Carrier 25HCD Instruction Manual download pdf (Page 7)

OUTDOOR FAN

RELAY

Y OUTPUT TO PRESSURE

SWITCHES AND CONTACTOR

THERMOSTAT INPUTS

T1 - ENABLES DEFROST

TIMER.MUST BE

ENERGIZED FOR

DEFROST TIMER

TO START

C - COMMON

O - REVERSING VALVE

SPEEDUP

HK32EA001

DEFROST THERMOSTAT

MUST BE CLOSED BEFORE

DEFROST TIMER BEGINS

A05332

Fig. 11 -- Defrost Control

Table 4 – Defrost Control Speedup–Timing Sequence

PARAMETER

MINIMUM

(MINUTES)

MAXIMUM

(MINUTES)

SPEEDUP

(NOMINAL)

30–minute cycle 27 33 7sec

50–minute cycle 45 55 12 sec

90–minute cycle 81 99 21 sec

10–minute cycle 9 11 2sec

5 minutes 4.5 5.5 1sec

Check Charge

Factory charge amount and desired subcooling are shown on unit

rating plate. Additional subcooling may be required to achieve

optimal heating performance based on the installed indoor unit.

(see Table 5 or 6).

Charging method is shown on information plate inside unit. For

TXV, use subcooling method. For piston, use superheat method.

To properly check or adjust charge, conditions must be favorable

for subcooling or superheat 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 (.018 kg/m) 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 super heat method for fixed

metering device and subcooling method for TXV. If any

adjustment is necessary, adjust charge slowly and allow system to

operate for 15 minutes to stabilize before declaring a properly

charged system. Refer to Table 5 or 6 for additional subcooling

required.

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 Residential Piping and Long

Line Guideline for special charging requirements.

Units with Cooling Mode TXV

Units installed with cooling mode TXV require charging by the

subcooling method.

1. Operate unit a minimum of 10 minutes before checking

charge.

2. Measure liquid service valve pressure by attaching an accur-

ate gage to service port.

3. Measure liquid line temperature by attaching an accurate

thermistor type or electronic thermometer to liquid line near

outdoor coil.

4. Refer to unit rating plate for required subcooling temperat-

ure.

5. Refer to Table 7. Find the point where required subcooling

temperature intersects measured liquid service valve pres-

sure.

6. To obtain required subcooling temperature at a specific li-

quid line pressure, add refrigerant if liquid line temperature

is higher than indicated or reclaim refrigerant if temperature

is lower. Allow a tolerance of 3_F.

25HBB / 25HBC / 25HCD

1 2 3 4 5 6 7 8 9 10 11 12

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Carrier 25HCD Instruction Manual Page 7

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