Is it possible to run two pumps off one pressure switch if they are different sizes and connected to each other with their own tanks?
Yes, it is possible to run two pumps of different sizes off a single pressure switch, even if they are connected to separate tanks. However, several factors need to be considered to ensure safe and efficient operation:
1. Pressure Setpoint Compatibility
- Both pumps and their associated tanks must operate within a compatible pressure range. The pressure switch will activate or deactivate both pumps based on a single setpoint, so the system must be designed to accommodate this.
2. Pump Sizing and Flow Distribution
- Since the pumps are of different sizes, their flow rates will differ. The system must ensure that the larger pump does not overwhelm the smaller pump or cause pressure surges. Proper flow balancing techniques, such as check valves, should be implemented.
3. Check Valves
- Install check valves on the discharge of each pump to prevent backflow from one pump to the other or between tanks. This ensures that each pump operates independently without interference.
4. Control Logic
- If you’re using a basic pressure switch, both pumps will turn on or off simultaneously. To operate them independently (e.g., alternating or staging the pumps), you may need additional control logic, such as a relay-based system or a programmable logic controller (PLC).
5. Tank Connections
- If the tanks are connected to the same system but serve different purposes, ensure the pressure equalizes across the tanks. Otherwise, pressure fluctuations may cause instability in the system.
6. Pressure Switch Capacity
- Verify that the pressure switch can handle the combined electrical load of both pumps. If not, use contactors or relays to manage the pump power.
7. Safety Considerations
- Ensure proper overload protection for each pump. This includes circuit breakers or motor protection devices specific to each pump’s size.
Practical Example
- A small pump could maintain pressure for low-demand periods, while a larger pump kicks in during high-demand periods. In this case, you might stage the pumps with a pressure switch and additional controls, where the smaller pump starts first and the larger pump activates if pressure continues to drop.
When it is possible, careful system designing is crucial. Consulting with a controls engineer or instrumentation specialist can help optimize the setup for reliable operation and ensure compliance with safety standards.