Tackling the power challenges of the smart home
Alan Beale understands the smart home. He installed a security system, with remotely-accessed cameras both inside and outside of his holiday home in Cyprus. He ran the camera data through an EtherCAT system with networked devices, instead of the home’s existing CAT5 system or unstable Wi-Fi. But the challenges to the smart home system reliability actually came from the power system.
The cameras started to malfunction, some worked while others didn’t, and the reasons for this were unclear. Suspecting the problem might be the power supply, Alan called an electrician to examine the issue. It took two days to understand the problem.
Eventually, they realised that the only other power-related change to the house had been its swimming pool heater system. The previous, failing system had been replaced with a new inverter-based phased heater, which saves electricity by varying the speed of the current. The pool heater worked fine, but the inverter was causing harmonic interference in the mains cabling. This was affecting the security cameras.
“In hindsight it was obvious,” said Beale. “We switched the heater off and the cameras started working. The problem was more difficult to spot because there’s a three-phase electrical supply to the house, to power the air conditioning and so on. It would have been more obvious with a single-phase supply.”
Nevertheless, Alan was unsure how the interference problem could be solved across his smart home. “I was worried that I’d have to send the pool back and go with a non-inverter system. They are hefty pieces of kit, around 100 kilos, and can cost around £4,000,” he said.
Instead, he contacted filter developer REO in the UK, which recommended the CNW 541 single-phase mains electromagnetic compatibility (EMC) low-pass filter. The EMC filter allows the mains frequency to pass through with very little attenuation. The inverter on the pool system caused EM noise, so using the CNW 541 on the input of the inverter would reduce these emissions and clean up the supply.
“Even though Alan’s problem was a very specific one that not many people have encountered, REO’s team was quickly able to identify the best solution. They also sent him a whitepaper, about how inverters can cause power issues with ethernet over a mains supply, to help him further understand the issue,” said Steve Hughes, managing director at REO.
“Big inverter systems are not commonly used domestically but are creeping into things like swimming pool heating systems and renewable generating systems. The CNW 541 was best suited, as it’s commonly used in industrial electronics or engineering applications.”
REO also suggested that Beale install a CNW901 choke, alongside the EMC filter, to handle the substantial single-phase maximum current generated by the heater upon startup, which sometimes exceeds 25A. The CNW901/35 supports 35 A for a bigger safety margin without a huge difference in cost.
“The installation couldn’t have been simpler and took half a day. A couple of queries were solved by following the drawings of installations on REO’s website. As soon as the filter and choke were connected, the problem was solved,” said Beale.
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