PT Connection To Pump

[Lenny]

Hi all.

Could someone please confirm where to connect a 4-20mA pressure transducer to AI2 in the attached photo. I believe it’s terminals 7 & 8 but the pump is not responding at all.

Thanks.

 

[Rocboni]

Basically you have a circulation pump with an attached inverter?

The analog inputs are AI1 and AI2 you can use either, you’ll have to configure the inverter parameters to allow PID control as per page 17 onwards of the manual, have you done this? Depends on what your trying to do with it though.

 

[Lenny]

Thanks for the reply.

AI2 has been configured in the grundfos go app for pump control via discharge pressure into a private water main. I've taken a 24V supply to the transducer from terminal 8 with the return from the transducer into terminal 7.

Screen is connected to gnd. The pump doesn't control to the pressure setrpoint at all.

 

[Rocboni]

Is there a jumper between 2 and 6 for start signal?

 

[Lenny]

Yes.

Starting to think it may be an issue with airlocking around the transducer due to its position as part of the pump assembly. With the loop calibrator connected in place of the transducer, the pump responds as it should.

 

[LeeH]

If the polarity is correct and the transmitter is healthy then I would say that’s the only thing it could be unless it has the wrong range of course.

 

[Lenny]

Sorry for not following up.

Turns out the fault was due to airlocking around the PT. The new VSD didn't like the setup so I moved the PT further along the discharge pipework and it worked fine.

Thanks for the replies, nothing worse than when you start doubting yourself!!