Rolair/Associate Engineering Unloader Valve

by Bill Key
(Gurley, AL USA)

Rolair air compressor manifold

Rolair air compressor manifold

Hello, Bill,

Great site...after a lot of reading I may well have answered my question but I'd like another perspective on my problem.

First, here's the details on the compressor:
Rolair/ Associate engineering corp
Hustisford WI 53034
Model 5715K17
SN: C04155
115/240 VAC 1.5 HP

Compressor : Chinook To-Italy 30400830
Motor: Marathon Electric, Wausau WI
Model: 9pa145tbdr5527af p
1.5 HP, 1740 RPM

My problem is that the OEM pressure switch died and I replaced it with a Mamco LF10-4H which has an integral Unloader Valve. It comes built on top of a 4 port manifold. Now, the OEM setup consisted of a machined 4 port aluminum manifold, the top one being for providing air to the simple pressure switch which was mounted via a nipple.

The other 4 ports were 1) a port into the tank, 2) a pop-off valve and 3) some kind of Conrader valve assembly which communicated back to the tank/pump Tee connector via a flex tube. This, I now think, is how they were (in this old configuration) performing the offload function, yes? (I say "old" because, in their latest versions of this compressor, they now use a Square D setup similar to the Mamco one I bought.)

And, if that was indeed how they implemented the offload process, I ought to be able to remove the Conrader valve, put a plug into that port, connect the flex hose up to the offload connector on the Mamco and be on my way? For reference, there's a graphic attached. The Conrader valve is the bit just to the right of the black rubber hose near the bottom of the graphic.

Thanks for the site again,
Bill Key
Howdy Bill...

You are welcome.

OK, the Conrader is a brand of PRV... that's pressure relief valve. You definitely want to have this plumbing into the tank circuit as this is what relieves overpressure if the pressure switch fails open.

A air pipe will send air from the tank via the air regulator, ending in a discharge coupler which keeps the air in the tank until you plug in the mating connector.

That pipe too often is connected to or through an air manifold.

The manifold may direct air to the PRV which is "sensing" the air in the system, and will open automatically when the tank pressure gets to its set point.

Often sitting on the manifold is the pressure switch, using the manifold as a base. The pressure switch is "sensing" the tank pressure via the manifold and trips on to send power to the motor when the tank pressure falls to the cut in set point, and off when the tank pressure gets to the cut out set point.

Pressure switches on the larger DIY air compressors will typically have an internal unloader valve, or an external unloader. Regardless of the type your compressor has, the unloader must be "fed" by a line that tees from the line to the tank check valve, and it must be upstream of that tank check valve.

Whatever your manifold set up ends up being, I believe as long as it meets the criteria above, what it looks like or what brand of components you use (as long as they are the same specifications - power wise) is immaterial.

The only time you'll want to ensure that you use OEM parts is when the air compressor is under warranty and by using non-OEM parts you may void warranty. On the other hand, if the air compressor is under warranty, it should be the vendor or their repair shop that's doing the work anyway.



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