We replaced our 20 yr old Daiken R/C A/C for a new 18kW Daiken 'Inverter' type R/C A/C a year ago, I discovered this new A/C is very noisy on HF bands, particularly across 7 MHz and 18 MHz, the new Inverter type A/C are more efficient at heating and cooling, however, the tradeoff is that the external compressor unit is radiating RFI (Radio Frequency Interference) and EMI from either the Inverter Power supply or the DC fans. It's bad enough dealing with RFI from damned solar panel Inverters, but at least dealing with a RFI source in my own place is easier than solar panel Inverters on someone else's roof.
The main times we use this A/C is in middle of winter and summer. At first I did not suspect the RFI was coming from the A/C, as if I switched it on or off, I would not see any change to the RFI at the HF receiver, as I discovered after many attempts, that there was a delay of a few minutes, i.e you switch on, the compressor unit it does not come on instantly and when you switch off, the compressor does not stop instantly. It took a while to catch on that it was indeed the A/C unit. Then I did various tests to determine from which end of the system, the internal blower unit or the external compressor unit was creating the RFI, it was pretty easy to determine it was coming from the external compressor unit. I remembered the A/C installer saying these are all Inverter type systems. That triggered my memory about friends working in commercial radio comms saying they use these Inverter A/C systems out on remote comms sites to cool the equipment in the comms sheds and that they create RFI. Now, I at least knew that the external compressor unit looks like the place where the Inverter Supply is located, or whatever is generating RFI hash is in the external unit.
I did a search on Google to see if anyone else discussing this type of issue and to see if anyone had some good ideas to fix it. For myself, I presuming I need to make use of some ferrite cores in the right place to knock down the interference. Found someone discussing his issue with his Fujitsu Inverter A/C system, so definitely a common issue. Plus some videos and a white paper on the topic. The Mitigation video gives the detailed technical understanding the issue and solutions.
Fujitsu inverter air conditioner radio interference - Fixya
Application_guide_aspects_of_electromagnetic_compatibility.pdf (abb.com)
Ruud Air Conditioner (HVAC) Radio Interference - YouTube
Mitigating Residential Heating, Ventilation and Air Conditioning (HVAC) RFI - YouTube
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.