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1 2010 Emerson Climate Technologies

Printed in the U.S.A.

AE-1327 R5

Application Engineering

B U L L E T I N

Economized Vapor Injection (EVI) Compressors

AE4-1327 R6 February 2011


B U L L E T I N

1. Introduction

The refrigeration Economized Vapor Injection (EVI)compressor was developed to provide improvedcapacity and efficiency. EVI compressor systemsbenefit over standard refrigeration compressor systems

of equivalent horsepower due to the following:

Capacity Improvement - The capacity is improvedby increasing the h (change in enthalpy) in thesystem rather than increasing mass flow. Thisis accomplished without increasing compressordisplacement.

SECTION PAGE

1. Introduction ........................................................1

2. Theory of Operation ...........................................1

3. Nomenclature .................................................... 1

4. ARI Low Temperature Ratings ........................... 3

5. Approved Refrigerants ....................................... 3

6. Approved Oils .................................................... 3

7. Power Requirements ......................................... 3

8. Application Envelope ......................................... 3

9. Control Requirements ........................................ 410. Discharge Temperature Control ......................... 4

10.1 Thermistor ...............................................4

10.2 Discharge Line Thermostat .....................4

10.3 Copeland Scroll Demand Cooling ..... 5

11. TXV and Heat Exchanger ...................................8

12. System Configuration ......................................... 8

12.1 Downstream Extraction ........................... 8

12.2 Upstream Extraction ...............................8

12.3 Heat Exchanger Piping Arrangements .... 8

13. System Design Guidelines .................................9

13.1 Heat Exchanger Sizing ........................... 9

13.2 Line Sizing ............................................1013.3 Heat Exchanger TXV Sizing ................. 10

13.4 Solenoid Valve & Ball Valve .................. 10

13.5 Current Sensing Relay .......................... 10

13.6 Multiple Compressor Applications .........10

14. Controlling Liquid Out Temperature .................. 11

Increased Energy Efficiency Ratio (EER) - Theefficiency improves due to the fact that the gainin capacity is greater than the increase in powerthat the compressor consumes.

Cost and Energy Advantage - Because asmaller horsepower compressor can be used toachieve the same capacity as a larger horsepowercompressor, there is an inherent cost advantage.

2. Theory of Operation

Copeland EVI scroll compressors are equipped withan injection connection for Economizer Operation.Economizing is accomplished by utilizing a subcoolingcircuit similar to that shown in Figure 1. This mode ofoperation increases the refrigeration capacity and inturn the efficiency of the system. The benefits providedwill increase as the compression ratio increases, thus,more gains will be made in summer when increasedcapacity may actually be required.

The schematic shows a system configuration forthe economizer cycle. A heat exchanger is used to

provide subcooling to the refrigerant before it entersthe evaporator. This subcooling process provides theincreased capacity gain for the system, as describedabove. During the subcooling process a small amountof refrigerant is evaporated and superheated. Thissuperheated refrigerant is then injected into the midcompression cycle of the scroll compressor andcompressed to discharge pressure. This injectedvapor also provides cooling at higher compressionratios, similar to liquid injection of standard ZF Scrollcompressors.

3. Nomenclature

The EVI compressor has a model designation as follows,with the sixth digit shown as a "V": ZF18KVE-TFD.

The model numbers include the nominal capacitywithout the economizer cycle for R-404A refrigerantat 60 Hz Low Temperature ARI rating conditions. (SeeModel Designation diagram on Page 3.)

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The P-h diagram shows the theoretical gain in system performance achieved by using theeconomizer cycle. The extension outside of the vapor dome is what allows for the extra enthalpy

increase in the evaporator, enhancing system performance. Although power increases due to thevapor injection into the compressor, there is still an efficiency gain given that the capacity gainsexceed the power increase.

Definition(s) Description

Tc Condensing temperature

Tli Liquid temperature entering H/X

Tlo Subcooled liquid leaving H/X

Pi Intermediate Pressure

Tsi Saturated temperature at intermediate pressureTvo Vapor temperature leaving H/X

Tvi Vapor temperature entering H/X

Tsc Liquid subcooling in H/X

M Evaporator Mass Flow

I Vapor Injection Mass Flow

THX Liquid temp out H/X-Liquid-Saturated temperature at intermediate pressure

TSC Liquid temp in to H/X-subcooled liquid temp out H/X

Figure 1Circuit Diagram and Cycle for EVI

(Upstream extraction shown here. See Section 12 for details.)

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Model Designation

1 Z = Compressor Family: Z = Scroll2 F = Low Temperature3 Nominal Capacity [BTU/h] @ 60 Hz and ARI

low temperature conditions using multipliersK for 1000, without vapor injection

4 Vapor Injection for EVI Operation5 POE Oil6 Motor Version7 Bill of Material Number

The EVI rating curves have been developed toincorporate performance improvements while utilizingthe economizer cycle. The capacity displayed is

with maximum possible subcooling at the exit of thesubcooling heat exchanger. Compressor performanceinformation can be obtained by accessing theOnline Product Information (OPI) database at www.emersonclimate.com.

4. ARI Low Temperature Ratings(-25F/105F, R-404A)

Model With EVI* Without EVIZF13KVE 20,100 Btu/hr 13,000 Btu/hrZF18KVE 29,200 Btu/hr 18,000 Btu/hrZF24KVE 34,200 Btu/hr 24,000 Btu/hrZF33KVE 47,900 Btu/hr 33,000 Btu/hr

ZF40KVE 62,500 Btu/hr 40,000 Btu/hrZF48KVE 72,000 Btu/hr 48,000 Btu/hr

*Maximum possible subcooling

ARI Low Temperature Ratings(-25F/105F, R-407A)

Model With EVI1,2 Without EVI1

ZF13KVE 15,700 Btu/hr 12,000 Btu/hrZF18KVE 23,600 Btu/hr 17,600 Btu/hrZF24KVE 27,500 Btu/hr 20,800 Btu/hrZF33KVE 38,100 Btu/hr 29,000 Btu/hrZF40KVE 48,800 Btu/hr 37,000 Btu/hr

1Dew point pressures assumed

2Maximum possible subcooling

Note: For performance of ZF*KVE models with otherrefrigerants, refer to the Online Product Information atwww.emersonclimate.com

5. Approved Refrigerants

R404A, R507 and R407A are approved for use withCopeland EVI scroll compressors. R407A requiresthe use of Demand Cooling for low temp operation.

6. Approved Oils

Polyol Ester (POE) lubricants are the only lubricantsapproved for the EVI compressor. For a complete

list of approved POE lubricants, refer to Form 93-11,Emerson Accepted Refrigerants/Lubricants.

7. Power Requirements

EVI compressors are only available for three phase power.

8. Application Envelopes

Figure 2

Figure 3

-29 -23 -18 -12 -7 -1 5 10

21

27

32

38

43

49

55

60

70

80

90

100

110

120

130

140

150

Evaporang Temperature (C)

Temperature(C)

Temperature(F)

Medium Temperature ZF**KVE Envelope (R-404A/R-507)Condions: 65F Return Gas, 260F Max DLT

-18

-12

-7

-1

4

10

16

0

10

20

30

40

50

60

-20 -10 0 10 20 30 40 50 60

Condensin

Condensing

Evaporang Temperature (F)

-46 -40 -34 -29 -23 -18

21

27

32

38

43

49

55

60

70

80

90

100

110

120

130

140

150


Temperature(C)

Temperature(F)

Low Temperature ZF**KVE Envelope (R-404A/R-507)Condions: 65F Return Gas, 260F Max DLT

-18

-12

-7

-1

4

10

16

0

10

20

30

40

50

60

-50 -40 -30 -20 -10 0 10

Condensing

Condensing


* For other return gas conditions contact your Application Engineerfor Demand Cooling requirements.

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9. Control Requirements

See Figure 6 for a detailed schematic for this system(shown for a single compressor application). Thefigure also shows the upstream extraction method fortapping the liquid for the heat exchanger; see Section12 for additional details.

10. Discharge Temperature Control

A discharge temperature control is not required on allcompressors.

Models ZF24KVE-TW*, ZF33KVE-TW*, ZF40KVE-TW*, ZF48KVE-TW* have an internal temperaturesensor and no other discharge temperature controlis required for applications using R-404A or R-507.No thermistor or thermostat is required when usingCopeland Scroll Demand Cooling for low temperatureapplications.

For models ZF13KVE-TF*, ZF18KVE-TF* use one ofthe following two methods for discharge temperaturecontrol.

10.1 Thermistor

For low temperature applications with R-407A,Copeland ScrollDemand Cooling is required for useto run all conditions within the approved operatingenvelope. Additional information on Demand Coolingis discussed in Section 10.3.

A thermistor in the compressor control circuit is usedto protect against high discharge temperatures andmust be wired to the rack control systems. The cut outtemperature is to be set at 280F. The temperatureresistance values for the sensor can be found inAppendix A.

The thermistor must conform to the curve characteristicsoutlined in Appendix A. The table expresses the ratioof the resistance at the indicated temperature andthe resistance at 77F (25C). The resistance at 77F(25C) is 86Kohms nominal. The curve fit is Ratio =0.8685e-0.257x, where x = resistance at the indicatedtemperature.

NOTE: The system controller must open thecontactor when the discharge line temperatureexceeds 280F

10.2 Discharge Line ThermostatAnother method of discharge temperature control isthe use of a discharge line thermostat. It is requiredin the compressor control circuit. The thermostatshave a cut out setting that will insure discharge linetemperatures below the 260F (127C) maximum

-46 -40 -34 -29 -23 -18

-18

-12

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-1

4

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0

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60

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80

90

100

110

120

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150

-50 -40 -30 -20 -10 0 10


CondensingTemperature(C)

CondensingTemperature(F)


Low Temperature ZF**KVE Envelope (R-407A)Condions: 65F Return Gas, 260F Max DLT

Figure 4

-29 -23 -18 -12 -7 -1 5 10

-18

-12

-7

-1

4

10

16

21

27

32

38

43

49

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-20 -10 0 10 20 30 40 50 60


CondensingTemperature(C)

CondensingTemperature(F)


Medium Temperature ZF**KVE Envelope (R-407A)Condions: 65F Return Gas, 260 F Max DLT

Figure 5

Figure 6

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limit. (This value differs from the cut out value set onthe thermistor because the temperature is measuredcloser to the discharge gas from the scroll when usingthe thermistor.) The discharge line thermostat shouldbe installed approximately 7 (178mm) inches from thedischarge tube outlet. If a service valve is installed at thedischarge tube outlet, the thermostat should be located5 (127mm) inches from the valve braze. For properfunctioning, it is recommended the thermostat should beinsulated to protect it from a direct air stream. Kits havebeen set up to include the TOD thermostat, retainer,and installation instructions. These thermostats mustbe used with " O.D. discharge lines to ensure properthermal transfer and temperature control. They workwith either 120 or 240 volt circuits, and are availablewith or without an alarm circuit capability. See Table 1for a list of discharge line thermostat kit numbers.

10.3 Copeland Scroll Demand Cooling

The Demand Cooling system uses modern electronicsto provide a reliable cost effective solution to highinternal discharge temperatures encountered in lowtemperature applications using R-407A. DemandCooling has traditionally been applied to the CopelandDiscus product line to control high internal dischargetemperatures that exceed the safe temperature limitfor long term stability of refrigeration oil. EmersonClimate Technologies has now approved the use ofDemand Cooling for the Copeland Economized VaporInjection (EVI) scroll product line using low temperatureR-407A. The integration of Demand Cooling with EVIscroll creates a wet-injection approach to dischargetemperature control. Emerson has approved the followingEVI scrolls for use in low temperature applications withDemand Cooling:

ZF13KVE

ZF(D)18KVE

ZF24KVE

ZF33KVE

ZF40KVE

The Demand Cooling module uses the signal of adischarge line temperature sensor to monitor dischargegas temperature. If a critical temperature is reached,

the module energizes a long life injection valve whichmeters a controlled amount of saturated refrigerantinto the vapor injection line. The injection will continueuntil the discharge line temperature reaches a lower

preset temperature. This process controls the dischargetemperature to a safe level. If, for some reason, thedischarge temperature rises above a preset maximumlevel, the Demand Cooling module will turn thecompressor off (requiring a manual reset) and actuateits alarm contact.

The injection valve orifice has been carefully chosen tobe large enough to provide the necessary cooling whenrequired but not so large that a dangerous amount ofliquid is injected, or that excessive system pressurefluctuation occurs during injection valve cycling. It isimportant to use the correct valve for the EVI scroll.

Performance data for Demand Cooling compressorsincludes the effects of injection when it is required. Theapproximate conditions where injection occurs are shownpreviously in Figure 5 for R-407A. At the conditionswhere Demand Cooling is operating, the performancevalues are time averages of the instantaneous values,since small fluctuations occur as the Demand Coolinginjection valve cycles.

The Demand Cooling system addresses the capacityand efficiency issues by limiting injection to those timeswhen it is required to control discharge temperaturesto safe levels. For most applications this will only be

during periods of high condensing temperatures, highreturn gas temperatures, or abnormally low suctionpressure. The Demand Cooling system has beendesigned to meet the same high reliability standardsas Scroll compressors.

Demand Cooling System Design

When Demand Cooling operates, it diverts refrigerationcapacity in the form of injected saturated refrigerantfrom the vapor injection circuit to the compressor (SeeFigure 7 for a typical single system schematic). DemandCooling injects a small amount of liquid to the vaporinjection stream to cool the discharge. This does notaffect the mass flow significantly. However, when the

valve injects the system will lose some capacity becausethe EVI pressure increases and thus decreases EVIperformance.

Note! A separate Demand Cooling kit is required foreach compressor.

The injection valve should be installed as close aspossible to the compressor vapor injection inlet, nomore than 3 feet. The line MUST be well insulated. If

Kit NumberConduit

ConnectorAlarm

Contact Lead

998-7022-02 Yes No

998-0540-00 No No

998-0541-00 No Yes

Table 1 - Discharge Line Thermostat Kit Numbers

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there is substantial heat gain along the vapor injectionline, injection may result in a substantial loss in vapor

injection capacity during Demand Cooling operation.In order to minimize this loss, good practice indicatesDemand Cooling operation be kept to a minimum throughproper system design and installation practices. Thereare three areas which can be addressed to minimize theimpact of Demand Cooling operation on performance:

1. Compressor Return Gas Temperature: Suctionlines should be well insulated to reduce suction lineheat gain. Return gas superheat should be as low aspossible consistent with safe compressor operation.

2. Condensing Temperatures: It is important whenusing R-407A as a low temperature refrigerant that

condensing temperatures be minimized to reducecompression ratios and compressor dischargetemperature.

3. Suction pressure: Evaporator design and systemcontrol settings should provide the maximum suctionpressure consistent with the application in order tohave as low a compression ratio as possible.

Demand Cooling With Copeland DigitalCompressor Controller

In order to control a Copeland Digital Scroll compressor,the Copeland Digital Compressor Controller (P/N943-0086-00) may be used in multiple compressorapplications. The digital compressor controller has itsown discharge temperature protection. However, forapplications requiring Demand Cooling, the DemandCooling module should have primary control of thetemperature protection.To ensure the Demand Coolingsystem functions appropriately, jumper the T1 andT2 inputs on the Copeland Digital CompressorController, with a 5kOhm, 1 Watt resistor.

Demand Cooling System Components

The Demand Cooling system consists of: the dischargeline temperature sensor, the Demand Cooling module,and the injection valve solenoid. The Emerson kit numbersfor each scroll model are shown in Table 3 (next page).

Demand Cooling SpecificationsDemand Cooling is designed to operate and protectthe compressor within the evaporating and condensingenvelope identified in Figure 5. Operating setpoints andcontrol actions are listed in Table 4.

Figure 7 - Typical Single Compressor System Schematic with Copeland ScrollDemand Cooling

CONDENSER

EVAPORATOR

M

L

A

S

DEMAND COOLING

CONTROL MODULE

ACCUMULATOR

SUCTION LINE

FILTER

COMPRESSOR

INJECTION

SOLENOID VALVESIGHT

GLASS

INJECTION

LINE

FILTER

INJECTION VALVE

ELECTRICAL

CONTROL LINE

TEMP SENSOR

LINE

MANUAL

SHUTOFF VALVE

VAPOR INJECTION LINE

LIQUID INJECTION LINE

RECEIVERLIQUID LINE

FILTER DRIER

HX

TXV

HX

TO CONTROL

CIRCUIT

TXV

TEMP SENSOR

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Figure 8 - Digital Compressor Controller Wiring Diagram

*

**

Protection controls such as high/low pressure controls andcompressor motor protection module go here.

Polarity must match system controller

Note: The Neutral to L1, M1, U1, V1 is connected together.

*

**

OR 5kOhm, 1W RESISTOR(for Demand Cooling Applications)

Note! Discharge line temperatures are measured externally and are for reference only.

Table 4

Discharge Line

Temperature

Demand Cooling Module

Operation

Approximate Sensor

ResistanceRising Through 258F Demand Cooling Solenoid ON 3,820

Falling Through 237F Demand Cooling Solenoid OFF 5,000

Rising Through 286F Alarm Contact Energized 2,620

At Room Temp (77F) Demand Cooling Solenoid OFF86,000 (when compressorhas cooled)

Kit Part Number

120V Demand Cooling for Copeland ScrollKit 998-1000-50

240V Demand Cooling for Copeland Scroll Kit 998-1000-51

Table 3 - Copeland Scroll Demand Cooling Kits

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Demand Cooling Wiring Schematic

The figure below shows a recommended wiringschematic for the Demand Cooling assembly.

12. System Configuration

There are two methods of controlling refrigerant flowat the heat exchanger - downstream and upstream

extraction.

12.1 Downstream Extraction

The downstream extraction is the preferred methodemployed in the United States. In downstreamextraction the TXV is placed between the liquid outletand vapor inlet of the heat exchanger. The advantageof downstream extraction is that subcooling is ensuredbecause the liquid is further subcooled as it flowsthrough the heat exchanger. Therefore, more subcooledliquid enters the TXV which increases the probabilitythat the valve will not hunt. The disadvantage with thismethod is that it is not as efficient as the upstreammethod; however, the difference is too small for

practical purposes. See Figure 10.

12.2 Upstream Extraction

In upstream extraction the TXV is placed betweenthe condenser and the heat exchanger. The TXVregulates the flow of subcooled refrigerant out of thecondenser and into the heat exchanger. With this typeof configuration there is a potential forflash gas whichwould cause the valve to hunt. See Figure 11.

12.3 Heat Exchanger Piping Arrangements

Best subcooling effect is assured if counterflow of gas

and liquid is provided as shown (see Figure 12). Inorder to guarantee optimum heat transfer, the plateheat exchanger should be mounted vertically andvapor should exit it at the top.

Figure 9

The normally closed (NC) contact of the alarm relay (L-M)should be wired in the compressor contactor control circuitso that opening this contact removes the compressorfrom the line and removes power to the CM.

11. Thermostatic Expansion Valve (TXV) & HeatExchanger

In order to properly use an Enhanced Vapor Injectioncompressor a thermostatic expansion valve (TXV) andheat exchanger are needed in the system. Emersonprovides a kit that has these components properly sizedfor the ZF13 and ZF18 single compressor applications,see Table 5. For multiple compressor applications, thesubcooling components may be designed using thesubcooling load and pressure and temperature dataprovided by the EVI calculator program.

Table 5

Model 24V 120V 240V Kits Include:

ZF13 985-

1500-00

985-

1500-01

985-

1500-02

TXV,

Solenoid Valve,

Current Sensing

Relay, Heat

Exchanger

ZF18 985-

1500-00

985-

1500-01

985-

1500-02

ZF24 N/A N/A N/A

ZF33 N/A N/A N/A

ZF40 N/A N/A N/A

ZF48 N/A N/A N/A

Heat

Exchanger

Vapor Outlet to

Compressor

Condenser

Outlet

TXV

LIT

VOT

SIT

UT

LOT

Figure 10 - Downstream Extraction

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13. System Design Guidelines:

NOTE: The following sections discuss system design

guidelines for the EVI product. Please refer to theEmerson Product Selection Software, which canbe found in the Online Product Information (OPI)database located at www.emersonclimate.com, forfurther information needed to accommodate yoursizing needs.

13.1 Heat Exchanger Sizing

Heat exchangers should be sized so that they haveadequate design margin for the entire range of systemoperation, but they should be optimized for normaloperating conditions. The parameters used to determinethe proper heat exchanger size are described below:

SIT = Heat Exchanger saturated evaporatingtemperature at its outlet pressure.

LIT = Liquid in Temp ~ Condensing Outlet LOT = Liquid Out Temp = SIT + TD VIT = Vapor In Temp ~ SIT + Loss VOT = Vapor Out Temp = SIT + Superheat H = Enthalpy Subcooling = LIT - LOT Superheat = VOT - SIT TD = LOT- SIT

The key parameter in determining the proper heatexchanger is the Saturated Injection Temperature(SIT). It is imperative the following procedure befollowed for optimized performance. The SIT has

been derived experimentally and can be approximatedby using Figure 13. After determining the SIT, a 10FCondenser Subcooling, TD, and Superheat are targeted.This is done in order to optimize system performancewhile at the same time maintaining system reliabilityand functionality. Once these parameters have beenestablished, the heat exchanger Btu/Hr capacitycan be established, which gives the required heatexchanger size.

Figure 13

Example of Heat Exchanger Sizing OptimizedZF18KVE 404A

Step 1 Know Conditions -25/105/0/65

Te/Tc / Cond SC / Suct RG

Step 2 Determine Flow Me 355 lb/hr

From Product Data

Step 3 Estimate SIT From Guideline 12

Step 4 Use the 10 Guidelines To Derive LIT = T

5901-

LOT = SIT + 10 22 HX SC = LIT - LO 73

= (T

- SIT-20) HX Btu/hr =M

x (Hft - Hlot) 9550

=355 x (47.0 - 20.1)

VO = Vapor temperature leaving H/X

VI = Vapor temperature entering H/X

LI = Liquid temperature entering H/X

LO = Subcooled liquid leaving H/X

Figure 12 - H/X Piping Arrangement

Figure 11 - Upstream Extraction

Vapor OutCond. Out

Liq. In

TXV

SIT

Liq. OutVapor In

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For multiple compressor applications the same processcan be used to determine the heat exchanger sizeneeded by adding together the individual heat exchangercapacities for each compressor.

13.2 Line Sizing

In single compressor applications, the vapor injectionline from the heat exchanger to the compressor shouldbe 3/8" - 1/2" and kept as short as possible in order tominimize pressure drop loss. The liquid line from the heatexchanger to the evaporator should be insulated and keptas short as possible in order to maximize the subcoolingat the evaporator. If a vapor injection header is used, theheader diameter should be such that the cross-sectionalarea is equal to the sum of the cross-sectional areas ofthe individual cross-sectional lines to the compressor.

For example, for four compressors, each with a 3/8"vapor injection line, the header tube diameter should bea 7/8" tube. In addition, the individual injection lines tothe compressors should tap into the header either ontop or on the sides of the header tube; a bottom tap willincrease the risk of returning liquid into the compressorthrough the vapor injection line.

13.3 Heat Exchanger TXV Sizing

TXV's should be sized so that they have adequate designmargin for the entire range of system operation, but theyshould be optimized for normal operating conditions.Select a TXV that is able to handle the Btu/hr capacity ofthe heat exchanger determined in the section above.

13.4 Solenoid Valve & Ball Valve

A solenoid valve is required to stop the flow ofvapor from the system to the compressor when thecompressor is in the off cycle. This must be a vapor

solenoid sized equivalent to or larger than the vaporinjection tube size. For minimum orifice sizes seeTable 6. For service purposes, a mechanical ball valve(not provided by Emerson) is also recommended in thevapor injection line.

Table 6

ModelMinimum

Orifice Size

Flow Control

Valve Series

ZF13 3/16" 200RB 3

ZF18 3/16" 200RB 3

ZF24 1/4" 200RB 4

ZF33 1/4" 200RB 4

ZF40 5/16" 200RB 5

ZF48 5/16" 200RB 5

13.5 Current Sensing Relay

To prevent the solenoid from remaining open during a"motor protector trip" a current sensing relay must beprovided that senses whenever the compressor is "off"and closes the solenoid to stop injection. See Table 5for a kit with the correct current sensing relay.

13.6 Multiple Compressor Applications

EVI can also be used in multiple compressorapplications. Unlike a standard compressor system, theEVI compressor system changes its delivered capacity

by changing the amount of sub-cooling provided at thesub-cooling heat exchanger. The result is that in highambient temperature conditions (summer operation)and in low ambient temperature conditions (winteroperation), the same number of compressors tend torun. It is important to note this since most personnelare used to seeing fewer compressors in operationin the cooler winter months compared to the hottersummer months; with EVI, almost the same number ofcompressors will be running in the summer and winter.

Multiple EVI compressors can be used with eithera single heat exchanger for each compressor or acommon heat exchanger for all compressors. In case

of a common heat exchanger, a solenoid valve shouldbe installed on each individual vapor injection line.Special care has to be given to the design of the heatexchanger and of the thermostatic expansion valve(TXV) to allow for part load operation. Good refrigerantdistribution is required in the common heat exchangeras well as sufficient velocities for oil return, even atpart load.

In the case of a large range of capacity modulation(more than 2 compressors in parallel), the use of an

Example of Heat Exchanger Sizing Fixed Liquid Temperature

ZF18KVE 404AStep 1 Know Conditions -25/105/0/65

Te/Tc / Cond SC / Suct RG

Step 2 Determine Flow M

355 lb/hr

From Product Data

Step 3 Use the 10 Guideline LIT = T

5901-

LOT user defined 50 HX SC = LIT - LO 45 HX [Btu/hr] = M

x (Hft - Hlot) 6140

= 355 x (47.0 - 29.7)

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Electronic Expansion Valve (EXV) or of two differentTXV(s) controlled by individual solenoid valves, mayimprove performance. For example, one at 100%full load and the second solenoid valve for 30% offull load. (See Figures 14and15). It is necessary toensure that the solenoid valves, vapor injection linesand header(s) are adequately sized in order to keeppressure drop to a minimum. At the same time, thelayout should be such that excessive amounts of oil donot accumulate in the header.

14. Controlling Liquid Out Temperature (LOT)

The LOT will typically be determined by the operatingcondition of the compressor. If the LOT needs to befixed at any specific value (for example, 50F) forpurposes of good system control, an EvaporatorPressure Regulator (EPR) valve may be introduced

at the vapor outlet of the subcooling heat exchanger.Table 7 shows approximate EPR settings for differentliquid temperature.

Emerson Climate Technologies Product SelectionSoftware can be used to determine the effect offixingLOT on the capacity and efficiency of the compressor.See Figures 15 and 16 on the following page.

Table 7

Figure 14

EVI Paralleling with HX Thermostatic valves of

different capacity

Figure 15

EVI Paralleling with HX Electronic Expansion

Valve (EXV)

R-407A (Based on Dew Point Properties)

Subcooler Liquid OutTemperature, F Approximate EPRSetting, psig (psia)

60 86.1 (100.8)

50 69.4 (84.1)

40 54.8 (69.5)

*Assumes a 10F DT across EVI Heat Exchanger

R-404A (Based on Dew Point Properties)

Subcooler Liquid OutTemperature, F

Approximate EPRSetting, psig (psia)

60 103.6 (118.3)

50 85.4 (100.1)

40 69.3 (84.0)

*Assumes a 10F DT across EVI Heat Exchanger

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Economizer Settings

Defaults To AutomaticFor Maximum Sub-cooling

Maximum Sub-cooling

Obtained

Economizer Settings Is Set

To Constant Liquid

Temp. For Fixing Liquid

Out Temperature (LOT)

Liquid Temperature Is

Fixed At Input Value

Figure 16Screenshot of Emerson Climate Technologies Product Selection Software Showing the Maximum

Sub-cooling Obtained When the Default Automatic is Selected for Economizer Settings.

Figure 17Screenshot of the Product Selection Software Showing the Constant Liquid Temperature at Outlet of the

Subcooling Heat Exchanger.

7/28/2019 AE1327

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AE-1327 R5


B U L L E T I N

7C 2.301308C 2.19180

9C 2.08830

10C 1.99030

11C 1.89720

12C 1.80900

13C 1.72550

14C 1.64640

15C 1.57140

16C 1.50000

17C 1.43230

18C 1.36810

19C 1.30710

20C 1.2493021C 1.19420

22C 1.14180

23C 1.09210

24C 1.04490

25C 1.00000

26C 0.95710

27C 0.91640

28C 0.87760

29C 0.84070

30C 0.80560

31C 0.77200

32C 0.74010

33C 0.7096034C 0.68060

35C 0.65300

36C 0.62660

37C 0.60140

38C 0.57740

39C 0.55460

40C 0.53270

41C 0.51170

42C 0.49180

43C 0.47270

44C 0.45440

45C 0.4370046C 0.42030

47C 0.40420

48C 0.38890

49C 0.37430

5C 2.53960

6C 2.41710

7C 2.30130

8C 2.191809C 2.08830

10C 1.99030

11C 1.89720

12C 1.80900

13C 1.72550

14C 1.64640

15C 1.57140

16C 1.50000

17C 1.43230

18C 1.36810

19C 1.30710

20C 1.24930

21C 1.1942022C 1.14180

23C 1.09210

24C 1.04490

25C 1.00000

26C 0.95710

27C 0.91640

28C 0.87760

29C 0.84070

30C 0.80560

31C 0.77200

32C 0.74010

33C 0.70960

34C 0.6806035C 0.65300

36C 0.62660

37C 0.60140

38C 0.57740

39C 0.55460

40C 0.53270

41C 0.51170

42C 0.49180

43C 0.47270

44C 0.45440

45C 0.43700

46C 0.4203047C 0.40420

48C 0.38890

49C 0.37430

95C 0.07870

96C 0.07641

97C 0.07420

98C 0.07206

99C 0.07000100C 0.06800

101C 0.06612

102C 0.06430

103C 0.06255

104C 0.06085

105C 0.05920

106C 0.05760

107C 0.05605

108C 0.05456

109C 0.05310

110C 0.05170

111C 0.05027

112C 0.04889113C O.04755

114C 0.04625

115C O.04500

116C 0.04372

117C 0.04248

118C 0.04128

119C 0.04012

120C O.03900

121C O.03793

122C 0.03690

123C 0.03590

124C 0.03494

125C 0.03400126C 0.03315

127C 0.03233

128C 0.03153

129C 0.03075

130C 0.03000

131C 0.02926

132C 0.02854

133C 0.02784

134C 0.02716

135C 0.02650

136C 0.02586

137C 0.02525138C 0.02465

139C 0.02407

140C 0.02350

141C 0.02295

142C 0.02242

143C 0.02190

144C 0.02139

145C 0.02090146C 0.02039

147C 0.01990

148C 0.01942

149C 0.01895

150C 0.01850

151C 0.01801

152C 0.01754

153C 0.01708

154C 0.01663

155C 0.01620

156C 0.01584

157C 0.01549

158C 0.01515159C 0.01482

160C 0.01450

161C 0.01418

162C 0.01388

163C 0.01358

164C 0.01328

165C 0.01300

166C 0.01275

167C 0.01250

168C 0.01226

169C 0.01203

170C 0.01180

171C 0.01157172C 0.01134

173C 0.01112

174C 0.01091

175C 0.01700

176C 0.01049

177C 0.01029

178C 0.10090

179C 0.00989

180C 0.00970

181C 0.00949

182C 0.00928

183C 0.00908184C 0.00889

185C 0.00870

186C 0.00853

187C 0.00837

188C 0.00821

189C 0.00805

190C 0.00790

-40C 33.60000-39C 31.44900

-38C 29.45200

-37C 27.59700

-36C 25.87300

-35C 24.27000

-34C 22.76100

-33C 21.35700

-32C 20.05100

-31C 18.83400

-30C 17.70000

-29C 16.63420

-28C 15.64040

-27C 14.71340-26C 13.84820

-25C 13.04020

-24C 12.28070

-23C 11.57100

-22C 10.90750

-21C 10.28680

-20C 9.70600

-19C 9.15880

-18C 8.64630

-17C 8.16620

-16C 7.71620

-15C 8.29400

-14C 6.89570-13C 6.52190

-12C 6.17110

-11C 5.84150

-10C 5.53190

-9C 5.23920

-8C 4.96400

-7C 4.70520

-6C 4.46170

-5C 4.23240

-4C 4.01530

-3C 3.81090

-2C 3.61820-1C 3.43670

0C 3.26540

1C 3.10300

2C 2.94980

3C 2.80520

4C 2.66860

5C 2.53960

6C 2.41710

Temp Ratio Temp Ratio Temp Ratio Temp Ratio Temp Ratio

Appendix A

AE1327

Documents