This SMC Chiller INR-497-001 has these temperature control\units for each of the two chillers. Note that the SDC20 part is very common and cheaply available on E-Bay for example but you have to pay attention to the exact part number to make sure it will work in your system. Examples are.

Part #C205GA00201 – Not Compatible

Part #C205GA006D1 – Not Compatible

Part #C206DD00201 – Compatible

Part # C206DA00601 – Not Compatible

Part #C200DA00601 – Not Compatible

In summary, pay close attention to these part number when looking for replacements. We learned the hard way that they are not equivalent.