Taking control of ventilation
Demand-controlled ventilation is an energy-efficient way of providing good indoor air quality. David Cook explains how it can be effectively added to existing systems with AC fans.
With the vast majority of commercial buildings fitted with inefficient and energy-hungry fans with AC motors that either have no controls or only simplistic controls, ventilation represents a key area for improving building performance. Not only do these inefficient fans cost more to run, but their unsophisticated controls provide low comfort levels which can lead to unproductive staff.
Indoor air quality is integrally linked to staff performance. The 2005 report ‘Impact of office design on business performance’, produced by CABE and the British Council for Offices (BCO) cited differences in productivity of 25% between comfortable and uncomfortable staff — due to basics, such as air quality, temperature, overall comfort, noise and lighting. Gaining potentially up to 25% in staff productivity is a huge incentive to improve indoor air quality.
Despite these clear benefits, companies may still find it impractical or consider it too expensive to replace AC fans with new efficient models. However, a new variety of controllers is now available designed to offer cost-effective demand-controlled ventilation to existing speed-controllable fans, improving their performance and operating efficiencies.
The benefits of demand ventilation on energy efficiency and indoor air quality are now well recognised, with ventilation responding to the exact demands of a room, supplying or extracting air only when and to the level it is required. As a result there is greater comfort for building occupiers, and the improved energy efficiency of the fans means a reduction in fuel costs and carbon emissions.
Providing AC fans with the functionality of demand ventilation, this new breed of controller offers significantly advanced regulation of existing fans installed in many typical HVAC applications. The control unit allows contractors to adjust ventilation operation according to demand readings gathered from a variety of sources — including CO2, temperature or occupancy sensors. The equipment also provides the capability to adjust and control fan speed remotely to ensure more efficient operation and, as a result, reduced fuel costs.
Versatility is crucial when retrofitting a controller in a wide range of specific applications. The new demand controllers therefore come in a number of options.
For example, units available in the Vent-Axia e-Demand series include: electronic voltage controller; frequency inverter from single phase to 3- phase; 3-phase frequency inverter; and single-phase frequency inverter.
Featuring minimum and maximum speed set points, two programmable relay outputs, fault condition and master/slave control via a 0 to 10 V output. The eDemand controllers also incorporate LCD multi-function displays with menu language options that include English, French, German and Italian. A mains switch with by-pass function also features on the electronic voltage controller. Meanwhile, all the controllers can be PIN-protected to save user settings.
These controllers incorporate a thermistor connection for complete motor protection and are IP54 rated. Frequency inverters have a built-in sine filter to protect the unit against transient currents that could damage the motors.
Although an increase in electromagnetic noise can be a problem when applying speed control to AC fans, eDemand frequency inverters effectively eliminate these issues, so occupants are not disturbed. Fans can also operate in parallel with no risk of motor damage, and screened motor cables are not required.
In addition, Vent-Axia has also launched eDemand auto changeover panels as part of the range for effective control over a wide range of AC speed-controllable twin fans. The changeover panels have been designed to complement the new eDemand controllers and are fully compatible for installation with these products.
The eDemand series of controllers are designed for easy installation, set up and configuration to ensure that ‘down-time’ is kept to the minimum when retrofitting the products. In occupied buildings downtime can be a serious concern for some clients, but with these new controllers a quick start-up can be ensured since each device has pre-programmed modes.
Demand-controlled ventilation is proven to improve efficiency and reduce carbon emissions. This affordable retrofit solution for existing AC fans enables consultants and contractors to help their clients benefit from a combination of good indoor air quality, reduced carbon emissions and lower energy bills.
David Cook is product marketing manager , industrial, with Vent-Axia.
