Mixing unit for underfloor heating

Today, among the heating systems used in everyday life, warm water floors are gaining popularity. Increased attention on the part of consumers to this method of heating is due to the high efficiency of heating floors, especially when the emphasis is on the quality of interior decoration of residential premises. Heating radiators do not always look aesthetically pleasing, while the water circuit hidden in the floor is completely invisible.

In this case, the installation of heating equipment also bribes. With proper planning and observance of all the necessary technological subtleties, making underfloor heating in your own home is quite realistic and within the power of everyone. In order to succeed, it is enough to have an idea of ​​​​how the underfloor heating works, which is included in the equipment. In the process of work, you will have to face not only the choice of the method of heating the coolant, the selection and laying of water circuit pipes and screed equipment. The key element of the «warm water floor» heating system is the underfloor heating mixing unit.

What is this equipment? What is its design and purpose? Let’s deal with these issues in more detail.

Why do you need a mixing unit for a underfloor heating system

Underfloor heating today can be found in almost any residential area. City apartments, if the design features of a residential facility allow, are often heated in this way. In many private houses, in cottages, water floors are a common phenomenon. Due to the design features, the underfloor heating system can be used both as a full-fledged, main heating of residential premises, and as an auxiliary heating option. Competent installation, the availability of appropriate equipment will allow you to use water floors with maximum efficiency. And it will help you with this, a mixing unit for your warm floors.

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Warm water floors is a low-temperature heating system. Unlike radiators, for the normal operation of heating water circuits, it is necessary to have a coolant whose temperature varies between 35-55⁰C. The water that circulates in the central heating system is much hotter, not to mention the heat carrier heated as a result of the operation of the heating boiler. The work of preparing water for water circuits is performed by a mixing unit. On top of that, through the system of collector inputs, the distribution of the coolant through the underfloor heating pipeline is carried out.

On a note: it should be said that a mixing unit or a mixing unit is necessary when you have expressed a desire to make heating in your house through underfloor heating. For other heating options, this technique is not required.

The principle of operation of the mixing unit

Like all other heating systems that use a liquid coolant, heating due to water-heated floors works in a similar way:

• heating source (autonomous boiler or central heating riser);
• supply and return pipelines, water circuits laid in the floor of a heated room;
• devices and instruments of the regulatory group.

Water is heated by the operation of the boiler or supplied to the system from the DHW line and central heating. In an autonomous boiler, water is heated to a temperature of 75-95⁰C, in the CH system the water temperature is slightly lower, 55-75⁰C. In accordance with health regulations, the ideal floor heating temperature should be 31⁰C, thanks to which a zone of comfortable stay is created in a heated room. In order to achieve such temperature parameters, water heated to a temperature of 35-55⁰C. The puff cake absorbs excess thermal energy, giving out optimal temperature indicators on the floor surface.

In order to direct the flow of water of the required temperature into the water circuit, a mixing unit for a warm floor is installed. Otherwise, the underfloor heating system will be a waste of money. Without adjusting the temperature of the coolant, your floor will turn into a hot pan, and the concrete screed and floor covering will soon become unusable.

Important! It should be remembered that the mixing unit can only work if ordinary water circulates in the heating system.

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The unit is mounted in the immediate vicinity of the heated room, where the heating circuit loops come to the surface. The equipment is connected to both pipes, to the hot water supply pipeline and to the return flow line. As a result of its work, the excessively hot coolant mixes with the cooled down, cooled down waste water, resulting in the optimum water temperature for the heating pipes.

Important! If the water in the system is not so critical for underfloor heating, it is not necessary to install a mixing unit. If an autonomous boiler works for heating and provides hot water for domestic purposes, you cannot do without a mixing unit.

It would be appropriate to say. Do not confuse the mixing unit and the manifold. The first is a set of equipment, each of which individually performs the functions assigned to it. The collector is an integral part of the mixing unit and is designed to collect and distribute water flows in the heating system.

Based on the configuration, the principle of operation of the mixing unit follows.

The heat carrier from the heating source enters the collector. The presence of a safety valve and a thermostat does not allow hot water to move freely further. At a high water temperature, the automatic mode is activated. The inlet valve opens and cold water is added to the hot fluid flow, flowing in the opposite direction. When the water reaches the required temperature values, the valve automatically closes, stopping the supply of hot water to the system. This process occurs constantly and uninterruptedly during the operation of the heating system.

Mixing unit completeness

The principle of operation of the equipment is simple and clear. Another thing is what devices and equipment provides the functionality of the entire unit. The easiest option that you can do yourself is a mixer equipped with a manifold, a safety valve and a circulation pump.

The first performs the task of distributing the flow through the water pipes of the underfloor heating. The safety valve provides hot water supply to the collector and control of the water heating temperature.

The circulation pump communicates the required speed to the water flow, ensuring the intensity and uniformity of water supply to the underfloor heating system.

A more complex mixer design is a whole set of additional elements. In addition to the devices already mentioned, a manifold, a safety valve and a supply pump, the kit of a conventional mixing unit includes:

• Bypass — an element that protects your equipment from overload and overheating;
• Drain, bleed valve;
• Shut-off valve;
• Air vents;
• Thermal relay.

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The mixing unit should be a compact design that can be successfully hidden in a manifold cabinet.

On a note: if it is planned to equip underfloor heating in several rooms, each of them will require its own separate mixing unit. You can install one single unit for all heating circuits, only in this case it is better to use a collector with a large number of inputs and an additional amount of safety fittings.

Mixers are usually equipped with three-way and two-way valves. The second is also called the supply valve. Thanks to its filling, thermostat and sensor, the valve reacts to the slightest change in the temperature of water heating in the system, opening or shutting off the water supply.

For heated rooms with an area of ​​more than 200 m² the use of a two-way valve is not recommended.

The three-way valve has several functions. Due to its design, the valve is capable of diverting and mixing. Thanks to such a device in the mixing unit, the hot water coming from the heating device is mixed with the return. Usually, valves with servo drives are placed on the mixture, which independently, in automatic mode, regulate the level of mixture. Complementing the mixing block with a three-way valve complete with a weather-dependent controller, you will receive a fully automated heating temperature control system. In addition, the three-way valve is designed to work with warm floors of a large area.

If you want to save on equipment, use manual adjustment valves. By saving on automation, you will get extra hassle for yourself. With manual adjustment, it is quite difficult to determine the optimal flow of the coolant in the system. Automation solves these issues easier and faster.

Installation of the mixing unit. Installation Features

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With the right selection of components, subject to all the necessary technical conditions, the installation of the mixer should not cause difficulties. Having determined the location of the mixing unit, having simulated the design of the manifold cabinet, start the assembly.

For the future. The underfloor heating control unit must have free access. Otherwise, you will have to face difficulties during operation.

First, the pipelines coming from the heater are connected. The collector is installed next. At the end, the system can be equipped with sensors for adjusting pressure, pressure and thermometers. It is important to determine the way the collector combs are located. The type of heating source your system is connected to determines how the distribution manifolds are connected. It can be an end connection or a regular one, top and bottom.

For the hot water supply line, it is better to use metal-plastic pipes or polymeric materials. These components are able to cope with pressure surges in the system, and perfectly withstand high temperatures.

Connection of equipment to water circuits is carried out in a clear sequence using fittings. Pipes are connected to the blue inlet pipes, through which the cooled water flows in the opposite direction. A water loop is connected to the red pipes, which provides floor heating in a heated room.

If you are planning to make a warm floor for heating large areas, you will definitely need a circulation pump. The large length of the water circuit, the large number of bends and the small diameter of the heating pipe lead to the fact that the circulation of the coolant in the system noticeably weakens. By installing a circulation pump, you will ensure the normal supply of prepared water to the heating circuits. It is recommended to install the pump at the beginning of the mixing unit, where the supply pipe is suitable and the return is connected.

The pump is installed in a strictly horizontal position. It is recommended to install pumps with several speed modes. These models allow you to manually determine the required feed rate and flow rate.

In custody

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Having become acquainted with the importance of the mixing unit for the “warm water floors” heating system, how its work is arranged, we can say a few words about setting up the equipment. Without proper training, it is better to entrust such a procedure to specialists — heat engineers. Despite the fact that the installation of a warm floor and the installation of a mixer are tasks that you can handle on your own, setting up a regulating group requires appropriate qualifications and knowledge.

For general information, we note a couple of steps that are associated with the process of setting up the mixer.

• It is better to remove thermal heads or valves with servo drives so that they do not affect the setting of the mixing unit;
• The bypass valve is set to a maximum value of -0.6 atm, making it currently inoperative;
• The position of the balancing valve is set according to the capacity calculations;

The calculations will be something like this:

Where, t1 is the temperature of the water in the supply pipe from an autonomous boiler or CH system;

t2supply is the water temperature at the inlet to the water circuit;

t2return is the return water temperature coming from the water circuit loop;

Kvt is a generally accepted coefficient, which is equal to the value of 0.9.

We take the average numbers for calculations, for the operation of an autonomous boiler:

t1=95 °С,

t2 supply = 45 °С,

t2arr = 35 °С.

As a result, we get:

This is the value that we set on the balancing valve.

Next, we set up the pump, taking into account the capacity of the balancing valve and the required intensity of water flow. If you cannot configure the pump taking into account the optimal parameters, set the minimum operating modes on it. In the future, when it becomes clear that the operating speed of the pump is not enough, reset the unit to a higher speed.

• The last stage is connected with balancing the water floor loop. Balancing valves cope with this task. If you have one branch of the heating circuit, balancing is not required.

In conclusion, it should be said that the assembled mixing unit and connected to the system requires mandatory tying with the entire heating system. By following all the necessary instructions and recommendations of specialists, entrusting the performance of hydraulic and thermal calculations to specialists, you can count on a successful outcome of your event. A mixing unit, assembled in accordance with all the rules, will allow your home heating system to work as efficiently as possible. In addition, you will significantly increase the level of comfort in the house and your own safety.