PUMP CONTROL SOLUTION NZ
CLIENT:  TAURANGA
PROJECT: Off Grid Pumping Station

SOLUTION:

We designed and built two individual control panels. The master control panel would automate the primary pumps. First, we designed a simple "independent"  PLC control system  using  a  Zelio  PLC  smart  relay  controller  to monitor the rain tank water level  and  temperature. The  rain  tank  circulation  pump  automation is controlled  by a tank  level pressure transducer and pump pressure transducer respectively. End user rain water demand would operate on pump pressure drop...eg when a tap is opened.

The next step was to install and program an additional Zelio PLC smart relay  controller in the same control panel for the grey water system. Again, we used the basis of this rain tank/pump program for a second simple  "independent" control system to monitor and automate the grey tank lift  pump for w.c cistern water demand and high level water diversion. We added PLC logic  for  the w.c cistern dosing. The grey water level is maintained by an ultrasonic level sensor at <65%. Water above  this level will trigger the grey water irrigation valve to open and diverts the excess grey water to the remote irrigation holding tanks and pumping station.

We designed and automated a simple filter backwash  cycle followed by a grey pump suction line purge to be performed at the end of every grey pump off cycle. This was done by  momentarily changing the VSD speed from 50Hz to 60Hz to maximize stored water pressure in the pressure tank, post pump cycle, in anticipation of the imminent  backwash cycle. This was able to provide an extra 20% pressure gain resulting in 85-90 psi for  the backwash water pressure. This pressure is dissipated within 5 seconds, through the filter and is necessary to perform the filter backwash thoroughly. The pressure drops post backwash to  22 psi at idle, so risks of leaks are very low. The backwash system has extended the filter maintenance schedules significantly to provide a reliable grey water system.

We designed and built a second control panel for the remote irrigation pump and tank automation. We wrote a dedicated program  for a third simple Zelio "smart relay" PLC  controller to automate the off the grid irrigation pumps on timed outputs throughout daylight hours. A diversion valve was added to alternate (or divert excess)  irrigation tank water to the greenhouse/gardens.

All  independent PLC systems were programmed to monitor water levels and temperature, low tank alarms and inline flow switches were incorporated to prohibit pumps running dry. Low pump pressure PLC logic was added to the programming as a precaution for the pumps.

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All three independent  PLC's were networked back using Modbus serial RTU to a master PLC with a custom HMI solely for monitoring, secondary control and alarms and events trending. We configured a wireless  transceiver RF (radio frequency) modbus RTU   network for the  irrigation pump station for remote local PLC network communication. Global monitoring and control is achieved from the ethernet network port on the HMI to the world wide web via a smart phone/device.