HVAC
Refrigerant charging field guide: superheat and subcooling
Charge by superheat on a fixed orifice and by subcooling on a TXV, read both numbers together to diagnose the charge, and record what proves it.
Direct answer
Charge a fixed-orifice or piston system by superheat and a TXV or EEV system by subcooling, because that reading is what tells you the charge is right for the metering device. Superheat is suction temperature above saturation; subcooling is liquid temperature below it. The equipment data plate and charging chart set the targets.
Key takeaways
- Charge a fixed-orifice or piston system by superheat and a TXV or EEV system by subcooling, matching the method to the metering device.
- Superheat equals suction line temperature minus saturation temperature at suction pressure; subcooling equals saturation temperature at liquid pressure minus liquid line temperature.
- TXV subcooling defaults to 10F to 12F when the plate is missing, but the data plate or charging chart governs the real target.
- Low charge reads high superheat plus low subcooling; overcharge reads low superheat plus high subcooling.
- EPA Section 608 prohibits venting refrigerant, including R-410A, R-32, and R-454B; recover into an approved cylinder before opening a charged system.
Charging by the number, and the rule that picks the number
Refrigerant charging is setting the amount of refrigerant in a sealed system so the metering device gets a solid column of liquid and the compressor gets nothing but vapor. You do not chase a pressure and you do not weigh by eye. You read the two numbers that tell you the state of the refrigerant where it matters: superheat at the suction line and subcooling at the liquid line.
The rule that governs everything below is short. Charge a fixed-orifice or piston system by superheat. Charge a TXV or EEV system by subcooling. The metering device decides which number is honest, and the equipment data plate decides the target. Get the method backward and you can chase a charge all afternoon and never land it.
The trouble on the job is rarely the math. It is judging charge on a system with bad airflow, on a dirty coil, in low ambient, on a blend with glide the tech ignored, or with a manifold that has never been checked against a known reading. Then nobody writes down the suction and liquid numbers, so the next tech starts over. A correct charge is two readings, a target from the plate, and a record that backs the verdict.
Do I charge by superheat or subcooling?
Charge by superheat on a fixed orifice or piston, and by subcooling on a TXV or EEV. The reason is the metering device. A fixed orifice is a dumb hole with no moving parts, so it cannot regulate flow to the evaporator. As you add charge, more liquid feeds the coil and superheat falls; as you pull charge, the coil starves and superheat climbs. Superheat tracks the charge directly, so it is the number you trim to.
A TXV is the opposite. The valve exists to hold suction superheat at a set value, commonly somewhere around 8°F to 12°F, by modulating flow as conditions change. Because the valve is actively holding superheat, superheat stops being a charge indicator on a TXV system. It will read close to target across a wide range of charge. So you read subcooling instead, because the liquid stacking up in the condenser, which is what subcooling measures, is the variable that moves with charge once the valve has superheat under control.
An EEV, the electronic version of a TXV, behaves the same way for charging purposes: it controls superheat, so you charge to subcooling. Use the method that matches the metering device on the system in front of you, not the method you used on the last call.
Superheat and subcooling, defined
Superheat is how many degrees the refrigerant vapor sits above its boiling point at the current pressure. Measure the suction line temperature near the outdoor unit, read the suction pressure, convert that pressure to a saturation temperature on the pressure-temperature chart for the refrigerant, and subtract. The difference is superheat. Any superheat at all means the refrigerant is fully vapor, which is what protects the compressor from drinking liquid.
Subcooling is the mirror image on the liquid side. It is how many degrees the liquid sits below its condensing temperature at the current pressure. Read the liquid line temperature, read the liquid pressure, convert that pressure to a saturation temperature, and this time subtract the line temperature from the saturation temperature. The difference is subcooling. Subcooling proves you have a full column of liquid feeding the metering device, with no flash gas.
Both numbers come off pressure converted to a saturation temperature, never off pressure alone. That is the part rookies skip. A suction pressure by itself tells you nothing about superheat until you turn it into a saturation temperature and compare it to a real thermometer on the line. The pressure-temperature relationship is the whole tool.
SH = Tsuction line − Tsat at suction pressureSC = Tsat at liquid pressure − Tliquid line- Superheat
- Suction line temperature minus the saturation temperature at suction pressure; vapor heated past its boiling point
- Subcooling
- Saturation temperature at liquid pressure minus the liquid line temperature; liquid cooled below its condensing point
- Saturation temperature
- The boiling or condensing temperature for a refrigerant at a given pressure, read from the P-T chart
Why the metering device picks the method
A fixed orifice has no feedback. The flow through it depends only on the pressure difference across it and the charge in the system, so the evaporator's appetite is never matched to its feed. Add refrigerant and the coil gets wetter and superheat drops. That direct link is exactly why superheat is the charging number on a piston system: move the charge and the number moves.
A TXV breaks that link on purpose. It senses suction temperature and pressure at the bulb and throttles flow to hold superheat where the valve is set. Once the valve is in control, you can add or remove a fair amount of refrigerant and superheat barely budges, because the valve compensates. So superheat tells you the valve is working, not whether the charge is right. The charge shows up downstream, as liquid backing up in the condenser, and that is what subcooling reads.
This is the single most common reason a charge will not settle. A tech puts a TXV system on a superheat target, watches superheat read fine no matter what, and keeps adding gas until subcooling is through the roof and the system is badly overcharged. Right number, wrong device. Read the subcool on a TXV.
What is a good superheat and subcooling target?
The target comes from the equipment, not from a rule of thumb. On a TXV system, a common subcooling target lands around 10°F to 12°F, but the number that governs is the one on the outdoor unit data plate, on the inside of the access panel, or in the manufacturer's literature. When the plate is missing or worn off, 10°F to 12°F of subcooling is a defensible default for a residential TXV system, and that is the only time you should use it.
Superheat is not a single number at all. On a fixed-orifice system the target superheat depends on the load, so it comes off the manufacturer's superheat charging chart or charging slider, indexed to the indoor wet-bulb temperature and the outdoor dry-bulb temperature. The same system might call for 5°F of superheat on a hot, humid day and 20°F on a cool, dry one. Reading a flat 'aim for 10' off memory is how a piston system ends up wrong half the year.
Subcooling drifts with conditions too. The same TXV system runs a little more subcooling when it is hot outside and a little less near 70°F outdoor, which is why the better data plates give a small range or a value tied to outdoor temperature rather than one figure. Read the plate, read the conditions, then judge the number.
| Metering device | Charge by | Typical target | Authority |
|---|---|---|---|
| Fixed orifice / piston | Superheat | From the charging chart, varies with indoor wet bulb and outdoor dry bulb | Manufacturer charging chart |
| TXV | Subcooling | Commonly around 10°F to 12°F | Data plate / rating plate |
| EEV | Subcooling | Per equipment, similar to TXV | Manufacturer literature |
The superheat charging chart and the conditions
Superheat is load-dependent because the evaporator's job changes with the air across it. More heat and moisture in the return air boils off the refrigerant faster, which raises the right superheat. Less load means the coil cannot fully boil the same feed, so the correct superheat is lower to avoid flooding the suction. One number cannot cover that range, which is why the manufacturer publishes a chart instead of a spec.
The two inputs are the indoor wet-bulb temperature, taken in the return air, and the outdoor dry-bulb temperature in the condenser's intake. Wet bulb captures both heat and humidity, which is the real load on the coil, so it is the right indoor measurement, not dry bulb. Cross those two on the chart, or feed them into the charging slider, and you get the target superheat for that moment.
Take a real wet-bulb reading with a sling psychrometer or a digital probe in the return, not a guess off the thermostat. The conditions move during the call, so re-check them if the day swings or the indoor load changes while you work. A superheat target read against last hour's conditions is the wrong target now.
Gauges, probes, and the P-T chart
The core kit is a way to read pressure, a way to read temperature accurately, and the pressure-temperature relationship that ties them together. A manifold gauge set works, but wireless probes have largely taken over because they clamp on, read suction and liquid pressure and temperature at once, and compute superheat and subcooling for you, with the glide for the specific refrigerant built in.
Temperature accuracy is where field readings go wrong. A loose pipe clamp, a thermometer that has drifted, or a probe not insulated from ambient air will throw superheat and subcooling by several degrees, and several degrees is the whole budget. Strap the temperature clamp tight to clean copper, insulate it from the outdoor air, and let it settle before you trust it. Check your probes against each other in the same spot now and then.
The pressure-temperature chart, or the digital tool that holds it, has to be the chart for the exact refrigerant in the system. R-410A, R-454B, R-32, and the older refrigerants each have their own saturation curve, and a blend with glide needs its dew and bubble values, not a single column. Charging an R-454B system off an R-410A chart is a quiet way to be wrong on every reading.
- Manifold / probes
- The gauge set or wireless clamp-on probes that read suction and liquid pressure and temperature
- P-T chart
- Pressure-temperature chart for a specific refrigerant, converting a measured pressure to a saturation temperature
- Temperature clamp
- A pipe-mounted thermistor or thermocouple; accuracy and insulation from ambient air decide the reading
R-410A, the A2L refrigerants, and temperature glide
The refrigerant in the system changes how you read saturation, so know what you are working on before you touch a gauge. R-410A has been the residential standard for years and behaves almost like a single substance, with so little temperature glide that one saturation number per pressure is close enough for field work. That is changing fast.
Under the AIM Act phase-down, new ducted equipment manufactured from January 1, 2025 moved to lower-GWP A2L refrigerants, mainly R-454B and R-32, with installation deadlines following in 2026. R-32 is a single-component refrigerant with negligible glide. R-454B is a zeotropic blend of R-32 and R-1234yf, so it carries temperature glide: its saturation temperature is a range at a given pressure, not one point. Confirm the adopted timeline and rules, because the dates and product cutoffs vary and continue to shift.
Glide is where blends bite. For a zeotropic refrigerant the liquid and vapor change temperature as they change phase, so the P-T chart gives two numbers at each pressure: a bubble point where liquid first boils and a dew point where the last liquid becomes vapor. The rule is fixed. Use the dew point for superheat and the bubble point for subcooling. Swap them and both readings are off by the glide, which can be several degrees on a higher-glide blend and enough to chase a charge that was already right.
Any refrigerant numbered in the 400s is a blend and should be assumed to have glide until you check. Most digital probe sets apply the dew and bubble points automatically once you select the refrigerant, which is one more reason to set the refrigerant correctly before you read anything.
Weigh-in charging: factory charge plus the line set
Weigh-in is the right method on a new or empty system, and it is the most accurate one when you can use it. The outdoor unit ships with a factory charge stamped on the data plate, sized to cover the unit plus a standard line set length, commonly 15 ft of liquid line. Evacuate the system, then weigh in that factory charge with a refrigerant scale, adjusted for how far your line set runs past the included length.
The adjustment lives on the data plate. For R-410A on a 3/8 in liquid line, the common figure is roughly 0.6 oz of refrigerant per foot of liquid line beyond the included length, and the A2L refrigerants run slightly different per-foot values because their density differs. The suction line adds little, so the adjustment is keyed to the liquid line. Use the manufacturer's per-foot number off the plate or the install manual, not a remembered constant, because it varies by refrigerant and line size.
Weigh-in gets you to a charge that should be close. On a fixed-orifice system you still verify with superheat, and on a TXV system you still confirm subcooling once the system is running in steady conditions. Weigh in to land in the ballpark, then trim by the number the metering device picks. The two methods are not rivals. Weigh-in is how you start an empty system; the running reading is how you finish it.
Evacuation and the micron gauge
A charge on a system that was never properly evacuated is a charge that is already failing. Air and moisture left inside raise head pressure, form acid in the oil, freeze at the metering device, and corrode the system from the inside. So before any refrigerant goes in on a new install or an opened system, you pull a deep vacuum and prove it held.
Use a micron gauge, not the needle on the manifold, because the manifold cannot resolve the range that matters. A common target is to pull the system to about 500 microns. POE-oil systems, which covers R-410A and the A2L refrigerants, are frequently taken lower because the oil holds moisture stubbornly. Confirm the target the manufacturer specifies for the equipment.
Hitting the number is not the test. Valve off the vacuum pump and run a standing decay test, watching the micron gauge with the pump isolated. If the reading holds below roughly 500 microns over the wait, the system is dry and tight. A quick rise means moisture still boiling off or a leak pulling in air, and you do not charge it. Pulling below 500 and staying below 500 after isolation are two different things, and the decay test is what separates them.
Why is my superheat high or my subcooling low?
Read superheat and subcooling together, because the pair points at the fault in a way neither does alone. Superheat tells you what is happening at the evaporator; subcooling tells you what is happening at the condenser. The combination separates a charge problem from a flow problem from an airflow problem.
Low charge shows as high superheat and low subcooling: the evaporator is starved and the condenser has no liquid to stack, so both numbers point the same way. Overcharge is the reverse, low superheat and high subcooling, with liquid backing up in the condenser and threatening to flood the suction line. A liquid-line restriction, a kinked line or a plugged filter drier, mimics a low charge at the coil with high superheat but holds normal or high subcooling, because the liquid is there, it just cannot get through. Low indoor airflow drags superheat down and can fake an overcharge. And a hunting TXV swings superheat up and down as the valve overshoots, which reads as an unstable charge that is really a valve or bulb problem.
Work the pattern, not a single gauge. The table below is the field shorthand, but confirm airflow and the metering device before you act on any of it.
| Condition | Superheat | Subcooling | Likely cause |
|---|---|---|---|
| Undercharge | High | Low | Add refrigerant by the correct method |
| Overcharge | Low | High | Recover in small steps and re-read |
| Liquid-line restriction | High | Normal to high | Drier or kink; liquid present but blocked |
| Low indoor airflow | Low | Normal to high | Set airflow first, then re-judge charge |
| TXV hunting | Swinging | Variable | Valve, bulb mount, or bulb charge |
Set the airflow before you judge the charge
Airflow comes before charge, every time. The evaporator's superheat depends on how much air is moving across it, so a system with restricted airflow gives you readings that look like a charge problem and are not. Charge to those readings and you have buried an airflow fault under a wrong charge, and now you have two problems.
Low airflow over the coil drops suction pressure and pulls superheat down, which reads like an overcharge. A tech who trusts that number recovers good refrigerant out of a correctly charged system, then the airflow gets fixed later and the system is suddenly low. The cause was a dirty filter or coil, a closed damper, or undersized return, not the charge. Measure total external static pressure and confirm the airflow is in range before you decide anything about the refrigerant. The duct static guide covers how to take that reading and read it against the blower table.
On a new install this is the order of operations: set and verify airflow, run the system long enough to stabilize, then charge. On a service call, the same. If the airflow is wrong, fix it first, because every charge reading you take before then is suspect.
Charging in low ambient and low load
You cannot charge accurately by superheat or subcooling in low outdoor temperature without the manufacturer's low-ambient method. As the outdoor air drops, head pressure falls, the condenser behaves differently, and the standard targets stop applying. A system that reads fine on a cold day can be badly off when summer load shows up.
Low indoor load does the same thing from the other side. A coil with little heat across it cannot boil the refrigerant the way the charging chart assumes, so superheat readings go soft and the chart's target no longer matches reality. Charging a fixed-orifice system on a mild, dry day against a chart built for design load is a known way to end up wrong.
When conditions are out of range, weigh in the factory charge plus the line-set adjustment and stop there, or follow the maker's specific low-ambient charging procedure, which may call for restricting condenser airflow to raise head pressure to a test point. Then verify the charge by superheat or subcooling when the weather and load come back into the chart's range. Do not force a reading the conditions cannot give you honestly.
The A2L safety and code shift
The A2L refrigerants are mildly flammable, which is what the 2L in the ASHRAE Standard 34 class means: lower toxicity, low flame propagation, but not the non-flammable A1 that R-410A is. That changes how you work around them. Keep ignition sources away during service, ventilate the space, use A2L-rated leak detectors and A2L-rated recovery equipment, and follow the brazing and purging steps the manufacturer specifies.
The equipment changed too. A2L systems carry refrigerant charge limits tied to room volume and require integrated leak detection that can shut the system down and run the fan to disperse a leak. Those mitigations are built into the listed equipment, so do not defeat them, and follow the install requirements for charge limits and detector placement.
The code side is moving with the refrigerants. Building and mechanical codes have been updated to cover A2L equipment, charge limits, and leak mitigation, and the adopted edition varies by jurisdiction. Confirm the code and amendments the authority having jurisdiction actually enforces, and the equipment listing, before you treat any A2L install or service as routine. This is new enough that the rules are still settling.
Recovery and EPA 608: no venting
You recover refrigerant. You do not vent it. EPA Section 608 of the Clean Air Act prohibits knowingly venting refrigerant during service, maintenance, or disposal, and that covers the HFCs and the A2L blends, not just the old ozone-depleting refrigerants. The list includes R-410A, R-32, and R-454B. Penalties run per day per violation, and there is no small-amount exception for a charged system.
Before you open a charged system, recover the refrigerant into an approved cylinder with certified recovery equipment. A2L refrigerants require A2L-rated recovery gear because of the flammability class, but the no-venting rule and the recovery requirement apply to them exactly as they do to A1 refrigerants. Technicians who handle refrigerant must hold EPA Section 608 certification.
This is the law, not a best practice, and it is the part of charging work an inspector or an auditor can check after the fact through your recovery records. Recover it, log it, and handle the cylinder right.
Heat pumps: charge in cooling, verify in heating
A heat pump runs the refrigerant both directions, so the side you call suction in summer is the discharge in winter, and the charging method has to account for that. The common approach is to charge a heat pump in the cooling mode, by the same rule as any other system: superheat on a fixed orifice, subcooling on a TXV, with the indoor coil acting as the evaporator the chart was built around.
Charging a heat pump in heating mode is harder, because the outdoor coil is now the evaporator and the standard charging chart is written for cooling. When cold weather forces a heating-season charge, follow the manufacturer's specific cold-weather or heating-mode procedure rather than the cooling chart, and verify the charge in cooling once the season turns.
Heat pumps also carry more refrigerant and longer line sets than a comparable straight-cool system, so weigh-in plus the line-set adjustment matters even more on these. Get the weighed charge right at install, then trim and verify by the running reading in the mode the chart supports.
The service record and the charge
A charge that nobody documented is a charge nobody can defend. Six months out, when a system runs low or short-cycles, the only thing that answers whether the charge was ever right is the record from the day it was set. The readings you took are the proof, and without them the next tech starts from zero.
Write down the state of the system, not just the verdict. The refrigerant type, the metering device, the suction and liquid pressures and line temperatures, the superheat and subcooling you calculated, the conditions you charged in, the target you held to and where it came from, and what you added or recovered. On a weigh-in, record the factory charge, the line-set length, the per-foot adjustment, and the total weighed in. That record is also where the EPA-required recovery logging lives.
What to document
Capture enough that another tech can reproduce your judgment without re-running the whole call. The state of the refrigerant at both lines, the conditions, the target and its source, and the verdict are the minimum. If you trimmed or recovered, record how much and why.
| Field to record | Why it matters |
|---|---|
| Refrigerant type | Sets the P-T chart and whether glide applies |
| Metering device | Decides superheat vs subcooling as the method |
| Suction pressure and line temp | The superheat reading and its inputs |
| Liquid pressure and line temp | The subcooling reading and its inputs |
| Superheat calculated | Charge indicator on a fixed orifice |
| Subcooling calculated | Charge indicator on a TXV or EEV |
| Indoor wet bulb, outdoor dry bulb | The conditions the target was read against |
| Target and source | Data plate or charging chart, not a guess |
| Verdict and amount added or recovered | The action and the recovery record |
Common mistakes
- Charging a TXV system by superheat, where the valve holds superheat fixed and hides the charge.
- Charging a fixed-orifice system by subcooling instead of the superheat charging chart.
- Judging the charge with bad airflow, a dirty filter, or a dirty coil never measured.
- Adding refrigerant to a system that was never evacuated and decay-tested.
- Ignoring glide on a blend: using one saturation number on R-454B instead of dew for superheat and bubble for subcooling.
- Charging in low ambient or low load against a chart the conditions cannot satisfy.
- Reading suction pressure as if it were superheat without converting to saturation temperature.
- Trusting a drifted thermometer or a loose pipe clamp, then chasing a charge that was already right.
- Venting refrigerant instead of recovering it, in violation of EPA Section 608.
Field checklist
Want this checklist to run itself on every job — with photo proof and a signed record crews can hand the customer? That's FieldOS.
Standards and references
The equipment manufacturer governs the charge. The data plate and the charging chart set the subcooling and superheat targets, the factory charge, and the per-foot line-set adjustment, and when they conflict with a rule of thumb, they win. The install and service manual carries the low-ambient procedure, the A2L charge limits, and the evacuation target for the specific unit.
EPA Section 608 of the Clean Air Act, at 40 CFR Part 82, Subpart F, controls refrigerant handling: it prohibits knowingly venting, requires recovery before a charged system is opened, and requires technician certification. It applies to the HFCs and the A2L blends, not just the older refrigerants. The AIM Act drives the phase-down to lower-GWP refrigerants and the manufacturing and install dates for the A2L transition; confirm the current deadlines because they have moved.
AHRI assigns the refrigerant designations such as R-410A, R-454B, and R-32. ASHRAE Standard 34 sets the safety classification, including the A2L class for the mildly flammable lower-GWP refrigerants. The mechanical and building codes adopted by the jurisdiction cover A2L equipment, charge limits, and leak mitigation. Cite the body that owns the point, and confirm the adopted edition and any local amendments with the authority having jurisdiction before you rely on a number.
Units, terms, and conversions
Charging numbers show up across a few units, so the same value can read differently on a gauge, a data plate, and a manual.
Superheat and subcooling are in degrees Fahrenheit in the field, degrees Celsius in metric literature, where a span of 10°F is about 5.6°C. Pressure is psig on most field gauges, with bar or kPa in metric sources. Vacuum during evacuation is in microns of mercury, where 500 microns is a deep vacuum far below atmospheric. Refrigerant charge is in pounds and ounces in the field and kilograms in metric data.
- Superheat / subcooling
- Degrees above the suction saturation temperature and degrees below the liquid saturation temperature
- Saturation
- The boiling or condensing state; saturation temperature is read from the refrigerant P-T chart at a measured pressure
- TXV / EEV
- Thermostatic or electronic expansion valve; both hold superheat, so they are charged by subcooling
- Glide
- The temperature spread of a zeotropic blend at one pressure; use dew point for superheat, bubble point for subcooling
- A2L
- ASHRAE Standard 34 safety class for mildly flammable, lower-toxicity refrigerants such as R-454B and R-32
- Microns
- Unit of vacuum during evacuation; about 500 microns is a common target before charging, confirmed by a decay test
- EPA 608
- Clean Air Act program requiring technician certification, refrigerant recovery, and no venting
FAQ
Do I charge by superheat or subcooling?
Charge a fixed-orifice or piston system by superheat, because superheat tracks the charge directly. Charge a TXV or EEV system by subcooling, because the valve holds superheat constant and subcooling becomes the reading that moves with charge. Match the method to the metering device, then confirm the target on the data plate.
What is a good subcooling for an air conditioner?
A common default is 10°F to 12°F of subcooling on a TXV system when the data plate is missing, but the rating plate or charging chart governs the actual target. Subcooling runs a little higher on a hot day and lower near 70°F outdoors, so read it against the conditions, not as one fixed number.
What does high superheat mean?
High superheat usually means the evaporator is starved, with too little refrigerant reaching the coil. On a fixed-orifice system that points to undercharge. Read it with subcooling first: high superheat plus low subcooling is undercharge, while high superheat with normal subcooling points to a liquid-line restriction or low indoor airflow.
What does low superheat with high subcooling mean?
Low superheat with high subcooling points to overcharge, with liquid backing up in the condenser and threatening to flood the suction line. Recover refrigerant in small steps and re-read between each. Confirm indoor airflow first, because low airflow can also pull superheat down and fake an overcharge reading.
What is A2L refrigerant?
A2L is the ASHRAE Standard 34 safety class for mildly flammable, lower-toxicity refrigerants like R-454B and R-32, now replacing R-410A in new equipment under the AIM Act phase-down. A2L systems need A2L-rated tools, leak detection, and ignition-source control, but recovery and no-venting rules apply the same as A1.
What microns do I pull a system down to before charging?
Pull the system to about 500 microns, then valve off the pump and run a standing decay test. If the reading holds near or below 500 microns the system is dry and tight; a fast rise means moisture or a leak. POE-oil systems are often taken lower. Never charge a system you did not evacuate.
Why do I use dew point and bubble point on R-454B?
R-454B is a zeotropic blend with temperature glide, so its saturation temperature is a range at a given pressure, not one number. Use the dew point from the P-T chart for superheat and the bubble point for subcooling. Mixing them up throws both readings off by the glide, several degrees on a higher-glide blend.
Can I charge a system accurately in cold weather?
Not accurately by superheat or subcooling without the manufacturer's low-ambient procedure. In low outdoor temperature the head pressure and readings shift, so the standard targets do not apply. Weigh in the factory charge plus the line-set adjustment instead, then verify by the running reading when conditions return to the chart's range.
Do I have to recover refrigerant, or can I vent it?
Recover it. EPA Section 608 of the Clean Air Act prohibits knowingly venting refrigerant, including R-410A, R-32, and R-454B, during service or disposal, with fines per day per violation. Recover into an approved cylinder with certified equipment before opening a charged system. A2L refrigerants require A2L-rated recovery gear.
People also ask
Codes cited in this guide
This guide is written and reviewed against the published standards below. Always confirm the current adopted edition with the authority having jurisdiction.