TROX has launched a new initiative of refurbishing VAV equipment and systems within its service division.
A comprehensive package which includes initial survey, VAV unit validation, report and recommendations, followed on, if required, by on-site rectification, modernisation and installation. With this single point responsibility, all work can be undertaken to suit the clients’ specific requirements bearing in mind that very often the offices are still occupied.

The need to change or upgrade VAV boxes can be seen from the staggering savings in energy and carbon emissions.

It is estimated that there are over 1,000,000 VAV boxes still operating mainly in the comfort air conditioning applications within the office sector. Some of the original VAV boxes had what was known as a mechanical damper. It incorporated springs and weights so that a range of pre-set air volumes could be controlled irrespective of downstream duct pressure changes.

These dampers required quite a high static pressure to get the actions of the springs and damper mechanism operational and typically 200Pa was required.

Lower pressures

Today’s VAV boxes and VAV valves require very much lower pressures to operate them with 20Pa being typical, which would show a significant energy saving over the original units.

This saving (200 - 20 = 180Pa) related to a building of, say, 40,000m2 with an airflow of 15 litres/sec/m2 would achieve a reduction of 308,000kwh per annum, or in terms of CO2 emissions a staggering 132,440kg. This in itself should be the motivation to the client to survey and refurbish his VAV system.

The accuracy with which these original VAV boxes can control the air flow depends very much on the life of the springs and other mechanisms.

Generally speaking VAV units which are in continuous operation would have a useful working life of 15 to 20 years. During the life of the unit, regular maintenance and monitoring should take place to ensure that they operate effectively.

Even with this maintenance there is a risk that operational difficulties will be found within the VAV unit which could lead to much wider variations in supply air volumes – that is the box drifts away from its normal tolerances. This leads to much wider fluctuations in temperature because the room at times could be over heated or over cooled.

Again there are significant energy issues when this happens since the VAV box is not effectively controlling the environment, and would further add to the CO2 emissions mentioned above.

The service division has already completed various projects such as Royal Sun Alliance Leadenhall Street where 480 VAV boxes had been installed on this six-storey building.

A complete survey revealed that specific upgrades could be provided rather than replace all units.

The work was undertaken by Trox Service Division whilst the building remained occupied.

Trox 01842 754545