Fan coil upgrades: Benefits of modern motors

In the case of occupiers or facilities managers in buildings with relatively old fan coils that rattle and squeak and begrudgingly go about their business, what can be done? By using modern EC motors, upgrading fan coils has become eminently possible, practical and worthwhile. In fact, the biggest problem sometimes, is simply knowing where to start. Clearly, an expert is required.

The programme will begin with a survey to gauge product viability, possible upgrade options, cost verses life extension and potential energy savings. Style and origin of the existing fan coil stock are not important since the latest EC fan and motor technologies fit the majority of AC units, irrespective of manufacturer and age. 

To start with, the old fans will be removed and replaced, including the fan deck if necessary, and inefficient transformers and speed switches replaced with a simple potentiometer. Air volumes will be reset to original design volumes or, if they are not available, a reference air volume will be taken before changeover and once installed, the new fans will be set to the same volume – simple. At this point, the new technology employed, will have halved the electrical consumption of the original fan coil motors.

A Variable Air Volume (VAV) system may be introduced, requiring fitting an additional VAV controller to adjust the fan speed/air volume according to thermal demand. If the units need to work hard, the fan speeds will be at design level and if the space is near or at set point, the fans will be at a predefined set back air volume, usually 70% of the design volume. The consequent reduction in air volume will save a further 30% of the original AC consumption making a total saving of 80% at setback. Also, the noise level will be reduced and the length of time between filter cleans extended. 

Experience has shown that the time between filter cleans can be extended by about 33%, so filters cleaned every six months will last for eight. With filters destined for cleaning (or replacement) 20 times over the following 10 years, this figure reduces to 15, a substantial saving in installations with hundreds of fan coils. Furthermore, since the VAV control device will always sit apart from the original waterside control system, it is immaterial whose controls were originally installed because the feature operates autonomously. 

Replacing all valves and controls on a project is possible but rarely viable from a cost/benefit perspective. However, if only a few valves require attention this can be dealt with. If on occasions, it is not possible to replace like with like, a compatible alternative will always be available.

With fan coil development advancing at a frenetic pace it is clear that new technology could bring many benefits to older fan coil stock. Also, a challenge looms whereby the technology currently applied, is becoming so specialised that facilities teams will stand little chance of keeping abreast with all the features of the equipment in their buildings

Current energy standards demand careful designs using the best, although  not always the cheapest products, but it would be wrong to prevent quality design effort from realising its full potential because modern buildings are not properly looked after.

If a fan coil has a 20 year life span and the UK 'consumes' 60,000 UK manufactured fan coils per year in that time, a million plus fan coils will be in use with many approaching or well past their planned lifetime. Many will be replaced completely but EC/DC technology has opened up new opportunities where money, time or disruption demand an alternative solution.