In order to make a floor heating as efficient as possible, you must follow some basic principles. In order not to look for too much information, I decided to make a top of the most common mistakes encountered in projects to make it easier for you to follow your underfloor heating project.
By the way, if you want to avoid headaches from the beginning, you better buy a floor heating project, if you have a project, you will receive a similar offer from all potential contractors.
What is the maximum length of the underfloor heating circuit?
The most common mistake is that of extremely long circuits, when the maximum circuit length is exceeded. Usually because of the lack of project or because we want to save on the size and number of distributors, circuits are too long. On thin pipes you should go with maximum 70 linear meters of pipe for underfloor heating on a circuit.
Radiant surfaces created on a long circuit have less power, long circuits have very high pressure drops, are harder to ventilate and generally cause most problems in operation.
What is the correct thickness of a screed for the underfloor heating system?
Pouring a very thick screed over the heating pipes into the floor is a mistake. From my point of view, a slimmer hole ensures an ideal thermal transfer between the pipe and the radiant surface. Here we can use 35 mm anhydrous screed. Generally, classic cement reinforced screeds are used in the 50 mm area.
The flap has a thermal resistance and practically above the thickness of 100 mm becomes an insulator, so the radiant surface heats very hard the heat transfer is slowed down and the response of the heating to the floor is very slow.
If we are forced to pour a hole over 70 mm my recommendation is that the underfloor heating be raised in the upper third of the screed.
How to assemble a mixing and pumping group correctly?
Some pumping and mixing groups mounted on the distributor have a more difficult to understand fluid flow, if you do not read the manual. It is often the case that they are mounted in the wrong direction, the result is that the underfloor heating circuits do not heat up or heat up very little.
I do not recommend the installation of these pumping and mixing groups on distributors, especially in installations with heat pumps. This type of equipment should only be used under certain conditions.
What is the correct size of the feed columns?
The supply columns for distributors in most projects are under-sized, the pipe is too thin. Generally, underfloor heating works with high flow rates to maintain a temperature difference between flow and low return, so larger columns are needed.
This mistake brings us more pressure drops in the installation, this means a higher consumption at the pump and in some situations it may mean a limitation of power.
How to repair a pipe for heating in the underfloor?
Repair a plated pipe with a hot air gun. This is an execution mistake. Generally PEX – A pipes have a so-called “shape memory” and between the layers of pipes there is an EVOH oxygen barrier.
If the pipe has been plated, the plating disappears in the case of PEX – A pipes heated with hot air but the oxygen barrier remains broken. This applies to any type of EVOH oxygen barrier pipe.
There are no tests and information regarding the evolution over time of these repaired skins, so it is recommended to change the pipe segment or cut it and use a connector.
Can a condensing boiler be connected directly to the underfloor heating system?
Usually this assembly system is practiced but it is not the brightest, it is ok for small surfaces up to 100 square meters. For larger surfaces we should use an additional pump and a hydraulic separator.
A central heating pump usually cannot provide the flow required for underfloor heating. Speed in the boiler would be much too high leading to premature erosion of the boiler heat exchanger.
Can we put insulation over the underfloor heating?
We cannot mount an insulation layer over the underfloor heating, but there are still such cases.
Do we need air vents for underfloor heating?
Lack of air vents or microbubble separator. In cases where the air accumulations are large, the circuits no longer work.
Can we pass a heating circuit in the floor through the radiator?
The passage of a heating circuit in the floor through a radiator or convector under the floor is a major mistake. Unfortunately, I also saw solutions.
It is not correct to combine these systems because they operate at different temperatures and flows. In principle