What You'll Learn

• What target zones are and why measureQuick uses color-coded ranges instead of single target values
• How the system profile (SEER rating, metering device, refrigerant type) determines the target ranges for each measurement
• How the SEER-to-CTOA 4-bucket system works and why different efficiency systems have different targets
• What green, yellow, and red zones mean on the diagnostic screens
• How outdoor temperature shifts the acceptable ranges during a test
• Why your targets look different from another technician's targets on a different system

What You'll Need

• Device: iPhone (iOS 15+) or Android phone/tablet (Android 10+) with measureQuick installed
• App version: v3.0 or later
• Account: measureQuick account (Basic or Premier)
• Context: A completed or in-progress cooling or heating test with probes connected, or Demo Mode enabled
• Knowledge: Basic understanding of superheat and subcooling (E3) and design temperature difference (E4)
• Time: 10 minutes to read

What Target Zones Are

Every HVAC measurement has an acceptable range, not a single number. A system's target subcooling is not exactly 10.0 degrees - it might be acceptable anywhere from 8 to 14 degrees depending on equipment type and conditions. measureQuick displays these ranges as color-coded zones on the diagnostic screen so you can see at a glance whether each measurement is acceptable, marginal, or out of range.

As Jim Bergmann explains in the Benchmarking video: "you've got my suction line superheat, my subcooling, everything is in the target zones, return air is a little bit low at 66 degrees in here, that's cool, supply or wet bulb and dry bulb are in their target ranges, electrical all looks good, EER looks good on the machine, so everything looks like it's pretty well running the way that we expected."

Target zones replace guesswork with engineering. Instead of memorizing a single superheat number for every system, the app calculates the acceptable range from the specific equipment profile you entered. Different systems get different targets because different systems have different design parameters.

Step-by-Step Guide

Step 1: Understand the Three Zones

measureQuick uses three color-coded zones for each measurement:

The boundaries between zones are not arbitrary. They are derived from manufacturer specifications, ACCA/ASHRAE standards, and the system profile you entered during project setup. A measurement in the yellow zone means the system is operating outside its design envelope but has not crossed into territory that would cause immediate harm or major performance loss. A red zone measurement indicates a condition that should be corrected.

On the diagnostic screen, you can view these zones in gauge mode (where the needle moves across colored bands) or in grid mode (where the cell background changes color). Both views present the same data - choose whichever is easier for you to read in the field.

Gauge view showing P-T dials with green, yellow, and red zones, plus superheat and subcooling readings below

Step 2: How the System Profile Determines Target Ranges

Target zones are not fixed. They are calculated from the system profile you enter when you start a project. The key profile inputs that affect targets are:

• SEER rating - determines the Condenser Temperature Over Ambient (CTOA) target, which drives subcooling and discharge temperature targets
• Metering device type - piston (fixed orifice) vs. TXV determines which refrigerant charge metric is primary (superheat for piston, subcooling for TXV)
• Refrigerant type - R-410A, R-22, R-454B, and R-32 have different pressure-temperature relationships that shift the acceptable ranges
• Nominal airflow setting - CFM per ton setting (typically 400 in dry climates, 350 in humid climates) affects the expected temperature split
• Equipment tonnage - affects capacity targets

This is why accurate system profiling matters. If you enter the wrong SEER rating or metering device type, the target zones will be wrong, and the pass/fail evaluation will not reflect the actual system condition. Garbage in, garbage out.

Step 3: The SEER-to-CTOA 4-Bucket System

One of the most important target zone calculations is the Condenser Temperature Over Ambient (CTOA) target. CTOA measures how many degrees warmer the condensing temperature is compared to the outdoor ambient temperature. Lower-efficiency systems run hotter condensers; higher-efficiency systems run cooler.

measureQuick uses a 4-bucket system to assign CTOA targets based on SEER rating:

The CTOA target cascades into other targets. Subcooling, discharge temperature, and head pressure targets all shift based on the CTOA bucket. A 13-SEER system with a CTOA of 20 degrees F will have different subcooling targets than an 18-SEER system with a CTOA of 15 degrees F, even if everything else about the two systems is identical.

This is why entering the correct SEER rating matters so much. A 16-SEER system profiled as 10-SEER would use a 25-degree CTOA target instead of 20, producing incorrect pass/fail results for the condenser-side measurements.

Tips:

• If you cannot determine the exact SEER rating from the data plate, the AI System Profiler (v3.5+) can extract it from a photo of the equipment label.
• When in doubt, a conservative estimate is better than a wrong one. Check the manufacturer's documentation if the data plate is illegible.

Step 4: How Outdoor Temperature Affects Target Ranges

HVAC systems perform differently at different outdoor temperatures. A system that produces 12 degrees of subcooling at 95 degrees F outdoor will produce different subcooling at 75 degrees F. measureQuick accounts for this by adjusting target ranges based on the current outdoor temperature reading from your probes.

This is the outdoor temperature compensation at work. As outdoor temperature rises, head pressure rises, and the acceptable ranges for condenser-side measurements shift accordingly. As outdoor temperature drops, the system operates at lower pressures and the targets adjust downward.

This is why measureQuick requires an outdoor temperature probe. Without it, the app cannot properly adjust the target zones to current conditions. If your outdoor temperature reading is missing or obviously wrong (for example, reading 120 degrees F on an 85-degree day because the probe is in direct sunlight), the target zones will be off.

Place the outdoor temperature probe in the shade, away from the condenser discharge air. The probe should read the actual ambient air temperature entering the condenser coil.

Gauge view showing outdoor air temperature, approach temperature, compression ratio, and discharge line measurements

Step 5: Interpreting Yellow Zone Readings

A yellow zone reading means the measurement is outside the ideal range but not in failure territory. How you respond depends on the context:

Single yellow measurement, everything else green: The system is performing well overall. Note the yellow reading and check whether it is trending toward green or red. If readings are still stabilizing, wait. If readings are stable and just barely in the yellow, this may be acceptable - use professional judgment.

Multiple yellow measurements: Several parameters at the edge of acceptable suggests the system is under stress. Look for a common cause. For example, low airflow can push several measurements into the yellow simultaneously.

Yellow reading that was green on a previous visit: Something changed. Compare to the benchmark (if one exists) to see the magnitude of the shift. Even though the system has not failed, it is degrading.

Yellow zone and the technician override question: You can override a warning-level finding based on your professional assessment. If subcooling is 1 degree into the yellow zone on a system that otherwise tests perfectly, an override may be appropriate. Document your reasoning.

Step 6: What Changes Targets Between Systems

Two systems on the same street can have completely different target zones. Here is why:

This is the core value of measureQuick's target zone system. It does the engineering for you. Instead of carrying a chart of superheat/subcooling targets for every combination of equipment type, efficiency, refrigerant, and conditions, the app calculates the correct targets from the system profile and current conditions. As one user on a third-party podcast put it: "measureQuick will explain, will tell you what the target range was, certain things will actually lead you to an article to explain."

Video Walkthrough

• YouTube: (6:40). Jim Bergmann demonstrates target zones in a live test, showing how benchmarked values lock in targets and how readings display against acceptable ranges. "All my targets are right within the ranges that I would expect to see, so this allows us to very accurately troubleshoot the system."

• YouTube: (5:38). Covers a specific improvement to how pressure target zones are displayed and calculated

• YouTube: (66,533 views, 72 min). Comprehensive walkthrough including target range display, ideal ranges, and how the app "significantly expanded the troubleshooting ability" through target zone calculations

• YouTube: . Covers acceptable ranges of operation during a live commissioning, including how green flags indicate measurements within target zones

Tips & Common Issues

My target zones look wrong for this equipment

The most common cause is an incorrect system profile. Check that the SEER rating, metering device type, and refrigerant type are correct. A TXV system profiled as piston (or vice versa) will display the wrong primary charge metric targets. Re-enter the system profile and the target zones will recalculate.

Targets keep shifting during the test

If the outdoor temperature probe is picking up condenser discharge air or direct sunlight, the outdoor temperature reading will fluctuate, and the target zones will shift with it. Move the outdoor probe to a shaded location that reads true ambient air entering the condenser.

Why does my 13-SEER system have different targets than my coworker's 13-SEER system?

If the refrigerant type, metering device, or CFM per ton setting differs, the targets will differ. Two 13-SEER systems - one running R-410A with a TXV and one running R-22 with a piston - will have substantially different target zones even though they share a SEER rating and a CTOA bucket.

Best practices for using target zones

• Always verify the system profile before relying on target zone pass/fail results. The targets are only as good as the profile data.
• Let the system stabilize (7-8 minutes minimum) before evaluating readings against target zones. Early readings during startup will often show yellow or red and then settle into green as the system reaches steady state.
• When readings are in the yellow, look for patterns. Multiple yellows on the same side of the system (all condenser-side, or all evaporator-side) usually point to a single root cause.
• Use benchmarking to lock in known-good targets for return visits. Once a system is commissioned and running correctly, the benchmark stores those target values for future comparison.

Reference Material

Gauge Screen Exercise

Gauge Screen Exercise - Page 1

Gauge Screen Exercise - Page 2

Related Articles

Prerequisites (complete these first):

• Superheat & Subcooling - The refrigerant-side measurements that target zones evaluate
• Design Temperature Difference - How expected temperature splits are calculated

Follow-up articles (next steps after this one):

• Reading Diagnostic Flags - Understanding the pass/fail indicators that result from target zone evaluation
• Component Pressure Drops - How individual component pressure drops have their own target ranges
• HVAC Vitals Score - How target zone results feed into the overall system performance score

Related in the same domain:

• Equipment & System Profiling - How to enter the profile data that drives target zone calculations
• A/C Service Workflow - Where target zones appear in the diagnostic workflow

Need Help?

If you have questions about target zone display or calculation:

• Check the Related Articles section above
• Contact measureQuick support: support@measurequick.com