LEVEL 4 BUILDING SERVICES TRAINING 3 0 Level

LEVEL 4 BUILDING SERVICES TRAINING 3. 0 - Level 3 Re-cap • Cooling Systems looked at within Level 3 included; – – – Through-the-wall packages Individual reversible heat pumps Split Unit packages Variable Refrigerant Flow (VRF) Ducted Installations Heat Recovery Ventilators (HRV)

LEVEL 4 BUILDING SERVICES TRAINING Level 3 Re-cap Other Forms of Cooling • Constant volume • Variable Air Volume (VAV) • Dual duct • Induction • Fan coils • Chilled beams and ceilings

LEVEL 4 BUILDING SERVICES TRAINING Constant Volume (CV) Systems • CV systems provide a fixed volume of air at a temperature and humidity determined by the conditions of the space being served. • Can be used for single zone applications, where only one set of internal conditions need to be satisfied. • Simple and relatively easy to maintain • Can be used to provide fresh air in air/water systems such as fan coil and chilled beam installations.

LEVEL 4 BUILDING SERVICES TRAINING Variable Air Volume (VAV) • Air based cooling system which can serve multiple zones in a building • Air supplied at constant temperature from central plant to VAV Terminal units • Thermostat controls damper on VAV units to regulate flow rate of cold air to match demand • Can be relatively energy efficient due to the ability to reduce the speed of the supply/extract fan(s) during periods of low to moderate loads. • VAV systems are particularly suited to buildings with a year round cooling load.

LEVEL 4 BUILDING SERVICES TRAINING Variable Air Volume (VAV) Types • There a number of types of VAV Systems available – Single Duct • Supplies cold air to the terminal Unit – Dual Duct • One duct supplies warm air, the other supplies cold air, these are mixed in the VAV terminal box • Ducts providing warm and cold air are commonly referred to as “Hot Deck” and “Cold Deck” • Thermostat controls damper which regulates flow from each “Deck” – Terminal Reheat • Used with single duct VAV system to increase air temperature when necessary within the space • Commonly utilises electric heater batteries or LTHW Coil

LEVEL 4 BUILDING SERVICES TRAINING Induction Systems • Outside air supplied to induction units via high velocity spiral ductwork • High pressure forces air through nozzles at greater velocity • High velocity air movement ‘induces’ secondary air over heating/cooling coil • Single pipe induction systems can provide heating or cooling separately and will require full changeover of system • Two pipe induction systems can change from cooling to heating much more easily.

LEVEL 4 BUILDING SERVICES TRAINING Fan Coil Units • Fan coil systems can satisfy the individual heating and cooling requirements of multiple zone buildings and enable good building flexibility • A typical fan-coil unit comprises a fan, heating coil, cooling coil and air filter, all housed in a metal casing • Supply air for ventilation only, not cooling, reducing duct sizes • 2 -Pipe fan-coil provides cooling or heating and requires full changeover, re-heat battery option for heating when out of heating season • 4 -Pipe fan coil utilise two coils, one for heating and one for cooling • Flexible ductwork connections from unit to supply grilles

LEVEL 4 BUILDING SERVICES TRAINING

LEVEL 4 BUILDING SERVICES TRAINING

LEVEL 4 BUILDING SERVICES TRAINING VAV System VAV Terminal Unit Fan Coil Unit System Fan Coil Unit

Centralised Systems Constant Volume (CV) Systems AIR HANDLING UNIT EXHAUST AIR FRESH AIR INTAKE HEAT REJECTION CHILLED WATER CIRCUIT AIR COOLED PACKAGED CHILLER SUPPLY AIR EXTRACT AIR OCCUPIED SPACE

Centralised Systems Variable Air Volume (VAV) Systems AIR HANDLING UNIT EXHAUST AIR FRESH AIR INTAKE SYSTEM CONTROL MOTORISED CONTROL DAMPERS WATER COOLED CHILLER CHILLED WATER CIRCUIT T T SUPPLY AIR EXTRACT AIR OCCUPIED ZONE 1 SUPPLY AIR EXTRACT AIR OCCUPIED ZONE 2

Centralised Systems Fan Coil Unit (FCU) System AIR HANDLING UNIT EXHAUST AIR FRESH AIR INTAKE T BEMS SYSTEM CONTROL CHILLED WATER CIRCUIT ZONE 3: FCU FAN COIL UNIT MCDs CHILLER CHILLED WATER CIRCUIT T ZONE 1: VAV T ZONE 2: FCU

Centralised Systems Induction Systems • Air recirculation induced by pressure difference. CHILLER CHILLED WATER CIRCUIT T OCCUPIED ZONE

LEVEL 4 BUILDING SERVICES TRAINING Chilled Beams • Long rectangular units, containing finned tube through which chilled water is pumped • Chilled water cools air surrounding unit causing it to fall to the occupied space below • Passive chilled beams rely on the buoyancy of the warm air to cause the air movement • Active chilled beams incorporate a small fan to assist air movement • Relatively warm chilled water temperatures allow sources of chilled water such as rivers, cooling towers, dry coolers and ground water

LEVEL 4 BUILDING SERVICES TRAINING Chilled Beams (Cont. ) • Quiet operation with limited maintenance requirements • No ventilation within system, so separate system may be required • Good airflow essential, some units have capacity to link ventilation air directly into the unit, increasing cooling output

LEVEL 4 BUILDING SERVICES TRAINING Chilled Ceilings • Comprises of small bore chilled water pipework connected in a meandering arrangement to a thin metallic ceiling panel • Panel cooled through contact and provided convective and radiant cooling to the space below • Can be accommodated within very shallow ceiling voids • Limited cooling output • Quiet operation with limited maintenance requirements • No ventilation within system, so separate system may be required

LEVEL 4 BUILDING SERVICES TRAINING Passive Chilled Beam Active Chilled Beam Chilled Ceiling

Centralised Systems Active & Passive Chilled Beams Air supplied to chilled beams directly serving zones. Air is conditioned at terminal units. • Controls • Positioning • Design Philosophy SUPPLY AIR ACTIVE CHILLED BEAM OCCUPIED ZONE 1 CHILLER CHILLED WATER CIRCUIT OCCUPIED ZONE 2 PASSIVE CHILLED BEAM

LEVEL 4 BUILDING SERVICES TRAINING Chilled ceiling in-situ

LEVEL 4 BUILDING SERVICES TRAINING Chillers • • Chill either water or water/glycol mix Chilled water is provided to cooling coils as part of the building’s cooling system, either directly to the air handling plant (CV and VAV) systems, or to terminal units within the space (Induction systems and Fan Coil Units) Chillers remove heat from a liquid by one of two methods; vapour compression or absorption refrigeration cycle Chillers come in 5 varieties, divided into the above 2 categories • • • Reciprocating Compression Scroll Compression capacity (from 0 to 400 k. W) Screw-driven Compression capacity (from 400 to 1, 500 k. W) Centrifugal Compression capacity (from 1, 500 to 7, 000 k. W) Absorption Chillers capacity (from 0 to 20, 000 k. W) and does not use refrigerants. Each of these systems can be used in one of two ways; • Air Cooled • Water Cooled

LEVEL 4 BUILDING SERVICES TRAINING Vapour Compression Chiller Types • Reciprocating Compression – Compressor uses pistons driven by a crankshaft to deliver gas at high pressure • Scroll Compression – Uses two interleaved scrolls to compress fluid – One scroll is fixed, while one orbits eccentrically, trapping & compressing fluid • Screw-driven Compression – Rotary type positive displacement mechanism utilising 2 rotating, intermeshing helical screw elements – As mechanism rotates, meshing and rotating produces series of volume-reducing cavities, compressing fluid • Centrifugal Compression – Complex radial flow turbo machinery – Cannot achieve high compression ratio of reciprocating compressors

LEVEL 4 BUILDING SERVICES TRAINING 3. Screw driven compressor 2. Scroll compressor 4. Centrifugal compressor 1. Reciprocation compressor

LEVEL 4 BUILDING SERVICES TRAINING Absorption Chiller Types • Absorption Chillers – Thermodynamic cycle driven by heat source, typically steam, hot water or combustion – Very low electrical power requirements compared to electrically powered chillers – This is outweighed by their large heat input requirements – Excel in energy efficiency terms where large amounts of high-grade waste heat is readily available, such as from incinerators – If water cooled, absorption chillers require far larger cooling towers than vapour compression type chillers.

LEVEL 4 BUILDING SERVICES TRAINING 5. Simplified diagram of a single effect absorption cycle

LEVEL 4 BUILDING SERVICES TRAINING Chillers – Air Cooled and Water Cooled • Air Cooled Chillers – Located outside, typically on roof plant space – Use air as heat transfer medium in a similar manner to external units for split air conditioning systems – Can be remote to unit or contained within ‘Package’ Chiller • Water Cooled Chillers – Incorporate the use of cooling towers – Cooling towers act as a heat sink for system, rejecting heat from water which is used as a heat transfer medium to provide evaporative cooling to the gases within the chiller system – Cooling towers can either be ‘wet coolers’ or ‘dry coolers’ – Wet cooling towers transfers heat from warmer water to cooler air by evaporation – Dry coolers transfer heat from warm water to cooler air by sensible heat transfer by convection

LEVEL 4 BUILDING SERVICES TRAINING Advantages – Air Cooled and Water Cooled • Air Cooled Chillers – – – Lower installed cost Quicker availability of purchase – off the shelf type standardisation No cooling tower or condenser pumps required Less maintenance No plant room required • Water Cooled Chillers – – Higher Efficiency Custom selections available Large cooling capabilities Indoor (basement) chillers location – Ideal where roof space is at a premium – Longer active life

LEVEL 4 BUILDING SERVICES TRAINING Warm air exhausted to atmosphere Fresh Air Chilled Water Supply Warm Water Return

LEVEL 4 BUILDING SERVICES TRAINING Refrigeration cycle for Air Cooled Chiller

LEVEL 4 BUILDING SERVICES TRAINING System Cycle for Air Cooled ‘Package Chiller’

LEVEL 4 BUILDING SERVICES TRAINING Air Cooled ‘Package Chiller’ Evaporative Cooling Tower Water Cooled Chiller Dry Cooler

LEVEL 4 BUILDING SERVICES TRAINING ANY QUESTIONS OR FEEDBACK