How to satisfy thermal preferences for minimum energy

Satisfying thermal preferences for the minimum amount of energy equals happy students and happy energy managers

Prefectirus – the centrally controlled energy management system from Prefect Controls, has been installed in 500 plus rooms within the halls of residence at Oxford Brookes University.

Finding the right solution

Gavin Hodgson, Oxford Brookes Energy and Carbon Reduction Specialist, knew exactly what he wanted when tasked with replacing the ageing and failing heating systems at The University’s Crescent and Warneford sites. He had envisioned the solution and was carrying out exhaustive research to see if there were companies manufacturing the solution he required, when he happened upon Prefect Controls as a result of a web search.

“ I was actually a bit disappointed when I found Prefect’s solution,” he confides, “as I had come up with the same idea, but they got there first! I suppose faced with the same issues you are bound to arrive at the same destination. A lot of work has gone into Prefectirus and there is unique intellectual property in it. Other companies may be looking into a similar system but no one has got there yet, there is so much technical development behind it. All our systems team like it because it works and it’s very, very good.”

Oxford Brookes looked at a number of refurbishment alternatives. They could have converted to a wholly ‘wet’ scheme or chosen a Building Management System, but time, cost and disruptive installation were considerations that made choosing Prefect easy – ‘Our best option was to stick with electric heating but try to get better control.” Gavin continues, “What I was interested in was the approach of an occupant-led heating system. Taking away one central controller and having individual controls in every single room. While still being able to provide some boundaries to the heat levels – basically Prefect were the only ones that could do it. We could have gone for a traditional BMS style approach, but it’s not cost effective because we would have had to put in Cat 5 network cabling to all the different controllers and it would have meant digging through walls, suspended ceilings being moved and so on.”

Easy, quick and cost effective to install

The use of Mains Borne Signaling was key to Prefect being chosen. Mains Borne Signaling uses the existing electrical wiring within a building to link the central controller to the nodes in the rooms that control the heat emitters and the water tanks, saving time and money and making installation quick and cost effective with little disruption to infrastructure.

“The project could not have progressed without Mains Borne Signaling, there were no wiring costs for us, we just put it in and it communicates through the electrical wiring. The alternative would have meant going with a BMS with remote controllers but it was Prefect’s solution of using Mains Borne Communication that allowed the refurbishment to go forward financially.” Gavin adds.

Complete visibility

Installing Prefectirus means that energy managers can effectively watch energy usage in every room 24/7 and set each one individually from central control, without the need to step inside any of the rooms. Occupiers have control over the temperature of their space and are able to adjust it to preferred levels within predetermined parameters.

“One of the surprising things is that by giving students the control we find that many turn down the heat from the default setting, this is a saving that we would never have seen if we only had a central control with each room set at 21 degrees. We would be ignoring that potential for savings. Some people are comfortable and prefer lower temperatures and indeed some people prefer it a little higher as well, like some of the overseas students, so it gives us more ability to – a phrase I’ve coined is – satisfy their thermal preferences for the minimum amount of energy. – That’s the kind of ethos that’s in place.”

People think they [the occupants] will just waste electricity if we just give them free reign, because they don’t pay for their utilities, here it’s all included in the rent, but it’s not true, they use it sensibly. You can see, on the Prefect system, each day in each room when it’s going on and off. Another side benefit of having a temperature sensor in each room is that you can police and detect when rice cookers are being used, if people are cooking in their rooms and they shouldn’t be or people have smuggled in an additional electric heater that they shouldn’t have, we can see that and then go in and investigate.”

Making money from a heating system?

Gavin is running a number of tests on the system to analyse the savings brought by the installation, but one of the bonuses he wasn’t expecting was to be paid by National Grid for allowing them to access water heaters through Prefectirus with the help of Open Energi – a service known as Demand Side Response.  

He explains, “The Open Energi system is technically just another control box, none of our heating programmes get over ridden, but for short durations (30 seconds now and then) when the national grid need it, the Open Energi box temporarily turns off or on the heating elements in the hot water cylinders, the students don’t notice because we have a stored volume of hot water, we have put in some protection, so if we know one cyclinder is very cold it will just ignore that one. It aggregates all of the different cylinders so that we can help the grid to even out some of the peaks and troughs in the voltage and the good news is they pay clients for this access.”

“We are playing our part in the bigger picture and also it is so easy for us to implement, all we need to do is have this new control box fitted alongside Prefectirus and meters attached near our main in-comer and then Open Energi do all of the work for us. We have had a trial to make sure that this works, but other than that what is the issue? It’s all just win win really.”

For more information about Prefect’s unique, centrally controlled energy management system visit