Vaillant aroVAIR VAZ-035-G1 – condensate collection tray for 3.5 kW cassette fan coil unit

Product detailed description

Vaillant aroVAIR VAZ-035-G1 – condensate collection tray for the 3.5 kW cassette fan coil

The VAZ-035-G1 is a condensate collection tray from the accessory range of the Vaillant aroVAIR product line, designed for the smallest power version of the KN series cassette fan coil – the VA 2-035 KN model with an output of approximately 3.5 kW. This component addresses an essential technical requirement of every fan coil operated in cooling mode: when chilled water (typically around 7 °C at the inlet) flows through the water heat exchanger, moisture from the surrounding air condenses on the cold fins of the exchanger, in exactly the same way that moisture forms on a cold glass in a warm environment. This condensate must be safely collected and drained away from the ceiling void to prevent it from dripping into the ceiling structure, soaking the insulation, or damaging the ceiling materials.

The collection tray is mounted directly under the body of the VA 2-035 KN unit inside the space above the ceiling and collects all the condensate produced on the exchanger during cooling operation. The condensate is drained from the tray through a connected drain hose or pipe, typically by gravity (with a slope towards the drain), or to a condensate pump if the structural conditions (for example insufficient slope to the nearest drainage point) do not allow gravity drainage. Without a correctly installed and functional collection tray, it is not possible to safely operate the fan coil in cooling mode.

Technical parameters

Why the collection tray is essential

From a physical point of view, the cooling mode of a fan coil is inextricably linked to condensate formation – as soon as the surface of the exchanger drops below the dew point temperature of the surrounding air, moisture begins to condense on it. The amount of condensate produced depends on the humidity of the room air and the intensity of cooling, but during normal summer operation it is a measurable quantity of water that must be continuously drained away. If the collection tray were missing, damaged, or incorrectly installed (for example without sufficient slope towards the drain), condensate would accumulate in the space above the ceiling and could cause the ceiling structure to become wet, damage the insulation, cause stains on the ceiling, or in the worse case even lead to mould growth. This is precisely why this tray is considered an essential part of every cassette fan coil installation that will ever use cooling mode, not just an optional accessory.

Installation

The tray is installed as part of mounting the body of the unit, before the final cover panel is hung – it is positioned under the exchanger so that it catches all dripping condensate, and is connected to a drain hose or pipe routed with a slope towards the nearest drainage point (sewage system, downpipe, or condensate pump tank). During installation it is important to ensure that both the body of the unit and the tray itself are level (or have a slight slope in the direction of drainage), because uneven alignment can cause some of the condensate not to be caught correctly or not to drain away. The tightness of the drain hose connection should be tested before the cover panel is hung, so that any leak is detected before it becomes inaccessible.

Maintenance and care

The collection tray and its drain connection require regular checks of drainage flow, especially before the start of the summer cooling season, when the unit starts producing condensate again after the winter break. During the season, dirt, algae or biofilm can gradually build up in the drain hose or directly in the tray (especially where moisture stands in the warmer environment above the ceiling), so occasional checking of drain flow, or simple flushing of the system, is recommended. A clogged or blocked condensate drain is one of the most common causes of leaks and water escapes from cassette units during the cooling season, so this check should not be overlooked during the annual service inspection.

Compatibility

This collection tray is designed exclusively for the smallest, 3.5 kW power class of the KN cassette range – the VA 2-035 KN model, whose smaller body footprint (647 × 647 mm platform together with the VA 2-035 NKP cover panel) also corresponds to the smaller size of this tray. For larger power classes (5 and 10 kW, models VA 2-050 KN and VA 2-100 KN), a separate, larger collection tray with code 8000022078 (VA 2-ADP 050-100K) is designed, corresponding to their larger footprint platform. When ordering, it is therefore necessary to choose the tray that exactly matches the power class of the installed fan coil body.

Condensate drainage solutions – gravity vs. pumped

In practice, condensate drainage from the collection tray is handled in two basic ways. The first and simpler one is gravity drainage – a hose or pipe routed with a constant slope (typically at least 1–2%) towards the nearest drainage point, whether this is a vertical sewage drain pipe, a rainwater downpipe (if local regulations allow it), or another suitable drainage point. This method is low-maintenance and reliable, provided a sufficient and constant slope is maintained along the entire route. The second solution, used where structural or layout conditions do not allow a gravity slope (for example when the nearest drainage point is higher than the tray itself, or the route passes through several obstacles), is the use of a small condensate pump, which actively pumps the collected water to a more distant or higher drainage point. The choice between these two solutions is made already at the design stage of the installation, based on the specific layout of the building and the position of the fan coil relative to available drainage points.

Regardless of the chosen drainage method, the collection tray is the first and fundamental link in the entire chain – it catches the condensate directly at the source of its formation (the exchanger), before it comes into contact with the surrounding structure. That is why the quality and correct sizing of this tray, matched exactly to the given fan coil model, is one of the key factors in the reliability of the entire condensate drainage system.

Preventing moisture problems in the ceiling void

Cassette fan coils are, by design, located in a hidden space above the ceiling, which is not normally visible and where any water leak may only become apparent indirectly after a longer time – for example through stains on the ceiling, a musty smell, or later visible damage to the ceiling materials. This is precisely why preventing condensate leaks is more important than with visible technical equipment, where any problem can be detected immediately. A functional and properly maintained collection tray together with an unobstructed drainage system is the main defence against this risk. In some installations, a safety float switch is additionally fitted, which automatically shuts off the cooling function of the unit if the level in the tray is exceeded (for example due to a blocked drain), preventing further accumulation of condensate – we recommend consulting such additional safety features with the installation company when designing a specific installation.

Why order the original VAZ-035-G1 tray

The original collection tray from the manufacturer guarantees an exact fit to the size and shape of the VA 2-035 KN unit body, correct positioning under the exchanger for complete condensate collection, and compatibility with the drainage system designed by the manufacturer for this specific model. This item is one of the basic, essential components of every cassette fan coil installation intended for cooling, and we recommend ordering it together with the unit body, cover panel and controller, so that the installation is functional and safe from the risk of condensate leaking into the ceiling void from the very start. It is a relatively low-cost item compared to the overall value of the fan coil installation, but its absence or malfunction can cause disproportionately high consequential damage to the building structure, so this component should not be overlooked or underestimated when ordering, even in cases where the cooling function is planned to be activated only some time after the initial heating installation.