Jon Rensink, Safety Consultant at Daniel Connal Partnership’s health and safety arm of DCP Safety & Training, talks to Adrian Barber of Prefect Controls about the issue of hobs being left switched on when kitchens are unoccupied.


John Rensink: What was the motivation for developing HobSensus?

Adrian Barber: Prefect have been involved with student accommodation since 1997, monitoring and regulating temperature in student rooms and saving energy. A customer enquired whether we had a product that would prevent hobs from being left on. It was a growing issue for them. So, we began to formulate a list of requirements and features and took our ideas back to them.

JR: What sort of things were on that list?

AB: Well, such a device would need to be tamper-proof and robust to survive in more challenging environments. Student kitchens aren’t renowned for being the tidiest of places. And, as we know with our heating controls, products can be knocked, pulled, bashed and abused, but must be resilient.

Simplicity of use and ease of installation are also important. It also needed to complement the aesthetic of any kitchen. And of course, the right price-point.

JR: How does it differ from other power cut-off devices?

AB: Most devices are basically timers. The button is pressed and the count-down starts. When the time elapses, the power goes off.

We wanted to broaden the scope so that the hob would always be safe when it was neglected. Whether the time had run out or not. But more importantly, when the temperature approached dangerous levels.

We use a 64-zone sensor in the head unit which monitors the temperature across the cooking surface. When it reaches 280°C in just one of those zones the unit enters trigger mode. An audible warning sounds, and amber LEDs flash. If no one reacts to this, and the temperature continues to rise, the beeping becomes more intense and the LED changes to flash red for a short time before cutting the power – making the hob and the kitchen safe.

JR: But if the timer turns off after 15 minutes, couldn’t a lot of damage already be done?

AB: No, because if the temperature reaches dangerous levels before the timer runs out, the Sensor will have already cut the power.

 JR: For such a clever device, is it easy to operate?

AB: It’s as simple as pressing a button. The LEDs start to flash green, showing the hob has power. The hob is then just used as normal.

We wanted to broaden the scope so that the hob would always be safe when it was neglected. Whether the time had run out or not. But more importantly, when the temperature approached dangerous levels.


JR: …and is it straight-forward to instal?

AB: There are two units. The Sensor Head is mounted on the wall, centrally, 600mm above the hob. The Power Switching Unit is connected between the hob isolator and the hob. It could be on the wall or below the worktop in a cupboard. A low voltage cable connects the Power Unit to the Sensor Head. Where this is impractical, because of splashbacks etc. the Sensor Head can use batteries. The two units communicate via Bluetooth. It usually takes a competent electrician about 45 minutes to fit.

JR: What about maintenance and servicing?

AB: A wipe over of the sensor with a damp cloth every now and then, will remove grease and dust that inevitably accumulates above a hob. Apart from that, if needs be, changing the batteries every couple of years.

JR: It sounds like HobSensus could be useful in every kitchen, but where are they mostly used?

AB: There are a lot in student kitchens, but enquiries from care homes, assisted living and social housing, and holiday lodges are also on the rise. We’ve sold quite a few to the domestic market, to carers and relatives of people who are elderly, or maybe living with dementia.

JR: Have you had feedback from customers?

AB: People who use HobSensus daily say they soon get used to it. Landlords and managers of accommodation seem happy, it gives them peace of mind that they are doing all they can to make their kitchens safer. Most importantly, there haven’t been any incidents in the kitchens where HobSensus is installed.