Carrier 30HW018-040, 060 Service, Capacity Control Steps Ð 30HW Standard Units, Steps Cylinders

Table 11 Ð Capacity Control Steps Ð

30HW Standard Units

UNIT	CAPACITY CONTROL	CAPACITY	OPERATING
30HW	STEPS*	%	CYLINDERS
018	1	33.3	2
	2	66.7	4
	3	100.0	6
025	1	50.0	2
	2	100.0	4
028	1	33.3	2
	2	66.7	4
	3	100.0	6
035	1	33.3	2
	2	66.7	4
	3	100.0	6
040	1	33.3	2
	2	66.7	4
	3	100.0	6

*Factory-installed hot gas bypass option adds an additional capacity step to that shown in this table.

SERVICE

ELECTRIC SHOCK HAZARD

To avoid the possibility of electrical shock, turn off all power to unit before servicing.

Do not attempt to bypass, short-out, or modify the con- trol circuit or electronic boards in any way to correct a problem. This could result in component failures or a hazardous operating condition.

Compressor Replacement Ð If a replacement 6-cylinder compressor has a center-bank cylinder head with discharge valve pad facing the pump end, remove head and install reverse ¯ange head from original compressor (dis- charge valve pad toward the motor end). Center-bank cyl- inder head cannot be rotated 180 degrees.

Be sure all the hardware from the old compressor is removed and installed on the new compressor, including the high-pressure switch snubber, the discharge gas thermo- stat (30HW025-040), the oil pressure safety switch (if equipped), and the low-pressure switch.

The compressor can be removed from either the front or the sides of the unit, depending on where clearance space was allowed during unit installation. The compressor and mount- ing hardware are mounted on a plate which is screwed down to the unit basepan. Remove the 4 screws holding the plate to the basepan and the plate should easily slide out of the unit. Mount the replacement compressor to the plate, slide the plate back into the unit and secure with the 4 screws.

Circuit Breaker(s) Ð The breaker(s) provides 3-leg over- load protection. Do not bypass connections or increase the size of the circuit breaker(s) to correct trouble. Determine the cause of the trouble and correct it before resetting the breaker(s). A tripped breaker must be manually reset by mov- ing the circuit breaker handle to OFF, then ON position. See Tables 4A and 4B for must-trip amps (MTA).

NOTE: One circuit breaker is provided per compressor.

Brazed-Plate Cooler and Condenser Heat Ex- changer Replacement Ð Brazed-plate heat exchang- ers cannot be repaired if they develop a leak. If a leak (re- frigerant or water) develops, the heat exchanger must be replaced. To replace a brazed plate heat exchanger:

1.Disconnect the liquid-in and liquid-out connections at the heat exchanger.

2.Check that the replacement heat exchanger is the same as the original heat exchanger. For the condensers, compare part numbers on the heat exchangers. For the coolers, in- sulation covers the manufacturer's part number. Make sure the depths of the replacement and original cooler heat ex- changers are the same.

3.Reclaim the refrigerant from the system, and unsolder the refrigerant-in and refrigerant-out connections.

4.Remove the four 1¤2-in. nuts holding the heat exchanger to the brackets. Save the nuts.

5.Install the replacement heat exchanger in the unit and attach to the bracket using the four 1¤2-in. nuts removed in Step 4.

6.Carefully braze the refrigerant lines to the connections on the heat exchanger. Lines should be soldered using silver as the soldering material with a minimum of 45% silver. Keep the temperature below 1472 F (800 C) under nor- mal soldering conditions (no vacuum) to prevent the cop- per solder of the brazed plate heat exchanger from changing its structure. Failure to do so can result in internal or external leakage at the connections which cannot be repaired.

7.Reconnect the water/brine lines.

8.Dehydrate and recharge the unit. Check for leaks.

Brazed-Plate Cooler and Condenser Heat Ex- changer Cleaning Ð Brazed-plate heat exchangers must be cleaned chemically. A professional cleaning service skilled in chemical cleaning should be used. Use a weak acid (5% phosphoric acid, or if the heat exchanger is cleaned fre- quently, 5% oxalic acid). Pump the cleaning solution through the exchanger, preferably in a back¯ush mode. After clean- ing, rinse with large amounts of fresh water to dispose of all the acid. Cleaning materials must be disposed of properly.

The mesh screens in front of the water/brine inlets of the heat exchangers should be cleaned periodically, depending on condition of the chiller water/brine.

Shell-and-Tube Condenser Cleaning Ð The shell- and-tube condenser tubes can be cleaned either mechani- cally or chemically. To clean them chemically, follow the procedure described in Brazed-Plate Cooler and Condenser Heat Exchanger Cleaning section above.

To clean the condenser tubes manually:

1.Order tubing brushes (Carrier part no. KC21AH105).

2.Close the valves on the condenser and relieve condenser water pressure. BE SURE TO PROVIDE DRAINAGE TO PREVENT WATER DAMAGE.

3.Remove the condenser heads and brush the tubes clean, removing scale and other deposits.

4.Inspect the head gaskets and replace if necessary.

5.Clean all gasket surfaces prior to reassembly.

6.Replace the water heads and torque the head bolts to 90 ft-lb (122 N-m). Allow the gaskets to set overnight and re-torque the bolts to ensure proper sealing.

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