1© 2011 Infosys Technologies Ltd.

© 2011 Infosys Technologies Ltd.

Roof Top Unit

CBSBU Project KT - Priyanka Rathore

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© 2011 Infosys Technologies Ltd.

Building Management System• Building Management Systems aims at maintaining smart buildings with the

integration of systems like Lighting, HVAC, Access control, Surveillance and EMS.

• HVAC i.e. Heating, Ventilation and Air Conditioning forms the major chunk of the entire system viz. 60-70% and then follows Lighting which forms approx.20-30% of the entire solution of green and smart buildings.

• HVAC consists of many systems which constitute the functioning of this huge process:

• Cooling Tower• Chiller Plant• Primary and Secondary chilled water pumps• AHU/FCU/RTU• VAV(Variable Air Volume)

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Air Handling Unit/Roof Top Unit

• Air Handling Units are same as Roof Top Units except for the fact that RTUs are always installed on roof top.

• Process followed in gist is as follows:

Sucks Air

•Fresh air damper lets the outside fresh air flow in. This damper is also sometimes called Fire Damper as it prevents the supply of air in case of fire inside the building. In this case, it is generally ON/OFF damper.

Conditions Air

• The air taken in goes through filter, cooling water coils and heating water coils to treat the air, i.e. to cool, humidify and dehumidify the air to meet the temperature and humidity requirements.

Circulates conditioned

air

• The treated and cooled air is now circulated through the supply air duct to the work areas. VAVs are used to maintain the supply air temperature in small rooms/cabins by controlling volume of air supplied.

© 2011 Infosys Technologies Ltd.

• Heating coil & valve• Cooling coil & valve• Discharge air Duct• Mixed air dampers section• Return air Duct• Mixed Air temp. sensor• Discharge air temp. sensor• Return Air temp. sensor• Fan/Blower • VFD(Variable Frequency

Drive)• Filters• Smoke Detector• Actuators

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RTU Components

• Click icon to add picture

• The damper section:

• Manually Operated for Outside Air/Exhaust Air

• Motorized Modulating

• Motorized On/Off

• Fire Dampers – Motorized /Fuse Link Operated

• Temperature Sensor:

• Temperature sensors are used for measurement of temperature of a room, Air Duct, Hot /Cold Water, Outside Air etc.

AIR DUCT TEMP. SENSOR ROOM TEMP. SENSOR IMMERSION TEMP. SENSOR

• Relative Humidity Sensor:

Relative Humidity sensors are used for measurement of Relative humidity of a Room, Air Duct, Outside Air etc.

• Differential Pressure Switch:

Differential Pressure switches are used for monitoring of Filter, Fan, Pump, Fire Damper, Water Flow, Air Flow Status of air handling systems.

Ex. Air differential pressure switch and Air Flow switch

• Differential Pressure Sensors/Transmitter:

Used for measuring diff. Pressure, positive pressure and vacuum.

• Valves & Actuators:• Valve Types

• 2 Way or 3 Way• Actuator Types

• Motorized• Magnetic• Pneumatic

• Operation• On – Off• Floating• Modulating

• Filters :• Pre Filters

• 70-80-% Efficiency .• Can filter particles of size upto 5-10 microns.• Reusable & Washable

• Fine Filters• 90-95 % Efficiency .• Can filter particles of size upto 1 to 2 microns.• Not Reusable

• HEPA(High Efficiency Particulate Air) Filters• 99.97% to 99.99995 % Efficiency .• Can filter particles of size upto 0.1 to 0.3 microns.• Used in Clean Room Applications.• Not Reusable

• ULPA Filters• PTFE Membrane Filters For State-of-the-Art Cleanroom Requirements

• PTFE (PolyTetraFluoroEthylene) Membrane combines ultra-high efficiency with negligible pressure drop

•High Resistance to Corrosive Environments (Acid, Alkali and Organics)

•Negligible Off-Gassing Properties (Boron, Sodium, Potassium, Silicon)

•99.99995% Minimum Efficiency.

• Filters :

The cross stacking of the filters is done to

increase the surface area.

• Coils :• Heating Coils• Cooling Coils

• Coil Construction• Copper with Aluminium fins,• 13 Fins /inch• Number of Rows, i.e. 4/6/8 depending

on the latent heat load & Bypass Factor.

• Fan/Blower :

Fan shall be operated from a

1) time clock

2) time schedule from the BMS

Fan’s rpm is maintained by a third party component

Known as VFD i.e., Variable Frequency Drive which is operated as per the Differential pressure required across the blower.

• Air Distribution System:• Constant Volume, Variable Temperature (CV)

• Delivered to all room areas regardless of individual room differences.• VAV -Variable Air Volume, Constant Temperature• Single Zone or Dual Duct

Functioning of RTU:

Fresh air taken in through fresh air

damper

• Fresh air temp. measured• Differential air pressure

across fan governs the blower’s speed

Air passes through cooling coils and heating coils for cooling, humidification and

dehumidification

Air from work area enters return air duct, smoke detector checks for the

fire

Return air gets in through mixed air damper and circulates again after

conditioning

Exhaust air damper when open lets the return air

out.

Types of RTU

Air Handlers can be categorized by:• Method of temperature control• Method of volume control• Method of air distribution

Types :• Mixed Air AHU• Treated Fresh Air AHU• 100 % Fresh Air AHU

Single Duct variation

• The exhaust air damper is not in this air handler; the building air is exhausted elsewhere, but the basic mixed air and other functions are unchanged.

© 2011 Infosys Technologies Ltd.

THANK YOU

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