How to fix the pressure of a Combi boiler?

We have come across a number of people grumbling about the fluctuating pressure on their boiler. This increase and decrease in the pressure of your boiler can probably be an outcome of a number of reasons which we have explained below along with the solution as in how to fix the pressure of a combi boiler.

What is a Combi Boiler?

A Combination boiler is a native space saving idea that serves you with a high efficiency water heater and a central heating in a single compact unit that operates to heat the water directly from the mains in order to cut down the installation of a hot water storage cylinder or the cold water storage tank in the loft.

What should be the pressure of my boiler?

The pressure of your boiler that can be viewed on the pressure gauge located on the system should have its needle pointing between the 1 and 2 bar as the correct amount of pressure. While some of the pressure gauges come with 2 needles, with the red needle serving as the marker and the black one showing the actual pressure. In that case, if your boiler is at the right pressure, then both the needles should be pointing at the same number. A number of other boilers have an LCD display to present water pressure in the system.

Why is my boiler pressure high?

The heated water expands as soon as the boiler begins to heat and causes the pressure gauge to increase. This is basically why the pressure of your boiler increases. Though the modern boiler systems comes with an in built pressure relief valve that is installed in order to control the quick leaps in the pressure, but in most of the cases a high pressure boiler puts unnecessary strain on the system, which eventually results in the breakdown of the unit.  

How to lower the boiler pressure?

  1. Check that the pressure relief valve is tightly closed- Re-pressurizing the boiler would require you to turn the valve or filling loop to pump water into the boiler and this might be easy to forget.
  2. Bleed your radiators- Keep bleeding the radiators to reduce the pressure in the central heating system and continue the process until the boiler pressure being read on the display has restored back to the safe levels.
  3. In case of the boiler pressure still persisting to be too high, the reason could either be the fault with the filling loop or you need to re-pressurize the expansion vessel. Though the pressure still might be irregular, the pressure relief valve would prevent the boiler from over pressurizing the system in order to help it from breaking down and carry on as usual as long as you are not experiencing loud, unusual noises.

Why is my boiler pressure low?

The most common reasons for a Combi boiler loosing pressure might be an outcome of a leakage in the pressure relief valve, an issue in the expansion vessel, air in your system, or a leak in the heating pipework itself. So in case the boiler pressure falls below 1 you would need to top up your system. While the steps to do this would surely part their ways depending upon the specific boiler models, we would highly recommend you to consult your boiler’s instructions.

How to increase the boiler pressure?  

In case of your boiler pressure being too low you need to top up the system that can generally be done in the following ways:-

  1. Initially, you need to turn off the boiler and wait for the system to cool, before making any further operations.
  2.  Operate the system using a filling link or loop- While this can be done in 3 ways :-
  3. External- For this you would need to attach the filling loop to the corresponding valves and slowly move the lever. The process needs to  be continued until the pressure needle moves into the green zone. Disconnect the external filling loop once you are done.
  4. Keyed filling link- For this you need to insert the internal filling key into the loop and twist it until it gets closed. Turn the nearby knob in order to allow the water to fill into the heating system. Continue the process until the pressure needle falls into the green zone. Once yo.u are done turn the knob back to its original position and remove the key.
  5. Keyless filling link- this is one of the easiest methods in which you simply have to move the filling lever until you hear the water entering the heating system. The lever needs to be kept lifted until the pressure needle moves into the green zone and then be released.
  6. Turn on the boiler in order to check if the pressure holds.
  7. In case you still find the pressure to be below the recommended limit then the problem might be with the gauge or the heating system. For this you would need to call a heating engineer in order to inspect and service your central heating system

Recommendation– If in case the results are found to be same even after the operation of the above mentioned techniques, please consult you heat exchanger as soon as possible.

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