CeilAir CW series Manuale dell'Operatore Scaricare il pdf (Pagina 34)

(©July, 2008)

CeilAiR OHS Series Installation, Operation & Maintenance Manual

ir Technology Systems, Inc.

2-23

This method of controlling head pressure allows the

condenser fan to run continuously. While the fan is

running, the flooded head pressure control valve

modulates the amount of discharge gas entering the

receiver. As the pressure increases, the valve diverts

more discharge gas to the condenser, allowing more

liquid to flow from the condenser to the receiver.

When using this method of head pressure regulation

there must be enough refrigerant in the system to

ensure adequate charge at the lowest expected

ambient temperature in which the system will be

operating. A receiver is used to store the extra

refrigerant when the condenser is not using it.

NOTE

Systems utilizing air cooled condensers must

not have a refrigerant line pressure drop greater

than 14 psig across the condenser and the in-

terconnecting piping to the condenser sections.

2.9.2.6 Flooded Head Pressure Control

(Condenser Model HES-CAA ,- 30°F)

Used for indoor installations where ambient condenser

air inlet temperatures may fall to -30°F. First, familiar-

ize yourself with Flooded Head Pressure Control as

discussed in Section 2.8.4.5. Instead of cycling the

fan on and off, the condenser fan speed is continuous.

The head pressure control valve diverts discharge gas

to the receiver causing liquid to back up in the

condenser, as described in Section 2.8.4.5, while the

fan continues to run.

2.9.3 Head Pressure Controls-

Water/Glycol Cooled Systems

In a water/glycol condenser, condensing temperature

is maintained by the liquid flowing through a regulating

valve and then into a liquid-cooled condenser. The

regulating valve opens to increase the liquid flow as

the refrigerant pressure rises (or closes as the

refrigerant pressure falls). The regulating valve is

factory set for the correct condensing temperature,

however, it can be adjusted to increase or decrease

the condensing temperature.

Head pressure regulating valves are available in 2-way

or 3-way configurations. Refer to the piping diagram to

determine which type of valve is provided. The location

and size of regulating valves varies with the size and

model of the A/C unit. Methods for adjusting the

valves for condensing pressure differ with the valve

types which can be differentiated by the maximum

water pressure rating of the valve, (150, 350, or 450

psig).

2.9.3.1 150 PSIG Pressure Valves

Adjustment is made by turning the slotted square

stem on top of the valve clockwise to increase the

condensing temperature or decrease water/glycol flow

and counterclockwise to decrease the condensing

temperature or increase the water/glycol flow. A

directional arrow is stamped on the metal housing of

the valve stem.

2.9.3.2 350 PSIG and 450 PSIG High

Pressure Valves

Adjustment is made by turning the round-holed knob

counterclockwise inside the valve's metal housing to

increase condensing pressure or decrease water/

glycol flow and clockwise to decrease the condensing

temperature or increase the water/glycol flow. A

directional arrow is stamped on the metal housing of

the valve stem.

2.9.4 Humidifier Adjustment

The humidifier has a capacity adjustment potentiom-

eter on the humidifier control circuit board. The

capacity potentiometer may need to be field adjusted if

the humidifier does not supply enough capacity for the

current room conditions.

CAUTION

Adjusting the capacity pot too high may result

in condensation within the system.

It is recommended that if the capacity potentiometer

requires adjustment, the adjustment is made in small

increments and verified. Refer to the humidifier manual

sent with your unit for the location of the capacity

potentiometer.

2.9.5 Belt Drive Blower (See Figure 13)

Systems with belt drive blowers are supplied with

adjustable sheaves to change the blower speed and

adjustable motor bases for belt tensioning. Follow the

following procedure to change the blower speed.

1. Turn system off.

2. Turn off all power to unit at non-fused service

switch, use lock-out tag-out procedure.

3. Remove the blower belt(s).

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CeilAir CW series Manuale dell'Operatore Pagina 34

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