AC System Pressure Chart(For All Refrigerant Types)

The AC system pressure chart provides both the low-side (suction) and high-side (discharge) pressures for different types of refrigerants under various ambient temperatures. This ensures the system runs efficiently and prevents compressor damage or poor cooling performance.

Below, we provide a comprehensive AC system pressure chart for the most commonly used refrigerants, including R-22, R-410A, R-134a, and R-12.

AC System Pressure Chart

Refrigerant Type	Ambient Temp (°F)	Low Side (PSI)	High Side (PSI)	Typical Application
R-22	70	58–70	145–250	Older home air conditioners
	80	65–75	170–300
	90	70–80	200–350
	100	75–85	245–400
	110	80–90	400–450
R-410A	70	100–125	300–410	Residential & commercial AC
	80	110–135	350–450
	90	120–140	400–475
	100	130–150	450–500
	110	140–160	500–550
R-134a	70	22–35	100–155	Automotive AC systems
	80	25–40	150–175
	90	30–45	175–200
	100	35–50	200–250
	110	40–50	250–300
R-12	70	25–30	140–160	Older car AC units
	80	30–35	160–180
	90	35–40	180–200
	100	40–45	200–230
	110	45–50	230–260
R-407C	70	60–65	220–250	Retrofit for R-22 systems
	80	68–73	250–290
	90	75–80	275–325
	100	80–85	300–350
	110	85–90	350–400
R-32	70	105–115	340–380	Inverter & split AC units
	80	115–125	380–420
	90	120–135	400–450
	100	130–145	430–480
	110	140–155	460–510
R-600a (Isobutane)	70	15–20	100–115	Domestic refrigerators
	80	20–25	120–135
	90	25–30	135–150
	100	30–35	150–165
	110	35–40	165–180
R-290 (Propane)	70	45–55	150–175	Commercial refrigeration
	80	50–60	175–200
	90	55–65	200–225
	100	60–70	225–250
	110	65–75	250–275
R-1234yf	70	20–30	135–155	Modern automotive systems
	80	25–35	150–175
	90	30–40	175–200
	100	35–45	200–225
	110	40–50	225–250
R-404A	70	45–55	210–240	Commercial refrigeration
	80	50–60	250–280
	90	55–65	290–320
	100	60–70	325–360
	110	65–75	360–400
R-507A	70	50–55	220–250	Low-temperature freezers
	80	55–60	260–290
	90	60–65	300–340
	100	65–70	340–380
	110	70–75	380–420
R-717 (Ammonia)	70	20–30	125–150	Industrial refrigeration
	80	25–35	150–180
	90	30–40	175–210
	100	35–45	200–240
	110	40–50	240–270
R-744 (CO₂)	70	400–450	1000–1200	CO₂ cascade & commercial systems
	80	450–500	1200–1400
	90	500–550	1400–1600
	100	550–600	1600–1800
	110	600–650	1800–2000
R-123	70	15–20	100–120	Centrifugal chillers
	80	18–22	115–135
	90	20–25	130–150
	100	22–28	145–165
	110	25–30	165–185
R-717/R-22 Mix	70	40–50	160–180	Industrial hybrid systems
	80	45–55	190–210
	90	50–60	220–240
	100	55–65	250–270
	110	60–70	270–290
R-502	70	45–50	220–240	Commercial & transport refrigeration
	80	50–55	250–280
	90	55–60	280–320
	100	60–65	320–350
	110	65–70	350–390
R-152a	70	25–30	130–145	Automotive & light cooling
	80	30–35	150–165
	90	35–40	170–185
	100	40–45	190–210
	110	45–50	210–230

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How to Use the AC System Pressure Chart

When checking or charging an AC system, follow these simple steps:

1. Connect gauges:

Attach the blue gauge to the low side (suction) and the red gauge to the high side (discharge).

2. Measure ambient temperature:

Use a thermometer to check the temperature near the condenser unit.

3. Compare readings:

Refer to the chart above and ensure your pressure readings align with the correct refrigerant and temperature range.

4. Diagnose issues:

• Low pressure on both sides → Low refrigerant or restriction.
• High pressure on both sides → Overcharge or dirty condenser.
• Low suction, high discharge → Blocked expansion valve or restricted orifice tube.

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Understanding AC System Pressure Readings

Before diving into the chart, let’s clarify what these pressures mean:

• Low-side pressure (Suction Pressure):
• This is the pressure on the evaporator or suction side of the system. It reflects how efficiently the refrigerant is absorbing heat inside the evaporator coil.
• High-side pressure (Discharge Pressure):
• This is the pressure on the condenser or discharge side, representing how well the refrigerant releases heat outside.
• Ambient temperature:
• The temperature outside or surrounding the AC condenser unit affects the pressure readings.

Proper refrigerant charging depends heavily on maintaining the correct balance between these pressures.

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Common AC Pressure Problems and What They Mean

Pressure Reading	Possible Cause	Effect on System
Low both sides	Low refrigerant charge	Poor cooling, compressor may short cycle
High both sides	Overcharge, dirty condenser	Overheating, poor cooling, compressor strain
Low suction / high discharge	Restriction in the system	Reduced cooling, possible compressor failure
High suction / low discharge	Faulty compressor valves	Loss of cooling capacity
Fluctuating pressure	Moisture or air in system	Inconsistent cooling, noise, and wear

Tips for Accurate Pressure Readings

1. Use the right refrigerant identifier:

Make sure you know which refrigerant your system uses before connecting gauges.

2. Allow system stabilization:

Let the AC run for 10–15 minutes before checking pressures.

3. Avoid direct sunlight:

High radiant heat can affect gauge readings.

4. Clean condenser coils:

Dirty coils increase high-side pressure readings, causing false diagnostics.

5. Use quality gauges:

Inaccurate gauges can lead to incorrect pressure interpretation.

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Why AC System Pressures Matter

Maintaining the correct pressure balance ensures:

• Efficient cooling performance
• Energy savings
• Extended compressor life
• Reduced maintenance costs

Incorrect pressures can lead to system inefficiencies, excessive energy use, or complete compressor failure, one of the most expensive AC repairs.

FAQs

What is the normal pressure for an AC system?

The normal pressure for most AC systems depends on the refrigerant type and ambient temperature. Generally, low-side pressure ranges between 30–40 PSI, and high-side pressure ranges between 150–250 PSI for systems using R-22 or R-134a. Modern R-410A systems operate at higher pressures, typically 110–140 PSI (low side) and 400–500 PSI (high side).

What should the pressure be on a 134a system?

For an R-134a system, the low-side pressure should be around 25–45 PSI, while the high-side pressure usually falls between 175–225 PSI under normal operating conditions at ambient temperatures between 80°F and 100°F. Always check both sides while the compressor is running for accurate readings.

What happens if my AC pressure is too high?

If AC pressure is too high, it indicates overcharging, restricted airflow, or a clogged condenser. Excessive pressure can cause the compressor to overheat, shut off, or even fail completely. It may also lead to poor cooling performance and increased energy consumption.

What AC pressures indicate a problem?

• Low both sides: Low refrigerant or system leak.
• High both sides: Overcharged system or dirty condenser coil.
• Low suction, high discharge: Restricted expansion valve or blockage.
• High suction, low discharge: Faulty compressor valves.
• Unbalanced readings always suggest that the system needs further diagnosis.

How to check AC pressure level?

To check AC pressure:

1. Connect manifold gauges, blue to the low side and red to the high side.
2. Run the AC system for 10–15 minutes.
3. Compare the readings with an AC pressure chart for the correct refrigerant type and temperature.
4. Ensure the readings fall within the expected range for your refrigerant (e.g., R-22, R-410A, or R-134a).

How much pressure should be there in 1.5 ton AC?

A 1.5-ton split AC using R-410A refrigerant typically operates at around 110–130 PSI on the low side and 400–450 PSI on the high side at 85°F ambient temperature. For R-22 systems, expect 60–70 PSI (low) and 200–250 PSI (high). These values can slightly vary depending on humidity, coil cleanliness, and ambient conditions.