ENERGY MANAGEMENT & SUSTAINABILITY
OPTIMISING SUSTAINABILITY PERFORMANCE
Shane Leather, Business Development Manager for Tall Buildings, Armstrong Fluid Technology.
Shane Leather, Business Development Manager for Tall Buildings, dfdgggArmstrong Fluid Technology.
When replacing heating, ventilation and air conditioning systems, one of the biggest pitfalls for facilities managers is the temptation to replace ‘like with like’. In the case of pumps (where the useful life may be in excess of 25 years) ordering a direct replacement for an ageing pump involves a serious missed opportunity. Pump technology, particularly pump control capability, has advanced beyond all recognition in the last decade. Embracing these ultra-efficient technologies and approaches can deliver significant reductions in building running costs, in addition to greatly improving the environmental performance and sustainability of the site.
A key area where facilities managers can deliver significant savings is by avoiding installation of unnecessary pump capability. In many commercial- scale premises around the globe, duty/standby pump installations are the norm.
On a day-to-day basis, one pump (sized for full duty) is operational while another of the same size is out of action - simply there to accommodate 100% redundancy in the event of routine maintenance or pump failure.
There are some projects, such as datacentres and hospitals, where only full duty standby will provide peace of mind. In many other applications, however, there are far more sustainable, efficient and cost-effective ways of safeguarding pump operation. Sizing pumps for 100% standby in these low and medium risk projects just escalates first installed and lifecycle costs unnecessarily. It also more than doubles the embodied carbon footprint of the installation, and takes up valuable space in the plant room or energy centre.
The reason why specifiers opt for duty/standby configurations is that they assume that, if you specify two smaller pumps to work in parallel (each sized for 50% of the design flow) this will only deliver 50% of the design flow if one pump fails, or is shut down for routine maintenance. However, this is not the case. The design flow capability from one of the latest generation of pumps is typically around 80% rather than 50%.
This is because the latest generation of pumps, for example the Armstrong Design Envelope (DE) range, are able to cover a wider range of operational conditions than traditional pump models. For very many buildings, the upper level of design flow provided by one Armstrong DE pump model is more than sufficient to maintain effective operation of the HVAC system whilst its opposite number is shut down for maintenance.
28 | TOMORROW’S FM
In reality, the maximum design load of HVAC systems is required very seldom. Research shows that today’s variable speed HVAC systems operate at between just 10% and 60% of design load, for around 90% of the time, irrespective of whether the requirements relate to heating or cooling. So 80% of design flow is more than sufficient to maintain effective operation, if necessary, with only one of the pumps actually in service.
Our analysis of the building load profile for one of our installations in Canary Wharf, London, for example, identified that demand only went above 80% of load on six days out of an entire year. If a pump was to trip on any of those six days, we can see from cooling and heating coil characteristics that approximately 95% or greater output from the emitters would still be delivered at 80% flow.
This approach (based on installing two smaller pumps working in parallel, rather than two larger pumps, sized for a full duty/standby configuration) offers the facilities manager considerable advantages in terms of first installed and lifecycle costs, as well as saving space in the plantroom, and improving the carbon impact of the installation itself. Full duty/standby installations, of course, typically double the embodied carbon for this
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