Carrier 25VNA8 Instruction Manual download pdf (Page 9)

Follow these steps to properly start up the system:

1. After system is evacuated, close the disconnects to energize

the ID and OD units to access the user interface (UI), Keep

system in off mode. Under the Advanced function menu,

on the Infinity Touch Control, access the REQUIRED

CHARGE CALCULATION screen. Enter the lineset

length and vapor tube diameter. The user interface (UI)

will now display the required charge adjustment (see Fig.

10 for example) for the lineset and an adjustment for a large

indoor coil if recognized as such by the UI.

2. Add or remove the required charge adjustment for lineset

length to liquid service valve.

Note: If lineset is less than 15 feet (--9.4_C), charge re-

moval may be necessary.

3. Fully open liquid and vapor service valves.

A14019

Fig. 10 -- Required Charge Adjustment Calculated in UI

4. Set User Interface to operate cooling in CHARGING mode.

Charging mode operates system compressor speed and fan

speeds to proper conditions to check the refrigerant charge.

NOTE: See Step 13 for charging check.

5. Wait for the specified stabilization time, depending on line-

set length. Compare subcooling at liquid line service valve

to Liquid Line Subcooling Target as shown CHARGING

screen (LiqLin SC TGT) (see Fig. 11 for example).

A14020

Fig. 11 -- Liquid Line Subcooling Target

Step 11 — System Functions and Sequence of

Operation

The 25VNA8 mod els u tilize either Infinity Touch Communicating

User Interface (UI) or conventional HP thermostat. When using UI

controls, a call for cooling will energize the outdoor fan and

compressor to run at lowest cooling demand. If this does not satisfy

cooling demand, the system will ramp up in stages until it satisfies

the demand. After coping with the higher demand, the unit returns

to lower capacity operation until the demand is satisfied or until an

increase in demand. When using a conventional thermostat, the

thermostat controls the staging of outdoor unit.

When all demand is satisfied, the compressor will shut off. As the

unit operates at lower capacity, system vapor (suction) pressure will

be higher than it is during a standard single--stage system operation

or during a higher capacity operation.

The user interface (UI) displays the operation mode and fault codes

as specified in the troubleshooting section. See Table 7 for codes

and definitions.

The conventional thermostat inputs are designed to work with most

indoor units. See AHRI for approved combinations. Connections

are Y/Y2, Y1, O, R, W, and C. Depending on thermostat and

indoor unit, the system will operate at 1 or 2 capacities in heating

or cooling mode.

NOTE: Only one code will be displayed on the outdoor unit

control board (the most recent, with the highest priority). The

latest codes are stored and can be accessed via the UI.

Upon a call for cooling through the UI (or the Y1 and/or Y2

connections in a non --communicating system), the Application

Operation Control (AOC) board (see Fig. 19) will open the EXV to

the fully open position. For heating, the AOC board will open the

EXV to a preset position, depending upon the conditions. Based

upon the indoor space demand and the outdoor conditions, the UI

will then request a compressor speed and outdoor fan motor speed.

If the conditions are correct for operation, the control board will

allow the requested operation to begin, but if the control board

determines that the conditions are not correct, the board will decide

what other operation nearing that condition is acceptable. The

inverter Motor Operational Control (MOC) then outputs the

three--phase PWM signal and frequency that gently ramps the

compressor speed up to stage 2, and then will adjust to the

demanded speed. The gentle ramp --up results in no locked rotor

amps to the compressor motor. The unit 0 for compressor LRA will

be stamped N/A (not applicable).

During operation, the AOC monitors itself and the compressor

operation along with the system pressures and temperatures. The

MOC board monitors the temperature, current and operational

status of the compressor, OD fan and the inverter itself. During

operation, the compressor speed will be adjusted to meet the

changes to the demand.

When the demand is satisfied, the inverter will ramp--down the

compressor speed and stop. The EXV will step down to the

completely closed position.

When the compressor stops, a 3.5 minute Time Guard period is

activated which is followed by opening of the PEV valve for 150

seconds to equalize the refrigerant pressure difference between the

high and low sides of the compressor. Upon equalizing the

refrigerant pressure, and an additional 15 seconds of the Time

Guard period, the compressor will be ready for the next operational

demand.

If there is a power cycle, the Pressure Equalizer Valve (PEV) will

open for 150 seconds before the compressor start--up. Opening the

PEV valve returns the discharge gas directly back to the suction

side of the compressor. This is done in either cooling or heating

mode so that the rotary compressor will start with a very low

pressure differential.

The 3.5 minute Time Guard can be bypassed by momentarily

shorting the Forced Defrost pins. Only the 3.5 minute time delay

can be bypassed. Because it is important for compressor reliability,

the 150--second PEV delay cannot be bypassed.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 ... 21 22

Comments to this Manuals

No comments

Carrier 25VNA8 Instruction Manual Page 9

Comments to this Manuals

Related products and manuals for Heat pumps Carrier 25VNA8