The Square D 8501XB40 Adder Deck expands a Harmony 8501X control relay to provide four additional normally open contacts. Designed for use with 8501 Type X relays (NEMA-style control relays), it uses screw-clamp terminals to accept copper conductors (AWG 18–12) and carries four standard contact cartridges configured as 4NO. The add-on deck adds four NO contacts to the base relay, enabling extra control circuits without replacing the main 8501X unit. It is rated for up to 10 A resistive at 600 VAC and features four standard contact cartridges for easy integration into industrial control panels.
