Anyone see any problems with this "2HP double stage air compressor"?

[Bob F]

Compare to the "5.5 HP" one.

[hubops]

I usually don't put much stock in online reviews, but the two associated with this device are not encouraging. John T.

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I think the first reviewer is an idiotic "mechanical engineer". The CFM value given by the compressor seller apparently refers to volume of free air sucked into the intake valve.

The second idiotic reviewer is talking about a 3-cylinder compressor he bought before, not this product. He probably broke the 3-cylinder compressor because he didn't put oil into the compressor before using.

[Bob F]

I was looking at the pic, showing the finned pipe going between the cylinders, which is common for 2 stage compressors, cooling the air from the big one before it goes into the small cylinder, but this one also has one intake filter on each cylinder. It is obviously a single stage compressor with 2 cylinders being sold as a "double stage" compressor. The pic really puzzled me.

I did find another picture on another site showing the finned pipe going into a "T" with the other cylinder output to the output connection.

I started looking at compressor "pumps" because my Kellogg 335TV started making horrible noises the last time I used it, and I haven't opened it up yet to see the damage. Hopefully, I can save it in the end, but looking at alternatives got me here.

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This DeWalt 2-stage compressor also has two intake filters. It might be an innovation to use as "two-cylinder single stage" when the pressure is low, like initial fill-up of the empty tank, or you deliberately set the tank pressure to 90 psi or something so 2-stage operation will be a waste of time. There might be a pressure valve inside the second stage to close up the intake valve at a preset pressure to switch the operation from single stage to 2-stage.

[Bob F]

You have quite an imagination. I suspected that the situation, for this

10HP compressor, is that it has 4 cylinders, One larger low pressure and one smaller high pressure in each "cylinder" you see on the compressor. I believe the cylinder head confirms that.

Even better

[invalid unparseable]

That DeWalt link I posted above has a cut-out view of the compressor at the 5th (bottom) thumbnail on the left pane. Click on the 5th thumbnail you can see the internal structure of the two individual heads. One head has an extra smaller piston, so the compressor has two low pressure piston and one high pressure piston in a total of two heads with three sets of internal piston-and-cylinder.

So the Amazon link in your original post may just be similar to this DeWalt compressor, a two-stage air compressor with two intake air filters.

[Bob F]

Both "heads" have 2 pistons, one large and one small, clearly. I missed that image previously, but it does show what I said above almost as clearly as the parts diagram I found for that compressor.

Nope. The other pic I found clearly showed the finned output going to a T with the output of the other side, making it a 1 stage pump with 2 pistons, unless it has two pistons in each side with no intercooling between them. Highly unlikely for that cheap of a pump.

Many 1-stage pumps are built that way. Same deal here.

The claimed "PSI" for the "2HP" pump also suggests 1 stage.

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It's true that you don't need a two-stage air compressor to achieve 115 PSI. The same ad is selling two different compressors. That explains the confusion.

[Bob F]

No. The words "Double Stage Replacement Pump" when you select the 2HP pump for something that is not that explain the "confusion"