Optimised start control#
With optimised start control (OSC), you tell the system what time you want the space with the thermostat to be what temperature, and it figures out when to turn the heating on, varying the start time to suit the conditions, learning from experience.
Several of the volunteer engineers for our less occupied venues predict that OSC will cut their venues’ gas use by 25-33%. Optimised start control is less critical for venues that are in use all day, but still a worthwhile feature. It usually costs a few hundred pounds to make the change. Some controls with OSC require a temperature sensor outside the building, and others just use the one on the thermostat by looking at how fast the temperature inside has been changing.
Old and very old boilers
Any boiler can use an optimising control, even if it’s an old on/off boiler. However, heating suppliers are often very reluctant to change the controls on existing boilers. We think that probably the profit margin just isn’t there for them. Electricians who take on a wider range of jobs might be more interested in the change.
Many community buildings have boilers that are at or near “end of life” and this is when heating suppliers show extreme reluctance. We can understand this. If the boiler is likely to fail soon, and does so soon after the control change, the client is likely to blame the supplier. We honestly don’t know whether changing the controls could make the boiler more likely to fail. The boiler will be turned on and off more often than usual, and more quickly, while the new system is being tested.
Unfortunately, different manufacturers use different names for the feature. Proper optimisation is common in modern “smart” controls, and there have been optimising controls for decades now, so it also offered in some traditional systems. Some common controls have optimisation but it is turned off by default. For safety, there will be a hard limit to how many hours ahead the system is allowed to come on, and on some models it will be too short for our buildings. If necessary, it’s possible to program building warmup in stages to get around the limit, but it’s easier and more efficient if you can find a model where the limit is high enough for winter conditions in your venue.
Very occasionally there are models that have a similar sounding feature, but really just have you select a constant amount of warm-up time to use, so read the documentation carefully on your shortlisted models.
It’s rare for controls to use “optimised stop control” to learn when to turn the heating off even though this would be very useful in some of our buildings.
Simpler explanation of optimised start (Heatmiser, one vendor)
Discussion of terminology with names of some controls (web forum)
We give examples of controls, but don’t assume they will be suitable for your building and how you use it - you have to think about the full set of things users can do using the buttons.