A Packaged Terminal Air Conditioner (PTAC) is a self-contained through-the-wall HVAC unit. Both the evaporator and condenser coils, the compressor, the fan motors, and the controls are housed in a single chassis that slides into a wall sleeve. The outdoor side of the chassis rejects heat (in cooling mode) through a grille on the exterior wall. The indoor side delivers conditioned air directly into the room.
PTACs are common in hotels, motels, assisted living facilities, apartments, and small commercial spaces. They range from 7,000 to 15,000 BTU and typically use R-410A refrigerant (newer units) or R-22 (older stock). Many include electric resistance heating or a heat pump reversing valve for heating mode.
Because everything is in one chassis, there is no ductwork, no separate outdoor unit, and no long refrigerant line set. This simplifies probe placement but limits what measureQuick can evaluate.
[Visual Reference] PTAC unit installed through an exterior wall. The indoor side has a discharge grille that delivers conditioned air into the room and an intake grille where room air enters the unit. The outdoor side has a vent grille for heat rejection (in cooling mode). The entire unit - evaporator coil, condenser coil, compressor, fan motors, and controls - is contained in a single chassis that slides into a wall sleeve.
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Selecting a packaged system type tells measureQuick that the condenser and evaporator are co-located. The app will not expect measurements from a remote outdoor unit.
Pull the PTAC chassis partially out of the wall sleeve to access the refrigerant circuit. Most PTACs slide out on rails after removing a few screws or releasing latches on the indoor trim frame.
Safety first:
With the chassis accessible, you can see both coils, the compressor, the refrigerant lines connecting them, and the service ports (if present).
[Visual Reference] PTAC chassis partially pulled from the wall sleeve on its slide rails, exposing the internal components. The evaporator coil is on the indoor side, the condenser coil is on the outdoor side, and the compressor sits between them. Refrigerant lines connecting the coils are short (often 6-12 inches), and service ports (if present) are accessible on the refrigerant tubing. The entire unit weighs 60-100 lbs.
Everything is within arm's reach inside the chassis. Probe placement:
No outdoor ambient probe is needed in the traditional sense. On a split system, outdoor ambient temperature affects condenser performance from a distance. On a PTAC, outdoor air enters the condenser side of the chassis through a grille just inches from the coil. If you want to capture outdoor conditions, place a temperature probe outside the exterior grille, but this is less critical than on a split system because the condenser airflow path is so short.
No manometer is needed. There are no ducts to measure.
measureQuick evaluates the subsystems it has data for:
| Issue | What You Measure | What It Looks Like in mQ |
|---|---|---|
| Dirty condenser coil | High head pressure, high subcooling, elevated discharge temp | Refrigerant charge may show as overcharged; high-side pressure above normal range |
| Dirty evaporator coil | Low suction pressure, high superheat, reduced delta-T | Refrigerant charge may show as undercharged; evaporator starved |
| Overcharge | Low superheat, high subcooling, elevated head pressure | Charge assessment flags overcharge; compressor running at elevated amps |
| Undercharge (leak) | High superheat, low subcooling, reduced cooling capacity | Charge assessment flags undercharge; low delta-T at supply |
| Compressor failure | Abnormal pressures (equalized or no differential), no temperature change across coils | Pressures equalize quickly after shutdown; superheat/subcooling calculations are meaningless |
| Restricted airflow (indoor fan failure) | Low suction pressure, evaporator icing, very low supply air temp at grille | Similar to dirty evaporator; check that the indoor fan is running at correct speed |
Dirty condenser coils are the single most common PTAC problem. Hotels and apartments rarely clean the condenser side of these units. When the condenser cannot reject heat, head pressure rises, efficiency drops, and the compressor works harder. measureQuick shows this as elevated high-side pressure and higher-than-expected subcooling.
measureQuick is most useful on PTACs when you need to:
measureQuick adds limited value when:
YouTube: - System profiling and probe deployment concepts that apply to packaged equipment
YouTube: (80 min, 13K views) - Measurement capture and evaluation principles applicable to any system type
Check the system profile. If you selected a split system type instead of packaged, the app expects outdoor unit measurements. Change the system type to Packaged. If you still want to capture outdoor temperature, place a probe outside the exterior grille of the PTAC.
Some smaller or older PTACs do not have standard Schrader service ports. You have two options: install a line tap valve (piercing valve) on the suction and liquid lines, or skip pressure measurements entirely. Without pressures, you lose superheat and subcooling calculations, but you can still evaluate temperatures, delta-T, and electrical performance.
If you cleaned the condenser but the evaporator is still dirty, suction pressure stays low and superheat remains elevated. Clean both coils. Also verify the unit's charge - if refrigerant leaked during the service, the system may be undercharged.
Short-cycling on a PTAC usually indicates a dirty condenser (high head pressure trips the high-pressure switch), a frozen evaporator (low-pressure cutout), or a failing compressor. Run the unit and capture pressures immediately after startup, before the safety trips. The pressure readings at the moment of cutout tell you which side is the problem.
Capillary tube systems (like most PTACs) are sensitive to charge. Superheat is the primary indicator, and it responds directly to charge level. measureQuick's charge assessment works well here. The short line set on a PTAC means less refrigerant volume variation from ambient conditions, so charge readings tend to be more consistent than on a split system with a long line set.
Prerequisites (complete these first):
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