CO2 Booster Systems From a

Service Mechanic’s Perspective

E360 Forum • Raleigh, N.C. • March 1, 2017

Andre PatenaudeDirector — CO2 Business Development

Emerson

Agenda

Global Regulations

CO2 System Architecture

CO2 as a Refrigerant

Seven Keys to Servicing a CO2 Refrigeration System

2

Global Regulations Confusing Time for End Users

• Rule-making process begins in 2017 with possible final rule late 2018

CARB: Short-lived climate pollutant

reduction strategy – proposal April 2016

Commercial application GWP limit Date

All refrigerant sales* 2,500 2020

Non-residential refrigeration 150 2020

AC (non-residential and residential) 750 2021

*Exception for recycled or reclaimed refrigerant

Environmental Canada (EC)

proposal November 26, 2016

Commercial application GWP limit Date

Refrigeration – centralized

systems (MT/LT racks)1,500 2020

Refrigeration – condensing units 2200 2020

Refrigeration – LT stand-alone 1,500 2020

Refrigeration – MT stand-alone 700 2020

Foams 150 2021

Mobile refrigeration 2,200 2025

AC – chillers 700 2025

Domestic refrigeration 150 2025

3

CO2 aka Refrigerant R-744

4

CO2 DX

CO2 DX

TRANSCRITICAL

BOOSTER

CO2 DX

CASCADESECONDARY

Selecting the Best System Booster vs. Cascade vs. Secondary

5

R-744 vs. HCFC/HFC

R-744 HFC / HCFC Impact on R-744 Systems

Global Warming Potential

Ozone Depleting Potential

1

0

1,300 to 4,000

0 for HFC / High for HCFC

Future Proof

Future Proof

Saturation Pressures

Operating Pressures

Standstill Pressures

(Power Outages)

Higher

Higher

Higher

Rapid Pressure Rise

Lower

Lower

Lower

Lower

Additional Safety Design

Specialized Components

Relief Valves/Tanks/ etc.

Pressure Relief Venting

Inert Gas

Flammability

Toxicity

Odor

Yes

A1

No

None

Yes

A1

No

None

Copper May Be Used

Not Flammable

Asphyxiate in High Concentrations

Leak Detection Required

Volumetric Mass Flow

Heat Transfer

High Ambient Performance

Low Ambient Performance

Higher

Higher

Lower

Good

Lower

Lower

Higher

Good

Smaller Tubes and Compressors

Better Thermal Efficiency

System Design to Compensate

Subcritical Cascade Favorable

Cost per Pound

Complexity of Systems

Adoption

Legislation/Regulations

Low

Higher

Low

Low

Higher

Lower

Higher

Higher

Economical

Higher First Cost, Training and Experience

Higher First Cost

Long-term Viability

R-744 Provides Many Benefits Over HFC Options.6

Refer to MSDS sheets.

Toxicity Levels

• 5,000 ppm (0.5 vol. % in air)

• 10,000 ppm is 1 vol. % in air

• Main alarm 15,000 ppm

• Levels from 0.04% to 20%

• TLV for CO2 = 5,000 PPM

• TLV for R-404A = 1,000 ppm

Max. workplace concentration initial alarm

7

Sublimation of Dry Ice

Dry Ice

Sublimation of Dry Ice

• CO2 expands 845 times going from solid to gas

• 1 liter of dry ice will produce 845 liters of gas at 15 °C at 14.7 psi

• Relative vapor density vs. air is 1.52

– It collects low areas

• Leak devices; locate approx. 18” off ground

• When CO2 turns to dry ice in the system, as it warms up, pressure

will build very quickly; must be aware of this.

• If an ice plug forms in a charging line set, flow will stop.

– Extreme care must be taken when this happens.

– The blockage will cause the CO2 trapped between the source

and the “plug” to rise very quickly.

– As soon as the plug melts

– If high-pressure source is not closed off, high pressure will force

the ice plug out the hose with a tremendous force.

8

Refrigerant R-744 (CO2) R-404A R-134a R-407A R-407F

Temperature at

atmospheric pressure

-109.3 °F

(-78.5 °C)

Temp. of

dry ice

-50.8 °F

(-46°C)

(Saturation

temp.)

-14.8 °F

(-26 °C)

(Saturation

temp.)

-41.8 °F

(-41 °C )

(Mid-point

saturation temp.)

-45. 5 °F

(-43 °C )

(Mid-point

saturation temp.)

Critical temperature 87.8 °F

(31 °C)

161.6 °F

(72 °C)

213.8 °F

(101 °C)

179.6 °F

(82 °C)

181.4 °F

(83 °C)

Critical pressure 1,056 psig 503 psig 590 psig 641 psig 674 psig

Triple-point pressure 61 psig 0.44 psia 0.734 psia 0.18 psia TBC

Pressure at a saturated

temperature of 20 °C815 psig 144 psig 68 psig 133 psig 139 psig

Global warming potential 1 3,922 1,430 1,990 1,824

Basic Properties of R-744 With R-404A and R-134a Refrigerants Commonly Used in the Retail Sector

9

Basic Properties of R-744 With R-404A and R-134a Refrigerants Commonly Used in the Retail Sector (continued)

Refrigerant R-744 (CO2) R-404A

Temperature at

atmospheric pressure

-109.3 °F

(-78.5 °C)

Temp. of

dry ice

-50.8 °F

(-46 °C)

(Saturation

temp.)

Critical temperature 87.8 °F

(31 °C)

161.6 °F

(72 °C)

Critical pressure 1,056 psig 503 psig

Triple-point pressure 61 psig 0.28.9 Hg

Pressure at a saturated

temperature of 20 °C815 psig 144 psig

Global warming potential 1 3,922

10

P. 7

Liquid and gas density

are the same only at

critical point.

https://www.youtube.com/watch?v=-gCTKteN5Y4

Pressure-Enthalpy Diagram of CO2

11

Pressure-Enthalpy Diagram, CO2

12

Transcritical Systems Can “Transition” From Subcritical to Supercritical

p. 17

13

Climatic Impact of CO2 System Architectures

14

European CO2 Market

15

More Than 10,900 CO2 Transcritical Stores Worldwide

16

Medium-

Temperature

R-404A

Low-

Temperature

R-404A

162 °F

Critical Point

R-404A

162 °F

Critical Point

R-404A

-20 °F Low

Temp.

+25 °F

Med.

Temp.

Products

• Mechanical TXV

• Mechanical EPR

• Mechanical CPR

and differential

valves

• Mechanical

pressure controls

• Typically, on/off

compressor

control

Traditional Supermarket System

17

CO2 Transcritical Booster Operation

Must Use

• Facility management system

• Electronic expansion valves

• High-pressure gas cooler

controls

• High-pressure and bypass

valves

• Superheat/de-superheating

valves

• Pressure transducers/temp.

sensors

• Electronic oil controls

• VFD condenser fans

• Digital or VFD compressor

suction group

700 -

1600

psig

580

psig

580

psig200

psig

450

psig

18

Transcritical CO2 Booster System — Animation

19

Seven Keys to Servicing a CO2 Refrigeration System

20

Accelerate America Article

2015 Natural

Refrigerant Guide21

Seven Keys to Servicing a CO2 Refrigeration System

• Three Main Differences Between HFC and R-744 Systems

1. High pressure

2. Low critical point

3. High triple point

• Dealing With Standstill Pressures

4. Managing power outages

5. Managing pressure reliefs

6. How to mitigate risk

• Peculiarities of R-744

7. Managing superheat

22

Refrigerant R-744 (CO2) R-404A

Critical pressure 1,056 psig 503 psig

Triple-point pressure 75 psia 0.44 psia

Pressure at a saturated

temperature of 20 °C815 psig 144 psig

Understanding the Differences: R-744 vs. HFC

1. High Operating Pressures

23

Understanding the Differences: R-744 vs. HFC (continued)

Where they occur

1. High Operating Pressures

24

The coefficient of expansion for R-744 is significantly higher than for

other refrigerants.

• The effect of a 36 °F (20 °C) temperature rise (from 14 °F to 50 °F)

• The pressure will increase from 638 psig (44 bar) to 3,481 psig to (240 bar).

Relationship between temperature and pressure of trapped liquid R-744

Pre

ssu

re (

psig

)

14,503

145

14.5

1,450

36°F

2843 psig

Trapped liquid

Understanding the Differences: R-744 vs. HFC (continued)

25

Understanding the Differences: R-744 vs. HFC (continued)

2. Low Critical Pressure (1,055 psig; 87.8 °F)

R-744 transcritical

booster system

https://www.youtube.com/watch?v=GEr3NxsPTOA Video of phase change of CO2

26

Efficiencies Great for Cold Climate

1020Hrs/yr

W/Std Gas Cooler

9 Hrs/yr

W/Adiabatic

Gas Cooler

202 Hrs/yr

W/Std Gas Cooler

Atlanta, Ga. Toronto, Ont.

2. Low Critical Pressure

27

Understanding the Differences: R-744 vs. HFC

3. High Triple Point (60.4 psig; -69.8 °F)

-109.3 °F

surface temp. of dry ice

28

I Fell Victim of Dry Ice During a Training Session

Originally drawn from

top to flash tank —

caused dry ice issue Correctly drawn off

of liquid line FD 29

Seven Keys to Servicing a CO2 Refrigeration System

• Three Main Differences Between HFC and R-744 Systems

1. High pressure

2. Low critical point

3. High triple point

• Dealing With Standstill Pressures

4. Managing pressure reliefs

5. Managing power outages

6. How to mitigate risk

• Peculiarities of R-744

7. Managing superheat

30

What’s a Standstill Pressure?

Standstill Pressure Occurs When System Is not Operating.

Effect on Standstill Pressures

• Ambient when below critical point; 68 °F (20 °C) = 812 psig

• Ratio of refrigerant charge to system volume

• For most systems, the standstill pressure is greater than the maximum operating pressure.

• When the standstill is the same as maximum operating pressure, then relief valves will vent unless there are means in place to reduce it.

31

CO2 Booster Refrigeration System

4. Managing Pressure Reliefs

Compressor

discharge

135 bar

1,958 psig

PRV vented

to outdoor

110 bar

1,600 psig

PRV

vented to

outdoor

45 bar

650 psig

PRV

vented to

outdoor

45 bar

650 psig

PRV

vented to

outdoor

35 bar

500 psig

PRV

vented to

outdoor

45 bar

650 psig

32

Pressure Relief Valve Installation

Flash tank

650 psig

2 PRV with

three-way valve

Gas cooler

1,600 psig

2 PRV with

three-way valve

33

Fresh

Frozen

1

2

R-744

section

to atmosphere

Advantage;

• Less stress on PRV

• Less CO2 discharged vs. PRV

• Lowers overall maintenance costs

Generator/UPS source

Unplanned Outages — “Burp Valve”

5. Managing Power Outages

34

Fresh

Frozen

1

2

R-744

section

to atmosphere

• Auxiliary condensing unit starts on power failure, which is

powered by generator

• Recirculates liquid from receiver/flash tank to keep the

saturation temperatures below the pressure relief point

Unplanned Outages — Auxiliary Condensing Unit on Generator

Generator Powers Auxiliary

Condensing Unit

5. Managing Power Outages

35

Backup Unit and Generator

Generator to keep

controller

and backup unit running

Auxiliary condensing unit

In case of power outage, keeps CO2 receiver temperature

down to prevent pressure relief from blowing off

5. Managing Power Outages

36

Managing Power Outages

• Generator and standby condensing units

• Need a refrigerant plan

– Local codes

– Stock, storage

– Getting it to the machine room

• Concerns with resumption of power Semi-hermetic

broken reed

Scroll thrust

surface galled

6. How to Mitigate Risk

37

System Startup Sequence, After Resumption of Power

Circuit Is Stage on to Avoid Overloading the Rack

Recovery Sequence After Failure

TIME INTERVAL LT RACK MT RACK

0–3 Minutes Pump down Pump down

3–6 Minutes 25% ON

6–9 Minutes 50% ON

9–12 Minutes 25% ON

12–15 Minutes 75% ON

15–18 Minutes 50% ON

18–21 Minutes 100% ON

21–24 Minutes 75% ON

24–27 Minutes 100% ON

6. How to Mitigate Risk

38

Steps to follow:

1. Low-temperature circuit OFF

• Let unit run for 3–5 minutes (minimum)

2. Medium-temperature circuit OFF

• Let gas cooler run for 3–5 minutes (minimum)

3. Turn evaporators OFF

System Shutdown — Planned

Care must be taken when shutting down a CO2 system. Go in stages to prevent

over-pressurization of the system leading to relief valve venting the charge.

6. How to Mitigate Risk

39

What Does Your Service Tech Need to Know?

Three Main Differences Between HFC and R-744 Systems

1. High pressure

2. Low critical point

3. High triple point

Dealing With Standstill Pressures

4. Managing pressure reliefs

5. Managing power outages

6. How to mitigate risk

Peculiarities of R-744

7. Managing superheat

40

Liquid to Suction Heat Exchanger to Assure Minimum 36 °F SH

7. Managing Suction Superheat

36 °F minimum

superheat

CascadeBooster

41

POE Oil Viscosity in CO2 vs. Suction Superheat

Oil temp.

measured

bottom of

sump

36 °F (18 °K SH)Floodback 0 °F (0 °K SH)

42

Floodback

Evaporator Cooling With Closed EEV

43

Evaporator Cooling With Closed EEV (continued)

• Issue with suction piping free

• Draining down into the case

• Corrected piping

• No free draining

44

Charging From a Remote Location

45

R-744 CO2 Sensitivity (PPM)

Liquid

Temperature

14 °F

(-10 °C)

32 °F

(-10 °C)

41 °F

(5 °C)

68 °F

(-10 °C)

Very Dry 8 11 13 20

Dry/Caution 14 19 22 34

Caution/Wet 29 39 46 72

Wet 46 63 75 116680 psig MWP

Moisture Indicators and Driers

680 psig MWP

46

System Cleanliness/Dryness

System Dryness

Oil Separator

Filter Photo

R744 CO2 Sensitivity (PPM)

Liquid Temperature 14 °F 32 °F 41 °F 68 °F

Very Dry 8 11 13 20

Dry/Caution 14 19 22 34

Caution/Wet 29 39 46 72

Wet 46 63 75 116

Steel Pipe

Special

CO2 Model

System

Cleanliness

47

Seven Keys to Servicing CO2 Refrigeration System

• Three Main Differences Between HFC and R-744 Systems

1. High Pressure

2. Low Critical Point

3. High Triple Point

• Dealing With Standstill Pressures

4. Managing Power Outages

5. Managing Pressure Reliefs

6. How to Mitigate Risk

• Peculiarities of R-744

7. Managing Superheat

48

Questions?

DISCLAIMER

Although all statements and information contained herein are believed to be accurate and reliable, they are presented without guarantee or warranty of any kind, expressed or

implied. Information provided herein does not relieve the user from the responsibility of carrying out its own tests and experiments, and the user assumes all risks and liability for

use of the information and results obtained. Statements or suggestions concerning the use of materials and processes are made without representation or warranty that any such

use is free of patent infringement and are not recommendations to infringe on any patents. The user should not assume that all toxicity data and safety measures are indicated

herein or that other measures may not be required.

Thank You!