AO Smith HZ311 True ZONE Zone Control Panel, 3-Zone, 8.12 Inch H x 8 Inch W x 1.86 Inch D, 24 V, 50/60 Hz, 6.25 VA, Push Button Terminals, -20 to 150 deg F, Gray • Robust push terminals • Common-sense LE Ds • Clean, professional installation • Smaller footprint • Variable speed fan control • 18 - 20 ga solid wire • For true zone systems Application: For conventional, single stage applications up to 3 zones(1h/1c)