H29A Series Compressor Applications. Application Bulletin 139

Transcription

1 H29A Series Compressor Applications Application Bulletin 139

2 Application Bulletin Subject: H29A Series Compressor Applications Number: 139 Release EN: J28319 Date: 4/26/02 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 H29A compressors are among the most advanced reciprocating compressors in the industry today. Mechanical design and gas management make the H29A compressors very efficient and quiet. The following guidelines were developed for the H29A compressors through actual system testing as well as laboratory testing. 1.0 Crankcase Heat A crankcase heater is not required on systems when the total system charge is below the compressor charge limitation. 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. Refer to Application Bulletin 135, Crankcase Heaters. Compressors 50,000 BTU and higher should use 40-watt crankcase heaters. 2.0 Accumulators Heat pump systems require an accumulator and all other systems should be tested to see if accumulators will be required to limit liquid refrigerant returning to the compressor (for suggested testing, see Application Bulletin 101, section 4 on Suction Line Accumulators). Systems with a total charge below the compressor charge limitation normally will not require an accumulator. A double-sided see-through sight glass installed in the suction line of the compressor during all tests will assist the system designer in making this decision. 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 H29A single-phase compressor employs the highest efficiency motor available today. Because of this ultimate efficiency, the compressor will always need some method of start assist. A PTCR start assist device may be 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 Page 2

3 start capacitor and potential relay are required. The PTCR device is not required when a start capacitor and relay are used. High torque start components are available for the H29A 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 Excessive Continuous Liquid Floodback Tests The following tests are for all systems including those designed with an accumulator. These tests are used to determine if the system needs design changes. Bristol testing has indicated that adding an accumulator as the only solution to excessive flooding, in most cases, is inadequate. 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 Test 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 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. If temperature is less than 50 F, system design must be changed. Page 3

4 5.1.2 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 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. 5.2 Cooling Mode Excessive Continuous Liquid Floodback Test 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. Page 4

5 6.0 Excessive Liquid Floodback Cycling Test 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 1. 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 1. 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. Test 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 1 Page 5

6 60 Hertz H29A Electrical Components Model Run Cap µfd/ volts Required Standard PTCR Start Cap High Torque GE Relay 3ARR3*XX* H29A353CBC 40/ C /330 3ARR22*3S* H29A383CBC 45/ C /330 3ARR22*3S* H29A423CBC 45/ C /330 3ARR22*3P* H29A443CBC 45/ C /330 3ARR22*3P* H29A473CBC 55/ C /330 3ARR22*3N* H29A503CBC 55/ C /330 3ARR22*3N* H29A543CBC 60/ C /330 3ARR22*3N* H29A583CBC 60/ C /330 3ARR22*24R* H29A623CBC 60/ C /330 3ARR22*24R* White- Rodgers 128**6-**X*X* 4*S* 4*S* 4*P* 4*P* 4*N* 4*N* 4*N* 5*R* 5*R* Table 2 Source for the PTCR 305 Series: Ceramite Corporation th Avenue Grafton, WI Phone: (414) Fax: (414) Source for the GE Relays: General Electric Appliance Control Division West Wall Street Morrison, IL Phone: (815) Source for the White-Rodgers Relays: White-Rodgers Division Emerson Electric Company 9797 Reavis Road St. Louis, MO Phone: (314) Indicates style of mounting bracket and other options Page 6

7 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 3). 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 3). c. Cool down time between starts should be five minutes on each starter. Bristol H29A Model Number Table 3 Standard Starter* Cera-Mite P/N +Suffix indicates style of mounting and other options (see Appendices 1, 2 and 3) Optional Starter** Cera-Mite P/N H29A353CBC 305C C19+/305C9/305C11 H29A383CBC 305C C19+/305C9/305C11 H29A423CBC 305C C9+/305C11 H29A443CBC 305C C9+/305C11 H29A473CBC 305C C9+/305C11 H29A503CBC 305C C9+/305C11 H29A543CBC 305C9+ *** H29A583CBC 305C C9+/305C11 H29A623CBC 305C C9+/305C11 *** 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: Ceramite Corporation th Avenue P. O. Box 166 Grafton, WI Phone: (414) Fax: (414) Page 7

8 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 1 Figure 2 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 1). 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 2). 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 8

9 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 3 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 9

10 Appendix 1 Page 10

11 Appendix 2 Page 11

12 Appendix 3 Page 12

13 Release EN Number J28319 Release Date 4/26/02 Revisions L /31/03 X /29/14 Page 13