How to Bleed Radiators on a Combi Boiler?

If the radiator is not emitting heat, just as it usually does, and when the heater is touched, it is hot at the bottom and cold at the top, then you need to purge the radiator. The process to bleed a combi radiator boiler is quite easy and can be done in about 20 minutes. You will also have to have access to the boiler to do this job correctly.

Why do we need to bleed the combi boiler?

This procedure evaluates the air they contain in place of the water usually found there. The presence of wind can induce whistling or noises, but notably higher heat losses of the heaters involved. This results in higher energy consumption, as well as a more significant load on the boiler. A heating body can even be hot on its lower part, but cold on its upper part.

It is therefore recommended to have the radiators flushed by a professional heating specialist during the annual maintenance, just before putting them back into service. Once the procedure is completed, your heating engineer can carry out a careful control of the pressure level in the boiler.

When do you have to bleed the combi boiler? 

You are advised to purge each of your radiators once a year or on-demand if you notice that one of your systems is not heating correctly or not at all, while the boiler is running.

Purge should be done, preferably before restarting your boiler, ideally in autumn; this will allow you to check the correct operation of your heating system. In case of problems, you can then bring in an experienced heating technician before the cold weather arrives.

Also, you should know that a multistory house promotes the appearance of air in the radiators. Remember to check their operation from time to time. 
There are warning signs that will put you in the ear like:

• completely cold radiators (or in part);
• the heat diffused is less intense than usual;
• of heaters making noises water flow or suspects whistles

Instructions

1. Turn off the heating system with the main switch. Your main switch is usually located near the boiler and will be marked.
2. Place the purge valve on the purge valve located on the top of the radiator combi. The purge valve will have to be a small copper screw embedded in the edge of the radiator, or it will be a small screw located on a button on the side. The screw will be either a regular slotted type or an Allen screw.
3. Cover the purge wrench with a rag and place a small empty bowl on the floor beneath it. This will prevent it from burning through the water.
4. Turn the purge key to the left about 1/4 inch back. The “whistling” air will be heard out. Wait until the hiss has stopped and a small amount of water has started to leave the valve. Turn the key clockwise to close the valve.
5. Go to the boiler and visually check the bar indicator on top. If less than 1 bar is read, water is added to the boiler until a full bar is displayed on the meter.

Tips and warnings

• If you lose the purge keys, a flat head screwdriver or small fine nose pliers will work just as well.
• If bleeding your combination boiler radiator does not solve the problem, there may be a more severe breakdown in the system, and a professional technician is required.