I have a 5 hp Sanborn compressor with air piped around my shop. I'm happy
with the setup but would like a tad more capacity. I also have a 3 hp
compressor sitting around doing nothing at the moment. Does anyone see any
issue with me just paralleling the 3hp and 5 hp compressors. They would end
up at opposite ends of the shop. Thanks in advance.
Here's what I think.... It would work, but you would have to adjust the
pressure on/off switches to be the same. If not, then only one compressor
would be doing all/most off the work. (unless you draw down on the tank
alot) And have the range between low and high set far enough apart where the
two compressors don't "buck" the motors.
I'd just pipe in the extra compressor tank and not plug it in to AC- that
would get more capacity. Save the motor for a "hot swapable spare" when the
5hp goes bad.
Now do you see the benefits of cross-posting, not multi-posting ?
(this same question is in rec.metal - got exactly the opposite answer)
I'd set the pressure switches a few psi apart. If you try to start
both motors together, you're likely to pop the workshop fuse.
Compressors take a lot of current on startup.
(Our workshop has a poor supply. Run the plasma cutter too high and
the fuse blows when the compressor starts up)
Die Gotterspammerung - Junkmail of the Gods
I might say you don't know what you are talking about. Aw hell, I will.
If he needs extra capacity, they both will be running while he needs it. He
can shut the other off when he doesn't need it.
How do two motors pumping air buck each other? Got me.
You should set the cut on of one of them a bit lower. That way the other
will run almost all of the time, while the other only comes on when the
pressure really gets drawn down.
Jim in NC
Overall CFM will not increase with just another tank. You need
another pump to put air into the tanks faster, so you can drain it
faster without running out. Just adding another tank will cause
slower on/off cycles for the one motor that runs (i.e. takes longer
before it kicks in, but runs longer before it stops).
If you use more CFM than the primary pump can replace, eventually the
pressure will fall below the cut-in for the secondary pump, and you'll
increase the CFM going into the tanks. If this new CFM now exceeds
the demand, eventually the tanks will fill up. If not, at least
you'll have less time to wait for the tank to refill.
Note that they make tanks with dual pumps, which operate just as I've
The original post talked about the HP ratings of the two compressors,
and never mentioned the tank sizes. One would infer that the OP was
interested in increasing the CFM capacity, not the storage capacity.
If the OP was interested in storage, the OP would have mentioned tank
sizes and not HP.
If the OP was interested in PSI, the OP would have asked about
changing the pressure switches.
And even if you're narrow-minded, the rest of us want to be helpful
and provide a wide range of information so that the OP can make an
Nope, I used to do it all the time before I bought a larger compressor. I
just set one to kick in a few PSI less than the other. That way only one
would run when air usage was low, but the second would kick in to help keep
up when needed.
That's exactly what happens in many industrial situations. I have engineered
many multiple compressor systems to run as you describe. One suggestion
would be to switch then on independently unless you need all the capacity.
That way you can run each machine occasionally rather than have the machine
with the lower setting sitting idle for a long time.
I don't see a problem as long as both compressors operate within the
same pressure ranges.
I can see where air from one compressor may damage the other compressors
cut off switch if the one compressor makes significantly more pressure.
Just remember that unless you use enough air to get the reservoir
pressure below the "on" setting of BOTH compressors, only the one with
the higher "on" setting will ever run. The other will only act as an
additional tank under most circumstances. In industrial settings with
multiple paralleled compressors the controls are often interconnected
so that they all come on or alternate or otherwise share the actual
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