J. Michael Carson P.E.

Senior Mechanical Engineer

Purdue University

THE MODERN

HVAC SYSTEM

HVAC Systems

Btu Ton Heat Gain & Heat Loss Air Handling Unit Fan Air Distribution Preheat Coil Cooling Coil Reheat Coil

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Double Duct Diffuser Grille Register Constant Volume VAV DOAS Chilled Beam UFAD

HVAC Systems

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HVAC Systems

Carrier

Fahrenheit

Watt

Fulton

Galileo

Celsius

Physical Sciences have a long

history of discovery

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HVAC Systems

Their work is based on energy transfer

Leading to today’s HVAC Engineer

The energy they transfer is

HEAT 4

HVAC Systems

Heat is always moving

Flows from higher energy (something hot)

to lower energy (something cold) 5

HVAC Systems

1 BTU = 1 lb of water 1°F

How we measure heat in America

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BTU (BRITISH THERMAL UNIT)

HVAC Systems

QUIZ #1

Circle your answer

1 Btu/Hr

1 BTH

1 BTUH

If it takes one hour to heat 1 lb of water 1°F the heat transfer rate would be …

“A foolish consistency is the hobgoblin of little minds”

Being well read engineers understand Ralph Waldo Emerson

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HVAC Systems

“A foolish consistency is the hobgoblin of little minds”

This helps you understand the HVAC engineer

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QUIZ #1

HVAC Systems

QUIZ #2 What was a favorite treat

Washington and Jefferson

served summer visitors?

How could they eat ice cream in the summer of 1700’s?

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HVAC Systems

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ICE HARVESTING

HVAC Systems

1 Ton

When one ton of ice melts in one day

(24 hours) what do we call the heat

absorbed by that ice each hour?

QUIZ #3

1 Ton = 12,000 Btu/Hr 11

HVAC Systems

No

Is there such a thing as one ton of heat? QUIZ #4

Now what did Emerson say? 12

HVAC Systems

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THE BACKBONE OF HVAC DESIGN

What makes heat?

Lights

People

Equipment

Walls & Windows

Solar

How do we get rid of the heat?

HEAT GAIN & LOSS CALCULATION

HVAC Systems

Originally installed in special rooms

Fan, Cooling coil, Ductwork, Filters, Diffusers & grilles, Condensing unit, etc.

What did we do if we had multiple rooms?

1950s more people wanted AC

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AHU (AIR HANDLING UNIT)

HVAC Systems

ADVANTAGES

HOW WE REMOVED THE PROBLEMS

• Everybody gets AC

DISADVANTAGES

• Exterior appearance

• Maintenance

• Noise

• Floor space

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1950S MULTIPLE AHUS

HVAC Systems

1960 CENTRAL STATION AHU

ADVANTAGES

• Serves many rooms

DISADVANTAGES

• One zone

• No outside air • Noise is isolated

• Localized maintenance, few pieces of equipment

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HVAC Systems

1960 CENTRAL STATION AHU

ADVANTAGES

• Serves many rooms • Noise is isolated • Low maintenance

DISADVANTAGES

• One zone • Air can’t get back

to the AHU

• Fresh air

Energy Tips

1. No more OA than necessary

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HVAC Systems

1963 CENTRAL STATION AHU

Energy Tips

1. No more OA than necessary

2. Fan operation

ADVANTAGES

• Serves many rooms • Noise is isolated • Low maintenance • Fresh air • Pressure Control

DISADVANTAGES

• One zone • Cools in winter

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HVAC Systems

1965 AHU W/ ECONOMIZER

Energy Tips

1. No more OA than necessary

2. Fan operation

3. Economizer operation

4. Damper operation

ADVANTAGES

• Serves many rooms • Noise is isolated • Low maintenance • Fresh air • Pressure Control • Economizer

DISADVANTAGES

• One zone

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HVAC Systems

OIL EMBARGO!!

1966 DOUBLE DUCT

ADVANTAGES

• Serves many rooms • Noise is isolated • Low maintenance • Fresh air • Economizer • Room level control • Flexible

DISADVANTAGES

• Uses a lot of energy

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Energy Tips

1. No more OA than necessary

2. Fan operation

3. Economizer operation

4. Damper operation

5. Remove simultaneous

heating and cooling

HVAC Systems

1975 SHUT-OFF VAV

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ADVANTAGES

• Serves many rooms • Noise is isolated • Low maintenance • Fresh air • Pressure Control • Economizer • Saves Money

DISADVANTAGES

• Poor air quality • Poor humidity

control • Poor temperature

control

SICK BUILDING SYNDROME!!

HVAC Systems

1980S VAV WITH REHEAT

1990S VFD!!!!

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ADVANTAGES

• Serves many rooms • Noise is isolated • Low maintenance • Fresh air • Pressure Control • Economizer • Saves Money

DISADVANTAGES

• No good speed control (mechanical)

HOW DO THEY WORK?

HVAC Systems

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60 Hz

60 Hz

45 Hz

30 Hz VFD OPERATION

HVAC Systems

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60 Hz

60 Hz

45 Hz

30 Hz VFD OPERATION

HVAC Systems

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60 Hz

60 Hz

45 Hz

30 Hz VFD OPERATION

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60 Hz

60 Hz

45 Hz

30 Hz

HVAC Systems

1990S VAV REHEAT VFD

BEEN THE WORKHORSE FOR

20 YEARS

WHAT IS ON THE HORIZON?

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DOAS

HVAC Systems

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DOAS

HVAC Systems

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DOAS

HVAC Systems

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DOAS

ADVANTAGES

• Small AHU • Small ductwork • Less energy??

DISADVANTAGES

• FCUs or other room level system

OFFICES, DORMS, ETC.

CHILLED BEAMS

HVAC Systems

CHILLED BEAMS

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HOW DO THEY WORK?

HVAC Systems

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CHILLED BEAMS

HVAC Systems

CHILLED BEAMS

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HVAC Systems

UFAD 34

CHILLED BEAMS

ADVANTAGES

• Small AHU • Small ductwork

DISADVANTAGES

• Can take many chilled beams

• Careful temp control

HVAC Systems

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UFAD

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UFAD

HVAC Systems

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UFAD

ADVANTAGES

• Small AHU • Small ductwork • Less energy??

DISADVANTAGES

• Careful construction details

• Careful temp control

J. Michael Carson P.E.

Senior Mechanical Engineer

Purdue University

THE END OF THE

MODERN HVAC SYSTEM