01 HVAC Basics

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HVAC

Technology Overview


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Page 2 8 March, 2014

Agenda

10:00 Introduction

10:15 HVAC Basics

11:00 Break

11:15 AHU Components

12:00 Lunch

13:00 Control Theory

14:30 B1 HVAC Overview

15:00 Tour of B1 plant rooms

16:00 Re-cap and Questions


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Heating Ventilating Air Conditioning

Why do we need HVAC?

Human operating parameters

Machine operating parameters

Health & Safety (Operating Theatres)


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Factors affecting comfort

Gender

Age

Health

Dress

Physical Activity

Air velocity (draughts)

HVAC Fundamentals


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Common Complaints

What is the possible or probable cause of each complaint?

And how would we remedy each?

Too hot

Too cold

Too drafty

Too stuffy

Too noisy Too stinky

HVAC Fundamentals


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What is Heating?

The addition of thermal energy

-Heatis added to produce a warmer, morecomfortable environment.

What is Cooling?

The removal of thermal energy

-Heatis removed to produce a cooler, morecomfortable environment.

Cooling is not added, rather heat is removed!

HVAC Fundamentals


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What is Humidity?

Its got a LOT to do with COMFORT!

Relative Humidity (RH).- ratio between the actual and the maximum water vapour the air

can hold presented as a percentage.

Amount of water vapour depends on temperature of the air; its allrelative.- Increases when the temperature falls.- Decreases as temperature rises.

Absolute humidity is a true measure of moisture content.

Wet bulb and dry bulb temperature measurement will reveal all.

HVAC Fundamentals


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Cooling and Heating follow distinct modes of transfer.

Heat transfer by

Conduction Radiation

Convection

HVAC Fundamentals


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Conduction - direct contact

from warmer to cooler surface.

Examples of Conduction:

Cooling and heating coils.

Cooling system in an car engine.

Heat gain through walls.

Heat loss through walls.

HVAC Fundamentals


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Convection

Colder air is more dense.

Examples of Convection:

Gravity system heating; warm air rises!

Radiators causes air convection.

Things that aid heat convection

- unrestricted airflow paths.

- volume of the transfer medium.- specific heat of the transfer medium.

HVAC Fundamentals


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Heat radiation takes the form of infrared waves

heat waves travel through a transparent medium until it strikes asolid surface.

Solid material absorbs the radiation and gets warmer.

Examples of Radiation transfer:

Sun shining on dark pavement.

A patio heater.

An overhead radiant unit heater.

Things that affect radiation

- colour of surfaces

- emissivity of glass.- reflective surfaces.

HVAC Fundamentals


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Determining Heating and Cooling Loads:

Design indoor conditions

- what are the comfort requirements?- Target temperatures and relative humidity.

(for human comfort usually 21Cand 50%RH)

Design outdoor conditions

- Geographic location.- Winter and summer dimension.- Use ASHRAE data.

Equipment then sized to meet Design Conditions

HVAC Fundamentals


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System Components

What do we need to monitor

1. TemperatureFor heat transfer the final control element is a valvepositioned by an actuator that controls the flow of water/steam.

2. Relative HumidityCorrection can be humidifier and dehumidifier.

3. CO2- Damper positioned by an actuator controlling flow of fresh

air into the system.

4. Static Pressure sensorFan speed control.

5. Outside air Temp/RH

6. Filter status

7. Fan status


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Energy Use

Typical commercial building


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System Components

Boilers 1 produce hot water (or

sometimes steam) for distribution to the

working space. This is done either byheating coils 2 which heat circulated air,

or through hot water pipes to radiators 3

Cooling equipment 4 chills water and

circulates through cooling coils 5. Air is

then blown through the chilled water

coils into the space 6. As part of the

refrigeration cycle, heat must also be

rejected from the system via a cooling

tower or air condenser 7.

Pumps are used throughout the system

to circulate the chilled and hot water to

the required areas throughout the

building.

Stale air is extracted, usually using a

fan, via separate ducts and expelled

outside 8


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System Components

Controls are used to orchestrate the

heat transfer process.

They turn equipment on or off and

adjust chillers and boilers, air and

water flow rates, temperatures and

pressures.

A controller incorporating one ormore temperature sensors 9 inside

the workspace sends a signal to the

heating or cooling coil actuators.

When there is a demand for heating

or cooling the controls also send a

signal to the chiller and boiler toenable as required.

Chillers and boilers often have their

own control panels.


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Hot Water Boiler

Heat

Coil

HeatCoil

Hot Water (kW out)

fuel (kW in)

kW transferred to air

HEAT!

Basic

Hot Water

Loop

Boilers


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Heat

Coil

HeatCoil

Basic

Steam

Loop

Heat

Coil

HeatCoil

Steamtraps

condensate

Steam Boiler

Boilers

fuel (kW in)

Steam (kW out)

kW transferred to air

HEAT!


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Staged boilers Base Loadingsmaller/larger

Commercial Boiler Design

B il C b i P i i l


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Boiler Combustion Principles

Laws of Thermal Dynamics:

1st law of thermodynamics - law of conservation;energy cannot be created or destroyed.

But it can be changed from one form to another.

Chemical energy is released during conversion;Hydrogen (H) + Carbon (C) + Oxygen (O2) > chemicalreaction = energy release, thermal energy (heat).

Elements recombine into newcompounds;

carbon dioxide (CO2) + water vapor (H2O) = gases ofcombustion.

2nd law; heat always flows from high temp to low temp.

C b ti P i i l


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Combustion Principles

Making Heat:

Combustion requires fuel, heat, oxygen.

Products of combustion:

CO2 H2O

N2 Heat (kWh)

C d i B il


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Condensing Boiler

The flue gases are cooled to the point where water vapor condenses out of thefuel/air mixture. Hence the name.

High efficiency condensing boilers convert more than 87-97% of their fuel intoheat, compared to 78% for conventional types.

They have either a larger or a second heat exchanger, which releases latent heat

that would otherwise escape up the flue.

High efficiency condensing boilers can be oil or gas.

Condensing boilers are the boiler of choice for all modern installations.

B T


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Burner Types

On / Off System

This is the simplest control system, and it means that either the burner is firingat full design rate, or it is off.

The disadvantage of ON/OFF is that the boiler is subjected to large and oftenfrequent thermal shock every time the boiler fires. Its use is limited to smallboilers.

Every time the burner shuts down and re-starts, the system must be purged byblowing cold air through the boiler passages. This wastes energy and reducesefficiency.

Advantage: Its cheap

High / Low

This is a slightly more complex system where the burner has two firing rates.The burner operates first at the lower firing rate and then switches to full firingas needed, thereby overcoming the worst of the thermal shock.

The burner can also revert to the low fire position at reduced loads, againlimiting thermal stresses within the boiler.

Modulating

A modulating burner will alter the firing rate to match the boiler load over thewhole load range.

Full modulation means that the boiler keeps firing over the whole range to matchthe load and minimize thermal stress.

B il C t


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Flame Detection

For safety boilers must

have a way of shutting off

fuel quickly if flame is lost.

Because of its ability to

detect only the true

signature of a flame,

ultraviolet is commonly

used.

Boiler Components


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Heat Distribution Systems

CirculatorsMoves hot water around a building.

Operate on Ferris wheel principle.

H t E h


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Heat Exchangers

Convectors

Moves heat into the space

Baseboard and Cabinet

H t E h


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Heat Exchangers

Duct re-heat or Air Handler

Fan Coil Unit (FCU)

Basic Refrigeration


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Basic Refrigeration

What are Btus?

Definition:

Heat required to raise

1 lb. water 1 F.

Heat can be sensible or

latent.

Other liquids, like

Freon, behave similarly,

but at differing

temperatures dependingon pressure.

Sensibleheat

LatentHeat of

Fusion

SensibleHeat

Latent Heat

of Vaporization(or Latent Heat

of Condensation)

SensibleHeat

212 200

100

32

0

300

Temper

atureindeg.

F.

BTU per pound of water

16 144 180 970 44

vaporsuperheating

liquid to vapour

(boiling)

vapor to liquid(condensing)

vaporcooling

liquidheating

liquidcooling

Ice

warming

Icemelting

Waterfreezing

Icecooling

Refrigeration


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Refrigeration

Basic refrigeration cycle: This is a liquid to air heat pump.

Notice the cut line between the high pressure side and thelow pressure side.

Refrigeration works because of this pressure difference.

Metering device

Cooled Air Hot Air

HPV

LPV

HPLLPL

Changes from

vapor to liquid

Liquid line

CONDENSEREVAPORATOR

COMPRESSOR

Changes from

liquid to vapor

Freezer application


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Freezer application

Heat is absorbed in the evaporatorthereby reducing the surrounding airtemperature.

The condenseris located outside the building.

Often referred to as a Split unit system.

Chiller Plant


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Chiller Plant

Chilled water is used to cool

the building.

Water is chilled in

evaporator.

Water absorbs heat in the

condenser.

Condenser water cooled by

evaporation principles.

Chiller components


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Chiller components

Typical evaporator

Water passing through the evaporator gives up heat as theliquid refrigerant boils (evaporates).

Side view

end view

Refrigerant liquid

inlet

Refrigerant

vapour outlet

Chilled water

outlet (7C)

Chilled water

inlet (13C)

shell

tubes

Rapid vaporization

(boiling)

Chiller components


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Chiller components

Typical Condenser

Water passing through the condenser absorbs heat as the

refrigerant vapour condenses.

Side view

end view

Refrigerant liquid

outlet

Refrigerant vapor

inlet

Cooling tower water

outlet (29C)shell

tubes

(condensing)

Cooling tower

water inlet (35C)

Chiller components


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Chiller components

evaporator

condenser

compressor

CHWS

CHWR

CDWR

CDWS

Hot, moist

air out

Outdoor

air in

Chiller and TowerThe refrigerant loop is basically the same as a split unit air conditioner.

Its all about heat transfer!

Cool in

Heat outHeat in

Cool outHeat out

Cool in

Heat ou t

Cool in

Dampers


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Dampers

Used to regulate air flow through an HVAC system.

Direct and regulate the flow of air in a system.

Distribute the conditioned air into the building space.

Enable critical smoke and fire control schemes.

Used in containment and pressurization schemes. Unitary equipment also utilize dampers.

Dampers can be compared to water valves; they exhibit many ofthe same control elements and must be correctly sized.

Damper Design


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Damper Design

Dampers can be categorized by

Blade design: single, multi, 3-V, airfoil, etc.

Blade rotation: parallel or opposed.

Shape: round or rectangle.

Leakage rating: standard or low leakage.

Application: ventilation, smoke, fire.

Damper Construction


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Damper Construction

Parallel Blade vs. Opposed Blade Designs

Each have their specific applications

Damper Flow Characteristics


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Parallel Blade Diverted Air Flow, better mixing

HTGEffective mixing

of air flows!

Outdoor

Return

Better temperature control

and improved coil efficiency.



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Opposed Blade Characteristics Better for straight line, laminarair flows

HTG

In a Face/Bypass application,

air flow is laminar, slips through

the coil fins more efficiently.


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Damper Applications


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Damper Applications

Terminal boxes: Regulate air flow into the space.

Damper Actuators


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Damper Actuators

Actuator Types

Pneumatic Electric Direct coupled Spring return Low torque / High torque

Valves


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Two way threaded

Three way Globe

Two way Flanged

disk

seat

Linear Motion

Valves

Butterfly

Valves come in many shapes and sizes.

Control valves are designed to regulatethe flow of a liquid.

Unitary

Two way valves


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Two way valves

Single Seated Valve

Suitable for tight shut off.

Large valves will require powerfulactuator to overcome the pressure

acting upwards on the stem.

Double Seated Valve

Pressure on the stem is equalised

therefore requires less force to close.Not suitable for tight shut off as

one seat will close before the other

due to valve or stem heat expansion

Three Way Valves


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Three Way Valves

B

A AB

B

ABA

Mixing ValvePosition of the valve stem will

regulate the liquid mix between

A port and B port.

Diverting ValveLiquid flow in port AB

Position of the valve stem will

regulate the proportion of liquid

passing to A port or B port.

Mixing valves


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Mixing valves

A

B

AB

Fixed temperatureVariable flow

The objective is to regulate the output of the heating coil.

Depending on the scheme the valve may be positioned

in the flow or return.

AB

B

A

VariabletemperatureFixedflow

Diverting valves


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Diverting valves

A

B

AB AB

B

A

The objective is to regulate the output of the heating coil.

Depending on the scheme the valve may be positioned

in the flow or return.

Fixed temperatureVariable flow

VariabletemperatureFixedflow


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Valves


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Valves

Ideally, a control system has a linear response over itsentire load operating range.

The sensitivity of the control to a change in temperature

is then constant throughout the entire control range.

A valve needs to be selected that can provides thislinear system response.

Linear Valves


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A valve that provides a flow-to-lift relationship that is directly

proportional.

0%

100%

Valve position

Flow

0% 100%

Equal Percentage Valves


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q g

A valve which changes flow by an equal percentage regardless of

flow rate.

These valves are designed to compensate for non-linear heattransfer characteristics of heating coils.

0%

100%

Valve position

Flow

0% 100%

0%

100%

Flow

Heat output

0% 100%

Flow Characteristics


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Linearity of system response determines a valves flowcharacteristic.

Non-Linear system

Response

Linear System

Response

Equal Percentage

Control Valve

Heatoutput

Valve position0%

100%

100%

Resultant

Temperature Sensors


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08/03/2014

Temperature Sensors

Resistance Temperature Devices (RTDs) changeresistance with varying temperature.RTDs have a positive temperature coefficient(resistance increases with temperature).

Example: PT100 PT1000 BALCO 500

Thermistors are solid-state resistance-temperaturesensors with a negative temperature coefficient.

Example: NTC 20K NTC10K

Temperature Sensors


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p

Temperature sensors aredesigned for use in- Room- Duct- Pipe- Outside (wall)

Models are available withsensing elements - PT1000- NTC20K

- BALCO500.

LF20 : AIR DUCT TEMP. SENSOR (NTC 20k)

T7412 : ROOM TEMP. SENSOR (PT1000/NTC 20k)

T7413A : IMMERSION TEMP. SENSOR (PT1000)

Humidity Sensors


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y

Polymer Capacitive Humidity Element

- Capacitance relative to dielectric gap- Humidity changes gap distance- Signal proportionate to humidity

level

Combined Relative Humidity andTemperature Sensors are available.

H7015 : DUCT RELATIVE HUMIDITY SENSOR

H7012 : ROOM RELATIVE HUMIDITY SENSOR

AHU Humidity Controls


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08/03/2014

y

Humidity- Jet spray- Steam

DehumidificationCooling coil used to reduce the moisture content.

Reheat coil will bring the supply air to the required temperature.

Differential Pressure Switch


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Differential Pressure switchesare used for monitoring thestatus of

Filters

FansPumps

Water Flow

Air Flow

DPS1000 : AIR DIFFERENTIAL PRESSURE SWITCH

TDIAP SERIS : AIR FLOW SWITCH

Differential Pressure Sensors


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Can measure differential pressure,absolute pressure and vacuum.

Used for measuring water and airflow.

DPT1000 : AIR DIFF. PRESSURE TRANSMITTER

ST 3000 Pressure Transmitter

CO2Sensor


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2

AQS 71-KAM

CO2measurement range 0...3000 ppm

corresponding to 0...0.3%CO2

State-of-the-art Non-Dispersion-Infrared(NDIR) technology to measure carbon

dioxide gas.

Centralised air systems


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Centralised systems are often based around an air

handling unit (AHU), which typically contains

heating and cooling coils, a humidifier, filter and a

fan to move the air.

The incoming air is drawn into the AHU and

passed over the coils to heat or cool the air as

required.

This conditioned air is then supplied by ductwork

to the rooms within the building.

The equipment is normally located in central plant

rooms but may be roof-mounted.

Refrigeration equipment provides chilled water for

the cooling coil(s) within the AHU.

The chiller may be water cooled, which will involvea cooling tower or cooled by outside air.

Hot water for the heating coils is provided by

boilers, which may be located in another plant

room.

HVAC system symbols


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HVAC system symbols

Cooling Battery

Heating Battery

Fan

HumidifierDamper

Filter

Valves

Pump

see page 296 of controls manual for more


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Air Handling Units


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Joe cool

Building Environment

Air Handling Unit

Fan

Chilled water

system

Htg & Clg Coils

Boiler

Hot water

system

Cooling

Tower

Chiller

supply air

distribution

system

EA

OA

RA

g

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