Modular pool/spa control system

A control system for a pool or spa installation, comprising:

• a housing mountable at a pool or spa installation, the housing including a high voltage compartment and a low voltage compartment;
• a processor positioned in the housing;
• a WiFi transceiver in communication with the processor and positioned in the housing;
• a relay positioned in the housing and controlled by the processor, the relay connectable to a power line that provides power to a first pool or spa component;
• a printed circuit board;
• and
• an RS-485 transceiver positioned in the housing and controlled by the processor, the RS-485 transceiver connectable to a second pool or spa component,
• wherein the relay is positioned in the high voltage compartment, the RS-485 transceiver is positioned in the low voltage compartment, and the processor (i) controls operation of the first and second pool or spa components in response to a control command received by the WiFi transceiver, and (ii) receives control commands from a power company on a demand side during a peak demand period, and
• wherein the processor, the relay, and the RS-485 transceiver are provided on the printed circuit board.