Choosing the right hard start kit can help AC compressors overcome starting stalls, reduce run-time stress, and save on energy during startup. The following 5 products pull from reputable brands and offer notable torque boosts, broad compatibility, and straightforward installation. Use this guide to compare options and select a kit that matches your unit’s tonnage, voltage, and maintenance needs.
Selected Products At A Glance
| Product | Brand | Model | Key Benefit |
|---|---|---|---|
| SPP6 Hard Start Capacitor Replacement (1/2 HP – 10 HP) | AMI PARTS | SPP6 | Increases starting torque up to 500% |
| SPP6 Hard Start Capacitor Replacement (2-Pack) | AMI PARTS | SPP6 | Same torque boost, two-pack value |
| SPP6 Relay/Capacitor Hard Start Kit | Seentech | SPP6 Kit | High-quality relay-capacitor combo, broad compressor range |
| MIFLUS SPP6 Hard Start Capacitor Kit | MIFLUS | SPP6 | Broad compatibility, easy parallel wiring |
| Supco SPP5 Hard Start Kit | Supco | SPP5 | Simple install with integrated relay and capacitor |
AMI PARTS SPP6 Hard Start Capacitor Replacement
The SPP6 hard start booster capacitor increases compressor starting torque by up to 500%. It is designed to fit air conditioning compressors ranging from 4,000 BTU window units to 120,000 BTU systems (1/2 HP to 10 HP). Replacements include part numbers such as SPP6, TJ90HS6, AP4502872, 35702, and others. The kit emphasizes a solid-state relay with minimal wiring and no loose parts, aiming to reduce service calls and provide an economical repair option.
AMI PARTS SPP6 Hard Start Capacitor Replacement (2-Pack)
This listing expands on the standard SPP6 kit with a 2-pack option, offering similar capabilities: 500% starting torque boost, broad compatibility from small to large AC units, and a replacement set including common part numbers like TJ90HS6 and HS650. It highlights usage across central air, heat pumps, and various appliances, with a caution to disconnect power during maintenance.
ATMA SUPPLY CSR-U1 Hard Start Device
This hard start kit is designed for 1- to 3-ton AC units and includes a hard start capacitor kit, cables, ties, and screws. It uses a multi-layer starting capacitor paired with a smart switch to deliver a quick, reliable start, reduces high-amp draw, and may lower energy use during startup. The kit emphasizes improved startup reliability and compact installation within common condensers.
SPP6 Relay/Capacitor Hard Start Kit – Seentech
Seentech’s SPP6 kit is a combined relay-capacitor solution that replaces numerous model numbers (SPP6, TJ90HS6, AP4502872, 35702, DST-6, ERPP6, HS6, HS650). It is advertised for use with a wide range of air conditioning compressors—from 4,000 BTU to 120,000 BTU units. The kit is promoted as durable and well-tested for long-lasting performance, with emphasis on straightforward wiring and reliable torque boost.
MIFLUS SPP6 Hard Start Capacitor Kit
The MIFLUS SPP6 kit increases starting torque by 500% and covers a wide range from 4,000 BTU window units up to 120,000 BTU commercial units. Installation instructions describe wiring the two wires in parallel with the run capacitor. The kit notes compatibility with PSC units and emphasizes disconnection of power prior to maintenance, with claims of easy parallel wiring and potential maintenance cost savings.
Supco SPP5 Hard Start Kit
Supco’s SPP5 kit provides a compact option for adding starting torque to AC compressors. It installs quickly across run capacitor terminals and includes both a relay and start capacitor for enhanced starting performance. It is described as a straightforward solution for improving start reliability in single-phase systems.
SUPCO SPP6 Hard Start Kit (Relays & Capacitors)
Sealed Unit Parts Co., Inc. offers a SPP6 relay-capacitor hard start kit with 500% starting torque. It is designed for permanent split capacitor single-phase air conditioning and heat pump systems. The product notes its country of origin as China and positions itself as a standard option for upgrading starting performance in various HVAC setups.
Long Term Replace CSR-U2 Compressor Saver Hard Start Capacitor
Designed for 3-1/2 to 5-ton units, the CSR-U2 hard start kit provides 3-4 color-coded wires for simplified installation. It aims to reduce start-up time by providing a strong multi-layer starting capacitor and smart switch, enhancing reliability while consuming less power during startup. It is UL-certified and intended to fit a broad range of common brands.
Buying Guide: Key Purchase Considerations
- Unit compatibility: Confirm tonnage (3/4 HP to 10 HP range) and voltage (115V–288VAC) to ensure the kit matches your compressor.
- Torque increase: Look for kits advertising up to 500% starting torque to maximize startup reliability, especially in hot climates or older systems.
- Wiring simplicity: Choose kits that offer minimal wiring steps, especially if you’re replacing a failed starter without rewiring the entire circuit.
- Component quality: Durable capacitors and reliable solid-state relays improve longevity and reduce service calls.
- Warranty and support: See if the seller offers a warranty and accessible customer support for installation guidance.
- Brand coverage: Broad compatibility across brands (e.g., TJ90HS6, HS6, HS650) can reduce the risk of a mismatch with your existing compressor model.
- Safety: Always disconnect power before maintenance and follow manufacturer instructions for parallel wiring with the run capacitor.
- Installation context: For centralized systems or heat pumps, verify the kit’s suitability for PSC units and non-PSC configurations.