Boiler pressure drop

Boiler pressure drop, a boiler’s pressure can drop for numerous reasons, let’s not focus too much on the why, but on the procedure to get it back to where it should be (1.5 bar).

First of all you will need to identify two key components:

• The filling loop
• The pressure gauge

Filling loop, what is it and where can I find it?

The filling loop is the name given to the component of the central heating system which links the cold main (pipe) to the primary central heating circuit (heating pipe).

There are two main types of filling loop:

• Built in
• External

Built in filling loop

A built in filling loops vary in design from manufacturer to manufacturer, however their principle function is the same. Nearly all built in filling loops are located directly underneath the boiler itself.

Below is an image of the built in filling of an Ideal Logic combi boiler.

Built in filling loop

External filling loop

An external filling loop can be located anywhere on the central heating circuit which gives it great location flexibility.

In many instances the filling loop will be located on the pipework within 1 meter of the boiler.

Again external filling loops can vary in design, however they all share similarities to the one illustrated below.

External filling loop

Pressure gauge, what is it and where can I find it?

Your boiler will have one of two types of pressure gauge:

• Hydraulic
• Digital

Hydraulic pressure gauge

A Hydraulic pressure gauge is usually positioned on the front face of the boiler, however it may also be positioned underneath boiler.

This type of gauge gives a visual indication of the system pressure as water within the primary circuit (heating system) directly affects the position of the gauge needle.

boiler pressure gauge

Digital pressure gauge

A digital pressure gauge will show a pressure reading on the boiler display itself. This will be either shown as digits or a virtual gauge.

The downside or limitation to this type of gauge is that boiler must be switched on for the pressure to be read. This may be an issue if the power supply is interrupted, during renovations works for example.

Digital pressure gauge

Boiler pressure drop

If the pressure on your boiler has dropped below 0.75 bar a safety pressure switch will prevent the boiler from firing, leaving you without heating and hot water until the pressure in the central heating system has been increased to 1 bar or above.

The process of doing this is very simple, it can be achieved in 5 easy steps:

1. Identify the filling loop
2. Identify the pressure gauge
3. Turn the filling loop isolation handle 90 degrees, at this point you will hear water entering the central heating system (some filling loops have 2 handles, turn both handles 90 degrees)
4. Return both handles to their starting positions when the pressure gauge reads 1.5bar (this is the ideal pressure when the central heating is cold)
5. Press the reset button on your boiler’s front panel (many models reset automatically)

It’s as easy as that. If you’re still unsure, watch this  short video

We hope you found this article helpful and informative.

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