CeilAir CW series Manuale dell'Operatore Scaricare il pdf (Pagina 31)

(©July, 2008)

CeilAiR OHS Series Installation, Operation & Maintenance Manual

ir Technology Systems, Inc.

2-20

ture-measuring device being well insulated. The

sub-cooling temperature should be approximately

10-20ºF.

NOTE

Under cold climate conditions it is recommended to do

the following:

6. Block off the intake air to the condenser with

cardboard (or reduce the water glycol flow) until a

constant discharge pressure (225-280 psig) can

be obtained. This will lower the possibility of

overcharging and avoid the occasional bubbles

that may appear in the sight glass during fan

cycling. (For units with fan cycling only.)

7. If the unit has a hot gas reheat option, the previous

steps are still followed except the hot gas reheat

valve must be opened to allow refrigerant to flow

into the reheat coil to obtain the proper amount of

unit charge. This process may need to be re-

peated several times, which can be done by

enabling a call for dehumidification. After cycling

the system through the hot gas reheat cycle,

recheck the system charge in the

COOLING-ONLY mode.

8. Ensure the crankcase heater is operational by

checking the amperage.

CAUTION

Remove the blockage to the air intake of the con-

denser (or restore the water/glycol flow).

9. Fill out applicable blocks of Warranty Registration

and Start-Up Checklist.

2.8.1.2.2 -30ºF Flooded Head Pressure Control

The following instructions are for charging systems with

flooded head pressure control using R-22 refrigerant.

1. Bleed air from hoses and "break" the system

vacuum by supplying R22 liquid to the service valve

of the receiver until the receiver is full. Then supply

R22 vapor to the suction port until the pressure is

raised to about 50 psig (low pressure switch

makes).

2. Refrerring to Section 3.0, start the system and

use the microprocessor controller to lower the

temperature set-point 3-5°F below room tempera-

ture. This will ensure cooling remains on during

charging procedure.

CAUTION

An adequate heat load must be supplied to the unit to

ensure a proper charge.

3. After starting the system, immediately supply

R22 vapor to the suction port until the liquid line

sight glass is clear of all bubbles.

4. Raise the discharge pressure to 300-325 psig and

hold it constant by blocking the air intake of the

condenser.

5. Once the discharge pressure has stabilized for 5 to

10 minutes, additional refrigerant R22 vapor must

be added to the suction port until the "float ball" in

the level indicator of the receiver begins to float.

CAUTION

Remove the blockage to the air intake of the con-

denser.

6. Take a superheat reading near the feeler bulb from

the thermal expansion valve. The ideal superheat

temperature is 12-15°F. The maximum allowable

superheat temperature is 20°F.

7. Ensure the crankcase heater is operational by

checking the amperage.

8. Fill out applicable blocks of Warranty Registration

and Start-Up Checklist.

2.8.2 R407C Refrigerant Charging

Procedures

R407C is a blended refrigerant recognized for being

safer for the environment. Refrigerants that are multi-

component blends have component parts with different

volatilities that result in a change in composition and

saturation temperature as evaporation and condensa-

tion occur. Typically, the composition of R407C vapor

is different than that of R407C liquid within a con-

tained system. The composition of liquid R407C

refrigerant remains relatively constant, however, the

refrigerant vapor tends to separate into its component

parts even when circulating. When charging a system

using blended refrigerants, it is essential that the

composition of the refrigerant is maintained. To

ensure correct composition, introduce R407C into the

system in liquid form rather than vapor form. Cylinders

which are not provided with dip tubes should be

inverted to allow only liquid refrigerant to charge the

system. Keeping the temperature of the cylinder

below 85°F will help to maintain the correct refrigerant

composition while the cylinder is emptied.

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CeilAir CW series Manuale dell'Operatore Pagina 31

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