Unit 309 Session 2 Central heating components

​Central heating components

​Heating systems are made up of many components, lets look at some common ones.
Firstly which do you already know?

Hotspot

Which hotspot is the pump?

Hotspot

Which hotspot is the Feed and expansion cistern?

Hotspot

Which hotspot is the Automatic bypass?

Hotspot

Which hotspot is the Mid-position valve?

Hotspot

Which hotspot is the Cylinder thermostat?

Hotspot

Which hotspot is the room thermostat?

​Central heating components

​Feed and expansion cistern

​Central heating components

​Feed and expansion cistern

​Central heating components

​Feed and expansion cistern

​Central heating components

​Feed and expansion cistern
Used in an open vented system to fill the system up with water.

Commonly located in the loft to locate it at the highest point of the system.  

​Central heating components

The base of the F&E should be at the same level as the cold water storage cistern and be fully supported over its base.
 

The main purpose of the F&E is to allow the heated water  

in the system to expand and to operate at atmospheric pressure.

​ 

• The F&E is commonly an 18-litre, black plastic cistern 

• The 15mm cold feed is located to the side of the F&E and should not have any valves.

The 22mm open vent from the primaries is located over the top of the F&E and must rise a minimum of 450mm above the water level. It should not have any valves.
 

The F&E should be located a minimum of 1 meter above the circulator (Pump). 

Open Ended

Why do you think the open Vent pipe needs to be a minimum of 450mm above the water level in the F&E cistern?

Open Ended

Why do you think the open Vent pipe and cold feed pipe should not have valves fitted?

​Open vent pipe 

The primary function of the open vent pipe is to provide a safety outlet should the system overheat. It also allows the system to operate at atmospheric pressure. 

Whilst filling the system with water and also in operation, the open vent allows the air to escape from the system. 

The open vent should not have any valves attached, as this could have disastrous effects if the valve was closed and the cold feed became blocked. 

The vent needs to be a minimum of 450mm above the water level to prevent the surge effect of the pump. 

The minimum pipe size is 22mm. 

​H frame  

​H frame 

Instead of an air separator, an H frame configuration is commonly used. 

The vent and the cold feed need to be installed on the flow from the boiler, on the suction side of the circulator, with a maximum of 150mm between them, ensuring that the circulator always draws on the cold feed.

​The correct layout of pipework ensures the neutral point of the system is at the base of the cold feed. 

​Air separator 

​An air separator is a device that removes air bubbles from heating systems.
They are used to: 

• Prevent problems: Air separators can help prevent corrosion, pump failure, and system noises 

• Improve efficiency: By removing air, air separators allow systems to operate more efficiently, consuming less energy and lasting longer
  

​Air separator 

​The correct layout of pipework and removal of air from the system reduces the noise in the system and lowers the risk of corrosion. 

​Circulator (Pump)

​Circulator (Pump)

​The circulator may have speed settings, which need to be set correctly to allow the system to heat up efficiently without any system noise. 

​Circulator (Pump)

The positioning of the pump is very important to produce positive pressure in the system and to avoid air entering the system and creating corrosion. 

The golden rule is that the circulator must always draw on the cold feed. 

The circulator may have speed settings, which need to be set correctly to allow the system to heat up efficiently without any system noise. 

​Two port motorised valve 

Commonly known as a zone valve

​Two port motorised valve 

Commonly known as a zone valve, this can be activated by a room or cylinder thermostat.  

This allows hot water and the heating circuits to be controlled separately. 

When there is a call for heat, the zone valve opens and allows water from the boiler to circulate around the pipework.
Likewise, when the thermostat is up to temperature, the zone valve is closed (isolates). 

​Three port mid-position valve 

​ 

Three port mid-position valve 

This valve controls the flow of water to both the heating and hot water circuits. It reacts to both the cylinder and room thermostat.

​ The three ports are labeled: 

• AB = flow from the boiler 

• A = central heating 

• B = hot water 

​Cylinder thermostat 

​Cylinder thermostat 

Situated one-third of the way up a hot water cylinder, governing the temperature of the hot water. This is linked to the zone valve or three port valve. 

These can be a bi-metallic strip, volatile liquid or gas type.

Commonly set to a maximum of 60⁰C. 

​Room thermostat 

​Room thermostat 

Situated 1.5 meters up a wall and approximately 3 meters away from a heat source, and not on an outside wall. 

These can be a basic bi-metallic type, or nowadays a programmable, Wi-Fi, app-activated and digital type, according to the customer’s requirements. 

More commonly, a compensating room thermostat can be fitted. 

​Automatic bypass valve 

​Automatic bypass valve 

Most modern systems are fitted with an ABV.

This allows a build-up of system pressure due to thermostatic radiator valves closing, with the circulator still working.

This is released through the system pipework, thus prolonging the pump life.  

​The ABV is fitted between the primary flow and return pipe; some boilers have an ABV already installed. This allows the flow of water through the boiler if the TRVs and zone valves close.

​Automatic air release valve 

​Automatic air release valve 

Fitted at high points in the system, these are commonly found fitted inside boilers. They allow air to be released from the system, closing automatically. 

Multiple Choice

To what height should the open vent pipe rise above the water level in a feed and expansion cistern in a fully pumped central-heating system? 

• 250mm

• 350mm

• 450mm

• 550mm

Multiple Choice

One of the main features of an open vent pipe to the primary circuit of a heating system is to: 

 

• decrease the water flow rate in the heating circuit.

• increase the water flow rate in the heating circuit. 

• fill the system with treated water. 

• relieve excess pressure in the system if it overheats. 

Multiple Choice

What is the maximum distance between the open vent and cold feed on an H frame? 

• 100mm

• 125mm

• 150mm

• 175mm

Multiple Choice

In the picture , which is the desired position for the pump to be fitted? 

• A

• B

• C

Multiple Choice

What component is shown in the picture?

• Radiator valve

• Pump

• Automatic bypass

• Air seperator

Multiple Choice

On a three port mid-position valve what connection is made to the AB port? 

• Flow from boiler

• Hot water

• Central heating

Multiple Choice

What component is shown in the picture?

• Radiator valve

• Pump

• Automatic bypass

• Air seperator

Labelling

Label the picture

Drag labels to their correct position on the image

Cylinder

Room thermostat

Pump

Feed and expansion cistern

Automatic by-pass

Labelling

Label the diagram

Drag labels to their correct position on the image

Automatic air vent

Motorised valve

Cylinder thermostat