Description
This Tech Note describes how the Observant C3 Platform can be used to control a DC Motor Pump or an AC Induction Motor Pump with a non-latching relay. The connection of a C3 to an electric motor according to this Technical Note should only be performed by an experienced electrician. Remote control capability should not replace local on/off control or any other fail-safe hardware. An Emergency Stop button and appropriate power disconnects should always be in place at the same location as the motor.
Application
A non-latching relay should only be used to control a pump in scenarios where the pump is on for less than 3 hours a day OR where the Field Unit is to be powered from mains power (ie. not reliant on solar). This is because non-latching relays will draw power whenever the pump is active and can, therefore, significantly drain a Field Unit's battery if the pump runs for longer periods.
If a pump needs to be on for greater than 3 hours a day and mains power is not available on site a Latching Relay should be used instead.
Safety Disclaimer
On-site installation including starter (if applicable), drive (if applicable), contactor, emergency stop and appropriate fail-safe circuits will not be provided by Observant. Observant C3 will interface with 12 VDC relay coil for on-off control.
Pump must be installed by a qualified electrician and/or mechanic. The connection of a C3 to an electric motor should only be performed by an experienced electrician. Fail-safe circuits must be included that are appropriate for remote operation. Remote monitoring and/or control through the Observant platform does not constitute or replace hard-wired safety shutoffs. An Emergency Stop button and appropriate power disconnects should always be in place at the same location as the motor.
Supported Hardware
Electrical motor contactors are typically controlled by high-voltage AC supplies. These need to be controlled by the nominal 12 VDC outputs of the C3 by using 12 VDC coil, mains-rated, contact relays.
The relays should meet the following electrical specifications:
- Nominal supply voltage: 12VDC
- Maximum current draw: 500mA
While any relay that meets the above specification can be used, the following relay has been used successfully in 240V pump control applications:
- Manufacturer: Finder
- Part number: 22.22.9.012.4000
Installation
- It is typical for the C3 and associated wiring to be housed within the same switch box as the electric pump contactor.
- Both the C3 and the relay(s) can be mounted on standard, 25 mm DIN rail.
- A 12 VDC power supply will need to be installed and connected to the auxiliary power input of the C3. This external supply ensures that the relay coils will be kept energized.
- All existing safety components including disconnects, fuses, overload protection and emergency stops should be left in place without modification.
The C3 uses one output to control one 12 VDC non-latching relay. In this case, Relay Coil A is energized continuously by the C3 (not pulsed) when the motor needs to run.
Figure 2 shows a typical RUN-OFF-AUTO control circuit controlled by a C3 when in AUTO mode. Non-latching Relay A is added as shown to allow remote control.
The polarity doesn't matter for most non-latching relays but the convention is to wire as follows:
Example 1
Example 2
The relay's datasheet will specify if polarity needs to be maintained.
Configuration
This setup corresponds to the 'Output Control' device in Global. This can be found under the 'Pump Control' category in Manage Equipment. If water flow is being monitored with a flow switch or pressure switch, choose the Input port that is monitoring the flow. Otherwise leave it as None. You can also feedback the pump status through an Input port if you're not monitoring flow.
The pump will be shut off automatically if there is no flow for the duration in the Timeout field. An alert will be sent if you are registered for alerts.
Note - a pulse output flow meter cannot be used as a flow indicator at this stage.
To set up pump automation, contact our Support Team.
Manuals, Links and Downloads
The Technical Note, Electric Pump Control is available for printing or downloading in either letter (OBS-USR-TN004-R1-LTR) or A4 (OBS-USR-TN004-R1-A4) format.