manualshive.com logo in svg

AAON CB-024, Installation Operation & Maintenance, Page: 46 / 56

Share
Download
AAON CB-024 Installation Operation & Maintenance Download Page 46

 

 

46 

 

 

Figure 18 – Modulating hot gas reheat with hot gas bypass piping, AHU above CU 

 

 

Summary of Contents for CB-024

Page 1: ...ion in this manual is not followed exactly a fire or explosion may result causing property damage personal injury or loss of life WARNING QUALIFIED INSTALLER Improper installation adjustment alteration service or maintenance can cause property damage personal injury or loss of life Startup and service must be performed by a Factory Trained Service Technician A copy of this IOM should be kept with ...

Page 2: ...l 16 Thermostat 17 Refrigerant Piping 18 General 18 Determining Refrigerant Line Size 18 Liquid Line Sizing 19 Suction Line Sizing 20 Hot Gas Bypass Line 22 Hot Gas Reheat 22 Predetermined Line Sizes 23 Startup 26 Compressors 26 Charging Refrigerant Adjusting Refrigerant Charge 27 Before Charging 27 Checking Liquid Sub cooling 27 Checking Evaporator Superheat 28 Adjusting Sub cooling and Superheat...

Page 3: ...tenance 37 Coils 37 E Coated Coil Cleaning 37 DX Cooling 39 Condenser Fan Motor 39 Replacement Parts 39 Warranty Service and Parts Department 39 Refrigerant Piping Diagrams 40 CB Series Startup Form 52 Literature Change History 55 ...

Page 4: ...ent line length 25 Figure 7 Variable Capacity Compressor Controller 32 Figure 8 Compressor Controller Flash Code Details 33 Figure 9 Adjustable Fan Cycling Switch 34 Figure 10 Piping Schematic of Example System using the LAC Valve 35 Figure 11 Adjustable compressor lockout 36 Figure 12 A C only piping AHU above CU 40 Figure 13 A C only piping AHU below CU 41 Figure 14 Modulating hot gas reheat pip...

Page 5: ...on and Liquid Line Schrader Valves Installation and Maintenance Easily Removable Panel Access to Service Compartment Run Test Report and Installation Manuals Included in Controls Compartment Color Coded Wiring and Wiring Diagrams 24V Control Circuit Transformer Option System Integration Split System Matching Modulating Head Pressure Control Single Point Power High Density Foam Compressor Sound Sup...

Page 6: ...ger statements are given to prevent actions that will result in equipment damage property damage severe personal injury or death ELECTRIC SHOCK FIRE OR EXPLOSION HAZARD Failure to follow safety warnings exactly could result in dangerous operation serious injury death or property damage Improper servicing could result in dangerous operation serious injury death or property damage When servicing con...

Page 7: ...ipment PPE be worn should be followed WARNING GROUNDING REQUIRED All field installed wiring must be completed by qualified personnel Field installed wiring must comply with NEC CEC local and state electrical code requirements Failure to follow code requirements could result in serious injury or death Provide proper unit ground in accordance with these code requirements WARNING ROTATING COMPONENTS ...

Page 8: ...carbon HFC refrigeration systems Refer to the compressor label for the proper compressor lubricant type CAUTION PVC PIPING PVC Polyvinyl Chloride and CPVC Chlorinated Polyvinyl Chloride are vulnerable to attack by certain chemicals Polyolester POE oils used with R 410A and other refrigerants even in trace amounts in a PVC or CPVC piping system will result in stress cracking of the piping and fitti...

Page 9: ...ual and all literature safeguarded near or on the unit COIL CLEANING Do not clean DX refrigerant coils with hot water or steam The use of hot water or steam on refrigerant coils will cause high pressure inside the coil tubing and damage to the coil CAUTION ENCLOSED AREA Do not work in an enclosed area where refrigerant or nitrogen gases may be leaking A sufficient quantity of vapors may be present...

Page 10: ...0 Standard 55 F Ambient B Adjustable Fan Cycling 35 F Ambient D Modulating Fan Pressure Control 35 F Ambient F Flooded Condenser Ambient Controls 0 F Option B G Flooded Condenser Ambient Controls 0 F Option D FEATURE 2 REFRIGERATION OPTIONS 0 Standard Split System Air Conditioner A External Hot Gas Bypass B Split System Heat Pump D Modulating Hot Gas Reheat F Options A D G Options B D FEATURE 3 CO...

Page 11: ...d to ensure the correct model sizes and voltages have been received to match the job requirements If repairs must be made to damaged goods then the factory should be notified before any repair action is taken in order to protect the warranty Certain equipment alteration repair and manipulation of equipment without the manufacturer s consent may void the product warranty Contact AAON Warranty Depar...

Page 12: ...refrigerant migration This means the compressor may cool down and liquid refrigerant may accumulate in the compressor Since the compressor is designed to pump refrigerant gas damage may occur when power is restored If power to the unit must be off for more than an hour turn the thermostat system switch to Off or turn the unit off at the control panel and then cut off the main power supply Leave th...

Page 13: ...ite mode Cooling only systems should be switched off at the thermostat during the heating season Wiring Diagrams Unit specific wiring diagram is laminated in plastic and located inside the controls compartment door General Maintenance When the initial startup is made and on a periodic schedule during operation it is necessary to perform routine service checks on the performance of the condensing u...

Page 14: ...t the unit s weight When rooftop mounted a steel frame must be provided that will support the unit above the roof itself for load distribution When installed at ground level a one piece concrete slab or composite condenser pad should be used with footings that extend below the frost line a substantial base that will not settle Slab should be surrounded by a graveled area for proper drainage and sh...

Page 15: ...bfreezing temperatures Heat pump unit bases are cutout under the outdoor coil to permit drainage of frost accumulation The unit must be situated to permit free unobstructed drainage of the defrost water and ice A minimum 3 inches clearance under the outdoor coil is required in the milder climates In more severe weather locations it is recommended that the unit be elevated to allow unobstructed dra...

Page 16: ...ration must be checked by a qualified technician prior to startup Wire power leads to the unit terminal block All wiring beyond this point has been done by the manufacturer and cannot be modified without affecting the unit s agency safety certification All units require field supplied electrical overcurrent and short circuit protection Device must not be sized larger than the Maximum Overcurrent P...

Page 17: ... not exceeded Wire control signals to the unit s low voltage terminal block located in the controls compartment If any factory installed wiring must be replaced use a minimum 105 C type AWM insulated conductors Thermostat If a thermostat is used for unit control thermostat should be located on an inside wall 4 5 feet above the floor where it will not be subjected to drafts sun exposure or heat fro...

Page 18: ...ugging or carryover Minimizing the refrigerant line size is favorable from an economic perspective reducing installation costs and reducing the potential for leakage However as pipe diameters narrow pressure reducing frictional forces increase Excessive suction line pressure drop causes loss of compressor capacity and increased power usage resulting in reduced system efficiency Excessive pressure ...

Page 19: ...igerant This will allow the refrigerant to withstand greater frictional losses without the occurrence of flashing prior to the TXV A moisture indicating sight glass may be field installed in the liquid line to indicate the occurrence of premature flashing or moisture in the line The sight glass should not be used to determine if the system is properly charged Use temperature and pressure measureme...

Page 20: ...the compressor and keep it from flooding back into the evaporator Crankcase heaters are provided to keep any condensed refrigerant that collects in the compressor from causing damage or wear Make sure to provide support to maintain suction line positioning and insulate completely between the evaporator and condensing unit It is important to consider part load operation when sizing suction lines At...

Page 21: ...ses in heating mode See the diagrams below Figure 4 Heat Pump Piping Schematic of Suction Vapor Flow Down in Double Riser Figure 5 Heat Pump Piping Schematic of Discharge Vapor Flow Up in Double Riser Suction Line Insulation The entire suction line should be insulated with a minimum 1 inch thick Armaflex insulation This prevents condensation from forming on the line and reduces any potential loss ...

Page 22: ...aporator when reduced suction pressure is sensed Field piping between the condensing unit and the evaporator is required Hot Gas Bypass Piping Considerations for Evaporator above Condensing Unit Pitch the hot gas bypass line downward in the direction of refrigerant flow toward the evaporator When installing hot gas bypass risers an oil drip line must be provided at the lowest point in the system T...

Page 23: ... following cycle assumptions are made Saturated suction temperature 50 F Saturated condensing temperature 125 F Sub cooling 10 F Superheat 15 F The liquid lines have been chosen to maintain velocities between 100 and 350 fpm The suction line diameters are selected to limit velocities to a 4 000 fpm maximum while a minimum velocity restriction is imposed by the ability to entrain oil up vertical su...

Page 24: ... and additional pressure losses in the suction and hot gas lines The total equivalent line length definition includes the height of vertical rise pressure drop through elbows and accessories and horizontal line length so elbows accessories and vertical rise must be considered when determining horizontal length available from the total equivalent line length The figure below is presented in terms o...

Page 25: ...2 1 2 7 8 1 2 1 2 CB 060 3 8 7 8 1 2 1 2 7 8 1 2 1 2 Hot Gas Bypass line Hot Gas Reheat line Figure 6 Riser height versus total equivalent line length Note Figure 6 is for R 410A split system applications with two step compressor CB 024 through CB 060 units The region of acceptable riser height is the lighter area Select the corresponding predetermined line size from Table 2 above Total Equivalent...

Page 26: ... be checked on all MOTORS AND COMPRESSORS of three phase units Condenser fan motors should all be checked by a qualified service technician at startup and any wiring alteration should only be made at the unit power connection CAUTION COMPRESSOR ROTATION Scroll compressors are directional and will be damaged by operation in the wrong direction Low pressure switches on compressors have been disconne...

Page 27: ...n the cooling mode heating mode must be rerun to verify proper operation After adding or removing charge the system must be allowed to stabilize typically 10 15 minutes before making any other adjustments The type of unit and options determine the ranges for liquid sub cooling and evaporator superheat Refer to the table of acceptable refrigerant circuit values when determining the proper sub cooli...

Page 28: ...cooling temperature is too high and the evaporator is fully loaded low loads on the evaporator result in increased sub cooling and the evaporator superheat is within the temperature range as shown in Table 3 high superheat results in increased sub cooling Correct an overcharged system by reducing the amount of refrigerant in the system to lower the sub cooling The system is undercharged if the sup...

Page 29: ...d approximately 40 of the receiver tank volume The unit will have to be checked for proper operation once the ambient temperature is above 80 F Air Flow Table 4 Performance Testing Air Flow Setpoints Model Cooling Stage 2 cfm Cooling Stage 1 cfm Heating Stage 2 cfm Heating Stage 1 cfm CB B 024 1 885 663 75 885 796 5 CB B 036 1 1250 937 5 1250 1125 CB B 048 1 1500 1125 1500 1350 CB B 060 1 1545 115...

Page 30: ... 96 8 57 161 0 84 249 8 111 369 1 138 526 6 31 98 8 58 163 8 85 253 7 112 374 2 139 533 3 32 100 9 59 166 7 86 257 5 113 379 4 140 540 1 33 102 9 60 169 6 87 261 4 114 384 6 141 547 0 34 105 0 61 172 5 88 265 4 115 389 9 142 553 9 35 107 1 62 175 4 89 269 4 116 395 2 143 560 9 36 109 2 63 178 4 90 273 5 117 400 5 144 567 9 37 111 4 64 181 5 91 277 6 118 405 9 145 575 1 38 113 6 65 184 5 92 281 7 1...

Page 31: ... 60 watts compressor Night and Weekend Unoccupied Operation To reduce the operating time of the unit when the space is unoccupied such as nights and weekends it is recommended that the temperature setting be raised about 5 F while unoccupied during the cooling season and lowered about 10 F during the heating season Compressor The compressors must be off for a minimum of 5 minutes and on for a mini...

Page 32: ...rding the capacity demand signal of the system The following table shows the linear relationship between the demand signal and compressor capacity modulation The compressor controller also protects the compressor against high discharge temperature Refer to Table 7 for the relationship between thermistor temperature readings and resistance values Table 6 Demand Signal vs Compressor Capacity Modulat...

Page 33: ...7 15 5 627 28 100 212 5 85 10 14 475 74 105 221 5 09 5 23 363 99 110 230 4 45 0 32 280 82 115 239 3 87 5 41 218 41 120 248 3 35 10 50 171 17 125 257 2 92 15 59 135 14 130 266 2 58 20 68 107 44 135 275 2 28 25 77 86 00 140 284 2 02 30 86 69 28 145 293 1 80 35 95 56 16 150 302 1 59 40 104 45 81 155 311 1 39 45 113 37 58 160 320 1 25 50 122 30 99 165 329 1 12 55 131 25 68 170 338 1 01 60 140 21 40 17...

Page 34: ... head pressure is set to 300psi and the differential is set to 100psi then fans will cut in at 300psi and cut out at 200psi Fan cycling and variable speed condenser fan head pressure control options allow mechanical cooling with ambient temperatures down to 35 F Figure 9 Adjustable Fan Cycling Switch Variable Speed Low Ambient Variable speed condenser fan head pressure control is a low ambient hea...

Page 35: ...re in the receiver allowing the system to operate properly CF Series condensers and condensing units use an LAC valve for low ambient operation LAC Valve The Low Ambient Control LAC valve is a non adjustable three way valve that modulates to maintain receiver pressure As the receiver pressure drops below the valve setting 295 psig for R 410A the valve modulates to bypass discharge gas around the c...

Page 36: ... Condenser Flooding PERCENTAGE OF CONDENSER TO BE FLOODED Ambient Temperature F Evaporating Temperature F 0 10 20 30 35 40 45 50 70 40 24 0 0 0 0 0 0 0 60 47 33 17 26 20 10 4 50 70 60 50 38 45 40 33 28 40 76 68 60 50 56 52 46 42 30 80 73 66 59 64 60 55 51 20 86 77 72 65 69 66 62 59 0 87 83 78 73 76 73 70 68 Compressor Lockouts Some units include adjustable compressor lockouts The compressor lockou...

Page 37: ...triction of airflow If unable to back wash the side of the coil opposite of the coils entering air side then surface loaded fibers or dirt should be removed with a vacuum cleaner If a vacuum cleaner is not available a soft non metallic bristle brush may be used In either case the tool should be applied in the direction of the fins Coil surfaces can be easily damaged fin edges bent over if the tool...

Page 38: ... salts may be beneath any soils grease or dirt therefore these barriers must be removed prior to application of this product As in all surface preparation the best work yields the best results Apply CHLOR RID DTS Apply directly onto the substrate Sufficient product must be applied uniformly across the substrate to thoroughly wet out surface with no areas missed This may be accomplished by use of a...

Page 39: ...be field furnished and installed if required by job conditions Condenser Fan Motor All original motors and bearings are furnished with factory lubrication They require no lubrication The electrically commutated condenser fan motor ECM is factory preprogrammed and requires no maintenance Replacement Parts Parts for AAON equipment may be obtained from your local AAON representative Reference the uni...

Page 40: ...40 Refrigerant Piping Diagrams Figure 12 A C only piping AHU above CU ...

Page 41: ...41 Figure 13 A C only piping AHU below CU ...

Page 42: ...42 Figure 14 Modulating hot gas reheat piping AHU above CU ...

Page 43: ...43 Figure 15 Modulating hot gas reheat piping AHU below CU ...

Page 44: ...44 Figure 16 Hot gas bypass piping AHU above CU ...

Page 45: ...45 Figure 17 Hot gas bypass piping AHU below CU ...

Page 46: ...46 Figure 18 Modulating hot gas reheat with hot gas bypass piping AHU above CU ...

Page 47: ...47 Figure 19 Modulating hot gas reheat with hot gas bypass piping AHU below CU ...

Page 48: ...48 Figure 20 Heat pump piping AHU above CU ...

Page 49: ...49 Figure 21 Heat pump piping AHU below CU ...

Page 50: ...50 Figure 22 Heat pump with modulating hot gas reheat piping AHU above CU ...

Page 51: ...51 Figure 23 Heat pump with modulating hot gas reheat AHU below CU ...

Page 52: ... there any visible shipping damage Yes No 2 Is the unit level Yes No 3 Are the unit clearances adequate for service and operation Yes No 4 Do all access doors open freely and are the handles operational Yes No 5 Have all shipping braces been removed Yes No 6 Have all electrical connections been tested for tightness Yes No 7 Does the electrical service correspond to the unit nameplate Yes No 8 On 2...

Page 53: ...eating Mode Heat Pump Only Pressure Saturated Temperature Line Temperature Sub cooling Superheat Discharge Suction Liquid Air Cooled Condenser Fan Alignment_____ Check Rotation_____ Nameplate Amps________ Number hp L1 L2 L3 1 ...

Page 54: ...ument any service repair or adjustments AAON Service and Warranty Departments are available to advise and provide phone help for proper operation and replacement parts The responsibility for proper start up maintenance and servicing of the equipment falls to the owner and qualified licensed technician Entry Date Action Taken Name Tel ...

Page 55: ...assigned July 2014 Updated service clearance drawing February 2015 Updated Feature 5 options to reflect standard exterior corrosion protection July 2015 Updated Replacement Parts instructions Added Features and Options section August 2016 Added Storage information Added guidelines for variable capacity compressors in the line sizing section Added double riser schematics and discussion for heat pum...

Page 56: ...7 It is the intent of AAON to provide accurate and current product information However in the interest of product improvement AAON reserves the right to change pricing specifications and or design of its product without notice obligation or liability Copyright AAON all rights reserved throughout the world AAON and AAONAIRE are registered trademarks of AAON Inc Tulsa OK ...

Reviews:

No comments