Bryant R-22 service manual Check Charge, Evacuation, Deep Vacuum Method

Evacuation

Proper evacuation of the system will remove non-condensibles and assure a tight, dry system before charging. The 2 methods used to evacuate a system are the deep vacuum method and the triple evacuation method.

Deep Vacuum Method

The deep vacuum method requires a vacuum pump capable of pulling a vacuum of 500 microns and a vacuum gauge capable of accurately measuring this vacuum depth. The deep vacuum method is the most positive way of assuring a system is free of air and moisture. (See Fig. 30.)

	5000
	4500
	4000						LEAK IN
	3500
MICRONS							SYSTEM
	3000
	2500
	2000
							VACUUM TIGHT
	1500
							TOO WET
	1000
							TIGHT
	500
							DRY SYSTEM
	0	1	2	3	4	5	6	7
				MINUTES
								A95424

Fig. 30 – Deep Vacuum Graph

Triple Evacuation Method

The triple evacuation method should be used when vacuum pump is only capable of pumping down to 28 in. of mercury vacuum and system does not contain any liquid water. Refer to Fig. 31 and proceed as follows:

1.Pump system down to 28 in. of mercury and allow pump to continue operating for an additional 15 minutes.

2.Close service valves and shut off vacuum pump.

3.Connect a nitrogen cylinder and regulator to system and open until system pressure is 2 psig.

4.Close service valve and allow system to stand for 1 hr. During this time, dry nitrogen will be able to diffuse throughout the system absorbing moisture.

5.Repeat this procedure as indicated in Fig. 31. System will then be free of any contaminants and water vapor.

EVACUATE

BREAK VACUUM WITH DRY NITROGEN

WAIT

EVACUATE

BREAK VACUUM WITH DRY NITROGEN

WAIT

EVACUATE

CHECK FOR TIGHT, DRY SYSTEM (IF IT HOLDS DEEP VACUUM)

CHARGE SYSTEM

A95425

Fig. 31 – Triple Evacuation Method

CHECK CHARGE

(See Charging Tables 11 & 13)

Factory charge amount and desired subcooling are shown on unit rating plate. Charging method is shown on information plate inside unit. To properly check or adjust charge, conditions must be favorable for subcooling charging. Favorable conditions exist when the outdoor temperature is between 70_F and 100_F (21.11_C and 37.78_C), and the indoor temperature is between 70_F and 80_F (21.11_C and 26.67_C). Follow the procedure below:

Unit is factory charged for 15ft (4.57 m) of lineset. Adjust charge by adding or removing 0.6 oz/ft of 3/8 liquid line above or below 15ft (4.57 m) respectively.

For standard refrigerant line lengths (80 ft/24.38 m or less), allow system to operate in cooling mode at least 15 minutes. If conditions are favorable, check system charge by subcooling method. If any adjustment is necessary, adjust charge slowly and allow system to operate for 15 minutes to stabilize before declaring a properly charged system.

If the indoor temperature is above 80_F (26.67_C), and the outdoor temperature is in the favorable range, adjust system charge by weight based on line length and allow the indoor temperature to drop to 80_F (26.67_C) before attempting to check system charge by subcooling method as described above.

If the indoor temperature is below 70_F (21.11_C), or the outdoor temperature is not in the favorable range, adjust charge for line set length above or below 15ft (4.57 m) only. Charge level should then be appropriate for the system to achieve rated capacity. The charge level could then be checked at another time when the both indoor and outdoor temperatures are in a more favorable range.

NOTE: If line length is beyond 80 ft (24.38 m) or greater than 20 ft (6.10 m) vertical separation, See Long Line Guideline for special charging requirements.

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