Wiring new shop compressor

[rls1160]

Hi everyone, last week I picked up a 3 Phase, Quincy QT-7.5 - 80, 2-stage compressor. There were 2 previous owners. The original owner swapped out the 7.5hp 3-phase motor for 5hp 3-phase motor and installed a 125PSI SD Pumptrol pressure switch.

My shop is powered by a 10hp American Rotary ADX Phase converter. I don't have the need to have this compressor running everyday or all day long. Only when needed to power pneumatic tools. I am a one person shop.

The only reason I can think of having this secondary on/off switch is to have essentially a kill switch that prevents the pressure switch from starting the compressor while the phase converter is not running.

I do not have any way of starting the RPC off a machine start switch. So this is all a manual process of starting tye RPC then starting whatever machine I am going to use.

Obviously I would have the RPC running prior to running the compressor.

WHAT I AM CURRENTLY WIRKINGBON AND HAVE QUESTIONS ABOUT:

The tank is rated for 200 psi and all high pressure relief valves are rated for 175 psi.

I have ordered a new pressure switch with a 135/175 on/off limits.

The motor controller is a Siemens 14DS-32A 3-phase 200/230 VAC
Max HP 7.5
Max Amps 27
Includes a Siemens SP 100 adjustable solid state overload relay CAT. NO. 48ASF3M20
 

My question is related to wiring the Siemens motor starter with secondary Siemens 49SBSB4 On/Off switch.

Why would there be duplicate on/off control switches?

There is a pressure switch
There is a secondary on/off switch added to the motor controller.

Secondly, how do I wire in the secondary on/off switch?

I am missing one wire from the secondary on/off switch. It looks like it needs to be wired between the two hots that run between the starter coil and the pressure switch?











This compressor has a pressure switch to control on/off based on pressure.

Can the additional on/off switch be wired to operate as an override or kill switch to disable the pressure switch to prevent tye compressor from starting if RPC is not running?

Thank you for any insights you may be able to offer.

Rick

 

[rls1160]

Here is a picture of the Siemens motor controller schematic.

 

[markba633csi]

I believe you want a series circuit:
From one hot you go thru the coil, then thru the pressure switch, then thru the second switch, then back to the other hot.
From the RPC you want to use the two line hots. Don't use the synthesized hot and a line hot. The synth hot may sag during startup.

 

[rls1160]

Hi Mark, Thank you for the information.
L3 from the RPC I believe is the synthesized leg of the 3-phase.

Is that correct?

 

[markba633csi]

I can't say, you'll have to refer to the RPC documentation or trace it out visually
The two line hots would measure 120 volts ac each to neutral, the synth hot is higher like 208 or something to neutral

 

[rls1160]

Thank you, that's what I thought.

Rick

 

[CJ5Dave]

How can the compressor start with the phase converter turned off?

 

[rls1160]

It can't Dave and I am aware of that.

All of my shop equipment is 3-phase. I use an RPC to generate the 3-phase needed to run my equipment. When I need to run a piece of 3-phase equipment I turn on the RPC then the equipment.

I do not leave the RPC running in idle mode continuously.

I just don't want the compressor trying to kick on under 230 volt single phase. That's why the discussion about the secondary on/off switch that is already part of the motor controller.swith box as I have shown in the attached pictures.

Rick

 

[Winegrower]

I wired a relay contact across the outside pressure switch, and a low voltage circuit to a switch inside the shop, so I can turn the compressor on and off remotely. By closing the contact across the pressure switch, the system thinks the tank is charged and stops normally. It won't start again until I open the contact. If it's already at working pressure, nothing happens. If not, the compressor turns on and charges and stops normally.

This has been a huge convenience.

By the way, I also added an automatic drain valve that is programmable and I've set to drain for 4 seconds every time the compressor starts. Also added a "Load Genie" unloader valve. I haven't had to drain the system manually in several years, and found no water ever in the line regulator drain cups.

 

[CJ5Dave]

Does the 230 single phase come through the RPC and then to 2 poles of the 3 phase compressor? If so the compressor cant get 220 single phase till the RPC does?