Heating system, boiler and burner maintenance

This year I had a few issues with our heating system at home: I’m going to describe what happened and what I learned from my little incidents.

Description of the heating system

Based on our experience, we decided to install an underfloor heating system when we built the new house, therefore we do not have any radiators to be seen: the heat is carried by a liquid which is constantly pumped through tubes running under our floor. The burner is a gas powered Remeha Calenta 35S+. We bought it and installed it during 2011.

I have understood that the “+” in the model name refers to the fact that this burner is built for the preparation of hot water to be used e.g. in the shower as well as the heating. Other models like the “35” have been developed for the heating system only.


Manuals for the burner (sadly in Italian language only, I wasn’t able to find them in English).


PM 2975 OGZ

The burner has a second computer on board, the so called PM 2975 OGZ, which is dedicated to the control of the temperature of the heating, of the hot water, the scheduling…  Sadly I have lost the manual explaining how this particular computer should be set. In any case I remember it wasn’t that clear. 

One example that explains the role of the PM 2975 OGZ is the following: the PM 2975 OGZ uses a temperature probe installed outside the house to measure the outside temperature and based on this information and on an algorithm it increases or decreases the heating temperature.

Maintenance duties

  • Every year let the company perform the maintenance of  burner
  • Every year have the chimney sweep clean the burner
  • Every three years have the plumber clean the pipes of the underfloor heating
  • Every five years have the boiler cleaned

During the year it is a good idea to check the pressure of the liquid in the circuit. It is known that the pressure may go down so that once or twice a year a refill needs to be made. The refill is usually done with water: you should take care of refilling slowly and avoiding air to get into the tubes. To do that it is recommended to add water into the refilling tube until it is completely full before opening the tap and letting the fresh water into the circuit.

Water pressure gauge
Our water pressure gauge

The recommended pressure is around 2 bars in the winter time, when the heating system is on, while in the summer the pressure may lower to 1.5 bars.

Why is it important to have the chimney sweep clean the burner?

Because of my ignorance I never called the chimney sweeper for 5 years: I was convinced that the regular maintenance performed by Elco was the only one regular maintenance to be made. But I was wrong. This year we realised that the heating system wasn’t capable of reaching the temperature we wanted while outside the temperature was going below zero. Also the water for the shower was hot, but not as usual. Therefore I started to worry and called Elco, announcing that the burner wasn’t working properly. As the technician arrived we checked the methane consumption over a period of time of some seconds and quickly he was able to tell me that the burner was working at a third of its capacity. Then he disassembled the whole burner and he discovered that it was clogged and that needed to be thoroughly cleaned. The Elco technician made what he could in order to start the burner again and on the first days of January I called the chimney sweeper.

As per the moment being everything works fine: the shower is hot enough and the heating works fine. Pressure in the tubes is around two bars.

The one thing I have realised is that the burner needs attentive care and should be checked ever now and then, maybe a quick look every month, in order to see if everything works fine or at least have a date to refer to, in case something suddenly stops working correctly.

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