MAGNA3 operation and control modes

MAGNA3 operation and control modes

Discover the various operation and control modes that MAGNA3 offers and find out what each mode offers.

The Grundfos MAGNA3 features both operating modes and control modes.

To use the control modes, the pump will have to be in normal operating mode, which is the factory default. The MAGNA3 also features three additional operating modes: Stop, Minimum and Maximum.

When in normal operating mode, the MAGNA3 gives you the full range of operating mode options you would expect from a state-of-the-art circulator pump.

But the intelligent AUTOADAPT and FLOWADAPT modes really set the MAGNA3 apart from the competition.

Note that the FLOWLIMIT control function can be applied to all MAGNA3 control modes.

The constant curve mode emulates the function of a fixed speed pump adjusted to a set duty point and running at a constant speed.

With MAGNA3, zero to 100% is no longer controlled on the pressure axis but on the flow axis. In effect, this means that any given MAGNA3 model will have a higher maximum flow than previous models with the same maximum head.

However, the variable speed MAGNA3 will give you access to much wider range of control algorithms.

The constant pressure control mode is suited for variable flow systems with very low-pressure losses and open systems, where pipe pressure loss is subordinate to static head.

In proportional pressure control mode, which is used in circulating systems, the pump continuously adapts its performance to varying flow and pressure demands. The MAGNA3 knows its RPM rate, power consumption and flow, and calculates where its actual duty point is in the QH-table based on these data. The pump moves back and forth on the regulation curve by measuring pump torque and adapting RPM. If there is little or no resistance, the system is open, and the pump ramps up. If the resistance is high, valves are closed, and the pump ramps down.

In AUTOADAPT mode, which is the factory default, the pump continuously adjusts its proportional pressure curve and automatically sets a more efficient one, without compromising on comfort. This eliminates the need for manual adjustments in 80% of all installations. In AUTOADAPT mode the default proportional pressure curve has a setpoint of 55% of the pump’s maximum head.

As valves begin to open, the duty point will move along this curve, ramp up RPM and increase flow discharge. If the system reaches its maximum curve, the duty point will follow this curve and create a new proportional pressure curve, based on the new system duty point. Then the process starts all over again.

The FLOWADAPT control mode combines the AUTOADAPT control mode and flow limit control function.

The default flow limit setting in the FLOWADAPT control mode is the intersection between AUTOADAPT's proportional pressure and maximum curves. This enables the MAGNA3 to make sure that flow rate is never exceeded, which can save the cost of a separate pump throttling valve.

In heating applications, your flow rate should be the nominal duty point Q. This is calculated by converting system heat demand into kilocalories per hours, using the point eight six conversion factor, and dividing this number by the temperature difference between the flow pipe and the return pipe.

For example: Imagine a new 10,000 square meter apartment building with a specified demand of 500 kilowatts and heated by modern radiators with a 20° Celsius temperature difference between the flow pipe and the return pipe.

To calculate the MAGNA3's nominal duty point and thus also its flow limit, you multiply 500 kilowatts by point eight six to get a converted heat demand of four hundred and thirty kilocalories per hour. Divided by twenty, this gives you a nominal duty point of 21.5 cubic meters per hour, which you then enter as the pump’s flow limit.

The constant temperature control mode is used in variable flow systems requiring a constant temperature at a user-defined point.

The pump is in charge of flow and no external temperature control is necessary; but an external temperature sensor can be used to provide setpoint input that differs from the temperature measured locally by the pump. This control mode is designed primarily for broad spectrum use in domestic hot water circulation and is thus intentionally slow to regulate.

The differential temperature control mode ensures a constant temperature drop across heating and cooling systems. The pump will maintain a constant differential temperature between the pump and the external sensor.

Finally, there is the constant flow control mode.

This is used in systems that demand constant flow independent of pressure losses, like chillers for air conditioning, heating or cooling surfaces.

Here the MAGNA3 automatically adjusts RPM to varying system resistance, to ensure that flow is kept constant at all times.