What is the significance of flow in underfloor heating?


Although the construction of a floor heating is very easy to understand, the control of the underfloor heating is very complicated. Which important terms and key figures as well as setting values ​​for underfloor heating exist and how they are related can be found here.

Basic significance of the flow

The more water through the pipes of a floor heating
flows, the more heat is given to the room. This is a fundamental insight in underfloor heating. If you want more heat, you have to increase the flow rate.

What you have to take into account, however, is that a floor heating also has a certain amount of self-regulation. At a very high return temperature (RLT), less heat flows from the floor to the room. The so-called spread thus has in addition to the flow rate so also an impact on the amount of heat in the room.

spread

Spreading is the difference between flow temperature and return temperature. The VLT is limited to 35° in modern systems. In older systems, however, flow temperatures of up to 55° are used.

Influence of the pipe length

The longer a heating pipe, the greater the resistance that the amount of liquid has to overcome. If the pump power remains unchanged, the flow decreases as the pipe length increases.

Ideally, the length of each heating circuit is the same, so that a constant flow rate can be maintained. If this is not possible for structural or technical reasons, a so-called hydraulic adjustment must take place during the planning:

The shorter heating circuits must be throttled (ie the flow rate in them reduced), in the longer heating circuits, however, the water must flow unthrottled. This is the only way to achieve the same temperature in all rooms via the respective flow rate. For regulation serve here flow meter.

At the same time, the spreading of the heating circuit increases, which also has to be considered in the planning. Another issue is the laying distance at the heating circuits. He also has an influence on the heat in the room.

Overview of the importance of pipe lengths and heating circuit lengths:

  • Effect on the flow rate
  • Effect on the spread
  • Consider the effects at the laying distance! (Closer installation recommended in front of the windows)
  • Consider the effects of built-in hydraulic balancing

Meaning of pumping power

The pumping power must be chosen so that the necessary heating heat (the so-called, exactly calculable heating demand of a room) can be achieved in any case and also in cold outside temperatures.

The more powerful the pump, the higher the flow rate can be. However, this is only possible in a limited scope, the pump power is not variable. In addition, the pump should preferably not run at full load, since the flow noise can generate.

Tips & Tricks

When reading plans, it is important to remember that heating systems often use° K (degrees Kelvin) instead of° C. But the conversion is relatively simple: The Celsius degrees are obtained by subtracting from the Kelvin degrees 273.15. When specifying a temperature difference (ie, for example, 3 K temperature difference) that is not true. There the temperature difference in Kelvin corresponds to the temperature difference in * C.
What is the significance of flow in underfloor heating?

FAQ - 💬

❓ What should the flow be on underfloor heating?

👉 To calculate the flow rate for each underfloor heating loop, take the loop length and divide by 40. For example, 100 m loop length/40 = 2.5 l/min flow for the underfloor heating loop. This guideline should help you to decide what expansion vessel to use, – 1000 m of pipe needs a 4l vessel.

❓ How does flow rate affect underfloor heating?

👉 Generally the flow temperature for UFH with a boiler is 50-55°C and around 40-50°C with a heat pump. The flow rate is the speed at which the warm water circulates around the room before returning back to the manifold. The faster the water flows, the more heat energy is being put into the room.

❓ What happens if underfloor heating flow rate is too high?

👉 Too much flow. Too fast a flow rate will not transfer the heat properly in the room. Set the flow meters to 1.5-2 for boiler system and 1 for heat pump use. Check the thermostat is calling for heat and switching the heat source/pumps on.

❓ Which is flow and return on underfloor heating manifold?

👉 How do manifolds for underfloor heating work? The manifold is made up of between 2-12 'ports' (where the tube connects) and these function in pairs of flow and return. The flow manifold (the top row of the diagram) is fed by the warm water, the temperature of which is shown on the temperature gauge (2).

❓ How do I know if my underfloor heating is working properly?

👉 A working underfloor heating system should be able to achieve and maintain an adequate temperature whilst also allowing an even temperature distribution across the whole floor area. There should be no leaks, pressure issues, or safety concerns. The underfloor heating system should also run efficiently.

❓ How can I make my underfloor heating more efficient?

👉 Insulation is key to any underfloor heating system. Having the right insulation and floor build up at the very beginning can increase efficiency from 50% instantly. This works by ensuring all the heat your underfloor heating is producing is heating the floor rather than 50% being lost to the substrate below.

❓ How do I balance my underfloor heating system?

👉 0:542:18Underfloor Heating Manifold Balancing

❓ What is the best way to control underfloor heating?

👉 Digital thermostats are by far the most popular choice now for underfloor heating because this control system helps the UFH operate more efficiently and offers the user more flexibility, meaning that the heating can be programmed around the lifestyle of the individual.

❓ Why is my underfloor heating not warm enough?

👉 If your electric underfloor heating isn't warm enough, you may need to adjust your thermostat settings or check the system's power output. This could also be down to the insulation in your home – check this before installation.

❓ How often should I flush my underfloor heating?

👉 A wet UFH system should be serviced as often as radiators are serviced – which is typically once a year. As wet UFH uses water from a boiler to heat a home, there are certain actions required to keep it running smoothly.

❓ What is the most economical way to run underfloor heating?

👉 System-wise, water-based underfloor heating is likely to work out as the very most economically friendly option, transporting hot water through your pipes to operate.

❓ Why is it important to know the heat output of underfloor heating?

👉 Knowing the heat output of an underfloor heating system is essential to ensure your room is heated to the desired temperature.

❓ How much water does the underfloor heating system use?

👉 This does not include feeder pipes to the manifolds or any radiators in the heating system. Clip rail usage for underfloor heating systems are 1.5 m per sqm floor area. To calculate the water content in our underfloor heating system use 0.12l of water per m pipe.

❓ What is underfloor heating&ventilation?

👉 Underfloor heating has gained significant popularity in recent years. Ventilation systems are sometimes also used for space heating, especially in commercial premises, causing the heat to be air-borne.

❓ What is the flow rate for the underfloor heating loop?

👉 For example, 100 m loop length/40 = 2.5 l/min flow for the underfloor heating loop. If the underfloor heating system contains any debris, it should be power flushed and a “Magna Clean” added, see link below;


Video Board: How to adjust flow rates on your Underfloor Heating System