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Understand unloader valves
- Thread starter Karl_T
- Start date
- Joined
- Jun 12, 2014
- Messages
- 4,824
I would suggest using a pressure switch with two NO contacts (these are fairly standard items for directly switching 240VAC see attached Square D pressure switch), one NO and goes to the VFD NO of relay output 1 to be used as an unloader solenoid. Set P6.02 = 14 which will close the VFD relay when the VFD is at speed. The second pressure switch NO connects the common of the VFD to multi functional input 1 which will signal a run command to the VFD. Be very sure that you do not cross the pressure switch contacts, so use L1 to T1 for the unloader, L2 to T2 for the VFD run command. I would use a 220/240VAC solenoid NC for the unloader, they are very low amperage, the one below is about is 0.03A. You need to make sure the solenoid is suitable for the maximum pressure, which I assume is 175 PSI. The VFD output 1 relay is rated at 250VAC/3A, you do not want to use HDO output, use RO1A and RO1C .
So when the pressure switch is activated both pressure switch contacts go to close, the VFD executes a run command from L2 to T2, L1 to T1 is closed but the VFD output relay will not close until the motor is at speed and the solenoid will then close (I assume the start up state of the unloader is NO). When the pressure limit is reached the pressure switch goes to open which turns off the input 1 run command and de energizes the solenoid. Agree with Jim that leave the VFD on during the day or when you want the compressor to be used. You can also add switch in series with input S1 so that when open the VFD will not start. I do this with my compressor contactor as opposed to having a main power disconnect.
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So when the pressure switch is activated both pressure switch contacts go to close, the VFD executes a run command from L2 to T2, L1 to T1 is closed but the VFD output relay will not close until the motor is at speed and the solenoid will then close (I assume the start up state of the unloader is NO). When the pressure limit is reached the pressure switch goes to open which turns off the input 1 run command and de energizes the solenoid. Agree with Jim that leave the VFD on during the day or when you want the compressor to be used. You can also add switch in series with input S1 so that when open the VFD will not start. I do this with my compressor contactor as opposed to having a main power disconnect.
- Joined
- Oct 14, 2014
- Messages
- 1,979
You're late to the party 
I did it as you outlined but SWMBO complained about VFD noise on her radio. So, changed it to have the second pressure switch contact bring in a contactor in front of the VFD. Yep, I used Mcmaster Carr's best air solenoid to get the 150 PSI rating.
I did have trouble understanding several parts of this manual - no where near as user friendly as the GS2 unit manuals from Automation Direct. I guess Chinglish is not my best subject
I did it as you outlined but SWMBO complained about VFD noise on her radio. So, changed it to have the second pressure switch contact bring in a contactor in front of the VFD. Yep, I used Mcmaster Carr's best air solenoid to get the 150 PSI rating.
I did have trouble understanding several parts of this manual - no where near as user friendly as the GS2 unit manuals from Automation Direct. I guess Chinglish is not my best subject