Emerson AE4-1395 User Manual

0 (0)

ApplicationApplicationEngi eeringEngineering

 

 

 

B

U

L

L

E

 

T

I

N

 

AE4-1395

L

I

N

 

B

U

L

 

 

E

T

AE4-1395

 

 

 

 

 

 

 

 

 

August 2012

3 to 15 Ton Copeland Scroll DigitalCompressors for Air Conditioning

TABLE OF CONTENTS

Section

Page

Safety

 

Safety Instructions.................................................

2

Safety Icon Explanation.........................................

2

Instructions Pertaining to Risk of

 

Electrical Shock, Fire, or Injury to Persons............

3

Safety Statements..................................................

3

Introduction

 

Nomenclature ........................................................

4

Digital Compressor Operation ...............................

4

How It Works ........................................................

4

Application Considerations

 

Operating Envelope...............................................

4

Solenoid Valve and Coil.........................................

5

Pressure Fluctuations............................................

5

Piping.....................................................................

5

Start Up and Shut Down........................................

5

Compressor Cycling...............................................

5

Sound Characteristics............................................

5

Internal Pressure Relief (IPR) Valve......................

5

High Pressure Control............................................

5

Low Pressure Control............................................

5

Scroll Temperature Protection................................

6

Crankcase Heaters................................................

6

Oil Type and Oil Removal .....................................

6

Power Factor..........................................................

6

Tandem Applications..............................................

6

Modulation Control.................................................

7

Application Tests

 

Oil Level Verification..............................................

7

Excessive Liquid Floodback Tests.........................

7

Operating Envelope Tests......................................

7

Section

Page

Digital Compressor Retrofit Applications

 

Reasons to Retrofit..................................................

7

Retrofit Applications To Avoid...................................

8

Performance Modeling.............................................

8

System Modifications...............................................

8

Compressor Selection & Change-Out...................

8

Refrigerant Flow Control........................................

9

Evaporator Air Flow................................................

9

Condenser Air Flow................................................

9

Modulation Control.................................................

9

Assembly Line Procedures

 

3 To 7.5 Ton Modulation Valve Brazing Procedure....

9

Pressure Testing......................................................

9

Service Procedures

 

Modulation Troubleshooting....................................

10

3 to 7.5 Ton Modulation Valve Replacement

 

Procedure................................................................

10

8 To 15 Ton Modulation Valve Replacement

 

Procedure................................................................

10

Scroll Compressor Functional Check......................

11

Figures & Tables

 

Digital Cycle Example.............................................

12

3 to 7.5 Ton Digital Scroll Cross Sectional View.....

12

8 to 15 Ton Digital Scroll Cross Sectional View......

13

3-7.5 Ton Operating Envelope................................

14

8-15 Ton Operating Envelope.................................

14

Compressor Capacity Graph..................................

15

Discharge Thermistors............................................

15

3 to 7.5 Ton Modulation Valve Piping......................

16

3 To 7.5 Ton Tandem...............................................

16

Modulation Troubleshooting....................................

17

Copeland Scroll Digital Family Features.................

18

Refrigerant Charge Limits.......................................

18

Torque Values.........................................................

18

Compressor Accessories........................................

19

© 2012 Emerson Climate Technologies, Inc.

1

Printed in the U.S.A.

 

Application Engineering

 

 

 

 

B U L L E

T

I

N

AE4-1395

Safety Instructions

Copeland Scrollcompressors are manufactured according to the latest U.S. and European Safety Standards. Particular emphasis has been placed on the user's safety. Safey icons are explained below and safety instructions applicable to the products in this bulletin are grouped on page 3. These instructions should

be retained throughout the lifetime of the compressor. You are strongly advised to follow these safety instructions.

Safety Icon Explanation

DANGER

WARNING

CAUTION

NOTICE

CAUTION

DANGER indicates a hazardous situation which, if not avoided, will result in death or serious injury.

WARNING indicates a hazardous situation which, if not avoided, could result in death or serious injury.

CAUTION, used with the safety alert symbol, indicates a hazardous situation which, if not avoided, could result in minor or moderate injury.

NOTICE is used to address practices not related to personal injury.

CAUTION, without the safety alert symbol, is used to address practices not related to personal injury.

© 2012 Emerson Climate Technologies, Inc.

2

Printed in the U.S.A.

 

Emerson AE4-1395 User Manual

Application Engineering

 

 

 

 

B U L L E

T

I

N

AE4-1395

Instructions Pertaining to Risk of Electrical Shock, Fire, or Injury to Persons

 

 

 

ELECTRICAL SHOCK HAZARD

 

WARNING

 

 

 

Failure to follow these warnings could result in serious personal injury.

 

 

 

 

 

 

Disconnect and lock out power before servicing.

 

 

 

Discharge all capacitors before servicing.

 

 

 

• Use compressor with grounded system only.

 

 

 

Molded electrical plug must be used when required.

 

 

 

Refer to original equipment wiring diagrams.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PRESSURIZED SYSTEM HAZARD

WARNING

Failure to follow these warnings could result in serious personal injury.

 

 

System contains refrigerant and oil under pressure.

 

Remove refrigerant from both the high and low compressor side before

 

 

removing compressor.

Never install a system and leave it unattended when it has no charge, a holding charge, or with the service valves closed without electrically locking out the system.

Use only approved refrigerants and refrigeration oils.

Personal safety equipment must be used.

 

 

 

 

 

 

 

 

BURN HAZARD

 

WARNING

 

 

 

Failure to follow these warnings could result in serious personal injury or

 

 

 

 

property damage.

 

 

 

Do not touch the compressor until it has cooled down.

 

 

 

Ensure that materials and wiring do not touch high temperature areas of

 

 

 

 

the compressor.

 

 

 

• Use caution when brazing system components.

 

 

 

Personal safety equipment must be used.

 

 

 

 

 

 

 

 

 

 

 

COMPRESSOR HANDLING

CAUTION

• Failure to follow these warnings could result in personal injury or

 

property damage.

Use the appropriate lifting devices to move compressors.

Personal safety equipment must be used.

Safety Statements

• Refrigerant compressors must be employed only for their intended use.

install, commission and maintain this equipment.

All valid standards and codes for installing, servicing, and maintaining electrical and refrigeration equipment must be observed.

© 2012 Emerson Climate Technologies, Inc.

3

Printed in the U.S.A.

 

Application Engineering

 

 

 

 

B U L L E

T

I

N

AE4-1395

Introduction

The 3 to 15 ton Copeland Scroll Digitalcompressors described in this bulletin include the follow compressor model numbers:

R-410A

R-22 & R-407C

ZPD34 to ZPD54K5

ZRD36 to ZRD81KC

ZPD61 to ZPD91KC

ZRD94 to ZRD125KC

ZPD103 to ZPD182KC

 

ZPD and ZRD digital scroll compressors are variable capacity compressors that can modulate down to 10% of full load. Digital scrolls are suitable for a variety of applications where a variable capacity compressor is useful, such as VAV applications, dedicated outside air units, units that typically used hot gas bypass for capacity control, and applications that require accurate control of temperature and humidity. Other applications include multiple compressor systems where modulation is required over the entire operating range of the system and in applications where compressor starting and stopping is unacceptable. Typical digital scroll model numbers are ZRD94KCE-TF5 and ZPD182KCE-TWD. This bulletin describes the operating and application differences with respect to the equivalent fixed capacity Copeland Scrollcompressors. The following Application Engineering bulletins should be consulted for non-modulating scroll application guidelines:

AE4-1331 1.5 to 5 Ton R-410A AE4-1365 5 to 7.5 Ton R-410A

AE4-1303 8 to 15 Ton R-22, R-407C & R-410A AE4-1312 1.5 to 7 Ton R-22 & R-407C

Nomenclature

The model number of the Copeland Scroll Digital compressors includes the approximate nominal 60 Hz capacity at the AHRI high temperature full load air conditioning rating point. An example is the ZPD120KCE-TFD, which has approximately 120,000 Btu/hr cooling capacity at the air conditioning rating point when operated on 60 Hz. Note that the same compressor will have approximately 5/6 of this capacity or 100,000 Btu/hr when operated on 50 Hz power. Please refer to the Online Product Information at www.EmersonClimate.com for more information on performance at part load.

Digital Compressor Operation

The digital scroll is capable of seamlessly modulating its capacity from 10% to 100%. A normally closed (de-energized) solenoid valve is a key component for achieving modulation. When the solenoid valve is in its normally closed position, the compressor operates at

© 2012 Emerson Climate Technologies, Inc.

4

Printed in the U.S.A.

 

full capacity, or loaded state. When the solenoid valve is energized, the two scroll elements move apart axially, or into the unloaded state. During the unloaded state, the compressor motor continues running, but since the scrolls are separated, there is no compression. During the loaded state, the compressor delivers 100% capacity and during the unloaded state, the compressor delivers 0% capacity. A cycle consists of one loaded state and one unloaded state. By varying the time of the loaded state and the unloaded state, an average capacity is obtained. The lowest achievable capacity is 10% which equates to 1.5 seconds of pumping during one 15 second cycle.

An example for the 15 second controller cycle: In any 15 second cycle, if the loaded time is 10 seconds and the unloaded time is 5 seconds, the average capacity is 66% or if the loaded time is 5 seconds and the unloaded time is 10 seconds the capacity during that 15 second period is 33%. See Figure 1 for a graphical representation of the digital cycle, and Figure 6 for a graph showing solenoid on-time vs. compressor capacity.

How it Works

The digital scroll compressor unloads by taking advantage of the Copeland Scroll compressor's axial compliance. All Copeland Scroll compressors are designed so that the compression elements can separate axially a few thousands of an inch. The 3 through 7.5 ton compressors described in this bulletin use a lift piston mechanism to separate the scrolls during the unloaded state. When the solenoid is energized the volume on top of the piston is vented to the low side allowing the piston and fixed scroll assembly to move axial away from the orbiting scroll. When the solenoid is de-energized the piston is forced down and the scrolls are loaded axially.

The 8 ton and larger digital scroll compressors employ a solenoid valve that is mounted on the side of the compressor that vents the intermediate cavity to the low side of the compressor during the unloaded state. During the loaded state the solenoid valve is deenergized and the intermediate cavity is pressurized to load the floating seal and scrolls axially.

Please refer to Figures 2 and 3 for cross sectional pictures of the two digital modulation mechanisms.

APPLICATION CONSIDERATIONS Operating Envelope

The operating envelope of the digital scroll compressors for all loading conditions is shown in Figures 4 and 5.

Application Engineering

 

 

 

 

B U L L E

T

I

N

AE4-1395

Compressor operation during the loaded state should always be inside of the envelope. The envelopes represent allowable operation of the compressor with

20F° suction superheat at rated voltage. If the specified modulation ranges are exceeded, overheating of the compressor and tripping of the overload can occur because of inadequate motor cooling.

Solenoid Valve and Coil

The external solenoid valve and coil specified by

Emerson must be used since this is a critical component for the proper functioning of this compressor. The solenoid valve and coil are designed for approximately 32 million cycles. Do not attempt to substitute replacement coils or valves; use only the replacement parts specified in Table 4. Refer to the Service Procedures section for information on changing the modulation valves.

Pressure Fluctuations

During scroll modulation the suction and the discharge pressure will fluctuate. This fluctuation should be observed during unit testing. The installation and setting of pressure controls should take this into account. During the unloaded state, the discharge pressure will decrease and the suction pressure will increase. This normal pressure fluctuation has had no observable effect on the reliability of system components, however, component manufacturers should be consulted to ensure the proper application of their products.

Piping

Unlike a variable speed compressor whose mass flow and gas velocity changes with its speed, the digital scroll’s pumping capacity is equal to its 100% capacity while it is pumping. For this reason the gas velocity remains high even during periods when the capacity demand is low. Because the mass flow and gas velocity remain high, piping may be designed as if it were designed for a non capacity controlled compressor. For vertical piping a trap every 20 feet should be sufficient to ensure proper oil return. This recommendation is based upon a minimum 1500 fpm velocity or higher. When the digital scroll compressor is part of a tandem, a double riser should be considered to assure that the velocity remains above 1500 fpm when only the digital scroll is running.

Start Up and Shut Down

To improve the starting characteristics of the digital scroll compressor, the the Emerson controllers delay loading the compressor for 0.1 seconds. Likewise, to eliminate the reverse rotation sound at shut down the compressor is unloaded 0.5 seconds before shut down.

© 2012 Emerson Climate Technologies, Inc.

5

Printed in the U.S.A.

 

Compressor Cycling

Because of the digital scroll's seamless capacity modulation from 10% to 100%, capacity short cycling should not be a problem for single compressors. However, if the digital compressor is in tandem with a non modulated scroll, short cycling of the non modulated compressor may be a problem if the system control is not designed and set correctly. The Emerson digital controllers have a built in two minute anti-short cycle timer to prevent short cycling.

Sound Characteristics

The sound spectrum of the loaded state and the unloaded state are different. Special consideration should be given to the transition sound between the loaded and unloaded states. If the transition sound is unacceptable, a heavy sound blanket should be applied to the compressor. Fabricating Services (www.fabsrv.com) is a one source for scroll compressor sound blankets.

The Emerson controllers unload the compressor a fraction of a second before shut down allowing the scroll set to unload, ensuring a relatively quiet shutdown.

Internal Pressure Relief (IPR) Valve

WARNING

A high pressure control must be used in all ZRD94-125KC and ZPD103-182KC applications because these compressors do not have internal pressure relief (IPR) valves.

High Pressure Control

As mentioned above, not all digital scrolls have IPR valves, therefore high pressure controls are required in some applications. The recommended maximum cut out setting is 425 psig (30 bar) for R-407C & R-22 and 650 psig (45 bar) for R-410A. The high pressure control should have a manual reset feature for the highest level of system protection. This pressure control must act independently of the digital compressor controller.

Low Pressure Control

Air-conditioning units can be protected against high discharge temperatures through a low pressure control in the suction line. Testing has shown that a cut out setting of not lower than 55 psig (3.8 bar) for R-410A and 25 psig (1.7 bar) for R-407C & R-22 will adequately protect the compressor against overheating from loss of charge, blower failure in a TXV system, etc. A higher level of protection is achieved if the low pressure control is set to cut out at 95 psig (6.7 bar) for R-410A and 55 psig (3.8

Application Engineering

 

 

 

 

B U L L E

T

I

N

AE4-1395

bar) for R-407C & R-22 to prevent evaporator coil icing. The cut in setting can be as high as 180 psig (12.5 bar) for R-410A and 105 psig (7.2 bar) for R-407C & R-22 to prevent rapid recycling in case of refrigerant loss.

For heat pumps, a cut out setting no lower than 20 psig (1.4 bar) is recommended for R-410A and 10 psig (0.7 bar) for R-407C & R-22.

Scroll Temperature Protection

Most digital scrolls do not have internal discharge gas temperature protection. In order for the Emerson controllers to operate properly an NTC sensor must be attached to the compressor discharge line as close as possible to the compressor discharge fitting. For best response the sensor should be insulated. See Table 1 of AE8-1328 for thermistor temperature vs. resistance values. Refer to Table 4 for part numbers of discharge line thermistors. Figure 7 illustrates the two different types of discharge thermistors.

The ZRD61 through ZRD81KC compressors have a discharge thermistor that is inside of a well in the top cap of the compressor. If this thermistor ever needs to be replaced, it should be replaced with either 985-0199- 00 or 085-0204-00 as listed in Table 4.

Crankcase Heaters

A crankcase heater is required if the system charge exceeds the system charge limits listed in Table 2. For more information regarding regarding heater part numbers and installation location please refer to the equivalent non-digital scroll Application Engineering bulletin listed on Page 4.

Oil Type and Oil Removal

Mineral oil is used in the ZRD*KC compressors for R-22 applications. Polyolester (POE) oil is used in the ZRD*KCE and ZPD*KCE compressors for R-22 & R-407C and R-410A applications respectively. See the compressor nameplate for the original oil charge. A complete recharge should be approximately four fluid ounces (118 ml) less than the nameplate.

It is an approved practice to use ZRD*KCE compressors with POE to replace ZRD*KC compressors with mineral oil in R-22 service applications. R-22 has been approved for use with both mineral and POE and some mixing of these oil in the system is acceptable.

If additional oil is needed in the field for POE applications, CopelandUltra 32-3MAF, Lubrizol Emkarate RL32-3MAF, Parker Emkarate RL32-3MAF/ Virginia LE32-3MAF, or Nu Calgon 4314-66 (Emkarate

© 2012 Emerson Climate Technologies, Inc.

6

Printed in the U.S.A.

 

RL32-3MAF) should be used. Copeland Ultra 22 CC, Hatcol EAL 22CC, and Mobil EAL Arctic 22 CC are acceptable alternatives.

If additional oil is needed in the field for mineral oil applications, Sonneborn Suniso 3GS or Chevron Texaco Capella WF32 should be used.

CAUTION

POE must be handled carefully and the proper protective equipment (gloves, eye protection, etc.) must be used when handling POE lubricant. POE must not come into contact with any surface or material that might be harmed by POE, including without limitation, certain polymers (e.g. PVC/CPVC and polycarbonate).

Power Factor

During the loaded state the digital scroll compressor operates at full capacity and the power factor is the same as a standard scroll. However, when the scrolls are unloaded, the power factor is much lower. If power factor is an important consideration, the correcting capacitors should be calculated using the full capacity data to avoid problems associated with over correction. See AE9-1249 for more information on power factor correction.

Tandem Applications

Tandem compressors follow the same application guidelines as single compressors outlined in this bulletin. The refrigerant charge limit for tandem compressors is shown in Table 2. A tandem circuit with a charge over this limit must have crankcase heaters applied to both compressors.

Tandem compressor assemblies are available for purchase from Emerson. In lieu of purchasing the assembled tandem, the OEM has the option to purchase the tandem-ready compressors to assemble the compressors into a tandem configuration in their manufacturing plant. Drawings of the tandem manifolds are available by contacting your application engineer. Figure 9 illustrates a typical tandem compressor assembly using 3 through 7.5 ton scroll compressors. Note that only one compressor in the tandem assembly is a digital scroll compressor. Customers that choose to design and build their own manifolds for tandem and trio compressor assemblies are ultimately responsible for the reliability of those manifold sets.

For more information on tandems, please refer to the non-modulating compressor Application Engineering bulletins listed on Page 4.

Loading...
+ 13 hidden pages