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5-2-1 Compressor Saver Hard Start Kit CSR-U3 3.5 to 5 Ton Units
National HVAC Parts

5-2-1 Compressor Saver Hard Start Kit CSR-U3 3.5 to 5 Ton Units

SKU: NHVAC-HARD-R89ZGL Brand: National HVAC Parts
$35.00 $47.25

Order before 3PM CST — ships same day.
Standard delivery 2-5 business days. Express options at checkout.

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5-2-1 Compressor Saver Hard Start Kit CSR-U3 3.5 to 5 Ton Units

A plug-and-play compressor hard start kit for 3.5 to 5 ton residential and light commercial AC units. Reduces compressor startup time by up to 50% and lowers inrush current, extending compressor life and preventing low-voltage startup failures during peak summer demand.

Key Features

  • Designed for 3.5 to 5 ton AC and heat pump compressors
  • Reduces startup time from 1 second to under 1/2 second
  • Lowers inrush current by up to 50% — protects against brown-outs
  • Universal plug-and-play installation — no wiring modifications needed

Specifications

  • Tonnage: 3.5 to 5 tons
  • Voltage: 187-264 VAC
  • Start capacitor: Built-in
  • Potential relay: Built-in

What's Included

  • Hard start kit with built-in relay and capacitor
  • Installation instructions

Ships same-day from our Houston warehouse on orders placed before 3PM CST.

Frequently Asked Questions

How do I know if my AC needs a hard start kit?

Signs include: compressor struggles to start on hot days, breaker trips on startup, lights dim when AC kicks on, or the compressor is more than 5 years old. A hard start kit is cheap insurance for compressor longevity.

Will this void my compressor warranty?

No, hard start kits are widely accepted by manufacturers and do not void warranties. Many manufacturers recommend them for systems in hot climates or on long line sets.

How do I install it?

Connect the two wires to the compressor contactor's load side — one to the Start terminal and one to the Common terminal. No wiring changes to the existing system are needed. Takes about 5 minutes.

What is the difference between CSR-U1, U2, and U3?

They cover different tonnage ranges: U1 for 1-3 tons, U2 for 2-3.5 tons (can overlap), and U3 for 3.5-5 tons. Choose based on your system's compressor size.

Shipping Information

  • Orders placed before 3PM CST ship same business day
  • Standard delivery: 2-5 business days
  • Express shipping available at checkout
  • Free shipping on orders over $75
  • Tracking number emailed upon shipment

Return Policy

  • 30-day returns on unused parts in original packaging
  • Electrical parts (capacitors, contactors, control boards) are final sale once installed
  • Email support@nationalhvacparts.com to initiate a return
  • Refunds processed within 5-7 business days

Frequently Asked Questions

Does this Hard Start Kits & Compressor Accessories fit my National HVAC Parts 5-2-1 Compressor Saver Hard Start Kit CSR-U3 3.5 to 5 Ton Units?
Yes. This is the factory-specified OEM hard start kits & compressor accessories for the National HVAC Parts 5-2-1 Compressor Saver Hard Start Kit CSR-U3 3.5 to 5 Ton Units. It is a direct drop-in replacement that fits without modification. Always verify the model number on your equipment nameplate before ordering.
How do I replace the hard start kits & compressor accessories on my National HVAC Parts 5-2-1 Compressor Saver Hard Start Kit CSR-U3 3.5 to 5 Ton Units?
Refer to your equipment service manual for model-specific steps. General approach: turn off power, photograph connections, remove old part, install new part, restore power and test. For gas components, hire a licensed technician. Email info@nationalhvacparts.com for guidance.
What symptoms mean I need a new hard start kits & compressor accessories?
Common symptoms: unusual noises, intermittent operation, complete failure, or visible damage. Visit our diagnostic hub for symptom-based troubleshooting.
Is this hard start kits & compressor accessories compatible with Bryant or Payne too?
Many National HVAC Parts parts are cross-compatible with Bryant and Payne since all three brands are manufactured by Carrier Global Corporation. The same physical part is often used across brand labels with different model numbers. To verify: check your Bryant or Payne equipment service manual for cross-compatible part numbers, or email info@nationalhvacparts.com with your model number.
Should I use OEM or aftermarket for my National HVAC Parts hard start kits & compressor accessories?
OEM recommended for reliability and warranty compatibility. OEM parts match exact factory specifications for proper fit, performance, and safety. While aftermarket alternatives cost less upfront, the risk of improper fit and reduced lifespan usually makes OEM the better value long-term.
How fast does National HVAC Parts ship?
Orders placed before 3:00 PM CST ship the same business day. Standard delivery is 2–5 business days anywhere in the continental United States. Express shipping available at checkout. We ship from Houston, TX to all 50 states. 30-day return policy on all parts.
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