I have a Mecer 2400VA similar to this in our complex guardhouse that provides backup power to CCTV and the comb intercom (controlling the gate access remotes). This causes a puzzling issue when the UPS is operating as the gate remotes work very intermittently and inconstantly. When the intercom system runs off its own battery or Eskom the remotes work without an issue. It seems the UPS is outputting a RF signal in the 400Mhz band blocking the remote's signal from reaching the intercom box outside.

Would popping a few of these clip on ferrites on to the leads coming from and to the inverter fix this?    

On 2022/06/24 at 3:05 AM, Timbo_vb said:

Would popping a few of these clip on ferrites on to the leads coming from and to the inverter fix this?

I've had little success with them. But it's certainly worth a try.

Suppressing RFI successfully is like a dark art.

31 minutes ago, Coulomb said:

Suppressing RFI successfully is like a dark art.

One part of this art is to always lead both wires of a circuit trough the same ferrite. Otherwise high current might magnetically saturate the ferrite that would nullify its effect. Such ferrites should be applied to all incoming and outgoing lines. Spark suppression capacitors on the terminals might also help.