Schedules, setpoints and manual mode: where controls waste money

The site's operating hours have changed, but the ventilation still starts as before. A pump has been left in manual mode after servicing. In one office, cooling is compensating for excessive heating.

This does not necessarily require a new platform. First, it is worth checking whether the existing controls meet current requirements. Building re-tuning involves precisely this: identifying operational problems through BAS data and adjusting controls. ¹

An extra hour is a measurable cost

Consider a ventilation system drawing 6 kW of electrical power. Assume analysis has confirmed that two hours of operation each day are not needed for occupancy, preparing the premises or other essential tasks.

Over 250 such days, the reduction in fan energy consumption is:

Δ E=6×2×250=3000 kWh

If the baseline consumption of these particular fans was 18 000 kWh over the same period, the calculated change is 16,7%. This is not 16,7% of the whole building's consumption. Heating, cooling and other loads are not included in this example.

The key condition is that these hours really are unnecessary. Switching off required ventilation cannot be called a saving.

Morning start-up should prepare the building for occupants

Starting at 6:00 may be necessary in freezing weather but unnecessary in mild conditions. The schedule should distinguish between the start of occupancy and the time needed to prepare the system.

The Optimal Start function in a conventional BAS can determine the required start-up lead time from zone temperatures, weather conditions and the rate of temperature recovery. PNNL describes this alongside the need to configure the operating calendar correctly. ²

We would therefore check the existing functions first, rather than sell external AI for a task the controller can already perform.

A manual override should not remain active without explanation

An operator temporarily forces equipment on. Later, the schedule issues a stop command, but the higher-priority manual override remains active.

This may be normal priority behaviour, not a fault. The Metasys documentation describes manual overrides, temporary overrides and command release separately. The manufacturer also warns that clearing priorities in bulk can produce an unexpected state. ³

We would provide a visible list of active manual overrides, showing who applied them, why and for how long they are permitted. If the platform supports temporary overrides, these can be used according to agreed logic. Emergency or protective actions must not be cancelled automatically under the guise of returning to the schedule.

Heating and cooling should share a common control logic

For conventional temperature control in a single zone, setpoints, transitions and the deadband where neither heating nor cooling is required should be coordinated. Unnecessary simultaneous heating and cooling is one of the optimisation opportunities considered by PNNL. ²

However, not every instance of simultaneous operation is a fault: other zones or a dehumidification process may have legitimate requirements. First establish the cause, then change the control sequence.

Do not simply add independent percentages

If we have already removed two operating hours, the next calculation of fan speed reduction must apply only to the remaining hours. Otherwise, the same energy will be counted twice.

After changing the schedule, check not only consumption but also indoor conditions at the start of occupancy. Success means meeting requirements at lower cost, not simply shortening operating hours.

Sometimes the least expensive upgrade does not start with a new control panel. It starts by restoring clear, up-to-date logic to the panel already in operation.