Tips for selecting and installing a circulator pump in central heating system
What is a circulator pump
A circulator pump is an electric motor housed in a steel casing. Its rotor transmits rotation through the shaft to the impeller. The rotation of the impeller creates a vacuum at the inlet pipe, drawing in the water. While turning, the impeller throws fluid under pressure into the circuit due to centrifugal force. A head is created, which is the driving force of the circulation in the heating circuit.
It is a device that changes the speed of liquid without changing the pressure. In heating systems, the circulator pump is installed for more efficient heating. In systems with forced circulation, it is an indispensable element. The installation of a circulator pump with three speeds makes it possible to change the amount of transferred heat depending on the temperature outside, thus maintaining a stable temperature in the room.
There are many circulator pumps, but in the heating circuits, “wet” and “dry” type designs are used.
If the rotor is separated from the contact with the liquid by an O-ring baffle, the structure is considered “dry”. During operation, a film of water forms between the rings, which, due to surface tension, seals the electrical part. As the abrasive wear progresses, the rings are compressed by the control spring. The pumps are used in systems with high flow rates. They are used in boiler rooms that heat several buildings. They have a good efficiency of 80%, but they are very noisy and require professional maintenance.
In pumps of the “wet” type, only the stator is isolated from the aqueous medium. The pumps with a wet rotor operate almost silently and can pump water without failure for more than 10 years. They have a lower efficiency (about 50%), but their characteristics are more than enough for heating any house. The power consumption of the pump is low, the energy consumption per hour with periodic switching on is 50-200 watts. The pumps have a three-stage load regulation.
Select a proper circulator pump
The choice of pump power depends on the area of the room, the requirements for the temperature and the boiler power. We proceed from the averaged indicators, calculating the characteristics of the circulator pump:
- For 10 m of pipe length, 0.6 m of pump pressure head is required. The regulated value for the pump is indicated in the performance curve, measured in meters of water column.
(Head – hydraulic resistance of the system. The value is measured in meters and, as a rule, is set by the value of the highest point of the pipeline.)
- The water flow rate is calculated according to the boiler performance. A 25 kW boiler heats 25 L / min, a 15 kW radiator needs a flow of 15 L / min.
The longer the circulation loop and the larger the cross-section of the pipes, the more powerful the circulator pump is required to heat the house. If the coolant is not water and more viscous, the pump requires increased power.
The characteristics of the acquired circulator pump should be 10-15% lower than the calculated values. If you install an over powerful pump in the heating system, you may encounter the problem of increasing power consumption, the appearance of excessive noise, and rapid wear of equipment parts. A low-power pump will not be able to pump the coolant in the required volume. Many models of modern circulator pumps are equipped with electronic or manual controls for the speed of rotation of the pump rotor shaft. The highest efficiency is achieved at maximum shaft speed.
Thermal valves, found in many heating systems, regulate the room temperature in accordance with the set parameters. The valve closes when the temperature rises. This increases the hydraulic resistance and, accordingly, increases the pressure. These processes are accompanied by the appearance of noise, which can be eliminated by switching the pump to low speed. Pumps with built-in electronics, capable of smoothly regulating pressure drops depending on changes in the amount of water, cope with this task more efficiently.
Install a circulator pump
It is recommended to install a circulator pump next to the boiler, before the first branch, but on the supply or return pipeline (better on return pipeline). Modern pumps are made of materials that can tolerate temperatures up to 100-115 ° C.
There is one important point at the installation site. If the heating system has two separate branches – on the right and left wings of the house or on the first and second floors – it makes sense to put a separate pump on each. This will make it possible to set the required thermal regime in each part of the house independently of the other, as well as save on heating in two-story houses. How? Due to the fact that the second floor is usually much warmer than the first, and much less heat is required there. In the presence of two pumps in the branch that goes up, the speed of water is set much less, and this allows you to burn less fuel, and without compromising the comfort of living.
The circulation pump is installed on a bypass, which is cut off from the main system by means of two ball valves. This arrangement of equipment allows you to repair or replace it without damage to the heating system of the house. In the off-season, the heating system can work without a pump, which is shut off using the same ball valves. When frost intensifies, the pump is turned on, opening the shut-off valves along its edges and closing the ball valve on the main circuit. This is how the direction of flow of the coolant is adjusted.
Most problems with the circulator pump arise due to the presence of mechanical impurities in the water (limescale, abrasive wear particles). They are able to jam the impeller and stop the motor. Therefore, a mesh filter must be installed in front of the pump.
Installation rules in the heating system
- For the convenience of dismantling, ball valves must be installed on both sides of the unit.
- To create a barrier to filter limescale and abrasive wear particles, it is advisable to install a special filter in front of the device.
- It is advisable to install an automatic or manual air valve at the top of the bypass path, which will allow accumulated oxygen to be removed from the system.
- Due to the fact that the installation of pumps in the heating system of different manufacturers has its own distinctive features, it is important to observe the installation direction indicated on the pump housing.
- The orientation of the pump rotor shaft must be strictly horizontal. Otherwise, air pockets can form, leaving the bearings without lubrication and sufficient cooling. This will lead to rapid wear of parts and quick equipment breakdown. There is an arrow on the pump casing in the direction of which the water in the system should move.
- Joints and threaded connections must be treated with sealants, and a gasket must be placed between the mating parts.
After the completion of the installation work, the heating system is filled with water. The air is then removed by opening the central screw located on the pump head. The emerging water will signal the complete removal of air bubbles from the pump. After that, the pump can be started up.
High efficiency circulator pumps of compact design, suitable for all HVAC applications, from boilers and heat pumps to Heat Interface Units (HIU) systems. It is controlled with all basic functions and also PWM function for remote control.