Comparison Rudes 15WBX-15 15 m

3/4"

vs Optima PTS15-11 11 m

3/4"

162 mm

— Centrifugal. As the name suggests, this type of pump uses centrifugal force. Their main element is the impeller installed in a round casing; the inlet is located on the axis of rotation of this wheel. During operation, due to the centrifugal force that occurs during the rotation of the wheel, the liquid is thrown from the centre to its edges and then enters the outlet pipe directed tangentially to the circle of rotation of the wheel. Centrifugal pumps are quite simple in design and inexpensive, while they are reliable and economical (due to high efficiency), and the fluid flow is continuous. At the same time, the performance of such units can drop with high resistance in the circuit.

— Vortex. Vortex pumps are somewhat similar to centrifugal pumps: they also have a round casing and an impeller with blades. However, in such units, the inlet and outlet pipes of the working chamber are directed tangentially to the wheel, and the blades differ in design. The method of operation is also fundamentally different — it uses the vortices formed on the wheel blades. Vortex units are significantly superior to centrifugal units in terms of pressure, but they are sensitive to contamination — even small particles entering the impeller can cause damage, significantly reducing efficiency. And the efficiency of vortex pumps is low — 2-3 times lower than that of centrifugal pumps.

The maximum flow of a pump is the amount of liquid it can pump in a certain amount of time.

Features of choosing the optimal performance option depend primarily on the purpose of the pump (see above). For example, for DHW recirculation models, the pump performance should not exceed the performance of the water heater. If the water heater is capable of delivering 10 litres per minute to the DHW circuit, then the maximum pump performance will be 10*60=600 L/h. The basic formula for calculating the performance of a heating system takes into account the power of the heater and the temperature difference at the inlet and outlet, and for the cold water system — the number of points of water intake. More detailed information about the calculations for each application can be found in special sources, and it is better to entrust the calculations themselves to professionals.

The head can be described as the maximum height to which a pump can lift liquid through a vertical pipe without bending or branching. This parameter is directly related to the pressure that the pump produces: 10 m of head approximately corresponds to a pressure of 1 bar (do not confuse this parameter with operating pressure — see more about it below).

The head is one of the key specs for most circulation pumps. Traditionally, it is calculated based on the difference in height between the location of the pump and the highest point of the system; however, this principle is relevant only for units that boost the pressure of cold water(see "Suitable for"). Circulation pumps for heating and DHW work with closed circuits, and the optimal pressure depends on the total hydraulic resistance of the system. Detailed calculation formulas for the first and second cases can be found in special sources.

The lowest pressure in the circuit where the pump is connected, at which it can perform the main task (see "Suitable for"), providing the claimed operating parameters. The technical features of many modern models are such that some of them can operate at almost zero pressure, simply by the presence of water in the pipe; therefore, this parameter may not be specified at all.

The highest liquid temperature that the pump is capable of operating normally.

The possibility of using the unit directly depends on this parameter (see "Suitable for"): for example, models for heating systems must tolerate a temperature of at least 95 °C, and for DHW supply — at least 65 °C. Well, anyway, this parameter should not be exceeded: an overheated pump will fail very quickly, and the consequences of this can be very unpleasant.

The electrical power consumed by the pump during normal operation and maximum performance.

This indicator directly depends on performance — after all, for pumping large volumes of water, an appropriate amount of energy is needed. And the power depends on two main parameters — electricity consumption and the load on the power grid, which determines the connection rules. For example, pumps with a power of more than 5 kW cannot be connected to ordinary household sockets; more detailed rules can be found in special sources.

Arrangement of the motor shaft in the normal operating position of the pump.

First of all, the general layout of the unit and its suitability for certain conditions depend on this parameter. So, with the most popular coaxial arrangement of holes (see below), the motor shaft, usually, is located perpendicular to the direction of water movement. This means that only a pump with a horizontal shaft is suitable for tapping into a vertical pipe. But for a horizontal line, the choice is related to which direction it is more convenient to turn the pump housing — up (when installed in a narrow, elongated niche) or sideways (when other objects above the pipe interfere with the vertical installation of the unit).

Note that there are universal models that allow both placement options.

It is the material from which the motor shaft in the pump is made.

— Cermet. It is a material that combines metals and their alloys with non-metallic components. In modern pumps, different types of cermets can be used, differing in price and quality; usually, the features in each case directly depend on the price category of the unit. However, it is well suited for household models with relatively low performance but is poorly suitable for professional use. Therefore, in pumps of more than 15,000 litres per hour, cermet shafts are rarely used.

— Stainless steel. This material is highly durable and reliable, due to which it is found in almost all categories of pumps — from relatively simple to professional, the performance of which is in the tens of thousands of litres per hour. However, it is somewhat more expensive than cermets.

It is the material from which the outer part of the pump housing is made.

— Stainless steel. As the name suggests, stainless steel is virtually corrosion-resistant. However, this is not its only advantage — this material is very durable and reliable, due to which it is used even in powerful high-performance models.

— Cast iron. This material is in many ways similar to steel — in particular, it is considered very reliable — but it has a slightly higher weight. On the other hand, in most cases, this is not a noticeable drawback, but cast iron costs a little cheaper than stainless steel.

— Brass. An alloy based on copper and zinc, which has a golden colour. The varieties used in circulation pumps are highly resistant to corrosion and even surpass stainless steel. Therefore, this option is well suited for water with a high oxygen content. The disadvantage of brass can be called a higher cost than that of the same steel.

— Bronze. Another copper-based alloy. According to the main features, this material is similar to the brass described above. — Plastic. Units with plastic housings are lightweight, inert to water, and completely unaffected by corrosion. Moreover, polymer materials allow almost any thickness of the body, which determines the requirements of the mould for casting the workpiece. The di...sadvantage of plastic is its low mechanical strength. The plastic housing can be damaged on the outside and outside due to any kind of impact.