Air Compressor Pump Up Time Calculator

Calculate how long your compressor takes to pump up from cut-in to cut-out pressure based on tank size and compressor CFM.

Understanding Pump Up Time

Pump up time is the duration required for your compressor to raise tank pressure from the cut-in to cut-out setting. This critical metric affects compressor cycling and system performance.

Key Pump Up Time Concepts

1. Pressure Band

The working range of your compressor:

  • Cut-In: Pressure when pump starts
  • Cut-Out: Pressure when pump stops
  • Typical band: 20-40 PSI
  • Wider bands reduce cycling

2. Tank Fill Time

Factors affecting fill time:

  • Tank volume (gallons)
  • Compressor delivery (CFM)
  • Pressure difference (ΔPSI)
  • Ambient conditions

3. Cycling Impact

How pump up time affects operation:

  • Short times = frequent cycling
  • Long times = extended run periods
  • Optimal: 1-3 minutes for most systems
  • Affects motor lifespan

Typical Pump Up Times by Compressor Size

Tank Size 5 CFM 10 CFM 20 CFM 30 CFM
30 Gallon 2.5-3.5 min 1.2-1.8 min 0.6-0.9 min 0.4-0.6 min
60 Gallon 5-7 min 2.5-3.5 min 1.2-1.8 min 0.8-1.2 min
80 Gallon 6.5-9 min 3.3-4.5 min 1.6-2.3 min 1.1-1.5 min
120 Gallon 10-14 min 5-7 min 2.5-3.5 min 1.7-2.3 min

Times shown for 30 PSI pressure band (e.g. 100-130 PSI) at 85% efficiency

Pump Up Time Calculation Method

Basic Formula

The pump up time is calculated using:

Time (minutes) = [Tank Volume × (P2 - P1)] / [CFM × 14.7 × Efficiency/100]

Where:

  • Tank Volume = In gallons
  • P2 = Cut-out pressure (PSIA = PSI + 14.7)
  • P1 = Cut-in pressure (PSIA)
  • CFM = Compressor free air delivery
  • 14.7 = Atmospheric pressure at sea level
  • Efficiency = Pump efficiency percentage

Optimizing Pump Up Time

Adjustable Parameters

Pressure Band

  • Wider band increases pump up time
  • Reduces cycling frequency
  • Typical 20-40 PSI difference
  • Adjust pressure switch settings

Tank Size

  • Larger tanks increase fill time
  • Provides more buffer capacity
  • Consider secondary tanks
  • Space and cost constraints

System Improvements

Compressor Matching

  • Proper CFM for demand
  • Multiple compressors
  • Variable speed drives
  • Correct pressure ratings

Efficiency Gains

  • Reduce air leaks
  • Maintain intake filters
  • Proper lubrication
  • Cooling system maintenance

Frequently Asked Questions

Q: What is a good pump up time for my compressor?

A: Ideal pump up times vary by application:

  • Small shop compressors: 1-3 minutes
  • Industrial units: 2-5 minutes
  • Continuous operation: 5-10 minutes
  • Should match your usage pattern

Q: Why does my compressor take longer to pump up?

A: Common causes of increased pump up time:

  • Compressor wear (rings, valves)
  • Air leaks in system
  • Dirty intake filter
  • Higher altitude operation
  • Increased demand during pump up

Q: How often should my compressor cycle?

A: Recommended cycling frequency:

  • Reciprocating: Max 6-8 starts/hour
  • Rotary screw: 4-6 cycles/hour
  • Centrifugal: Continuous operation
  • Excessive cycling reduces motor life

Q: Can I increase my pressure band to reduce cycling?

A: Yes, with considerations:

  • Wider bands reduce cycling
  • Ensure tools work at lower pressure
  • Don't exceed tank/component ratings
  • Typical max band: 40-50 PSI
  • Adjust pressure switch carefully

Troubleshooting Pump Up Issues

Slow Pump Up Symptoms

  • Check for air leaks (soapy water test)
  • Inspect compressor valves and rings
  • Verify intake filter cleanliness
  • Test actual CFM output
  • Monitor voltage during operation

Rapid Cycling Problems

  • Check pressure switch operation
  • Inspect check valve for leaks
  • Verify tank drain operation
  • Assess demand during pump up
  • Consider larger tank if appropriate