1. Objective of the session.
Aims of the session.
To enable you to identify the main component parts of a domestic heating system.
Objective of the session.
To teach you what the main parts of the heating system are, what is there function, what could go wrong with them and how could the fault be corrected.

2. Use the following presentation to identify the component parts of the domestic heating system.
If you get stuck as the tutor.
To identify faults look at the faults page and discuss first in your group and then with your tutor what could go wrong.

3. Fully Pumped System

4. Boiler The boiler is the part of the system that heats the water.
It burns fuel (oil, gas, coal & wood) in a chamber within the boiler; at the top of this chamber there is a heat exchanger (like a reverse radiator) that takes the heat from the combustion and transfers it to the water.
The exhaust gasses are vented outside via a flue or chimney sometimes the exhaust is fan assisted.
Faults

5. Radiator
Radiators are the most common type of heat emitter encountered in domestic properties.
They can come in many different sizes, shapes and styles, but they all work in the same way.
Hot water passes through the core of the radiator transmitting heat to the metal outer of the radiator via conduction.
Some of the heat given off by a radiator (15%)is radiated, the majority of the heat given off by a radiator (85%) is given off by convection.
Faults

6. Indirect Hot Water Cylinder
A hot water cylinder heats and stores hot water used for washing in the bath, sink, basin, etc..
There are two separate water systems within the cylinder;-
The primary circuit brings hot water through the cylinder from the boiler. This circuit is usually in the form of a copper coil.
The secondary circuit is water that we are going to wash with this comes from the cold water storage cistern into the bottom of the cylinder and is heated by the primary circuit.
Faults

7. Three Port Mid-Position Valve
The three port motorised valve is a device that switches the direction flow of hot water from the boiler to the heating system, the hot water cylinder or both.
The valve consists of two main components a motor that turns a valve and the body of the valve.
The valve can switch the flow from the boiler port AB to port A, Port B or both.
Port A is typically connected to the domestic hot water.
Port B is typically connected to the central heating system.
Faults

8. Water Pump The water pump circulates the hot water through the system.
The pump is powered buy a the mains electricity and controlled by the motorized valve.
Faults

9. TRV
The Thermostatic Radiator Valve (TRV) controls the temperature of each individual radiator.
They use a wax of liquid sensor that expands with heat and shuts the valve.
Faults

10. Lock Shield Valve
A lock shield valve is found on the other end of a radiator to a TRV.
The lock shield valve controls the flow of water through the radiator; these are an important part of balancing the heating system.
Faults

11. Cold Water Storage Tank
The cold water storage tank holds a supply of water in the highest point of the house for use by the heating system.
They must be covered to stop insects and dust getting in to the water supply.
They must be insulated to protect them from the cold in the winter and the heat in the summer.
Faults

12. Float Operated Valve
The float valve controls the water supply to the cold water storage tank.
As the water level drops the float falls and activates the valve; once the water level rises to the required level the float rises and turns the valve off.
Faults

13. Boiler
The boiler is a very complicated device made up of many components that must all work.
There is a fuel supply through a small pipe.
There is a burner to burn the fuel.
There is a heat exchanger that takes the heat from the burner and transfers it to the water.
The flue / chimney takes the exhaust gasses away from the boiler.
There thermocouple detects the temperature and turns the burner on if the water is too cold and off if the water is too hot.

14. Radiator
The radiator is a metal envelope that has hot water passing trough it to heat the room/house.
The radiators are typically made of steel.
The radiator is connected to the water pipes using compression fittings.
The water pipes are made of copper there is a reaction that can take place between the two metals (galvanic corrosion) that causes the steel to rust at a rapidly increased rate

15. Indirect Hot Water Cylinder
The hot water cylinder has two separate water systems inside it.
The primary water has chemical inhibitors in it and can pick up contamination from the radiators and boiler.
The secondary water is what people wash in.
The outer shell of the cylinder is very thin and made of a relatively soft material copper.

16. Three Port Mid-Position Valve
The three port switch consists of two main parts;-
The valve, which has precisely machined valve seats that seal the water.
The electric motor, that turns the switch.
The valve is operated electrically. There are cables that run to the motor to power the valve.

17. Water Pump
The water pump like the three port valve has two main components;
The electric motor. This powers the pump.
The impeller. This is like a propeller on a ship, it pushes water through the pump and system.
The impeller runs on bearings to make it spin freely if these seize up they put an additional load on the motor.

18. TRV The TRV is made up of two parts;-
The temperature control head; the top part of the valve that you set the temperature with.
The valve; that adjusts the flow of water through the radiator.
The control head is large and vulnerable to damage if bumped.
The valve is operated via a ‘pin’ that is depressed by the control head, if not used the ‘pin’ can seize.

19. Lock Shield Valve
The lock shield valve is mechanically connected to the radiator using a screw thread and compression fitting.
The valve has a washer to aid the sealing of the water flow.
Once set the valves are rarely adjusted for years at a time.

20. Cold Water Storage Tank
Cold water storage tanks must now be sealed.
Older water tanks had open tops.
Water tanks must be insulated.
A warning pipe must be connected to the water tank to indicate if there is a problem with the float operated valve.
The warning pipe should be the size larger than the supply pipe.

21. Float Operated Valve
The float operated valve is located inside the cold water storage tank.
The valve only operates if fitted correctly.
The float must ‘float’
The valve has a rubber seal.