttle element adjusts the quan­tity of gas required based on the gas quality. For example, with L-gas a larger quan­tity flows through than with H-gas. This means that both settings are crucial for ensuring a correct gas-air mixture ratio over the entire modu­la­tion range.

The D01 valve is the first one that ebm-papst included in its product range and is suit­able for a very wide power range of 8 to 120 kW. Thanks to its compact dimen­sions, the D01 is a space-saving solu­tion for inte­gra­tion into the boiler.

Fig. 2: The gas valve range from ebm-papst for pneu­matic networks. (Graphic | ebm-papst)

Low power, big impact: the E01 valves

For lower power classes of up to 81 kW, the engi­neers at ebm-papst have further refined the D01 prin­ciple and provided an even more compact solu­tion: the E01 valve. The crucial differ­ence lies in the design of the safety valves. Instead of being distrib­uted across two coils, they are combined in a single module. This uses less mate­rial and also saves more energy as there is only one coil that has to be ener­gized. The E01 is avail­able in two versions: for power ranges from 1.5 to 57 kW and 3 to 81 kW.

More flex­i­bility: the F01 valve

The gas valve is becoming much more impor­tant in elec­tronic networks. Here, the mixing ratio is not controlled by the vacuum but by the elec­tronic actu­a­tion of the gas valve. Instead of reacting passively, it thus actively controls the gas supply. This means that, in contrast to pneu­matic networks, the valve does not have to be manu­ally set in advance to suit the respec­tive gas type and quality, as the system adapts to the gas.

The valve needs a para­meter to ensure it knows how much gas it should provide for mixing with the air. ebm-papst relies on what is known as ioniza­tion tech­nology for this, which uses the elec­trical conduc­tivity of the flame. If a voltage is applied, the so-called ioniza­tion current can be measured directly in the flame using an elec­trode. This can be used to draw conclu­sions about the combus­tion quality: If the current is too weak, the valve receives the signal to supply more gas; if it is too high, it restricts it.

Fig. 3: The gas valve range from ebm-papst for elec­tronic networks. (Graphic | ebm-papst)

To ensure that the gas valve can actively control the gas supply, it has to be designed differ­ently than in a pneu­matic network. With the F01 series, ebm-papst offers the ideal valves for all power classes between 1.8 and 762 kW (see Fig. 3). In terms of the safety tech­nology, the devel­opers relied on the same system as for the E01. However, a stepper motor with inte­grated pres­sure regu­lator is used on the outlet side. This motor can precisely vary the flow rate and, in turn, the amount of gas.

If the flame sends the signal that combus­tion is not optimal, this patented solu­tion can take the appro­priate coun­ter­mea­sures flex­ibly. This means that, in an elec­tronic network, it almost doesn’t matter which fuel is flowing through the pipes. What’s more, the manu­fac­turers have to worry much less about the different gas types and qual­i­ties – the combus­tion is always optimal, effi­cient, and envi­ron­men­tally friendly.

Fig. 4: All three gas valve types from ebm-papst shown as sectional views. The gas flows in from the left (1). The two safety valves (2) are opened by one (E01, F01) or two (D01) elec­tro­mag­netic coil(s). In the D01 and E01, the oper­ating valve (3) is used to regu­late the pres­sure and quan­tity. (Graphic | ebm-papst)

Three valves with a whole host of bene­fits

The D01 valve

• Tried and tested in everyday oper­a­tions for many years
• Compact dimen­sions mean greater flex­i­bility for manu­fac­turers
• Easy access to elec­trical connec­tions and settings
• Precise adjust­ment of the gas-air ratio using the offset and main flow throttle setting

The E01 valve

• Gas valve with one coil with coaxial double safety valve and a die-cast housing
• This makes it even smaller and allows for low elec­trical power
• Produced in ever-increasing volumes since 2014
• Easy access to the connec­tions
• High offset accu­racy and thus optimum compen­sa­tion of pres­sure fluc­tu­a­tions in the supply network

The F01 valve

• Elec­tronic control system means that manual settings are no longer required
• Patented solu­tion comprising stepper motor and inte­grated pres­sure regu­lator
• Opti­mized design enables fully auto­matic mounting
• Very precise control in a power range of 1.8-762 kW
• Modular design enables the valve to be opti­mally combined with other system compo­nents

The perfect combi­na­tion

Whether it’s a pneu­matic or elec­tronic network, it is crucial that all compo­nents in a combus­tion system are perfectly coor­di­nated with one another. This means that the blower and valve have to be a good match. ebm-papst offers the following possible combi­na­tions:

Blower Gas valve
RadiMix VG 71 & VG 100 E01 and G15 F01
RadiMix VG 108 G20 D01 and G32 F01
VG 145 G20 D01 and G32 F01
RG 175 G32 F01 and G40 F01
G1G 170 G40 F01
G3G 200 G40 F01

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