Vaillant quick installation set L11 for ecoCOMPACT/auroCOMPACT

Product detailed description

Quick-fit set L11 for Vaillant ecoCOMPACT and auroCOMPACT

The quick-fit set L11 is original Vaillant supplementary hydraulic accessory for stationary condensing boilers with an integrated storage tank from the ecoCOMPACT and auroCOMPACT ranges. Unlike the basic set L10, which handles the first direct (unmixed) heating circuit, the L11 set additionally contains a three-way mixing valve with an actuator, which allows the water temperature in the second heating circuit to be controlled independently of the first – typically to a lower value than required, for example, for underfloor heating compared to radiators.

The L11 set is therefore always installed together with the basic set L10, and never on its own – the L10 handles hydraulic separation of the boiler circuit (low-loss header) and the pump of the first circuit, while the L11 adds a second high-efficiency pump, a three-way valve with an actuator and related hydraulic accessories for the second, mixed circuit. The combination of L10 + L11 thus allows a single ecoCOMPACT or auroCOMPACT boiler unit to serve two independently controlled heating zones with different water temperatures.

This arrangement is common especially in new buildings combining different types of heating emitters within a single property.

Technical characteristics

• Purpose: Vaillant ecoCOMPACT (VSC, VCC) and auroCOMPACT (VSC D), supplementary set to the basic L10
• Function: hydraulic solution for the second, mixed (controlled) heating circuit with independent water temperature
• Main components: high-efficiency electronically controlled class A circulation pump, three-way mixing valve, electric valve actuator, connecting fittings, installation material
• Control: the actuator of the three-way valve is controlled by the boiler controller (e.g. multiMATIC 700) according to the set or weather-compensated curve of the second circuit
• Installation: directly into the boiler unit casing together with the L10 set, without the need for an external manifold
• Typical use: second circuit with a lower or otherwise controlled temperature, for example underfloor heating alongside the direct radiator circuit of the first L10 set
• Max. operating temperature: up to 110 °C (on the boiler circuit side, the temperature after the mixing valve is controlled according to the setting of the second circuit)
• Fittings material: brass/steel depending on the specific component, resistant to common heating water parameters

Why a mixed circuit is needed

Many modern heating systems combine several types of heating emitters with different temperature requirements within a single property – typically underfloor heating, which requires a significantly lower water temperature (usually around 30–40 °C) than conventional radiators (commonly 45–70 °C depending on sizing). If both types of emitters were supplied directly from the same unmixed circuit set for the radiator temperature, the underfloor heating would be significantly overheated, uncomfortable, and in many cases even in conflict with the technical limits of the given floor covering.

The three-way mixing valve with actuator in the L11 set solves exactly this problem – it mixes cooled return water with hotter water from the boiler in a ratio that brings the resulting temperature to the requirements of the given (usually lower) heating circuit, independently of the temperature set for the first, direct circuit handled by the L10 set.

This makes it possible to operate both circuits simultaneously, each at its own precisely suitable temperature, without them competing with each other or requiring a compromise setting common to both types of heating emitters.

This separation of control is the main reason why Vaillant offers the L11 set as a separate item in addition to the basic L10 set, instead of a single universal solution common to all types of circuits.

Installation

Installation of the set must be carried out exclusively by an authorised technician with professional qualification for the installation of gas and heating equipment, always in combination with the basic L10 set already installed (or installed simultaneously) in the boiler casing. Commissioning also includes setting the control (weather-compensated or fixed) curve of the second circuit in the boiler control unit, which then automatically controls the position of the three-way valve actuator according to the current outdoor temperature or the required indoor temperature.

When designing the system, we recommend determining in advance which circuit will be handled as direct (L10) and which as mixed (L10 + L11), since this choice is based on the actual temperature requirements of the individual heating zones of the given property and is part of designing the hydraulic scheme of the system.

Changing this decision after installation is complete is technically more demanding than making the right choice already at the design stage, so we recommend raising this topic with your heating supplier right at the beginning of system planning.

Compatibility

The L11 set is intended exclusively as a supplement to the basic L10 set for Vaillant ecoCOMPACT (VSC, VCC) and auroCOMPACT (VSC D) boilers – on its own, without the L10 set, it is not functional, since the L10 handles the basic hydraulic separation of the boiler circuit (low-loss header) to which the L11 connects. The set is not interchangeable with hydraulic accessories of other Vaillant boiler ranges with a different design of built-in hydraulic components.

When ordering, we therefore always recommend stating the exact boiler model and the information that the L11 set is being ordered as a supplement to an already installed or simultaneously ordered L10 set.

Maintenance and care

As part of the regular annual boiler service inspection, we recommend checking:

• smooth operation and noise level of the pump of the second circuit,
• functionality and smooth movement of the three-way valve actuator throughout the entire control range,
• tightness of the connecting fittings of the set,
• correct achievement of the set (lower) temperature in the second circuit as expected, for example for underfloor heating.

The mixing valve actuator is a mechanical element with moving parts, so its regular functional check during the annual inspection is clearly recommended to be somewhat more thorough than for the electronic pump itself, which requires no lubrication or manual maintenance.

If the service technician detects a slowed or jerky reaction of the actuator during inspection, we recommend replacing the component without unnecessary delay, since its gradual failure outwardly manifests itself only as inaccurate temperature control of the given circuit, and a layperson can easily overlook this cause or explain it differently, for example as a problem with thermal comfort in the room.

Why choose an original Vaillant part

The L11 set is designed to work precisely together with the basic L10 set and with the boiler's control electronics, which automatically operates the mixing valve actuator according to the set curve of the second circuit. The original part guarantees correct mechanical and functional compatibility without the need for additional programming or control modifications, which is not always a given when assembling an equivalent solution from components of various manufacturers and may require additional settings that the original part handles automatically.

The place of the L11 set within the modular concept of hydraulic accessories

The hydraulic accessories for ecoCOMPACT and auroCOMPACT are designed as a modular system of three mutually combinable sets – the basic L10 and two supplementary variants L11 and L20 – which covers the most common hydraulic configurations of family houses without the need for an individual design of an external manifold. While L20 adds a second direct circuit with the same temperature as the first, the L11 set is the only one of the three that solves a truly independently controlled (usually lower) temperature of the second circuit thanks to the three-way mixing valve with actuator. The choice between L11 and L20 therefore directly depends on whether the second heating circuit in the given property needs its own temperature control, or whether the same temperature as the first circuit is sufficient.

Typical wiring example

A common example of using the L11 set is a family house where the ground floor is heated by an underfloor system (requiring a water temperature usually in the range of 30–40 °C) and the upper floor by radiators (requiring a higher temperature, commonly 45–70 °C depending on radiator sizing). In such a configuration, the radiator circuit on the upper floor is handled by the basic L10 set as a direct circuit with a temperature corresponding to the boiler setting, while the underfloor heating on the ground floor is connected via the L11 set, which uses the three-way valve and actuator to maintain a lower, independently controlled temperature regardless of the current setting of the first circuit. The same principle applies to other combinations of zones with different temperature requirements, for example in an extension or a separate heating branch with a different type of heating emitters.