HEATING SYSTEM DESIGN

WHAT COMPONENTS ARE COMBINED TO DESIGN AN ;

OPEN

VENT HEATING SYSTEM

DIFFERENT AREAS OF SYSTEM

HEATING SYSTEM PRIMARY CIRCUIT FEED & EXPANSION AND OPEN VENT DHW SECONDARY CIRCUIT

There are also many different types of system pipe design to be considered.

TWO-PIPE

SINGLE-PIPE

OPEN VENT SYSTEMS

Commonly installed over recent years Open due to the system radiators, cylinder and calorifier being open to atmosphere. Expansion and Contraction of heated water is accommodated by the feed & expansion cistern Water is supplied to the system by the use of the Feed & Expansion pipe (cold feed)

OPEN SAFETY VENT PIPE

Safety device which enables the removal of steam or high temperature water in the event of boiler controls failure. Generally installed to the main heating flow or directly to the boiler No valves must be installed on the vent pipe Correct positioning is essential due to the introduction of more powerful pumps

FEED AND EXPANSION PIPE (COLD FEED)

Dual functions are to feed water into the system and also when the system is raised in temperature permit water to expand into the feed and expansion cistern The main function is to handle the expansion of heated water within the system It also has to assist the safety vent pipe in the event of overheats within the heat exchanger Commonly a lockshield gate valve is installed generally found at the connection to the heating system

FEED AND EXPANSION CISTERN

The cistern is connected to the cold mains water supply through a ball operated float valve It provides two functions, which are to replenish the system after installation or remedial work and also to accept the expanded heated water from within the system. Common components are the open safety vent pipe, ball operated float valve, feed and expansion pipe, and an overflow/warning pipe

SEALED SYSTEMS

The system is sealed to atmosphere, therefore corrosion is reduced within the installation The system can operate at a higher temperature than an open system No feed & expansion cistern is required An Expansion vessel accommodates expansion and contraction within the system A Pressure relief valve is installed as a safety feature similar to the open vent pipe

EXPANSION VESSEL

The vessel should be installed on the suction side of the pump, this point will be termed the neutral point The vessel is divided into two compartments separated by a flexible diaphragm The sealed compartment is charged with nitrogen or air The diagrams above indicate A. the expansion vessel in a cold state, B. when the temperature increases, C. when the system is at operating temperature

PRESSURE RELIEF VALVE

Must be installed on the appliance or the flow pipe The valve must open when the pressure increases above the set system pressure The valve must discharge in a safe manner through a pipe to low level The pressure relief valve must not be used to drain the system

TWO-PIPE SYSTEM

The preferred method of installing a heating circuit is to use two pipes, one being the flow from the heat source, the other being the return to the heat source The main advantage is the same flow temperature ia available to each radiator There are many different types of two-pipe systems available for installation

TWO-PIPE SYSTEM

SINGLE-PIPE SYSTEM

A single pipe design is the simplest type of installation, using one pipe to supply all heat emitters on the circuit Pipe sizes are generally larger to overcome resistance A disadvantage is that the same flow and return temperatures cannot be maintained

Radiator return water mixes with single pipe flow

SINGLE-PIPE SYSTEM

The reduction in temperature at the flow and return connections to the heat emitters is not desired although this can be unavoidable With reference to the diagram above, the first radiator A. will receive water at the boiler output mean temperature, after circulation through the radiator the water will lose temperature due to some heat being extracted for output of the radiator The water is then circulated through the return connection of the radiator at a lower temperature and mixes with the single pipe thus reducing the mean temperature of the water within the system, the water is then circulated further to radiator B. where the process continues

GRAVITY CIRCULATION

A gravity central heating system depends on the density of hot and cold water Cold water is heavier than Hot water, therefore the cold water will drop and the hot water will rise through a system Gradually through the years these type of systems were modernised with the installation of further controls and components

FULLY PUMPED HEATING AND HOT WATER SYSTEM

PRIMARY FLOW & RETURN

Modern practice is to use a positive form of circulation, for both heating and hot water Pumped circulation allows for smaller diameter pipework A flexible approach to pipe routes A cost effective and efficient installation Independent control of both domestic hot water and heating Greater heat recovery and control of temperature within the system

SUMMARY: KEY POINTS

Pump position Pump head Open vent and cold feed position Correct pipe size Pipe layout Negative and Positive pressure The correct installation of controls Determining the index radiator on the circuit Balancing of the system

OPEN VENT SYSTEM

Group 1- Heating System Group 2- Primary Circuit Group 3- Feed & Expansion/ Open Vent Group 4- DHW Secondary Circuit

QUESTIONS

WHAT IS THE ADVANTAGE OF A 2-PIPE HEATING DESIGN The same flow and return temperatures can be maintained NAME THE TYPE OF CYLINDER WHICH IS SUPPLIED BY THE PRIMARY FLOW & RETURN? An Indirect Cylinder WHAT IS THE PURPOSE OF THE FEED & EXPANSION CISTERN? To accept expanded heated water & replenish the system

AT WHAT TEMPERATURE IS DOMESTIC HOT WATER STORED? 60C

WHAT AREA OF THE HEATING SYSTEM IS OF MOST BENEFIT? ALL AREAS ARE OF BENEFIT TO THE SYSTEM

PRESSURISATION UNIT

PLATE HEAT EXCHANGER

TWIN PUMP HEAD

FAN COIL UNIT

WHAT ADVANTAGE WOULD THE INSTALLATION OF THESE COMPONENTS HAVE ?