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Optimise your energy saving this winter

By Gavin Lane
5th December 2019

Why now?

This blog offers facilities managers and energy managers some great technical tips to cut down on energy waste, costs and reduce the overall environmental impact of their assets during Winter.

Firstly, a quick win for facilities teams to reduce energy wastage is to update plant time schedules to account for office closure over this period. Further technical tips are discussed below.

Is your heating system operating effectively?

  1. All scheduled maintenance has been completed.
  2. Ensure an effective boiler control strategy is in place. For example, lead boiler enabling when common flow temperature is 70°C and lag boiler enabling when temperature drops to 65°C.
  3. For further control, compensate boiler flow temperature setpoint based on outside air temperature (OAT). For example, 70°C at OAT = 5°C or below, and 60°C at OAT = 15°C or above. The flow can be reset higher for DHW pasteurisation routines when needed.
  4. Where boilers have their own time schedules, ensure these are in line with building occupancy.
  5. For demand led heating ensure that there are no demand signals causing the heating system to activate outside of normal operating hours or in frost conditions.
  6. Check the frost control strategy – ensuring primary and secondary setpoints are suitable and that frost sensors are operating correctly. If AHUs need high frost protection set points (above 5°C) then a review may be required.
  7. If not already in place add in a demand hold off strategy on FCU circuits as spaces are often too warm by the afternoon, even on cool days.

Are your chiller controls correct?

  1. Ensure outside air temperature hold offs on chillers are correct to avoid unnecessary cooling (usually around 10°C).
  2. If the difference in temperature between chiller flow and return temperature is less than 1.5°C, review chiller and pump control strategies, scheduling and hold-offs to ensure it is operating efficiently.

Are you optimising your ventilation system?

  1. Ensure dead bands are wide enough (+/- 1°C) to avoid heating and cooling systems fighting each other.
  2. If AHU supply air temperature is compensated, ensure compensation curve ranges are suitable for requirements in the building.
  3. Ensure Optimiser parameters are appropriately set to ensure spaces are sufficiently conditioned for the start of occupancy whilst also not coming on too early. Consider setting optimiser controls to a dead band set point that is between 21°C and 22°C. Optimiser control strategies are often complex and can lead to heating and cooling plant being brought on earlier than required to deliver to specific temperature set-points. Carbon Credentials’ Building Analytics and engineering support can help to identify issues by reviewing current operation, specifying optimiser control strategies and supporting implementation and monitoring to ensure optimum performance.
  4. Check filters in AHU’s. Clogged filters lead to decreases in energy efficiency and potential damage to mechanical systems.

Are the following checks included in your walk-arounds?

  1. Keep windows and doors closed when the heating is on to avoid heat loss.
  2. Check for passing valves (leakage) on heating and cooling coilsThis blog offers facilities managers and energy managers some great technical tips to cut down on energy waste, costs and reduce the overall environmental impact of their assets during Winter. for main AHU’s and FCU’s. Passing valves affect the system’s ability to reach floor temperature set points and lead to unnecessary energy consumption.
  3. Check that Thermostatic Regulator Valves (TRVs) on radiators are working correctly and set to maintain a reasonable set-point.
  4. Investigate comfort condition complaints as these may be due to faulty equipment or drafts. Carbon Credentials can assist by providing an investigation checklist.