Last edited 05 Jul 2021


An optimiser is a control system employing an optimum start algorithm.

Optimum start is: ‘…a control system or algorithm which starts plant operation at the latest time possible to achieve specified conditions at the start of the occupancy period.’

Optimum stop is: ‘…a control system or algorithm which stops plant operation at the earliest possible time such that internal conditions will not deteriorate beyond preset limits by the end of the occupancy period.’

Ref Non-domestic Building Services Compliance Guide For Scotland, 2015 Edition v1.1, published by the Scottish Government, Building Standards Division in April 2018.

The Illustrated Guide to Mechanical Building Services, Third Edition (BG 31/2017), by David Bleicher, published by BSRIA in 2017, describes an optimiser as: ‘…a time switch which can control the length of time needed to pre-heat a space before the start of the occupancy period. It does this by measuring the internal and external temperatures and calculating the point at which the heating plant needs to be switched on. The advantage that optimisers have over conventional time switches is that excessive pre-heating during mild weather is avoided and energy is saved. In practice, the optimiser is usually combined with a compensator in a single unit.’

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