A controller , comprising: a housing , wherein the housing includes: a housing body that includes an enclosed compartment containing control and communication electronics, and a wiring compartment ; and a housing cap attached to the housing body to enclose the wiring compartment ; at least one terminal block positioned within the wiring compartment that provides one or more connection points for wiring , the at least one terminal block electrically couples the control and communication electronics within the enclosed compartment to the one or more connection points; and at least one cover attached to the at least one terminal block , wherein said at least one cover is formed from an electrically insulating material and covers connection areas of said at least one terminal block ; characterized in that : - said housing cap is removably attached to said housing body ; - said at least one cover is removably attached to said at least one terminal block and is flexible, so that it can be flexed to slip over said at least one terminal block ; - and said at least one cover includes a cover surface and a plurality of sidewalls extending from the cover surface , wherein said plurality of sidewalls are deflectable outwards through application of a force and are resilient and rebound to a rest shape after removal of the force, so that said plurality of sidewalls exert a retaining force on said at least one terminal block in the rest shape to retain said at least one cover in place on the at least one terminal block (214, 216.). a housing , wherein the housing includes: a housing body that includes an enclosed compartment containing control and communication electronics, and a wiring compartment ; and a housing cap attached to the housing body to enclose the wiring compartment ; a housing body that includes an enclosed compartment containing control and communication electronics, and a wiring compartment ; and a housing cap attached to the housing body to enclose the wiring compartment ; at least one terminal block positioned within the wiring compartment that provides one or more connection points for wiring , the at least one terminal block electrically couples the control and communication electronics within the enclosed compartment to the one or more connection points; and at least one cover attached to the at least one terminal block , wherein said at least one cover is formed from an electrically insulating material and covers connection areas of said at least one terminal block ; - said housing cap is removably attached to said housing body ; - said at least one cover is removably attached to said at least one terminal block and is flexible, so that it can be flexed to slip over said at least one terminal block ; - and said at least one cover includes a cover surface and a plurality of sidewalls extending from the cover surface , wherein said plurality of sidewalls are deflectable outwards through application of a force and are resilient and rebound to a rest shape after removal of the force, so that said plurality of sidewalls exert a retaining force on said at least one terminal block in the rest shape to retain said at least one cover in place on the at least one terminal block (214, 216.). <EOS>