Carrier 040-420 User Manual
Page 41
Temperature Reset Based on External Temperature If de-
sired, temperature reset can be based on an external tem-
perature, such as space or outdoor-air temperature. This re-
quires a thermistor
Part No.
located in
the space or outdoor air and wired to terminals as follows
(also see Field Wiring section on page 71):
4 in/4
out
Module
and
At the field configuration step, select external tempera-
ture reset by entering
q
when CRTYP 0 appears. Then
enter set points as described previously in Example 5. See
Fig. 5.
Temperature Reset Based on 4-20
Signal- If desired,
temperature reset can be based on a 4-20
signal. For
proper connections, refer to Field Wiring section on page
71 and Fig. 6.
At the field configuration step, select 4-20
reset by
entering
q
when CRTYP 0 appears. Then enter set points
as described previously in Example 5. See Fig.
Demand Limit, 2-Stage Switch Control This control has
been designed to accept demand limit signals from a build-
ing load shedding control. The demand limit function pro-
vides for 2 capacity steps. The keypad is used to set the 2
demand limit set points, which range from 100 to 0% of
capacity. Capacity steps are controlled by 2 field-supplied
relay contacts connected to the designated chiller terminals.
(See Field Wiring section on page 7 1 and Fig. 6.)
Example 6
Changing Reset Type
To change type of reset, first log on as shown in
Table 11. Also refer to Set Point Function section, page 39,
for information on entering reset set points using reset
feature.
KEYPAD
DISPLAY
ENTRY
RESPONSE
COMMENTS
FLD CFG
C S P T Y P 0
CRTYP 0
CRTYP 1
CRTYP 2
CRTYP 3
F i e l d c o n f i g u r a t i o n
s u b f u n c t i o n o f
s e r v i c e f u n c t i o n
S c r o l l p a s t s i n g l e c o o l i n g
set point
No reset has been
s e l e c t e d
Return water temperature
reset is selected and
activated
Reset type is changed to
space or outdoor-air
temperature reset and
activated
Reset type is changed to
4-20
signal reset
and activated
CRTYP 0
Reset is deactivated
RESET REFERENCE
TEMP
ERATUR
E
AIR
OR
Fig. 5
Cooling External Temperature Reset
4 1