Module 3: • Domestic Heating/MMA Welding • Unit 2 – Domestic Heating Systems • Duration – 10 Hours
In unit 2 we learn how to: • Describe the working principles and types of domestic heating systems. • List the basic components of domestic heating systems and describe their function. • List common and alternative sources of heat energy. • Draw schematic representations of domestic heating systems.
Key Learning Points • Rk Principles of domestic heating systems. • Rk Types of heating systems. • Rk Components of heating systems. • Rk Pipework layout. • D Drawing of domestic heating systems. • RkLocation and function of safety valves. Location and function of vent pipe, cold feed pipe. • Rk Primary flow and return pipework, cylinders. • Sc Gravity circulation. • Rk Fully pumped circulation. • Rk Function, location, components of circulation pumps. • Rk Types of radiators and radiator valves. • Sc Heat transfer in heating systems. • P Filling arrangement for sealed systems. • Rk Function, location, size of expansion vessel in sealed systems. • Rk Sources of heat energy, solid fuel, gas, oil. • Rk Alternative sources of energy • P Communication.
Wet Central Heating Fire Extinguishers • Pipework Problems • Sealed Systems • Boiler Types
Operator Protection • No open-neck shirts;Ultra-violet rays will burn the skin. It is most definitely not similar to sun tanning. • Regulation inflammable overalls only;Arc-welding produces large amounts of hot sparks which will set flammable clothing alight. • No trainers/runners to be worn;The steel metal plate used are heavy and sharp. Wear steel toe-cap boots. • Overalls not around waist;Sparks will set casual tops alight • Always wear protective clothing;Arc-welding produces heat, glare, sparks, ultra-violet & infra-red rays and harmful fumes. Welding gauntlets must be worn at all times. Face masks are designed to deflect fumes and should therefore be held close to the face. Gas welding goggles will not afford protection for the face against the light intensity or the radiation and must not be used. Shade 11 EW filters are required in the face mask for manual metal arc welding. Always wear protective goggles when chipping slag.
Basic Pipework Layouts Gravity Circuit
Heat Emitters • Radiators • Convectors
Radiator Controls • Lockshield • Customer Control
Possible Radiator Problems • Reverse Circulation
Possible Radiator Problems..continued • Commoned Returns
Sealed Or Pressurised Systems • Typical Sealed System
Pressure and Temperature Safeguards • Pressure Release Valve & Discharge Pipe
Filling and Maintaining the System Water • Temporary Filling Loop
Maintaining the Water Level • Automatic Top Up Bottle
Common Problems • Temporary Filling Loop • Checking and Recharging Expansion Vessels • Overfilling a System • Defective Expansion Vessel
Domestic Central Heating Main Equipment • The main equipment required in a domestic heating system consists of: • A Boiler • An Indirect Cylinder • A Feed and Expansion Cistern or Expansion Vessel • A Circulating Pump • Radiators
Domestic Central Heating Systems • The are two main types of domestic central heating systems: • The Open Vent System - This system incorporates a feed and expansion cistern, vent pipe, and cold feed. • The Sealed System - In this system the expansion of water is taken up by an expansion vessel.
The Open Vent System • The basic equipment in an open vent system: Feed & Expansion Cistern Indirect Hot Water Storage Cylinder Boiler
Cold Feed to the Heating System Standard Gate Valve
Radiator Valves • Each radiator is fitted with two valves: • A Handwheel valve on the flow • A Lockshield valve on the return Handwheel Radiator Valve (Flow) Lockshield Radiator Valve (Return)
The One Pipe System of Central Heating Ring Main Circuit Flow Return
Pump, Safety Valve, and Drain Cock Safety Valve Pump Drain
The Two Pipe Heating System of Central Heating Return Flow Return
The One Pipe System of Central Heating • Advantages: • Only one pipe is necessary to convey hot water to the radiators • Cheap to install • Disadvantages: • Hot water passing through the first radiator is cooled and returns to the main flow pipe • This water then supplies the next radiator and has the effect of producing a lower temperature • Only suitable for small single storey buildings