Signs of a Refrigerant Leak in a Commercial HVAC System

A refrigerant leak in a commercial HVAC system usually shows up as warm air from the supply registers, rising energy bills, or ice forming on the evaporator coil. Those three things together are a strong signal. Left alone, a leak forces your compressor to work harder, shortens its life, and violates EPA Section 608 regulations once a certain threshold of refrigerant loss is confirmed.

What You’ll Notice First

Warm air is the most common complaint. Your thermostat is set the same as always, but the building won’t cool down. Tenants or staff start complaining by mid-morning.

Ice on the indoor unit (evaporator coil or refrigerant lines) is counterintuitive but common. Low refrigerant drops the pressure in the coil below the point where it can absorb heat properly, so moisture in the air freezes onto it instead. If you see frost or a solid ice block on the indoor unit, shut the system down and call someone.

Higher electric bills without a change in usage are worth flagging. The compressor is running longer to chase a setpoint it can’t reach.

Oil stains near refrigerant line fittings, the service valves, or the condenser are a visual clue. Refrigerant oil circulates through the system with the refrigerant, and when refrigerant escapes at a leak point, oil deposits there too. Look for a greasy residue or discoloration on the copper lines and fittings.

Hissing or bubbling sounds near the unit can happen with larger leaks, though many leaks are silent.

Where Leaks Actually Come From

In commercial rooftop units and split systems, most leaks trace back to a few spots:

Schrader valves (the service ports you connect gauges to) develop small leaks over time, especially on older equipment. The rubber o-ring or internal seal degrades, or debris gets lodged in the valve. They’re cheap to fix.

Brazed joints can develop pinhole leaks years after installation if there was a weak spot in the joint or if the system has been vibrating against a hard mount. These take more work to find and repair.

Evaporator coil failures are the expensive ones. Formicary corrosion, which is a chemical reaction between copper tubing and organic acids from cleaning products, adhesives, paints, or off-gassing from building materials, eats tiny pits into the coil walls. It’s common in commercial kitchens and in tightly constructed buildings where volatile compounds stay trapped in the air stream. A corroded evaporator coil often needs replacement rather than repair.

Vibration wear on the refrigerant lines themselves, particularly where a line runs through sheet metal or rubs against a support bracket, can abrade the copper over years of operation.

How a Technician Finds It

A tech will start by connecting gauges to check system pressures. Low suction pressure is a strong indicator of low refrigerant charge. That alone doesn’t pinpoint the leak, but it confirms there’s a problem worth chasing.

From there, the standard methods are electronic leak detection and UV dye. Electronic detectors are sensitive and good for open equipment rooms. UV dye gets injected into the system, circulates with the refrigerant oil, and shows up under a UV light at the leak point. Some techs use both.

Nitrogen pressure testing (pressurizing the system with dry nitrogen and checking for pressure drop) is standard practice after a repair, before recharging, to confirm the fix held. It can also help locate a leak in the first place since the system can be pressurized above normal operating levels.

For hard-to-find leaks, especially in evaporator coils tucked inside air handlers, a tech may need to pull panels and work methodically through the coil sections.

What’s Your Job vs. the Tech’s Job

You can and should do a few things before the service call:

• Walk the equipment. Look for ice, oil stains, or anything obviously wrong.
• Check your filter. A clogged filter causes some of the same symptoms (warm air, coil freeze-up) and is worth ruling out first. A dirty filter is not a refrigerant leak.
• Note when you first noticed the problem and pull your last two utility bills if you have them. The tech will ask.
• If you see ice on the unit, turn it off or switch it to fan-only mode so the ice can thaw. Running a system with a frozen coil can burn out the compressor.

Do not add refrigerant yourself. Refrigerant handling requires EPA 608 certification, and topping off a leaking system without fixing the leak is both a regulatory issue and a waste of money. The refrigerant will just escape again.

When to Call a Pro

Call when you notice any combination of the symptoms above, especially warm air plus rising bills. Don’t wait to see if it gets better on its own because refrigerant systems don’t self-heal.

If the system is an older R-22 unit, keep in mind that R-22 has been phased out and what’s available now is reclaimed refrigerant at higher cost. A significant leak on an R-22 system is often a good time to evaluate whether a replacement makes more sense than a repair.

For Bay Area commercial properties, the regulations around refrigerant handling and leak reporting (CARB and EPA rules both apply here) add a layer of documentation that a qualified contractor needs to handle correctly.

We work on commercial HVAC systems across the Bay Area, rooftop package units, split systems, and larger central plant equipment. Call us at (925) 999-4095 or visit bayareahvacservice.com. We’ll get you on the schedule fast, often same or next day when we can.

Key takeaways

• Warm supply air, ice on the evaporator coil, and rising energy bills are the most common signs of a refrigerant leak.
• Oil stains near fittings, service valves, or refrigerant lines are a visual indicator worth checking during a walkthrough.
• Check your filter first since a clogged filter can mimic the same symptoms, but refrigerant handling requires EPA 608 certification and has to go through a licensed tech.
• Formicary corrosion from organic acids (cleaning products, adhesives, off-gassing building materials) is a common cause of evaporator coil failure in commercial buildings and often requires coil replacement.
• Older R-22 systems facing a significant leak may be better candidates for replacement than repair given current reclaimed refrigerant costs.

Related questions

Written by Andrew Kuznetsov. Andrew is the founder and owner of Bay Area HVAC Service (ADRIUM Service Solutions). He holds a California Contractor License (CSLB #1136642), EPA 608 certification, and completed factory training at the Daikin/Goodman plant in Houston in 2025. He writes from direct field experience, not marketing copy.

Further reading

• Mitsubishi Hyper-Heat (H2i): How It Keeps Putting Out Heat When It Gets Cold in the Bay Area , Most people think heat pumps quit when it gets cold. Mitsubishi's Hyper-Heat (H2i) line is built to keep working as temperatures drop, which matters more here than folks expect, especially on cold mornings and up in the East Bay hills.
• Mitsubishi Mini-Split Blinking a Fault Light? What It Means and What to Do , A blinking light on your Mitsubishi indoor head is the system telling you something is wrong. Here is what the blink pattern means, the checks you can safely do yourself, and when to bring in a factory-trained tech.
• Why Your Mitsubishi Mini-Split Is Leaking Water Inside (and How to Fix It) , A Mitsubishi mini-split dripping water inside almost always comes down to condensate that can't drain. Here's what causes it, the safe checks you can do yourself, and when to call a tech.