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Note: Systems utilizing air cooled condensers must not
have a refrigerant line pressure drop greater than
14 psig across the condenser and the
interconnecting piping to the condenser sections.
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, familiarize
yourself with Flooded Head Pressure Control in Section
"Flooded Head Pressure Control," p.
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
Pressure Control," p. 32
section, while the fan continues to
run.
Head Pressure Controls-Water/Glycol Cooled
Systems
In a water/glycol-cooled 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 and 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 deter-
mine 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).
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 counter
clock- wise to decrease the condensing temperature or
increase the water/glycol flow. A directional arrow is
stamped on the metal housing of the valve stem.
350 psig and 450 psig High Pressure Valves
Adjustment is made by turning the round-holed knob
counter-clockwise 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.
Humidifier Adjustment
The humidifier has a capacity adjustment potentiometer
on the humidifier control circuit board. The capacity
AH-SVX008C-EN
potentiometer may need to be field adjusted if the
humidifier does not supply enough capacity for the current
room conditions.
It is recommended that if the capacity potentiometer
requires adjustment, the adjustment is made and verified
in small increments. Refer to the humidifier manual sent
with your unit for the location of the capacity
potentiometer.
32.
"Flooded Head
Blower Adjustment
Belt Drive Blower
Figure 23. Belt drive blower
Systems with belt drive blowers (see
sup- plied with adjustable sheaves to change the blower
speed and adjustable motor bases for belt tensioning.
Perform the following procedure to change the blower
speed.
1. Turn the system off.
2. Turn off all power to the unit at the non-fused service
3. Remove the blower belt(s).
4. Loosen the set screw in the side of the sheave with an
5. Remove the sheave key.
6. Adjust the blower speed by closing the sheave one half
7. Replace the sheave key and tighten the set screw.
8. Proper belt tension is achieved when the belt has a
NOTICE
Equipment Damage!
Failure to follow instructions could result in equipment
damage.
Do not adjust the capacity potentiometer too high as it
could cause the formation of condensation within the
system which could result in shorts and corrosion.
MOTOR BASE
TENSION NUT
BLOWER
switch; use a lock-out/tag-out procedure.
Allen wrench.
turn to increase speed or opening the sheave one half
turn to decrease speed.
deflection of 1/2 in. per foot of span between the
Installation
LOCKNUT
MOTOR
NAMEPLATE
VARIABLE OR
ADJUSTABLE
PULLY
MOTOR BASE
BELT
FIXED PULLEY
Figure 23, p.
33) are
33
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