The pressure in the boiler rises. Wall mounted double-circuit gas boiler. Repair part 2

Hello dear visitors! In the last post on the topic of boilers, the reasons were considered why in a double-circuit boiler, it falls, then it grows.

The turn has come to find out the reasons why the pressure in the boiler can constantly rise, or rather, rise until the safety relief valve is triggered.

Given that the principle of operation of most boilers is similar, this malfunction can manifest itself in different models. But, I will tell you on the example of the ARISTON CLAS 24 FF boiler, since the boiler of this particular model is used by me.

The pressure in the boiler rises

When the pressure in a double-circuit gas boiler falls, it is somehow understandable, but when the pressure itself rises! What could it be? However, this is exactly what I had to face one day. This was discovered thanks to a safety relief valve. He began to relieve pressure by spitting water from the boiler. The pressure gauge showed a pressure exceeding 3 bar.

First of all, I released the pressure in the heating system through, and began to observe the readings of the pressure gauge, the pressure slowly but surely increased. The first thought, I began to skip the make-up tap, pulled it up, nothing has changed. Then I took out a manual for boiler maintenance (the Manual can) began to examine the hydraulics diagram, and quickly realized that the reason was in the secondary heat exchanger.

So there are two reasons why the pressure in the boiler can gradually, but constantly increase: 1) Does not hold the make-up tap. 2) Secondary heat exchanger defective

Secondary heat exchanger for gas boiler

The fact is that the water that is used for hot water supply (hot water supply) is heated by water that is used for the CO heating system. For these purposes, the secondary heat exchanger serves. It is designed so that two isolated from each other channel for water flow. One channel with heated water, and the other with the one that needs to be heated.

In this case, a large contact area between heated water and heated water is provided through the metal plates. When a partition is broken inside the heat exchanger (a small fistula appears), then an exchange of liquids begins to occur, the water from the water supply system, the one that needs to be heated, has a stronger pressure and begins to be pushed into the heated water channel. That is, it enters the heating system circuit, thereby causing an increase in pressure in the system.

How to replace the secondary heat exchanger in a gas boiler

It changes elementary, well, at least in the Ariston boiler.

The new heat exchanger came with four gaskets and two bolts for fastening. To remove, you need an asterisk socket wrench. It is necessary to turn off all the water supply taps to the boiler, drain the water from the boiler through the drain valve, or it is possible through the relief valve. We open the boiler, find in its bowels the location of the secondary heat exchanger and its attachment points - two bolts, we unscrew, they can stick to it, therefore, with some effort. The bolts are here, see the photo below. There are only two bolts. Third photo, larger view.

Unscrewed ... remove, check that the rubber rings (gaskets) do not remain in the joints, they stick to them.

We prepare a new heat exchanger, install new gaskets, assemble in the reverse order. Further, do not forget: Close the tap through which the water was drained, open the supply taps and fill the boiler with water through the make-up tap to the required pressure 1.2 -1.5 bar. Never try to light the boiler without filling it with water.

Making sure that nothing flows anywhere…. we launch.

Addition: It will not be superfluous to expel air from the boiler after filling. To do this, turn on the boiler and press the ESC button on the control panel for more than 5 seconds. The purge mode will turn on for 6 minutes, the pump will drive water without igniting the burner. The accumulated air will escape through the air release valve. You can forcibly turn off the purge mode by pressing ESC again.

The buttons are a little lower! Thanks!