A Series Inertia Compressor Applications. Application Bulletin 115

Transcription

1 A Series Inertia Compressor Applications Application Bulletin 115

2 Application Bulletin Subject: A Series Inertia Compressor Applications Number: 115 Release EN: 006X04 Date: 1/6/92 Revision EN: Z27301 Date: 10/2/15 This Application Bulletin is for air-to-air air conditioning and heat pump applications only. For other applications or deviations from this Bulletin, please call Bristol s Applications Engineering Department at (276) The Bristol Inertia compressors are the most advanced reciprocating compressors in the industry today. Changes in the suction and discharge valves make the Inertia very tolerant to liquid slugging and liquid floodback. As a result, the requirements for accumulators have been relaxed. The following guidelines were developed for the A Series Inertia compressors through actual system testing as well as laboratory testing. 1.0 Crankcase Heat Since the Inertia compressor has the ability to handle liquid refrigerant, a crankcase heater is not required on systems with a total charge of 15 pounds or less. Total charge includes the allowance for the tube size and length plus the tolerance of the charging equipment. Immersion type 30 and 40 watt PTCR crankcase heaters are available. To increase the longevity of the compressor bearings a crankcase heater is recommended to prevent liquid refrigerant from migrating into the compressor. Liquid refrigerant can dilute the oil causing excessive bearing wear. Compressors 50,000 BTU and higher should use 40-watt crankcase heaters. 2.0 Accumulators Due to the Inertia s ability to handle liquid refrigerant, an accumulator is only required on systems with more than 15 pounds total charge using certain metering devices (see Figure 1 and Section 5). Large volumes of liquid refrigerant repeatedly flooding back to the compressor during the off cycle, defrost cycle or excessive floodback during steady operation can dilute the oil to the point that the bearings are inadequately lubricated causing excessive bearing wear. 3.0 Motor Protection Inherent internal line break motor protection is provided. 4.0 Starting Characteristics The H25A single-phase compressor requires a PTCR start assist device when used on systems where the pressure equalizes in the off-cycle. If non-bleed expansion valves are used or other reasons exist that will not allow pressure equalization prior to compressor start-up, then a start capacitor and potential relay are required. PTCR is not required when start capacitor and relay are used. Medium and high torque start components are available for the H25A models. To determine the components needed for each application, start tests must be run at worst case conditions (lowest voltage, highest ambient and highest pressure differential) the unit is designed to operate. PTCR s and start components for each model are listed in Table 1. Page 2

3 The H26A/H27A single-phase compressors require either a PTCR or high torque start capacitor and relay. A PTCR can be used if only a light assist is needed, such as in systems where the pressure equalizes in the off-cycle. Start tests must be run at worst case condition (lowest voltage, highest ambient and highest pressure differential) the unit is designed to operate. If the compressor occasionally fails to start, a time delay should be installed on the condenser fan motor to reduce the discharge pressure after the compressor turns off. Start components for each model are listed in Tables 2 and 3 (see pages 7 and 8). 5.0 Excessive Continuous Liquid Floodback s The following tests are for the systems using compressors identified in Figure 1 of the Application Guidelines on page 5. These tests are used to determine if a system requires an accumulator. Two excessive liquid floodback tests are required on heat pumps. One for the heating mode and one for cooling. Air conditioners will require the cooling test. The test set up is the same for heat pumps and air conditioners. Before starting the test, thermocouples should be attached to the suction and discharge tubes approximately 10 to 12 inches from the compressor. A thermocouple should also be attached to the sump of the compressor (as close to bottom center as possible, all TCs must be insulated). The system charge for this test should be 20% greater than design specifications using a 25 foot line set. The 20% overcharge simulates commonly found overcharge in the field. The evaporator should be elevated 5 feet above the condensing unit. Should you have any questions, please call Bristol s Applications Engineering Department. 5.1 Heating Mode Excessive Continuous Liquid Floodback The defrost control must be disconnected to prevent unit from defrosting. Outdoor ambient must be 17 F DB, 15 F WB and indoor ambient 70 F DB, 60 F WB maximum. Outdoor unit fan motor must be disconnected. Run unit until pressures and temperatures are stabilized. See examples and Discharge superheat should not be less than 50 F. Examples: For R22 at 168 psig discharge, the saturated condensing temperature is 90 F Example No. 1: Assume actual discharge temperature of 140 F Discharge superheat = 140 F- 90 F = 50 F Therefore no system design change is required Example No. 2: Assume actual discharge temperature of 130 F Discharge superheat = 130 F - 90 F = 40 F Therefore system design change is required If temperature is less than 50 F, system design must be changed Sump temperature should be 30 F warmer than the saturated temperature equivalent of the suction pressure. Example: For R22 at 15 psig suction, the saturated evaporator temperature is -12 F Example No. 1: Assume actual sump temperature of 28 F D temperature = 28 F - (-12 F) = 40 F Therefore no system design change is required Page 3

4 Example No. 2: Assume actual sump temperature of 15 F D temperature = 15 F - (-12 F) = 27 F Therefore system design change is required If temperature is less than 30 F, system design must be changed. Note: Discharge superheat may run as low as 10 F (5.6 K) during start-up operation, as long as the temperature increases steadily and exceeds the minimum value before the compressor cycles off. The sump over saturated suction temperature should also be above the minimum value before cycling off. Extended operation is normally required to heat up the oil sump adequately, especially with low discharge superheat. 5.2 Cooling Mode Excessive Continuous Liquid Floodback Operate the system for 1 hour; outdoor unit must be in 95 F DB, 75 F WB ambient and indoor unit at 67 F DB, 57 F WB with evaporator air flow reduced 50% to simulate dirty air filter Discharge superheat should not be less than 50 F. Example: For R22 at 260 psig discharge, the saturated condensing temperature is 120 F Example No. 1: Assume actual discharge temperature of 170 F Discharge superheat = 170 F- 120 F = 50 F Therefore no system design change is required Example No. 2: Assume actual discharge temperature of 150 F Discharge superheat = 150 F F = 30 F Therefore system design change is required If temperature is less than 50 F, system design must be changed Sump temperature should be 50 F warmer than the saturated temperature equivalent of the suction pressure. Example: For R22 at 68 psig suction, the saturated evaporator temperature is 40 F Example No. 1: Assume actual sump temperature of 70 F D temperature = 70 F - 40 F = 30 F Therefore no system design change is required Example No. 2: Assume actual sump temperature of 65 F D temperature = 65 F - 40 F = 25 F Therefore system design change is required If temperature is less than 30 F, system design must be changed. Note: Discharge superheat may run as low as 10 F (5.6 K) during start-up operation, as long as the temperature increases steadily and exceeds the minimum value before the compressor cycles off. The sump over saturated suction temperature should also be above the minimum value before cycling off. Extended operation is normally required to heat up the oil sump adequately, especially with low discharge superheat. Page 4

5 6.0 Excessive Liquid Floodback Cycling This test is run to determine how much liquid actually gets into the compressor during system on/off cycles. To complete this test a sample compressor must be obtained with a sight tube to measure liquid level in the compressor or set the compressor on calibrated scales to measure pounds and ounces. Evaporator should be elevated 5 feet higher than the condensing unit. System charge for this test should be 20% greater than design specifications using a 25 foot line set. Operate the system in the cooling mode for 1 hour before testing at each of the ambient temperatures indicated in Table 4. Shut outdoor unit off (compressor and fan). Keep evaporator blower running. System on/off time and number of cycles is different for each of the 3 tests shown in Table 4. Observe and record the amount of liquid refrigerant (height or weight) at the start of each on cycle. If the compressor slugs or makes a metallic sound on start up, system design change is required. No. 1 No. 2 No. 3 Indoor Ambient ( F) Outdoor Ambient ( F) System On-time (Minutes) System Off-time (Minutes) Number of On/Off Table 4 Bristol Compressors "A" Series Inertia Application Guidelines Type System Heat Pump Air Conditioner Indoor Coil Refrigerant Metering Device Non-Bleed TXV Bleed Type TXV Capillary Tubes Fixed Orifices Non-Bleed TXV Bleed Type TXV Capillary Tubes Fixed Orifices Outdoor Coil Refrigerant Metering Device Non-Bleed TXV Bleed Type TXV Capillary Tubes Fixed Orifices Non-Bleed TXV Bleed Type TXV Capillary Tubes Fixed Orifices Excessive Continuous Liquid Floodback *Total System Charge (Lbs.) > 15 Lbs. < 15 Lbs. > 15 Lbs. < 15 Lbs. > 15 Lbs. < 15 Lbs. > 15 Lbs. < 15 Lbs. Excessive Liquid Floodback Cycling Not See Section 5.1 See Section 5.2 See Sections 5.1 and 5.2 Not See Section 5.2 *Total system charge includes the allowance for the tube size and length plus tolerance of charging equipment. Figure 1 Page 5

6 H25A Inertia Electrical Components Starting Components 60 Hertz Model Run Cap µfd/volts Standard PTCR Start Cap Medium Torque GE Relay 3ARR3*XX* White-Rodgers 128**6-**X*X* Start Cap High Torque GE Relay 3ARR22*XX* White-Rodgers 128**2-**X*X* H25A32QCBC 40/ C /250V *3L* 4*L* /330V *3S* 4*S* H25A35QCBC 40/ C /250V *3L* 4*L* /330V *3S* 4*S* H25A38QCBC 45/ C /250V *3L* 4*L* /330V *3S* 4*S* H25A42QCBC 45/ C /250V *3L* 4*L* /330V *3P* 4*P* H25A46QCBC 55/ C /250V *3L* 4*L* /330V *3P* 4*P* H25A50QCBC 55/ C /250V *3L* 4*L* /330V *3N* 4*N* H25A54QCBC 60/ C /250V *3L* 4*L* /330V *3N* 4*N* H25A56QCBC 60/ C /250V *3L* 4*L* /330V *3N* 4*N* H25A62QCBC 60/ C /250V *3L* 4*L* /330V *24R* 5*R* + Indicates style of mounting bracket and other options Table 1 Page 6

7 H26A Inertia Electrical Components Starting Components 60 Hertz Model Run Cap µfd/volts Standard PTCR Start Cap High Torque GE Relay 3ARR22*XX* White-Rodgers 128**2-**X*X* H26A32QCBC 40/ C /330V *3S* 4*S* H26A35QCBC 40/ C /330V *3S* 4*S* H26A38QCBC 45/ C /330V *3S* 4*S* H26A42QCBC 45/ C /330V *3P* 4*P* H26A46QCBC 55/ C /330V *3P* 4*P* H26A50QCBC 55/ C /330V *3N* 4*N* H26A54QCBC 60/ C /330V *3N* 4*N* H26A56QCBC 60/ C /330V *3N* 4*N* H26A62QCBC 60/ C /330V *24R* 5*R* + Indicates style of mounting bracket and other options Table 2 Page 7

8 H27A Inertia Electrical Components Starting Components 60 Hertz Model Run Cap µfd/volts Standard PTCR Start Cap High Torque GE Relay 3ARR3*XX* White-Rodgers 128**6-**X*X* H27A28QCBC 35/ C /330V *3U* 4*U* H27A32QCBC 40/ C /330V *3S* 4*S* H27A35QCBC 40/ C /330V *3S* 4*S* H27A38QCBC 45/ C /330V *3S* 4*S* H27A42QCBC 45/ C /330V *3P* 4*P* H27A46QCBC 55/ C /330V *3P* 4*P* H27A50QCBC 55/ C /330V *3N* 4*N* H27A54QCBC 60/ C /330V *3N* 4*N* H27A56QCBC 60/ C /330V *3N* 4*N* H27A62QCBC 60/ C /330V *24R* 5*R* + Indicates style of mounting bracket and other options Table 3 Page 8

9 7.0 Recommended PTCR Usage PTCR recommended by Bristol Compressors are in two classifications: standard starter and optional starter. a. Standard starters* can be used where the PTCR ambient does not exceed 115 F and/or the voltage does not drop below 197 volts (Table 5). b. Optional starter** should be used where the PTCR ambient exceeds 115 F and/or the voltage is or can be below 197 volts (Table 5). c. Cool down time between starts should be five minutes on each starter. Bristol Inertia Model Number Standard Starter* Cera-Mite P/N Optional Starter** Cera-Mite P/N H27A28QCBC 305C C19+/305C9/305C11 H25A/H26A/H27A32QCBC 305C C19+/305C9/305C11 H25A/H26A/H27A35QCBC 305C C19+/305C9/305C11 H25A/H26A/H27A38QCBC 305C C19+/305C9/305C11 H25A/H26A/H27A42QCBC 305C C19+/305C9/305C11 H25A/H26A/H27A46QCBC 305C9+ *** H25A/H26A/H27A50QCBC 305C C9+ H25A/H26A/H27A54QCBC 305C9+ *** H25A/H26A/H27A56QCBC 305C9+ *** H25A/H26A/H27A62QCBC 305C C9+ Table 5 +Suffix indicates style of mounting and other options (see Appendices 1, 2 and 3) *** Where no optional starter is available, a system time delay greater than five minutes can be evaluated before reverting to a start capacitor and relay (see electrical data sheet). Source for the PTCR 305 Series: Vishay Americas One Greenwich Place Shelton, CT USA Phone: (402) Business-Americas@Vishay.com Source for the GE Relays: General Electric Appliance Control Division West Wall Street Morrison, IL Phone: (815) MARS 250 Rabro Drive East Hauppauge, NY Phone: (800) Source for the White-Rodgers Relays: Manitowoc Relay & Protectors, Inc. 1429B Wentker Court P. O. Box 146 Two Rivers, WI Phone: (820) afond@lakefield.net Page 9

10 8.0 PTCR Start Assist Device The PTCR, or start thermistor, can be used on Bristol s H25A/H26A/H27A Inertia compressor. This bulletin is issued to inform users about how the PTCR operates and also to provide some guides for system design and troubleshooting. 8.1 How the PTCR Operates: Figure 2 Figure 3 These devices are intended to provide additional starting torque for permanent split capacitor type motor compressors by increasing the current in the auxiliary winding during starting. The devices are to be connected across the run capacitor (in series with the auxiliary or start winding, see Figure 2). When the devices are near room temperature, the resistance is low. Upon energization, the PTCR material rapidly (approximately in 1/2 second) heats up and the resistance increases to a value that permits only milliamperes of current to flow (see Figure 3). Essentially, the devices are selflimiting in current. Note that any wires in the control box should not touch the case of the PTCR since the PTCR case temperature may reach 200 F (93.3 C). Also, wiring used when connecting to the terminals of the PTCR should be rated 105 C. 8.2 PTCR Troubleshooting Step 1: Certain problems may lead to start failure in new, properly wired units. They include: a. Voltage measured at the compressor terminals during start-up is too low. b. Compressor discharge and suction pressures are not equalized. c. Improper thermostat location: If the indoor thermostat is incorrectly located, it may short cycle, meaning the thermostat may open and close the compressor contactor within a period of a few minutes. The unit should be off for approximately five minutes for the PTCR to cool sufficiently. d. Opening and closing the disconnect while servicing the unit: During installation and service, there are many reasons why a service technician may wish to restart a unit shortly after it was shut off. Again, units equipped with a PTCR must remain off for approximately five minutes. Page 10

11 8.2.2 Step 2: e. Control box temperature: Very high air temperatures (on a black roof for instance) and intense sunlight can increase the temperature of the control box and everything in it. These hotter temperatures may extend the time required for the PTCR to cool. If the compressor should short cycle before the PTCR is able to cool enough to start the compressor, the compressor may hum but not rotate (lock rotor). Eventually the compressor or system overload may open. If abnormal conditions occur that prevent the PTCR device from assisting the compressor in starting, the optional starter listed in Table I should be used in place of the standard starter. Measure the resistance: Remove the PTCR from the unit. Wait at least ten minutes for the PTCR to cool before measuring the resistance. Leave the jumper wire in place on 305C9 and 305C11 as shown in Appendix 1. The resistance of a cold PTCR measured with an ohmmeter should be as follows: 305C9 PTCR: Between 10 and 20 ohms 305C11 PTCR: Between 15 and 25 ohms 305C19 PTCR: Between 20 and 40 ohms 305C20 PTCR: Between 25 and 40 ohms Page 11

12 Appendix 1 Page 12

13 Appendix 2 Page 13

14 Appendix 3 Page 14

15 Release EN Number 006X04 Release Date 1/6/92 Revisions L /31/03 X /29/14 Z /2/15 Page 15