frequently asked questions about boiler and apartment metering units
Boiler and apartment metering assemblies are key components for the proper functioning and energy efficiency of every heating system, yet their selection often raises questions regarding sizing and functionality.
Role of the non-mixing boiler assembly
The non-mixing boiler assembly primarily serves to separate the hydraulic cycle of the boiler from the heating system, thus preventing condensation in the cold boiler and ensuring stable operation. In this configuration, the pump in the module circulates the heat transfer fluid directly through the boiler and then to the radiators or floor heating without mixing cold water back into the boiler.
This type of assembly is ideal for systems where it is not necessary to regulate the temperature of the water entering the heating units, as everything depends on the boiler's performance. For standard home applications, we recommend checking the offer of the Non-mixing boiler module HEAT BLOC K31 DN 32 without pump, which provides a solid foundation for your installation.
Significance of the bypass valve in the system
The bypass valve is a critical component that protects the boiler from overheating in the event that heat demand in the system drops below the minimum required for its safe operation.
- When all thermostatic heads close, the pressure in the system rises and the valve opens.
- The water then recirculates back into the boiler, maintaining minimum flow and preventing thermal shock.
- Without this component, damage to the heat exchanger or activation of the safety valve could occur.
In practice, we have encountered cases where an installation without a bypass led to frequent boiler shutdowns due to excessive temperature differences. Therefore, it is advisable to consider a set with an integrated bypass valve, such as the Non-mixing boiler assembly with bypass valve DN 32.
Difference between Grundfos and DAB pumps
The choice of pump manufacturer in the boiler module often depends on maintenance requirements, noise levels, and the availability of spare parts in our country. While the German Grundfos is known for extreme reliability and long service life, the Italian DAB offers an excellent price-to-performance ratio with modern electronics.
When selecting a specific model, it is important to note that the model with the Non-mixing boiler module DN 32 with DAB.EVOSTA3 60/180 pump can be more economically advantageous for smaller buildings, while the Grundfos UPM3 Auto L is the choice for more demanding users seeking maximum stability.
Specifications of apartment metering assemblies
Apartment metering assemblies are used to accurately measure the supplied hot water and heat for individual apartments, and must meet strict legislative standards regarding energy billing. These assemblies are designed to allow easy disassembly and replacement of the meter without the need to drain the entire installation.
- They are equipped with a filtration system to protect the meter from impurities.
- They include shut-off and control valves for both sides (supply and return).
- They can be delivered either with a protective housing against the external environment or as a standalone assembly without a housing.
For standard apartment solutions, the version apartment metering assembly without housing with Kv 2.75 is often selected, which is sufficient for most apartment units and allows for easy installation behind the wall or in a shaft.
Sizing of pipe diameter DN and pump performance
An incorrectly selected pipe diameter or a too weak pump can lead to inefficient heat transfer and increased operating costs, while an oversized assembly causes unnecessary pressure losses and noise.
For standard single-family homes, a DN 32 diameter is most often sufficient, which covers needs up to approximately 25 kW boiler output. When selecting a pump, the head is decisive, as it must cover the furthest point in the system plus losses in the boiler and fittings. If you need advice on a specific calculation, see the article on what DN diameter and pump performance you need for a boiler module.
Hydraulic separation and three-way valves in practice
Mixed boiler assemblies are a necessity in modern low-temperature systems, where the goal is to operate floor heating or fan coils at temperatures of 35 to 45 °C, while a condensing boiler requires a higher temperature (e.g., 60 °C) for optimal efficiency. The key component here is the three-way valve, which mixes hot water from the boiler with cold water from the return line.
In a properly dimensioned mixed system, the three-way valve is controlled based on the temperature difference between the supply and return water. If the difference is too small, the valve opens towards the boiler (increasing the supply temperature), and if the difference is large, it opens towards the system (diluting the water). An important aspect is also the placement of the pump; in the classic solution, it is located on the supply line before the valve, but in some specific modules, it may be placed on the return line after the valve, which changes the hydraulic properties of the entire system.
The Critical Role of the Strainer Basket and Its Maintenance
Many plumbers underestimate the importance of the strainer basket in the boiler assembly, although it is the first line of defense against mechanical impurities. In new constructions, where the pipes are full of welding slag, gravel, or construction dust, filtration can be critical for protecting not only the pump, but also the radiator heads and three-way valves.
| Type of impurity | Consequence without a filter | Solution |
|---|---|---|
| Welding slag | Pump jamming / damage to impellers | Regular replacement of the basket |
| Teflon tape | Clogging of measuring devices / valves | Fix installation + cleaning |
| Corrosion (iron oxide) | Clogging of radiators / low flow | Chemical disinfection of the system |
Therefore, in every installation, we recommend checking the condition of the filter after the first week of operation and then cleaning it regularly. In the case that you use quality components such as boiler modules with an integrated filter, you will ensure long-term functionality without the need to dismantle the entire system.
Mounting Positions and Space Requirements
One of the most common problems during renovations is the incorrect choice of location for the installation of the measuring assembly. While technically it is possible to mount the assembly in a horizontal or vertical position, there are certain limitations that should be considered.
- Vertical mounting: Is preferred for air venting, but requires sufficient space above the assembly for servicing and pump removal.
- Horizontal mounting: Allows for compact placement, but care must be taken to ensure that the pump is not mounted "head up" if the manufacturer does not allow it.
- Frost protection: In unheated areas (garage, basement), it is necessary to insulate the assembly or use versions with a housing that have thermal insulation properties.
When selecting an apartment heating assembly, always check if a version with extended threads or adapters is available, which will allow connection to existing pipes without the need to cut and join them. This is especially true for older apartment buildings with steel pipes, where it is often necessary to use reductions to plastic.
Electrical Connection and Flow Control
Part of a modern boiler assembly is not only the hydraulics, but also electrical control. "Auto" or "Smart" type pumps can regulate their performance themselves according to the pressure in the system, but they require proper connection to a 230 V network and a signal from the thermostat.
In mixed assemblies, it is crucial to correctly program the three-way valve. The servomotor must respond to the signal from the heating controller so that it does not move against the pump. An incorrectly set limit switch or missing phase can lead to the valve remaining in the same position, which can cause either boiler overheating or insufficient heating of the rooms.
Today, it is common practice to use modular control units that integrate the control of the pump, valve, and bypass valve into one unit. Such solutions reduce the risk of incorrect wiring and allow for simple fault diagnosis via LED indicators on the module.
Hydraulic Separation and Pressure Balance
Most modern boilers require a fixed minimum flow, which is practically achieved using a hydraulic four-way divider or a bypass circuit, thus eliminating the boiler's dependency on apartment consumption.
Common Questions
How to distinguish between a mixed and non-mixed assembly?
A non-mixed assembly has only one circuit (boiler – system), while a mixed assembly includes a three-way valve for mixing cold water from the return branch, which allows the temperature of the water in the radiators to be regulated lower than the temperature from the boiler.
Why is the three-way valve not moving in a mixed assembly?
Possible reasons include mechanical jamming, missing voltage signal from the control unit, or incorrect timer configuration; the solution is to check the electrical connection and possibly maintain the servomotor.
Is regular maintenance of pumps in modules necessary?
Yes, the pump operation should be checked at least once a year, the filter cleaned, and deposits removed if necessary, which will extend the pump's lifespan by several years.
Thorough compliance with these rules when selecting and installing boiler and apartment measuring units ensures not only a long lifespan of your heating system, but also optimal energy costs throughout the entire heating season.
Do you have a question about this topic?
Are you unsure or dealing with a specific situation in your household? Write to us – we are happy to help.