Topping up my central heating system and other  FAQ's

Topping up my central heating system

Most modern combi boilers will show a fault code if your pressure drops below 1bar - 0.5 bar.
This can happen if you decide to check your radiators for air and bleed them with a radiator key or if you have a slow leak somewhere on the radiator circuit.
The air escaping from the radiator as you bleed it is causing the pressure in the boiler to drop, so you need to replace this air with water by topping up your boiler pressure. This is done at the filling loop which is usually underneath the boiler (shown in picture below) You must open the lever or levers (usually black in colour) and re-pressurise the system pressure to between 1-1.5 bar. Make sure you leave the taps you opened in the same position you found them when your done!




What heating system is right for me?

Combi boiler

Combi boilers are designed to give instant hot water and are ideal if space is at a premium. They can be installed in any room of the house. They give good hot water pressure as they are fed directly from the cold main. Combi boilers are sized depending on your cold water pressure and flow rate - if these aren’t good enough then a combi won’t be right for you. If you use lots of hot water, have two or more bathrooms or have more people than bedrooms in your house then a combi might not be the most cost effective way of heating your hot water. A conventional system or system boiler may be more suitable for you in this instance. 

Conventional boilers

This is the old type of system which requires a hot water cylinder and two tanks in the attic to supply water for your hot water and heating. The controls are all external and are usually located in the airing cupboard. This system would be used if you have low water pressure, use lots of hot water or as a cheaper solution to upgrading your boiler to a condensing boiler. 

System boiler

This is a sealed system which doesn’t require a tank in the attic for the central heating. Many of the controls required for a heating system are housed inside the boiler meaning quicker and easier installation. System boilers require a cylinder to provide hot water. 


What is a condensing boiler?

Condensing boilers are a lot more efficient due to the fact that new heat exchangers inside the boiler are far more efficient at transferring heat from the burning gas to the water inside your heating system. This causes the products of combustion to leave your boiler at a much cooler temperature which means the water vapour created in the combustion process is cool enough to condense inside the boiler. This water known as the condensate must be piped to a drain or a waste pipe as it is slightly acidic. 


How can I reduce my gas bills?

Installing an A-rated high efficiency boiler could save you as much as £305 a year depending on how inefficient your current system is. Installing a room thermostat, timer and thermostatic radiator valves can also greatly reduce your heating bills. Installing a Smart Thermostat would take this even further

How often should I need to top up the pressure in the heating system?

When the heating system is cool, the pressure should be between 1 and 1.5 bar on the pressure gauge (the indicator needle would usually be in the green section). If pressure is below 0.5 bar (down in the red section), water has been lost from the system and must be replaced. Note: The red part of the dial could also indicate the pressure being too high (about 2.75 bar or more). If the pressure gauge indicates high pressure as a result of over filling, you will need to bleed a radiator until the pressure gauge returns between 1 and 1.5 bar.

If pressure rises by more than 1 bar when the heating is up to temperature then the expansion vessel may require repressurising. This will require a service engineer. The pressure in the system will usually require topping up once or twice a year. If you are having to repressurise your heating system much more frequently, please contact your installer.

Do my radiators need bleeding?

Over time it is normal for air to build up in your radiators which can affect their efficiency. When air builds up it will mean some areas of radiator will be colder than others. You can normally tell if your radiators need bleeding as they will be colder at the top than at the bottom. If this is the other way round (cold at the bottom and hot at the top) this could mean that sludge has built up in your radiator and you might need your system cleaned.

How does servicing help boiler efficiency?

Boiler efficiency naturally drops over time, as debris builds up within the system it can stop the boiler working at its maximum perfomance. 

If the debris is left and not flushed out it can cause damage to your boiler and system.To decrease the risk of damage to your boiler, it is recommended that you get the boiler serviced regularly, removing debris and potential blockages and therefore ensuring that the boiler is working to the best of its ability.

HeatGlow's Top Picks for Thermostats

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