Air Compressor: 7.5 HP, 25.1 CFM @ 175 psi

[FatherWes]

I don't think I can attach a link, but there's potentially a heck of a good deal on a compressor at BCauction.ca auction number: A248776

It's a Speedaire, Air Compressor: 7.5 HP, 25.1 CFM @ 175 psi
Too big for my needs (and power supply), but for someone with the need and power, this could be a great buy. Current bid is $898.88,

The bad news, Auction closes at 19:05 Pacific time. Sorry for the short notice, but I saw the auction a couple minutes ago.

 

[Former Member]

Oh would I love that kind of air supply with a larger tank, but as you said the power requirements.....

 

[Darren]

That due to startup current. My 5hp Devilbis with the same cfm/pressure rating draws 19-20 amps running for comparison.

 

[FatherWes]

That due to startup current. My 5hp Devilbis with the same cfm/pressure rating draws 19-20 amps running for comparison.

Good info.

The risk is the 5 to 6 times in-rush current at startup.
I think a person might beat that with some kind of soft start system?

 

[Chicken lights]

I’m pretty sure that’s my exact compressor, mines getting tired but she still works fine. It’s not a commercial unit, there’s plenty of times I need to wait for it to catch up

No problems with it starting on a 15 amp 220 circuit

 

[Darren]

Good info.

The risk is the 5 to 6 times in-rush current at startup.
I think a person might beat that with some kind of soft start system?

Mine pulls over 100 very breifly at startup but has never tripped the 40 amp breaker its on. Also for motor startup ONLY, nothing else on the circuit, you can upsize the breaker ~250% for a given wire size to eliminate nuisance tripping. The wire is sized for the FLA on the motor plate. There's a chart in the codebook and online. For me a 40A breaker is fine on #10 teck cable.

 

[Former Member]

VFD is the answer.

 

[Former Member]

Start up under load is usually about 2.5 to 4 times the running load depending on load during start. Compressors are among the worst (and so are elevators) as they start under full load.

There are several methods to reduce this on compressors, unloader valves during startup brings your to the bottom end of the current requirement. Or VFD's and constant torque motor, your start up current will stay very close (if not identical) to your full load running current (this is how we did years ago at the start of using VFD's in the elevator industry).

For my money VFD while more costly offers the best longer term on several planes.

 

[Darren]

AVE did a video a while back about running a compressor on a VFD to boost output. It was pretty interesting. Mine came with a 5hp 3 phase motor. If I didn't have a new replacement motor sitting on the shelf already, a VFD would have been my first choice for sure.