Spring is already upon us and with it comes a great opportunity for achieving energy efficiency and improving tenant comfort. Outside temperatures are slowly increasing and occupant behaviour will start to change  as warmer days become more frequent.

Buildings themselves will also start to change. Less thermal heat will dissipate from the building envelope overnight and as the days get warmer, more thermal heat is absorbed during the day. The challenge for facility managers is to anticipate the changes in building performance, while not adversely impacting tenant comfort.

Reducing heating and cooling conflict and maximising free cooling are the key to achieve success.  Here are three things you can do right now to improve building performance and tenant comfort using real-time BMS analytics data and Buildings Alive’s daily REF message to detect abnormal operations and identify tuning opportunities which will balance energy efficiency and tenant comfort outcomes

Chiller lockout temperature

Chiller lockout can restrict the chiller(s) to trigger if there is a false or low cooling demand from the VAVs which often results in energy waste and chiller short cycling. This technique depends upon increasing or decreasing the lockout temperatures.  The example below shows how do different chiller lockout temperature SP make difference to the energy profile.

The first figure below shows which the lockout temperature set to 17C the chiller is short cycling due to low cooling demand from the building (left hand side). By increasing the lockout temperature to 18C the chiller short cycling was eliminated (right hand side), thereby achieving energy savings and smoother operation.

Detect issues with economy cycle control

Utilising outside air during spring season can effectively reduce chiller plant operating hours and maintain good CO2 level within buildings. Here we demonstrate an example of using BMS data to detect abnormal economy cycle control. From the first figure above. We can see this AHU wasn’t fully utilising its free-cooling capabilities, as the cooling valve was open but outside air damper was staying at its minimum position. We recommend performing the following process after detecting the issue:

  • Confirm and fine-tune the economy cycle lockout temperature (or enthalpy) setpoint to fully capitalise on free cooling with outside air.
  • Perform a visual and functional inspection to determine the operating condition of critical equipment such as stuck dampers, faulty sensors or disconnected actuators.

The second figure above shows how was the data graph looked like after the issue was fixed. The morning free cooling is now fully utilised which greatly reduced the cooling load in the morning.

Review optimum start/stop times

An optimised building starts its cooling cycle so when the first tenants enter the building it has just reached its set point. Cooling the building too early results in unnecessary energy wastage. The same is true for the close of the business day, whereby the system is optimised to automatically turn off as needed.

To ensure you have the right start and stop times review the  historical zone temperature data to identify the optimised start/stop time for the HVAC system. The figure below shows average floor temperature profile on one of the hottest spring day. From this graph we can see that it takes ~ 45 mins for the floor temperature to reach desired setpoint in the morning, and ~0.5 hour to increase half degree before COB. We can then estimate that the earliest start time is ~45 min before the lease time. It is also possible to stop the plant ~30 mins without affecting the thermal comfort.

We have identified three things you can do right now to help improve the performance of your building during spring.  Check your chiller lockout temperatures; make the most of free cooling and optimise your start and stop times. However, there may be more that could be done.

What is your spring strategy? Contact Buildings Alive to discuss your strategy for spring.

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