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Duty cycle: the number that decides whether it finishes the job
Updated
A small air compressor makes a lot of heat. Duty cycle is the maker's rule for how long it can run before it must rest. For a quick top-up you will never hit it. For a flat, four low tires, or truck tires, you can. Many listings leave it out, and the manual is the only place to find it.
What the listings I read say
| Inflator | What the listing states |
|---|---|
| AstroAI AIRUN H | Shuts itself off after 15 minutes of continuous use. 10 minute cool-down recommended |
| VIAIR 88P | 25 minute duty cycle at 30 PSI |
| ETENWOLF Vortex S6 | Maker claims 100% duty cycle, with four F150 tires from 0 to 35 PSI without a break as the example |
| AstroAI L7, Airmoto, DEWALT DCC020IB | No run limit in the bullets I read. Check the manual before a long job |
These are maker claims. Note the pressure next to the VIAIR figure. A duty cycle is always tied to a pressure and a temperature. Higher pressure or a hot day means less run time.
Will the job fit inside the limit?
Estimated run time with a 35 L/min unit like the AIRUN H, using the calculator's math. Its limit is 15 minutes.
| Job | Compact car, 195/65R15 | Midsize SUV, 235/65R17 | Full-size truck, 275/65R18 |
|---|---|---|---|
| Top up four tires, 28 to 35 PSI | 3.9 min | 6.5 min | 9.7 min |
| One tire from flat to 35 PSI | 4.2 min | 7.0 min | 10.4 min |
| Four tires from 15 to 35 PSI, after airing down | 10.3 min | 17.3 min | 25.7 min |
Top-ups fit with room to spare. One flat fits. Airing four SUV or truck tires back up from 15 PSI after a trail does not fit in one run. That is a job for the VIAIR 88P or the ETENWOLF Vortex S6, and even then with breaks if the maker calls for them.
How to work within a run limit
- Do the lowest tire first, in case the unit needs a rest before you finish.
- Rest it between tires on a long job. Moving the hose is not a rest. Switch it off.
- Keep it out of direct sun, and do not set it on hot pavement if you can avoid it.
- If it shuts itself off, that is the thermal protection working. Wait the full cool-down. Do not restart it over and over.
- The hose end and the pump body get hot. VIAIR 88P owners mention this. Handle the chuck with a glove or a rag after a long run.
- Stay with it while it runs. Do not leave any inflator running unattended.
All six picks, with their stated limits, are on the shortlist.