To eliminate line noise from the RSH controller first check that the controller is connect to a good Earth ground. We also recommend that a noise filter be placed on the incoming AC power line near the C11 or C11 controller.
Misumi offers a noise filter that will work to reduce the noise on the AC line for most applications. The Misumi part number for this filter is EXRS-NF1.
If this filter doesn’t reduce the noise on the AC line sufficient for your application. We recommend that you add a 0.5 kW to 1 kW line isolation transformer. This transformer is readily available from an electrical supply house.
See Tech Notes RS-11-001: How to Reduce AC Power Line Noise from the C11 & C11 Controllers.