Ducted Air Conditioning Systems

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Ducted Installation

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Ducted air conditioning is probably the quietest and most versatile of all air conditioning systems. A ducted system is often the most practical choice for larger areas requiring cooling and air distribution which is likely to be beyond the reach of normal ‘split type’ units. This system is designed for areas with suspended or false ceilings.

We supply all the major brands including Daikin, Mitsubishi, LG, Panasonic, Toshiba, Sanyo and Hitachi. The discreet grilles can be located almost anywhere allowing them to blend in with interior décor. These grilles facilitate uniform temperature distribution and air flow to larger or partitioned areas.

This system is ideal for both domestic and office environments. Combined heating and cooling versions of these systems attract 5% VAT for residential installations. This is due to the government recognising that these systems are energy efficient.

To find out How Air Conditioning Works, we have created a helpful guide.

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Bespoke Ducted Air Conditioning Design

Having a ducted air conditioning system is usually the most aesthetically pleasing type of air conditioning installation however it is often also the most complicated owing to the technical limitations, particularly if the system has been incorrectly designed. We are often called in to offer an expert opinion as to why a system is not working (even newly installed systems) where we usually find that there have been errors in calculating how the system should have been installed and what equipment should have been used.

The most important aspect is to ensure that the correct airflow is sent into the room for distribution via the grilles; in the first instance, you need to the correct airflow to reach the grilles. When calculating this airflow, you need to determine the amount of static pressure, i.e. the amount of force required to push air not only to reach a specific point but also at the correct velocity.

For example if we had a standard garden hose that was one meter long and we tried blowing down it, the air will come out easily but, if the hose was 10 meters long, it would be significantly harder to blow through. Sticking with our 10 meter hose analogy, if we added lots of twists and bends the force required will increase even more. It is these calculations of the length, diameter and bends that determine the correct specification of the Air Handling Units that would be required.

It is always best practise to only cool one room via a single air handling unit; trying to cool two rooms from the same unit, leaves occupants of the second room with no control whatsoever over temperature or indeed any functionality at all including switching the unit on or off. Multiple units might be required in the same room if the area is very wide or long.

We often see installations that don’t work correctly because they have been put together using standard ‘off the shelf’ grilles where no consideration has been given with regards to air flow. The Air Conditioning Company design bespoke systems and have grilles made to order where not only are the air flow, velocity, design and colour taken into consideration but also the static resistance of the grilles themselves.

The technical listings of Air Handling Units should always specify the amount of static resistance (measured in Pascals) that the unit can cope with. We have used the following example to show how the correct unit size is determined:

We have a room that is 7x6 meters that requires both cooling and heating. The area is therefore 42m² and will require 150 watts of cooling per square metre equating to just over 6Kw of duty from the Air Handling Unit. We have selected a Mitsubishi Heavy Industries Ducted Inverter System that is able to handle 100 Pascals of resistance for this example.

The client has specified that they want four supply vents, each one spaced five metres from the unit and each five metre length of ducting between the unit and the grilles will have a two 90 degree bends. Before we can proceed, we need to calculate if this is going to be possible. Every meter of ducting generates approximately 1-2 Pascals of static resistance, a 90° bend will create 10 Pascals of static resistance and grilles can range from 0-50 Pascals.

This means that the 20 metres of ducting will generate 20 – 40 Pascals of resistance, the eight 90 degree bends will generate 80 Pascals and that is before you have calculated the static resistance of the grilles. From this simple calculation, you can see that the 120 Pascals of static resistance will result in an underperforming unit as the unit is only specified to accommodate 100 Pascals. Reducing the grilles and ducts to two would result in 60 Pascals of static resistance which is a workable solution, subject to the grille specifications.

You may think that simply installing a larger unit that can accommodate more resistance is the answer. In part, this may be true, but an overpowered unit (for the space) will create drafts and wind noise.