Electric Heat Air Handler Wiring Diagram - HTR, BTDR, EHR, 60A Breakers

This document is a schematic wiring diagram for an electric-heat air handler / evaporator unit (HVAC equipment), not an automotive wiring diagram. It shows a low-voltage field connection box with a thermostat terminal board (R, C, W1, W2, E, OT1, OT2, OT3), a control transformer (TR), four electric heater elements with thermal limits (HTR1–HTR4 TL), sequencer/relay contacts (M1–M8, R1), a blower time-delay relay (BTDR), an electric heat relay (EHR), and the evaporator motor (EM) with its run capacitor (RC). Evaporator motor lead colors are identified: purple = common, black = high speed, yellow = low speed. Power distribution shows two banks of 60A circuit breakers (positions 1–4) with jumpers for single-circuit power supply, line-in connections, branch circuits, and instructions for copper or aluminum power supply wiring with equipment grounds. Five installation notes appear along the edge (partially cut off), covering line splices, purple wire connection, time-delay relay placement, composite low-voltage wiring, and optional wiring changes at W1-W2. A footer states controls are shown with utilities on and thermostat off, and that replacement wires must be 105°C rated and sized per national code. Wire color codes (PK, BR, BL, BK, PU, Y, G, R, W) are marked throughout the schematic.