Energy Management

HORSES FOR COURSES

In these belt-tightening times Adrian Barber looks at the individual benefits of Local control versus a Building energy Management System for controlling heat in multi-occupancy dwellings.

The energy crisis has brought into sharp focus the need to cut consumption of energy. Everyone is feeling the pinch, but for organisations that provide rooms in the form of Purpose-Built Student Accommodation (PBSA), Halls of residence or Homes of Multiple Occupancy (HMOs) the issue is multiplied. The reason being that a lot of this accommodation includes energy costs within the rental price.

Unless constructed in recent years, many buildings use antiquated heating controls, if any! Storage heaters, simple on/ off panel heaters or wet heating systems with no meaningful radiator control are, remarkably, still common place.

PBSA has addressed some of the issues, but in our survey work, we still come across rooms where corners have been cut to save on build-cost and control is simply not effective.

For Managers of these premises their quest to reduce energy consumption is nigh on impossible. They have no metrics, insight, or control!

The two methods I am comparing here are, Local and Central Control.

Both fundamentally do the same thing: They reduce unnecessary use of energy by controlling the heat input available to the room occupant.

A default temperature is set that maintains a comfortable environment. If the occupant requires more heat, they press for a boost which raises the temperature for a period. When this time elapses, the control reverts to default. If a room is unoccupied for a longer spell, heat input is reduced further until the occupant returns. If windows or doors are opened, heat input is also reduced until they are closed. So, what are the criteria to consider when choosing between Local and Central control?

SIZE MATTERS

Both options are suitable for large sites, However, for those with fewer than 50 rooms, Local Control is the cost-effective option. All that is needed is one Control Unit per room and one Programming Handset per site.

Central Control becomes viable for 50+ rooms where the additional features and remote access are more advantageous.

INSTALLATION

The installation of a Local Control Unit requires connection via a double pole isolator to the heat source. Units can arrive pre-programmed and set to work immediately.

Central Control is a similar process within the room, with the addition of a Power Unit. However, Master and Secondary Interface Units (MIFU and SIFU) are required for communication. Data is transferred to and from room units, MIFUs and SIFUs via the buildings existing electrical circuit, a process known as Mains Borne Signalling (MBS). This negates the need for lengths of data cabling and makes installation expeditious.

FEATURES

Local Control manages heat input to rooms. Models with PIR Absence detection will make greater savings. A 2-event per day 7-day programmer enables automated on/off use and Opti- Start will bring a room to temperature at a scheduled time by learning the thermal dynamics of the space. This is all programmed on each Control Unit with the dedicated infrared handset. Both systems automatically reduce input if windows or doors are opened, without the need for external sensors. And both are tamper-proof.

Central Control does all the above, but remotely. In addition, the system collects data from each room. Humidity, Light, Sound pressure and CO 2 can all be monitored, water heating can be controlled, and leaks detected.

Signals are sent in both directions with MBS, therefore additional equipment such as water Shut-off Valves can be instructed to close if leaks are detected.

COLLECTION OF DATA/MANAGEMENT REPORTING

The adage ‘if you can measure it, you can manage it’ rings true with Central Control. All Data transmitted on the system is displayed on the secure portal and viewed on any internet connected device. This provides Managers with complete remote access to adjust

profiles for individual rooms, monitor environmental conditions and measure energy use. Management reports are easily produced and downloaded. This is not available with Local Control.

TRAINING, MAINTENANCE AND FUTURE PROOFING

Both systems are intuitive and require only basic training to programme.

Having a separate Control Unit and heater means wet or electric systems can be controlled. Also, if either unit develops a fault, the replacement is cheaper, quicker, and less impactful on the environment.

Both options are software based and therefore are upgraded when new features or settings are developed.

SAVINGS

Depending on location, building type and previous control methods, Local Controls typically save 30%. While 40% is not uncommon with Central Control, particularly when water heating control is part of the system.

BACKING A WINNER

In this two-horse race, circumstances will dictate the appropriate solution. However, significant savings, ease of use and installation mean the investment will certainly pay out. And, with energy prices on their current trajectory the pay-back period is reducing month on month! www.prefectcontrols.com