York YCAJ44HE8, Инструкция по установке, эксплуатации и обслуживанию, Страница: 78 / 92

78 YORK INTERNATIONAL
FIG. 31 – PIPING DIAGRAM
LD02184
to water temperature. The regulating valve which be-
comes activated when the solenoid is energized, is con-
trolled by suction pressure to modulate the flow of gas in
a bypass connected from the compressor discharge to
the cooler inlet. The following text will explain how the
hot gas solenoid is activated by the microprocessor in
both return and in leaving water control.
LWT Control Hot Gas Operation
The hot gas solenoid is energized when the leaving water
temperature falls below the “Target” water temperature, if
the compressor is on its minimum stage of loading. Hot
gas may then be fed according to the suction pressure
and the pressure regulating valve setting. Once acti-
vated, the micro will keep the solenoid energized until
the leaving water temperature rises above the high limit
of the Control Range or until the load becomes so low
that the hot gas can no longer keep temperature within
the control range and the micro turns the compressor off.
Details for setting the pressure regulator follow.
RWT Control Hot Gas Operation
The hot gas solenoid is energized if the compressor is on
its minimum stage of loading and the return water tem-
perature falls below the following point:
ULCR - CR + CR/20
Where: UCLR = Upper Limit of Control Range
CR = Control Range Differential
Example: In a typical system that requires a 45°F
leaving water temperature, we will have a
10° control range (CR) differential which
gives us an Upper Limit of Control Range
(ULCR) of 55°F. Therefore, plugging the
numbers into the formula:
55 - 10 + (10/20) = 45-1/2°F
The hot gas solenoid will be activated at 45-1/2°F in the
example above and hot gas may then be fed according to
the suction pressure and the pressure regulated valve
setting. Once activated, the micro will keep the solenoid
energized until the return water temperature rises above
the temperature designated by the formula:
ULCR - CR + CR/10
Where: UCLR = Upper Limit of Control Range
CR = Control Range Differential
Example: 55 - 10 + 10/10 = 46° F
If temperature continues to drop while the Hot Gas is
energized, the Hot Gas will be de-energized when the
compressor cycles off on temperature.
Procedure For Setting The Hot Gas Regulator
(Ref. Fig. 31)
1. If desired, set the control panel data to show suction
pressure.
2. Adjust the pilot power assembly adjustment screw
2 to approximately the middle of its adjustment
range.
3. The chiller must be running and stabilized on the
minimum stage capacity. In establishing this condi-
tion, it may be necessary to deactivate the regulator
by de-energizing the solenoid 1 .
4. Adjust the adjustment screw 2 in the clockwise
direction to open the valve at a higher pressure
(sooner) or in the counterclockwise direction to open
the valve at a lower pressure (slower response). The
valve is feeding when the valve outlet feels warm to
the touch.
The adjustment is correct when system suction
pressure rises to a point nearly equal to normal run-
ning pressure at the midpoint in the “Control Zone”.
5. Further minor adjustment may be necessary to be
certain that the valve opens fully before the tempera-
ture point at which the compressor stops due to a
fall in Return or Leaving Water Temp.
6. Repeat this procedure on the other system.
NOTE: Hot gas should not be considered as an addi-
tional step of unloading when programming the
number of steps of loading/unloading.