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The new pumps work differently

In this article, modern pumps with automatic pressure control are considered. And what does this give us?

To see the difference in performance of modern pumps from non-modern ones, one must understand how a conventional three-speed circulation pump works.

A conventional three-speed circulation pump:

We have already become accustomed to such a pressure-consuming pump schedule

Характеристика насоса (Characteristics of the pump) - this is a pressure-flow characteristic of the pump. It shows how the flow rate varies with the influence of a certain head loss resistance. The higher the flow in the pipe, the less pressure the pump creates (small hydraulic resistance of the system). The lower the flow rate, the greater the pump pressure (high hydraulic resistance)

What is hydraulic resistance?

Точка пересечения (Intersection point) shows the actual flow and head loss (in meters).

Характеристика системы (Characteristics of the system) - this is the pressure-supply characteristic of the system as a whole. The system can be either a closed pipeline ring (heating) and not closed (water supply).

Find the pump work point in this program:

More about the program

There is another way to work pumps. For example,


Such a pump is ideal for a heating system


1. Reduces power consumption, only in case of switching off certain branches (circuits).
2. Do not use bypass valves.

This pump has 7 modes of operation:

1. The fixed speed 1 (that is, the power in mode 1)
2. The fixed speed 2 (that is, the power in mode 2)
3. The fixed speed 3 (that is, the power in mode 3)
4. PP1 (Proportional control, Mode 1)
5. PP2 (Proportional control mode 2)
6. CP1 (Stabilization of pressure, Mode 1)
7. CP2 (Stabilization of the head, Mode 2)

In this pump, only 7 operating modes can be selected. That is, you can not select CP2 at 1 fixed frequency.

What is a fixed frequency?

The answer is very simple! This is the same as the three speeds of conventional circulation pumps. They set the power consumption of the pump. In the first mode, the minimum energy consumption. In the second, average consumption. In the third mode, the maximum power consumption and, accordingly, the pump head output. In fixed-frequency modes there is no automatic pressure adjustment. In these 3 modes there is an imitation of the normal operation of the pump with a curved graph without stabilization and any correction of the head.

There is a special plus in the fixed frequency of the blades. This allows a stable discharge characteristic. That is, reducing the voltage will not affect the reduction in pump head, as it does in conventional pumps.

Why adjust the 1,2,3 pump speed (fixed frequency)?

When designing the heating system, it is also necessary to calculate the circulation pump. In the coldest time, the heating system needs the maximum flow of the coolant. In a warm time, the heating system needs a lower flow rate of the coolant. For more efficient operation of the heating system, these features of the pump must be taken into account. That is, work in low power or more power. And these modes (1,2,3) allow us to set the required capacity of the heating system. Of course, such petty calculations pay off for large projects. And for a private home may not be a particularly effective measure. For example, if the heating system was designed with errors in the choice of diameters, and this led to an increase in the pump's power, then adding a pump with an economic advantage can mock the designers. That is, by knowing the right choice of diameters, you could unload the energy consumption two or three times, rather than 20-40% by introducing an economical pump or changing the pump's speed itself.

And imagine: The most running circulating pump consumes 60-100-130 watts. electricity. 1 mode 60 watts. 2 mode of 100 watts. 3 130 W mode. And try to predict the time when you are going to change the pump speed regimes. On average, the pump will consume 100 watts. And try to calculate how much you will spend money on electricity. That is, the maximum consumption of 130 W is minus the average of 100 W = we get 30 watts of energy saving. And tell me, which of the owners of private houses is engaged in switching the pump speeds? This consumption is comparable to the consumption of one or two light bulbs.

21600 (W х h) / month. For example, 2.5 rubles / kW. Then the savings will be 54 rubles / month.

That is, putting the pump in the 1st operating mode, you can save on electricity. The only question is how qualitatively your system will work. And to understand this there is such a thing as a hydraulic calculation of the heating system.

What is the Hydraulic calculation of systems?

Why do I need a stable pump head for the heating system?

When you have branches in the heating system, which are switched off automatically, then this will be some kind of salvation from the fact that the pump has been running for as long as necessary to give out the flow to the remaining branches of heating. That is, stabilizing the pump pressure, we stabilize the flow in each branch of the heating system. That is, when you turn off different contours (branches), the flow in other branches (contours) does not change. Only here from the scheme will depend on how much the flow will vary. With a radiant heating system, the flow rate will be more stable. The advantages of the schemes are described here:

What is a circuit, a branch, a ring in the heating system?

This effect allows the pump to run as much as the consumption of the heating system. That is, the more disconnected branches, the less the pump consumes electricity.

What is proportional pump control?

This is when the pump head rises as the flow increases.

There are two cases that need to be clarified:

1 случай. It saves energy by reducing consumption. When the house is warm, the longer the branches (circuits) can be turned off, and this indicates that the heat output can be reduced and at this point the pump starts to operate at a low flow rate.

That is, when the consumption of the entire heating system is reduced, this indicates that less heat is required. And if you need less heat, you can reduce the consumption of each heater. Thus, the effect of reducing the energy consumption of the pump is achieved.

2 case. This mode is necessary if the stabilization of the head does not work well enough. This is some strengthening of the effect of the heating system.

This function is useful when the heating system with the stabilization of the head is not effective due to the peculiarities of the operation of the units in the heating system. Well, for example, you have badly matched diameters in the heating system and no balancing valves help to establish the necessary costs. In cases of increased costs, we simply add pressure to these problematic nodes of the heating system. That is, this mode saves the work of the heating system in cases of its inefficient operation.


Proportional control (PP) gives more energy savings than the stable pressure (Cp) of the pump.

Due to what does this pump save energy?

Energy saving appears only if you compare work with a conventional pump without adjusting the head.

That is, when a regular pump continuously consumes the same value of power W without any changes. And with a decrease in consumption, power consumption can increase. A modern pump with automatic control can monitor power consumption downwards.

The GRUNDFOS ALPHA2 L pump consumes as much as necessary to maintain pressure and flow in individual branches (circuits). Provided that the branches (circuits) are disabled. That is, savings occur at the moment when branches (circuits) are cut off and at this point the pump starts to consume less electricity.


If the branches (circuit) are not automatically cut off in the heating system, the pressure-corrected pump is useless for saving energy.

Look at the real flow charts of pumps

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Date added: 04.09.17 The address of the page: