Collector for underfloor heating: types, connection diagrams

When installing water floor heating, a considerable number of pipes are laid – several segments, which are called contours. All of them are wound up on a device that distributes and collects a coolant – a collector for a warm floor.  

Purpose and types

A warm water floor is distinguished by a large number of pipe contours and a low temperature of the coolant circulating in them. Basically, heating of the coolant to 35-40°C is required. The only boilers that can operate in this mode are condensing gas boilers. But they are rarely installed. All other types of boilers produce more hot water at the outlet. However, it cannot be launched into the circuit with such a temperature – too hot a floor is uncomfortable. To lower the temperature, you need mixing nodes. In them, in certain proportions, hot water is mixed from the supply and cooled from the return pipeline. After that, through a collector for a warm floor, it is fed to the circuit.

In order for all circuits to receive water of the same temperature, it is supplied to the underfloor heating comb – a device with one input and a certain number of outputs. Such a comb collects cooled water from the circuits, from where it enters the boiler inlet (and partially goes to the mixing unit). This device – supply and return combs – is also called a collector for underfloor heating. It can come with a mixing unit, or maybe only combs without any additional “load”.

Materials

The collector for a warm floor is made of three materials:

• Of stainless steel. The most durable and expensive.
• Brass. Average price category. When using a high-quality alloy, they last a very long time.
• polypropylene. The cheapest. To work with low temperatures (as in this case), polypropylene is a good budget solution.
  

When installed, the inputs of the underfloor heating circuits are connected to the supply manifold of the collector, and the outputs of the loops are connected to the return pipeline comb. They are connected in pairs – to make it easier to regulate.

Equipment

When installing a water-heated floor, it is recommended to make all circuits of the same length. This is necessary so that the heat transfer of each loop is the same. It’s just a pity that this ideal option is rare. Much more often there are differences in length, and significant ones.

To equalize the heat transfer of all circuits, flow meters are installed on the supply comb, and control valves are installed on the return comb. Flowmeters are devices with a transparent plastic cover with graduations. There is a float in the plastic case, which marks the speed at which the coolant moves in this loop.

It is clear that the less coolant passes, the cooler it will be in the room. To adjust the temperature regime, the flow rate on each circuit is changed. With this configuration of the collector for underfloor heating, this is done manually using control valves installed on the return comb.

The flow rate is changed by turning the knob of the corresponding regulator (they are white in the photo above). To make it easier to navigate, when installing the collector assembly, it is advisable to sign all the circuits.

This option is not bad, but you have to adjust the flow rate, and therefore the temperature, manually. This is not always convenient. Servo drives are installed at the inputs to automate the adjustment. They work in tandem with room thermostats. Depending on the situation, the servo is given a command to close or open the flow. In this way, maintaining the set temperature is automated.

The structure of the mixing unit

The mixing group for underfloor heating can be built on the basis of a two-way and three-way valve. If the heating system is mixed – with radiators and underfloor heating, then there is also a circulation pump in the unit. Even if the boiler has its own circulator, it will not be able to “push through” all the loops of the warm floor. That’s why they put the second one. And the one on the boiler works for radiators. In this case, this group is sometimes called a pump-mixing unit.

Diagram on a three-way valve

A three-way valve is a device that mixes two streams of water. In this case, it is heated supply water and colder water from the return pipeline.

A movable control sector is installed inside this valve, which regulates the intensity of the flow of colder water. This sector can be controlled by a thermal relay, manual or electronic thermostat.

The scheme of the mixing unit on the three-way valve is simple: the hot water supply and return are connected to the valve outlets, as well as the outlet that goes to the supply manifold of the underfloor heating collector. After the three-way valve, a pump is installed that “presses” the water towards the supply comb (the direction is important!). A little further than the pump, a temperature probe is installed from a thermal head mounted on a three-way valve.

Everything works like this:

• Hot water comes from the boiler. At the first moment, it is passed by the valve without admixture.
• The temperature sensor sends information to the valve that the water is hot (temperature above the set temperature). The three-way valve opens the water intake from the return.
• In this state, the system works until the water temperature reaches the set parameters.
• The three-way valve shuts off the cold water supply.
• In this state, the system works until the water gets too hot. Next, the submess opens again.

The algorithm of work is simple and understandable. But this scheme has a significant drawback – it is possible that in case of failures, hot water will be supplied directly to the underfloor heating circuit, without admixture. Since pipes in a warm floor are laid mainly from polymers, they can collapse with prolonged exposure to high temperatures. Unfortunately, this shortcoming cannot be eliminated in this scheme.

Please note that in the diagram above, a jumper is drawn in green – bypass. It is needed in order to exclude the possibility of the boiler operating without flow. This situation can occur when all shut-off valves on the underfloor heating collector are closed. That is, a situation will arise when there will be no coolant flow at all. In this case, if there is no bypass in the circuit, the boiler may overheat (even overheat for sure) and burn out. If there is a bypass, water from the supply through the jumper (made by a pipe whose diameter is one step smaller than the main one) will be supplied to the boiler inlet. Overheating will not occur, everything will work normally until the flow appears (the temperature in one or more circuits does not drop).

Diagram on a two-way valve

A two-way valve is placed on the supply from the boiler. A balancing valve is installed on the jumper between the supply and return pipelines. This device is adjustable, it is adjusted depending on the required supply temperature (usually adjusted with a hex key). It determines the amount of cold water supplied.

A two-way valve must be installed controlled with a temperature sensor. As in the previous scheme, the sensor is placed after the pump, and the pump drives the coolant towards the comb. Only in this case the intensity of hot water supply from the boiler changes. Accordingly, the temperature of the supplied water at the pump inlet changes (the cold flow is set and stable).

As you can see, cold water is always mixed in such a scheme, so in this scheme it is impossible for water to enter the circuit directly from the boiler. That is, the scheme can be called more reliable. But the mixing group on a two-way valve can only provide heating for 150-200 square meters of warm water floors – there are no valves with a higher capacity.

Selection of valve parameters

Both two-way and three-way valves are characterized by capacity or performance. This is a value that displays the amount of coolant that he is able to pass through himself per unit time. It is most commonly expressed in liters per minute (L/min) or cubic meters per hour (m³/hour).

In general, when designing a system, it is required to make a calculation – to determine the capacity of the underfloor heating circuits, take into account the hydraulic resistance, etc. But if the collector for the warm floor is assembled by hand, calculations are made extremely rarely. Most often based on experimental data, and they are as follows:

• valves with flow up to 2 m³/ hour can provide the need for approximately 50-100 sq.m. underfloor heating (100 squares – with a stretch with good insulation).
• if the productivity (sometimes referred to as KVS) is from 2 m³/ time up to 4 m³/ hour, it is fashionable to put them on systems in which the area of ​​u200buXNUMXbthe warm floor is not more than XNUMX squares;
• for areas over 200 m2, a capacity of more than 4 m is required³/ hour, but more often they make two mixing nodes – this is easier.

The materials from which the valves are made – two-way and three-way – brass and stainless steel. When choosing these elements, you should take only branded and proven ones – the operation of the entire underfloor heating depends on their work. There are three clear leaders in quality: Oventrop, Esby, Danfoss.

There is one more parameter by which you need to choose – the limits for adjusting the temperature of the coolant. The characteristics usually indicate a fork – the minimum and maximum temperatures. If you live in the Middle Strip or south, during the off-season, a comfortable indoor temperature is maintained if the lower adjustment limit is 30 ° C or less (it is already hot at 35 ° C). In this case, the adjustment limits may look like this: 30-55°C. For more northern regions or with poor floor insulation, they are taken with an adjustment limit of 35 degrees. When assembled, the mixing group is installed in front of the collector for underfloor heating. Then the coolant of the required temperature enters the circuit.