James D. Stoller, P.E., LEED GA

Facilities Engineering

Mechanical Engineer

Purdue University

THE MODERN

HVAC SYSTEM

We are going to cover

200 years of HVAC

history in 50 minutes

HVAC Systems

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1. Black Text: the main points

2. Blue Text: personal superfluous

comments

3. Red Text: questions for audience

participation

4. Yellow Text: hint of the next slide

To help you follow the slides – here the “text rules”

5. Green (& others) text: I ran out of

colors so I had to use something

different

HVAC Systems

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1. Black Text: the main points

2. Blue Text: personal superfluous

comments

3. Red Text: questions for audience

participation

4. Yellow Text: hint of the next slide

To help you follow the slides – here the “text rules”

5. Green (& others) text: I ran out of

colors so I had to use something

different The goal of this presentation

Energy Audit Tips

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10.

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In one slide let’s review two centuries:

1600 to 1800

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You will walk away with 12

specific energy audit tips

HVAC Systems

Carrier

Fahrenheit

Watt

Fulton

Galileo

Celsius

A long history of discovery

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Leading to today’s HVAC Engineer

HVAC Systems

Our work is based on energy transfer The energy we transfer is …

HEAT

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HVAC Systems Heat is always moving

Flowing from higher energy (hot)

to lower energy (cold)

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Too much heat gain

in the summer

Our Job: Remove

some heat

HVAC Systems Heat is always moving

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Too much heat loss in the winter

Our Job: Add some heat

Flowing from higher energy (hot)

to lower energy (cold)

HVAC Systems

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In America:

What term is used measure heat flow?

How does America compare to other countries?

BTU (British Thermal Unit)

HVAC Systems

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QUIZ #1

IP – Imperial Units Inches, pounds, BTU, etc.

easy to remember if think IP = “Inch Pound”

SI – Metric Units Meters, grams, calorie, etc.

The rest of the world

USA

How many countries use IP units?

Who uses SI units?

I have heard

they are both

moving to SI

Myanmar (Burma) Liberia

Let’s discuss one BTU

HVAC Systems

1 BTU = 1 lb of water 1°F

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HVAC Systems

QUIZ #2

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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HVAC Systems

QUIZ #3 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 #4

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HVAC Systems

1 Ton

QUIZ #4

1 Ton = 12,000 Btu/Hr

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HVAC Systems

No

Is there such a thing as one ton of heat? QUIZ #5

What did Emerson say?

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ICE: Only AC choice for 200 years

HVAC Systems

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1865 – Ice cooled bed

1900 –Ice cooled RR sleeper

1905 – Ice cooled church service

1914 – Ice cooled theater

HVAC Systems

What two things killed the ice industry & ushered in

the age of mechanical refrigeration? QUIZ #6

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1. A couple of warm winters around 1915

Didn’t take long for mechanical refrigeration to make the jump from beer to human comfort

2. Beer

The first step in designing an

HVAC system

(consistent brewing all year)

HVAC Systems

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This is the backbone of HVAC design

In this room from what sources

could heat come?

Lights

People

Equipment

Walls & Windows

Solar

Starting in the 1920’s how did we get rid of the heat?

HEAT GAIN & LOSS CALCULATION

Sum the BTU from all those heat sources and you have the heat gain

HVAC Systems

Originally installed in special rooms (NY Stock Exchange, boardroom)

Fan

Conditioning multiple rooms required multiple units

By the 1950s people wanted AC in different rooms

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1940 AHU (AIR HANDLING UNIT)

Cooling Coil & Condensing Unit

SA Ductwork

Filters

Diffusers

Grilles RA Ductwork

Heating Coils

HVAC Systems

ADVANTAGES

• Everybody gets AC

DISADVANTAGES

• Use a lot of energy

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1950S MULTIPLE AHUS

What is in their energy toolbox?

You don’t like this, who can you call for help?

You call the energy police (auditors)

Energy Audit Tips

Look for grossly oversized equipment

Look for leaks in the building envelope

Look for leaks in the ductwork

Set the summer set points as high and the

winter set points as low as possible

Verify operating schedule

Let’s return to our AHU discussion

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2.

3.

4.

5.

HVAC Systems

Being engineers we developed a

way to address the problems

• Exterior appearance (condensing units are placed on any flat surface)

• Maintenance

• Noise (these things shake and rattle)

• Floor space

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1950S MULTIPLE AHUS

ADVANTAGES

• Everybody gets AC

DISADVANTAGES

• Use a lot of energy

HVAC Systems

1960 CENTRAL STATION AHU

ADVANTAGES

• Serves many rooms

DISADVANTAGES

• One zone (who gets the thermostat?)

• No outside air (the air is stale and stuffy)

• Noise is isolated

• Localized maintenance, few pieces of equipment

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We know how to

address this problem

Keep your eyes on these areas

HVAC Systems

1960 CENTRAL STATION AHU

What do our energy auditors

have to say about OA flow?

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Bring OA into the building

Relieve OA out of the building

Energy Audit Tips

Look for grossly oversized equipment

Look for leaks in the building envelope

Look for leaks in the ductwork

Set the summer set points as high and the

winter set points as low as possible

Verify operating schedule

Let’s return to our AHU discussion

1.

2.

3.

4.

5.

Verify proper building pressure

Verify OA flow 6.

7.

HVAC Systems

1960 CENTRAL STATION AHU

ADVANTAGES

• Serves many rooms • Noise is isolated • Low maintenance

DISADVANTAGES

• One zone • Pressure loss in return

air ducts so air can’t get back to the AHU • Fresh air

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We engineers know how to

move the air back to the AHU

HVAC Systems

1963 CENTRAL STATION AHU

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Fans are the largest energy

user in the mechanical

system

So what do our energy

auditors have to say about

fan operation?

Energy Audit Tips

Look for grossly oversized equipment

Look for leaks in the building envelope

Look for leaks in the ductwork

Set the summer set points as high and the

winter set points as low as possible

Verify operating schedule

Let’s return to our AHU discussion

1.

2.

3.

4.

5.

Verify proper building pressure

Verify OA flow 6.

7. 8.

9.

Verify SA & RA fan operation

Verify that all VFDs are in ‘auto’ and controlled & functioning

properly

HVAC Systems

1963 CENTRAL STATION AHU

ADVANTAGES

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

DISADVANTAGES

• One zone • Mechanically cools

in winter

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• Pressure Control Let’s see how we prevent

mechanical cooling in the winter

HVAC Systems

1965 AHU W/ ECONOMIZER

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A properly operating

economizer can save a lot of

energy

A poorly operating

economizer can either

• Not save much energy

• Waste energy

So what do our energy auditors have

to say about economizer operation?

Energy Audit Tips

Look for grossly oversized equipment

Look for leaks in the building envelope

Look for leaks in the ductwork

Set the summer set points as high and the

winter set points as low as possible

Verify operating schedule

Let’s return to our AHU discussion

1.

2.

3.

4.

5.

Verify proper building pressure

Verify OA flow 6.

7. 8.

9.

Verify SA & RA fan operation

Verify that all VFDs are in ‘auto’ and controlled & functioning

properly

10.

11.

Verify that all economizers are functioning properly

Investigate whether OA temp based reset is appropriate

HVAC Systems

1965 AHU W/ ECONOMIZER

ADVANTAGES

• Economizer

DISADVANTAGES

• One zone

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• Serves many rooms • Noise is isolated • Low maintenance • Fresh air • Pressure Control 50 years ago how did we give

each room its own temp control?

HVAC Systems

OIL EMBARGO!!

1966 DOUBLE DUCT

ADVANTAGES

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

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Systems like this were the

preferred design for many

years

What happened in 1973-4

to change this?

HVAC Systems

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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1975 we changed the

design to save energy

HVAC Systems

1975 SHUT-OFF VAV

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ADVANTAGES

• Saves Money

DISADVANTAGES

• Poor air quality • Poor humidity

control • Poor temperature

control

SICK BUILDING

SYNDROME!!

HVAC Systems

1975 SHUT-OFF VAV

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ADVANTAGES

• Saves Money

DISADVANTAGES

• Poor air quality • Poor humidity

control • Poor temperature

control

1985 we added reheat coils

HVAC Systems

1980S VAV WITH REHEAT

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Been the workhorse for over 30 years

There is one LARGE

weakness if this system

isn’t controlled properly!

Let’s assume ….

40°F 60°F 55°F

80°F

What is the problem?

What do our energy auditors have to say

about simultaneous heating & cooling?

How can you fix it?

Energy Audit Tips

Look for grossly oversized equipment

Look for leaks in the building envelope

Look for leaks in the ductwork

Set the summer set points as high and the

winter set points as low as possible

Verify operating schedule

1.

2.

3.

4.

5.

Verify proper building pressure

Verify OA flow 6.

7. 8.

9.

Verify SA & RA fan operation

Verify that all VFDs are in ‘auto’ and controlled & functioning

properly

10.

11.

Verify that all economizers are functioning properly

Investigate whether OA temp based reset is appropriate

12. Trend controls operation to verify proper set-up, coding, &

functionality

Energy Audit Tips

Look for grossly oversized equipment

Look for leaks in the building envelope

Look for leaks in the ductwork

Set the summer set points as high and the

winter set points as low as possible

Verify operating schedule

1.

2.

3.

4.

5.

Verify proper building pressure

Verify OA flow 6.

7. 8.

9.

Verify SA & RA fan operation

Verify that all VFDs are in ‘auto’ and controlled & functioning

properly

10.

11.

Verify that all economizers are functioning properly

Investigate whether OA temp based reset is appropriate

12. Trend controls operation to verify proper set-up, coding, &

functionality

Any questions about our 12 Energy Audit Tips?

HVAC Systems