How to install a circulation pump in a heating system

Circulation pump – an essential element of the heating system, ensuring continuous circulation of the heat transfer fluid, guaranteeing the normal operation of the gas or other boiler, heating radiators, and providing comfortable conditions. Simultaneously, any errors or malfunctions with it potentially lead to problems with the boiler itself.

What to do before installing the pump

A mandatory step before starting the installation of the circulation pump remains the flushing of the entire heating system. This will remove existing contaminants from the system, reduce the layer of corrosion on the internal surfaces. Before installing in a new heating system, be sure to complete all installation work.

How to install a circulation pump in a heating system

Where to place the pump

Current standards indicate that the installation of a circulation pump with a drive from a three-phase (single-phase) motor requires the presence of a set of protective equipment, and the specific installation location relative to the device is absent in the recommendations. Regarding the latter, there is an opinion that the device should only be installed in the return for several reasons (in reality, they are erroneous):

  • A lower temperature increases the service life (in reality, the circulation device is designed for 110 degrees, and the temperature of the carrier is within 80-90);
  • Fluid densification hinders water pumping by the device (in reality, a 20-degree difference almost does not affect density).

How to install a circulation pump in the heating system

A serious mistake would be to install the ACV circulation device or devices from other brands in the central part of the system, as all radiators of the heating system before it will experience a parasitic phenomenon due to reduced pressure.

In reality, the installation location of the De Dietrich circulation device to the heating appliance is determined solely by the convenience of technical maintenance, repair, so there are no errors here by definition. The only exception is a solid fuel boiler.

How to install a circulation pump in a heating system

How to install a circulation pump in a heating system with a solid fuel boiler

For this type of equipment, the nuance is that it cannot be stopped quickly. If you close the damper to stop, gases will enter the liquid supply pump. This potentially leads to an explosion, emergency release of the heat transfer fluid through the valve, so the circulation pump cannot be installed to the boiler on the supply pipe.


When installing a circulation pump in the heating system, a quality piping of the equipment is performed, ensuring quick and convenient disassembly, installation. Another reasonable solution is to install a filter before the circulation device, saving on the installation of one valve and simultaneously removing dirt from the flow.

Circulation pump installation scheme

The specific scheme for installing a circulation pump in the heating system depends on the principle of its operation and the method of movement of the heat transfer fluid.

Forced liquid circulation

The installation of a circulation device usually follows the scheme in the instructions for the return before the heating gas or other boiler (mandatory when the latter is operating on solid fuel) or after it, but definitely before the first radiator. For convenience of device maintenance, water shut-off valves are installed on both sides, and a mesh filter for cleaning contaminants is mounted. This way, the heat supply through the pump will remain the same, and the equipment will last longer.

How to install a circulation pump in a heating system

Natural liquid circulation

With proper design and installation of the heating system with a natural movement system of the heat transfer fluid, the installation of a Grundfos circulation pump or another device is not required, but in practice, a pump is installed. It is important to correctly make the piping, as errors in calculations, installation lead to inadequate operation of the device and the entire heating system. When installing the device, several points are taken into account:

  1. The scheme in the instructions implies the mandatory presence of a full-flow valve in the main line;
  2. The installation of the circulation pump goes on the bypass, and the resistance should be at or below the same level as the full-flow valve, which will maintain water movement when the pump is turned off;
  3. A check valve is not installed on the piping, as low water velocity or propylene glycol will not open it, and a hydraulic lock in the piping will lead to blockage of the entire system.

When performing the pump piping to supply heat to the system in this case, a 40mm diameter pipe is used, and when installing the device, a slope is maintained, ensuring air venting upwards and water drainage downwards.

Connecting equipment to the electrical network: how to do it safely?

When connecting a circulation pump by ACV, De Dietrich, or other brands to a gas or solid fuel boiler, choose a cable that matches its power and number of phases. The typical solution is a copper wire with a core section of at least 1 mm² (depending on the power) and rubber insulation. For a single-phase heat pump, a three-core wire is suitable, while for a three-phase pump, a four-core wire is necessary. When laying the cable, it is important for it to be physically isolated from pipes, electric motors, and the pump housing itself. When connecting independently, adhere to the traditional color-coding rule:

  • Red, brown, or white insulated wire is for phase;
  • Blue or light blue insulated wire is for neutral;
  • Yellow-green insulated wire is for equipment grounding.

You will find the connection diagram for the circulation devices in the instructions. Be sure to study it to eliminate the risk of incorrect connection and potential errors.

How to install a circulation pump in a heating system

Getting started: how to correctly start the circulation pump

Electrical component check

Before each start of the circulation device, all current-carrying parts (wires, cables, junctions) must be checked for insulation damage. It is essential that the cables are insulated from contact with the pump. The reason for this is the heating of the latter, which ultimately leads to insulation damage.

System filling

Before the first start of the pump, it is essential to fill the system with a heat transfer fluid. The absence of the fluid when using a circulation pump with a “wet” rotor leads to rapid overheating and failure. This is because the liquid acts as a coolant, removing excess heat. For models with a dry rotor, the presence of water in the system is less critical but potentially leads to a breach of sealing due to wear of sealing rings, resulting in leaks. The outcome is the need for repair.


After filling the system with the heat transfer fluid, open the air vent valves. Then perform the following actions:

  • Open the valve in front of the circulation device;
  • Fill the Grundfos or other manufacturer’s pump with water;
  • Start the pump and open the valve at the outlet after the unit;
  • Wait a few minutes and turn off the pump;
  • Conduct secondary air release through existing valves.
How to install a circulation pump in a heating system

During operation, monitor the pressure level in the heating system and add more water or heat transfer fluid if necessary. The presence of air in the system, leading to decreased heating efficiency and accelerated wear of the circulation pump, will be indicated by cavitation noise (hum) from it.

What speed should the pump operate at?

The speed of operation of the heating system pump, determines its power consumption and performance. In general, the higher it is, the faster the hot water passes through the system and the more heat it gives off, but at the same time, the intensity of wear increases. Specific operating modes are determined by the pump model for a gas or solid fuel boiler. The minimum value is usually in the range of 30-35 liters per minute, and the maximum is in the range of 80-90. When determining the circulation speed, follow these recommendations:

  • The maximum pump speed from the instructions is usually used during system bleeding when it is necessary to overcome airlocks by replenishing the heat transfer fluid volume;
  • If the temperature difference between the inlet and outlet of the circuit exceeds 1-2 degrees Celsius, increase the speed;
  • In spring or during thaw periods, reduce the speed of operation.

Types of equipment malfunctions: how to troubleshoot?

The pump does not start, even though everything is assembled and connected according to the scheme:

  • Check the quality of the connection and the presence of power supply;
  • Exclude rotor blockage by unscrewing the plug and inserting a screwdriver into the slot on the shaft to try to turn it clockwise;
  • Contact a service center where they will perform a drive continuity test and fix any other malfunctions.

The pump stops after starting:

  • A shaft blockage is possible, which needs to be flushed with a special solution;

Increased noise level:

  • Reduce rotation speed;
  • Remove air from the heating system, which also hinders heat delivery.