Carrier 69NT20-531-300 manual Refrigerant Leak Checking

gauge. If a vacuum is indicated, emit refrigerant by cracking the liquid line valve momentarily to build up a slight positive pressure.

g.When opening up the refrigerant system, certain parts may frost. Allow the part to warm to ambient temper- ature before dismantling. This avoids internal con- densation which puts moisture in the system.

h.After repairs have been made, be sure to perform a refrigerant leak check (refer to paragraph 6.5), and evacuate and dehydrate the low side (refer to para- graph 6.6).

i.Check refrigerant charge (refer to paragraph 6.7).

6.5 REFRIGERANT LEAK CHECKING

WARNING

Never use air for leak testing. It has been determined that pressurized, air-rich mix- tures of refrigerants and air can undergo combustion when exposed to an ignition source.

a. The recommended procedure for finding leaks in a system is with a R-134a electronic leak detector. Test- ing joints with soapsuds is satisfactory only for locat- ing large leaks.

6.6 EVACUATION AND DEHYDRATION 6.6.1 General

Moisture is the deadly enemy of refrigeration systems. The presence of moisture in a refrigeration system can have many undesirable effects. The most common are copper plating, acid sludge formation, “freezing-up” of metering devices by free water, and formation of acids, resulting in metal corrosion.

6.6.2 Preparation

a.Evacuate and dehydrate only after pressure leak test. (Refer to paragraph 6.5.)

b.Essential tools to properly evacuate and dehydrate any system include a vacuum pump (8 m3/hr = 5 cfm volume displacement) and an electronic vacuum gauge. (The pump is available from Carrier Trans- icold, P/N 07-00176-11.)

c.If possible, keep the ambient temperature above 15.6_C (60_F) to speed evaporation of moisture. If the ambient temperature is lower than 15.6_C (60_F), ice might form before moisture removal is complete. Heat lamps or alternate sources of heat may be used to raise the system temperature.

d.Additional time may be saved during a complete sys- tem pump down by replaceing the filter-drier with a section of copper tubing and the appropriate fittings. Installation of a new drier may be performed during the charging procedure.

b. If the system is without refrigerant, charge the system with refrigerant 134a to build up pressure between

2.1to 3.5 kg/cm@ (30 to 50 psig). To ensure complete pressurization of the system, refrigerant should be charged at the compressor suction and economizer service valves and the liquid line service valve. Also, the area between the suction modulating valve and evaporator expansion valve may not be open to these charging points. Pressure between these components may be checked at the low side access valve (item 11, Figure 2-2) or by checking that the suction modulat- ing valve is more than 10% open at controller func- tion code Cd01. The suction modulating valve may be opened by use of the controller function code Cd41 valve override control (refer to paragraph 6.19). Re- move refrigerant cylinder and leak-check all connec- tions.

NOTE

Only refrigerant 134a should be used to pres- surize the system. Any other gas or vapor will contaminate the system, which will require additional purging and evacuation of the sys- tem.

c. If required, remove refrigerant using a refrigerant recovery system and repair any leaks.

d. Evacuate and dehydrate the unit. (Refer to paragraph 6.6.)

e. Charge unit per paragraph 6.7.

6-3

1	2	3
		4
		5
		6
		S D
	11
	9
	10	7
		8

1.	Liquid Service Valve	6.	Suction Service Valve
2.	Receiver or Water	7.	Vacuum Pump
	Cooled Condenser	8.	Electronic Vacuum
3.	Compressor		Gauge
4.	Discharge Service	9.	Manifold Gauge Set
	Valve	10.	Refrigerant Cylinder
5.	Economizer Service	11.	Reclaimer
	Valve

Figure 6-5. Refrigeration System Service

Connections

6.6.3 Procedure - Complete system

T-309