An array of solutions under HTM 03-01

Hospital ventilation systems

HTM 03-01, published in June 2021, offers detailed advice on hospital ventilation systems. Amongst the technical requirements around maximum coil/filter velocity, spare motor or fan sets, and so on, the top level concerns may be summarised as capital and running costs, comfort for patients, noise, reliability and routine maintenance, and life expectancy.

And stepping back from the technical detail, one must note that the requirements are complicated, and the specification is open to interpretation in many areas.  Indeed, interpretation of the spec may be queried by whoever signs off the design of the system – and this person may be different from the original consultant.

We all know that every project is different and that design specification and manufacturing require a flexible approach, ideally based on extensive experience of similar scenarios.  Let’s look at a specific example.

Run and standby

As you know, ventilation units originally had belt-driven fan assemblies, made up of an impellor and a motor on a common frame, connected and driven via belts and pulleys.  The pulley sizes were calculated to ensure the fan was running at the correct speed to deliver the required air volume.  

To reduce the risk of downtime, due to snapped belts or motor failure, HTM specification dictates that all fans should be in a “run and standby” format, with two duplicate fan assemblies – should one fail, the other would automatically kick in.  This would then set of an alert, and remedial work could be carried out in a timely fashion, eliminating the potential for missed operations and so on.

The majority of modern fan assemblies are direct-drive “plug fans,” with the motor being directly attached to the impellor and speed controlled via an inverter.  These are more efficient, as there is no power loss through the belts/pulleys – but also will not fail due to a snapped belt, as there are no belts.

Therefore the only potential issue is motor failure, which is very rare but does occasionally occur over time.  In this case, the question should occur to the specifier: why stick blindly to the spec and have “run and standby,” when you could have a whole array of smaller fans doing the job?

To get a better and more detailed understanding of VES Healthcare premises ventilation, you can view the Healthcare premises brochure.