Carrier 25HBB Check Charge, Final Checks, Heating Check Chart Procedure, Care and Maintenance

25HBB

The electronic defrost timer sequence is enabled when the T1 input on the board is energized. The timer starts only when the defrost thermostat is closed and the contactor is energized.

Defrost mode is identical to cooling mode except that outdoor fan motor stops and second-stage heat is turned on to continue warming conditioned spaces.

To initiate defrost, the defrost thermostat must be closed. This can be accomplished as follows:

1.Turn off power to outdoor unit.

2.Disconnect outdoor fan motor lead from OF2 on control board, see Fig. 9. Tape lead to prevent grounding.

3.Restart unit in heating mode, allowing frost to accumulate on outdoor coil.

4.After a few minutes in heating mode, liquid line temperature should drop below closing point of defrost thermostat (approximately 30°F/-1.11°C).

5.Short between speedup terminals with a flat-blade screwdriver. This reduces the timing sequence to 1/256th of original time. (See Table 4.)

6.When you hear reversing valve change position, remove screwdriver immediately; otherwise, control will terminate normal 10-minute defrost cycle in approximately 2 seconds.

NOTE: Length of defrost cycle is dependent upon length of time it takes to remove screwdriver from test pins after reversing valve has shifted.

7.Unit will remain in defrost for remainder of defrost cycle time or until defrost thermostat reopens at approximately 65°F (18.33°C) coil temperature of liquid line.

8.Turn off power to outdoor unit and reconnect fan motor lead to OF2 on control board.

Check Charge

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.

T1 - ENABLES DEFROST

TIMER.MUST BE

ENERGIZED FOR

DEFROST TIMER TO START

C - COMMON

O - REVERSING VALVE

OUTDOOR FAN
RELAY
DEFROST THERMOSTAT	HK32EA001
MUST BE CLOSED BEFORE
DEFROST TIMER BEGINS
Y OUTPUT TO PRESSURE
SWITCHES AND CONTACTOR
SPEEDUP

Heating Check Chart Procedure

To check system operation during heating cycle, refer to the Heating Check Chart on outdoor unit. This chart indicates whether a correct relationship exists between system operating pressure and air temperature entering indoor and outdoor units. If pressure and temperature do not match on chart, system refrigerant charge may not be correct. Do not use chart to adjust refrigerant charge.

Final Checks

IMPORTANT: Before leaving job, be sure to do the following:

1.	Ensure that all wiring is routed away from tubing and sheet
	metal edges to prevent rub-through or wire pinching.
2.	Ensure that all wiring and tubing is secure in unit before
	adding panels and covers. Securely fasten all panels and
	covers.
3.	Tighten service valve stem caps to 1/12-turn past finger
	tight.
4.	Leave Owner’s Manual with owner. Explain system
	operation and periodic maintenance requirements outlined

THERMOSTAT INPUTS

			A05332
	Fig. 9 - Defrost Control
Table 3 – Defrost Control Speedup-Timing Sequence
PARAMETER	MINIMUM	MAXIMUM	SPEEDUP
	(MINUTES)	(MINUTES)	(NOMINAL)
30---minute cycle	27	33	7 sec
50---minute cycle	45	55	12 sec
90---minute cycle	81	99	21 sec
10---minute cycle	9	11	2 sec
5 minutes	4.5	5.5	1 sec

in manual.

5. Fill out Dealer Installation Checklist and place in customer

file.

CARE AND MAINTENANCE

For continuing high performance and to minimize possible equipment failure, periodic maintenance must be performed on this equipment.

Frequency of maintenance may vary depending upon geographic areas, such as coastal applications. See Users Manual for information.

6