Refrigerant Leaks & Charging – Quick HVAC Fixes

❄️ Refrigerant Leaks & Charging

Keeping the Lifeblood of Cooling Systems Where It Belongs

🧠 Why Refrigerant Matters

Refrigerant is what moves heat out of your home during cooling—and into your home during heating (with heat pumps).

It needs to stay:

🛠️ If refrigerant leaks out, even a brand-new system will stop cooling or heating properly.

Symptom	Likely Cause
Weak cooling, long run times	Low refrigerant charge
Ice on the evaporator coil	Low pressure causing freezing
High indoor humidity	Poor latent heat removal (coil too warm)
Hissing or bubbling sounds	Physical leak in tubing or coil
Visible oil stains	Refrigerant leaks often carry compressor oil
High superheat readings	Undersupplied evaporator
Low suction pressure	Leak or restriction

Location	Why It Leaks
Evaporator coil	Thin tubing, formicary corrosion
Outdoor coil (condenser)	Damage from impacts, corrosion
Schrader valve cores	Aging seals, mechanical damage
Service ports	Cap missing or loose, microleaks
Braze joints	Poor original brazing or vibration fatigue
Line set (copper piping)	Pinhole leaks from rubbing or chemical attack

📍 Most residential leaks happen in the indoor evaporator coil after 5–10 years.

Method	How It Works	Pros / Cons
Soap Bubble Test	Spray fittings; look for bubbles	Cheap, only works for larger leaks
Electronic Leak Detector	Sniffs refrigerant gas	Fast, good for pinpointing leaks
UV Dye Injection	UV light reveals dye at leak point	Messy, but good for tiny leaks
Nitrogen Pressure Test	Pressurize system, listen for leaks	Very accurate, no refrigerant wasted
Vacuum Decay Test	Pull deep vacuum, watch for rise	Good for hidden microleaks

🧠 Best practice: pressure with dry nitrogen (no more than 300–500 psi depending on equipment ratings), not refrigerant.

Charging a system correctly is critical for performance and efficiency.

Step	What to Do
Evacuate System	Pull deep vacuum to < 500 microns
Confirm No Vacuum Rise	System must hold vacuum for at least 10–15 min
Charge by Factory Specs	Use the tag—charge by weight first
Fine-Tune by Superheat/Subcooling	Adjust for field conditions

Method	When to Use	How It Works
Weigh In (Preferred)	When system is empty or near-empty	Add refrigerant based on factory charge amount (e.g., 5 lbs 4 oz)
Subcooling (TXV Systems)	Fine-tuning after weigh-in	Target subcool value (e.g., 10–12°F) from manufacturer chart
Superheat (Fixed Orifice)	Fine-tuning for piston/orifice systems	Target superheat based on outdoor temp + indoor wet bulb chart
Sight Glass (Rare)	Older commercial systems	Look for clear refrigerant flow, no bubbles

🛠️ Use a digital scale for precise charging. Superheat = good for fixed orifice. Subcooling = critical for TXV.

Mistake	Why It’s a Problem
Charging without fixing leak	System will leak down again, customer will be upset
Charging by pressures only	Ambient conditions trick readings; inaccurate
Using compressor to pull vacuum	Ineffective—traps moisture and acid risk
Overcharging “just in case”	High head pressures, compressor stress
Skipping vacuum after leak fix	Moisture stays in system = acid + failure risk

EPA 608 Certification is required to handle refrigerants legally in the U.S.
Always recover refrigerant properly—venting is illegal and environmentally harmful.
For A2L refrigerants (mildly flammable like R-32, R-454B):
🚨 Special leak detection and charging procedures apply. Always check manufacturer guidelines!

Finding leaks and charging properly isn’t just about getting the system running—it’s about:

👉 Want help calculating target superheat/subcooling?
Check out our [HVAC Charging Calculators →] or [Refrigerant Leak Detection Guides →]