Complete Wiring Guide for Supco Hard Start Kit Installation
Install the auxiliary relay module across the compressor’s run and start capacitors, following the LRA (Lock Rotor Amps) rating specified on the motor’s nameplate. Most aftermarket boosters require two connections: one wire to the common (C) terminal of the run capacitor and a second to the hermetic (H) terminal on the compressor. Verify the booster’s voltage rating–125 VAC units are incompatible with 240 VAC systems.
Remove power at the disconnect switch before attaching the booster. Use a multimeter set to ohms mode to confirm zero continuity between the booster’s leads; any reading above 0.5 Ω indicates internal failure. Connect the first lead directly to the start capacitor terminal–not the relay post–and crimp with a 16-14 AWG ring lug. The second lead must attach to the compressor’s common winding terminal, typically marked “C” or left unlabeled on single-phase motors. Avoid looping wires around posts; secure with a 1/4″ screw and lock washer.
Reapply power only after verifying the booster’s red indicator LED illuminates within 1.5 seconds of compressor activation. If the LED remains off, reverse the two leads–polarity is critical but often miswired. Monitor current draw with a clamp meter: LRA should spike then settle below 70% of nameplate FLA within three seconds. Failure to stabilize indicates incorrect booster sizing or a defective run capacitor, both requiring replacement.
Ground the booster’s metal casing to the compressor’s ground lug using a 12 AWG green copper wire. Ensure no bare wire strands contact live terminals–not even insulation–to prevent arcing. Label each connection with heat-shrink tubing: black for common, yellow for start capacitor, and red for compressor terminal. Photograph the final layout for reference during future troubleshooting.
Installation Guide for Relay-Based Compressor Activation Modules
Connect the potential relay’s line terminal to the compressor’s common (C) terminal using 14-gauge wire rated for 30A. The start capacitor lead must attach directly to the relay’s S terminal, while the run capacitor connects to the M terminal. Verify phase sequence on single-phase 230V systems–reverse leads if the compressor fails to engage within 3 seconds. Installation requires a torque wrench calibrated to 12-15 in-lbs for terminal screws to prevent arcing.
Use this reference for model-specific connections:
| Model Series | Recommended Capacitance (µF) | Voltage Tolerance | Max Ambient Temp (°C) |
|---|---|---|---|
| SCR9L | 88-108 | ±10% | 70 |
| SRC4P | 147-180 | ±5% | 60 |
| SCR22 | 216-250 | ±8% | 65 |
Troubleshooting Relay Failures
If the compressor hums but doesn’t start, measure resistance across relay contacts–values below 0.5Ω indicate contact welding. Replace immediately if the relay draws more than 1A during activation. Check for voltage drop across the start capacitor; readings above 2V during operation signal imminent failure. Always discharge capacitors through a 20kΩ resistor before servicing to avoid arcing injuries.
For 3-phase systems, bypass the relay entirely–direct-wire the auxiliary capacitor bank to the motor’s start winding. Use a current-sensing switch set to 150% of full-load amps to disconnect start components once the motor reaches 75% speed. Secure all connections with heat-shrink tubing to prevent moisture ingress in high-humidity environments.
Installation Locations for Boost Capacitors Across Compressor Types
On Copeland scroll compressors (models ZR, ZP, or ZF), connect the auxiliary relay directly to the compressor’s terminals–specifically the common (C) and start (S) posts–ensuring the thermal protector remains undisturbed. Avoid mounting the device on the discharge line or near refrigerant inlet valves, as vibration can loosen connections over time. For older Hermetic reciprocating units (e.g., Tecumseh AE or Embraco EG), position the relay on the side panel close to the compressor shell, but route wires away from high-temperature exhaust tubing to prevent insulation degradation.
Carrier and Bryant single-phase units with 30Hz–60Hz motors (like the 06D series) require the relay to be secured to the compressor’s electrical box cover using the provided adhesive pad or a #8 sheet metal screw. Wire polarity isn’t critical, but failure to keep contacts within 6 inches of the compressor housing may result in nuisance tripping of the overload protector. For Emerson Climate Technologies’ tandem scrolls (e.g., ZXT models), split the relay’s output leads–one to each compressor’s start terminal–while ensuring both run capacitors remain in parallel on the run winding.
Danfoss Maneurop hermetic compressors (TN, NL, or FR lines) demand the relay be installed on the PS terminal block, not the external capacitor bracket, to comply with EN 60335 safety standards. Space constraints often dictate surface-mounting on the condenser frame, but use ferrule crimps instead of solder for UL compliance. On Ranco compressors (OEM for Whirlpool and GE), the relay must bypass the existing potential relay entirely; disconnect the factory PTC device and splice the new assembly in its place using heat-shrink tubing rated for 125°C minimum.
For scroll compressors in heat pump applications (e.g., Mitsubishi or Daikin), the relay should attach to the outdoor unit’s control board via quick-connect spade terminals, never directly to the compressor terminals–high back-EMF during defrost cycles can damage the module. Verify torque specs: 12–15 in-lbs for terminal screws (copper wire) or 20–25 in-lbs for aluminum lugs. Never daisy-chain the relay’s power lead through secondary switches (e.g., defrost timers or pressure cutouts), as voltage drops below 198V on 230V systems may cause improper disengagement.
Step-by-Step Connection Guides for Single-Phase and Polyphase Motor Configurations
For single-phase compressors, route the auxiliary relay’s red lead to the run capacitor’s terminal, ensuring the black lead links directly to the motor’s start terminal. Verify the relay’s coil voltage matches the system’s supply (typically 115V or 230V) before securing connections with a torque wrench (12-15 in-lbs). Bypass this step only if the motor lacks a start capacitor–conventional permanent split-capacitor (PSC) units require no additional components.
Polyphase (three-phase) setups eliminate auxiliary relays entirely. Connect the motor’s leads in a delta or wye configuration based on the nameplate voltage ratings:
- Delta: Bridge L1-T1, L2-T2, L3-T3 (230V systems).
- Wye: Pair T4/T5/T6 to a common neutral, then link L1-T1, L2-T2, L3-T3 (460V systems).
Use a multimeter to confirm phase-to-phase voltage (±10% tolerance) before energizing; uneven readings indicate an open winding or incorrect supply.
For single-phase applications with dual-voltage motors (e.g., 115V/230V), identify the split winding diagram on the nameplate. Connect the common (C) and run (R) terminals for low voltage, or series-link the windings (S+R bridged) for high voltage. Add a potential relay only if the motor’s locked-rotor amps exceed 50A–otherwise, pressure switches or current-sensitive relays suffice. Ground the motor frame via a #10 AWG copper conductor to the nearest bonded point.
When retrofitting older systems with solid-state relays, remove any existing mechanical contacts before installation. Mount the relay atop the compressor using vibration-dampening pads if ambient temperatures exceed 120°F. Wire the control circuit in series with the overload protector, ensuring the relay’s pick-up voltage aligns with the motor’s start winding (typically 200-300V for 230V systems). Test operation by cycling the system three times; failure to disengage within 2 seconds warrants checking for improperly sized run capacitors or shorted windings.
For three-phase motor protection, integrate a phase monitor relay set to trip at 15% voltage imbalance or 3-second phase loss. Connect the relay’s output to the contactor’s coil circuit, not the motor directly. In variable-frequency drive (VFD) applications, omit the run capacitor entirely–VFDs inherently regulate start-up torque. Always label leads with heat-shrink tubing marked in accordance with ANSI C2-2023 Section 4.2.7 to prevent cross-phase errors during maintenance.
Identifying Correct Terminals on Capacitors and Relays for Proper Connection
Locate the hermetic terminal markings on the capacitor’s casing–typically labeled “C” (common), “HERM” (hermetic), and “FAN” for dual-run types. Single-run capacitors use “C” and “FAN” or “HERM” exclusively. Verify polarity with a multimeter: the C terminal reads near-zero ohms when probed with either remaining terminal, confirming its role as the reference point. Reverse-engineer legacy units by tracing the thicker wire from the compressor motor to its capacitor lead–this invariably connects to HERM. For relays, match the 9-pin or 5-pin socket to the manufacturer’s schematic: pins 1 and 2 (line voltage), 5 (start winding), and 4 (run winding) are universal for potential relays. Solid-state relays replace mechanical contacts with a triac output–consult the datasheet for MT1 (anode) and MT2 (cathode) orientation.
Troubleshooting Terminal Misidentification
If the compressor fails to start or hums excessively, swap the HERM and C leads–this isolates incorrect terminal assignment as the root cause. For relays, use an ohmmeter to test continuity between pin 1 (L1) and pin 2 (L2) during startup: a reading under 50 ohms confirms proper engagement. Dual-voltage systems require splitting the capacitor’s C terminal–one lead to the run winding, the second to the common junction of the start winding. Avoid improvising labels; miswired relays risk burning out the coil or triac within seconds of power application. Replace capacitors showing bulging cases or oil leakage immediately–these often correlate with terminal failure from thermal stress.