Rex Burkheimer wrote:
> Using the aforementioned Craftsman Professional 6-hp oilless compressor, cfm
> rating 11 @90 psi, with a D/A sander, the compressor would stop altogether
> for about 15 minutes. Then it would presumably cool down and start again.
> It was only running the one sander, albeit more or less continuously. Is
> this just exceeding the duty cycle? This is normal? Any way to reduce or
> eliminate this, short of buying another compressor?
>
>
Hi Rex,
The pump on any air compressor should not run for more than 2/3 of the time. If
you are sanding constantly and your compressor cycles off and on running for 6
or 7
minutes to build pressure, shutting off and running off the tank for 2 or 3
minutes,
you are getting close to the threshold, but it should be ok.
If you pump is running more than 2/3 of the time, you need a bigger compressor.
I'm not sure from the way you desribed it, but if your compressor is actually
cutting
out for periods of time (not just running off the stored air in the tank), then
you are
definitely are exceeding its rating. The only thing that would make the
compressor
cut out would be the thermal overload switch on the motor shutting down due to
overheating.
I think (hope) though, you probably are just running off the air stored in the
tank.
While you are using the compressor, watch the pressure gauge -- your compressor
will
probably kick in at around 100 psi, and cut out at 125 psi -- this is normal.
If your
compressor is shutting down before it reaches its rated capacity (most single
stage
units cut out at 125 psi), then you probably are overheating it.
I do think, though, that your compressor should be able to run your DA with no
problem
unless it is worn or unless you are not supplying sufficient current (your
compressor
probably requires 15 amps).
You can test for current starvation very simply with a decent volt meter.
Measure your
voltage at the compressor receptacle when the motor is not running, and then
when the
compressor is running at near maximum pressure (say at 120 psi). If there is
more than
a 2 % difference in the voltages when the motor is off and when it is at full
load, then you
are starving the motor and this will cause overheating as well.
Example:
If you had an actual 220 VAC with no load, then 215.6 VAC at full load is the
maximum acceptable voltage drop.
First thing to check, though, is to see what the pressure is when the unit cuts
out. If it is sitting
at or around 125 psi, you should be fine.
doug
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