Carrier 30HH - Manual (Page 24)

30HH,HJ
INSTALLATION
Carrier
Two eight ampere fuses protect the control cir­
cuit against overload. The control light will be
on
whenever the control circuit is energized.
Disengage the fuse caps to remove blown fuses.
The "X" values (Table 10) were established by
experimentation and are such that the compres­
sor is prevented from cycling more than once
in a five minute period.
Fig. 28 - Gauge Panel (30HH,HJ045)
The throttling range is determined as follows;
Throttling Range (modulating) =
Design Rise + "X”
The throttling range setting is arrived at by
entering the graph below at the "set point” and
moving across an amount equal to the throttling
range. The setting is read from the top scale
and will fall somewhere between min. - F. To
illustrate, with a 30HH065 Chiller, a 4-compres­
sor unit, at a 10 F design rise, 45 F leaving
chilled
water temperature, the set point would
be 45 - 1 = 44 F. The throttling range would be
10 + 1 = F.
Entering the graph at 44 F and moving across
11
F indicates a throttling range setting of just
under "A”.
Table 10 - ”X” Values, F
WATER REGULATING VALVE
The water regulating valve should be set to
maintain the most economical head pressure as
determined by the design engineer, based on the
relative cost of water and electricity in a given
area. It should not be adjusted to compensate
for high head pressures caused by fouled con­
denser
tubes, excess refrigerant or the pres­
ence of noncondensables. Due to changes in
water temperatures, it may be necessary to
adjust the valve seasonally. After adjusting for
the economical head pressure, the machine
should be shut down. The water regulating valve
should shut off the flow of water in a few min­
utes. If it does not, it will be necessary to
raise the head pressure setting. The water reg­
ulating
valve is used for city water and in
some cases with multiple units on a single
cooling tower.
TEMPERATURE CONTROLLER ADJUSTMENT
The chilled water temperature controller must
be adjusted in the field before initial startup.
Two adjustments are required - Set Point (main
scale, 15 - 90 F) and Throttling Range (modu­
lating, min - F).
The set point is determined as follows ;
Set Point = Design Leaving Chilled Water
Temperature - ”X”
Design Rise F
No. of Comp. 8 10 12
1 2.0 2.5 3.0
2 2.0 2.5 3.0
3 1.25 1.5 1.75
4 .75 1.0 1.25
S E T P O I N T
A D J U S T M E N T S C R E W
T H R O T T L I N G R A N G E ( M O D U L A T I N G )
^ A D J U S T M E N T S C R E W
T H R O T T L I N G
R A N G E
S C A L E
Fig. 29 - Chilled Water Temperature
Controller
24