40
YORK INTERNATIONAL
nored and the chiller will start-up when water tempera-
ture allows, unit switch permits, and system switches
permit.
Normally this key is not used unless an emergency
forces the chiller to require operation during a period
where the programmed Daily Schedule is calling for the
chiller to be OFF (Daily Schedule Shutdown).
Once activated, MANUAL OVERRIDE is only active for a
period of 30 minutes. It is for servicing only and is de-
signed so that if let on accidentally, the microprocessor
will automatically return to the Daily Schedule.
SELECTION OF RETURN OR LEAVING CHILLED LIQUID CONTROL
GENERAL
The user has the ability to select the type of chilled liquid
temperature control by choosing either Return or Leaving
Temperature Control. This provides the ability to fine tune
the method of control for comfort cooling or batch/pro-
cess cooling loads.
In many cases, comfort cooling will be best controlled by
RETURN WATER CONTROL. This will assure a mini-
mum of cycling compressors/loaders with stable leaving
chilled liquid temperatures as long as water flow GPM is
held constant and the Control Range (CR) is correctly
programmed.
LEAVING WATER CONTROL is also suitable for com-
fort cooling, but may produce slightly more cycling de-
pending upon the RATE SENSITIVITY programmed. Op-
tional stages of loading are recommended to reduce cy-
cling. In most cases, Leaving Water Control will be more
precise unless compressor cycling is encountered. An-
ticipation and timers are built into the microprocessors
control algorithms to eliminate compressor and loader
cycling enabling LEAVING WATER CONTROL to be
used in most applications. The control algorithm utilizes
PID control.
For batch and process applications, LEAVING WATER
CONTROL will allow for precise temperature control. In
these applications chilled liquid temperature control is
more important than compressor/loader cycling. When
LEAVING WATER CONTROL is utilized, it is recom-
mended to have optional steps of loading on each com-
pressor. This assures minimum tonnage per step which
reduces the possibility of compressor and loader cycling
that is critical to precisely controlling temperature.
MANUAL
OVERRIDE
M A N U A L
O V E R R I D E
RETURN WATER CONTROL may also be used on
batch and process application and should provide ad-
equate control. However, it will prove to be less respon-
sive with slightly more leaving chilled liquid temperature
variation. RETURN WATER CONTROL may become
necessary to use if too much compressor cycling is
noted with corresponding water temperature fluctuation
when in Leaving Water Control.
After determining the mode of control best suited for the
application (RETURN OR LEAVING WATER CON-
TROL), the micro panel must be interrogated to deter-
mine whether it is programmed for RETURN or LEAVING
WATER CONTROL. This can be accomplished by
pressing the OPTION key in the DISPLAY section of the
keypad. This allows the user to determine the present
mode of control without gaining access to the Micropro-
cessor Board and visually checking the sometimes diffi-
cult to determine Dip Switch position. When the OPTION
key is pressed, a message
“THE FOLLOWING ARE
PROGRAMMED”
will appear on the display for 3 sec-
onds. The display will then scroll through the 8 dip switch
selections, each appearing for 3 seconds. The 4th dis-
play will tell the user whether leaving or return tempera-
ture is programmed on Switch 4. The 4th display mes-
sage will read either
“RETURN WATER CONTROL” or
“LEAVING WATER CONTROL”
and will appear for 3
seconds. The display will then scroll through the 8 dip
switch selections, each appearing for 3 seconds.
If a change is required, position Switch #4 on dip switch
S1 on the Microprocessor Board (Fig. 12) as indicated:
RWT CONTROL: SW 4 OPEN
(left side pushed down)
LWT CONTROL: SW 4 CLOSED
(right side pushed down)
because in most cases a special Holiday Schedule is
only necessary once in a several month period. It also
eliminates the need for operator intervention to erase the
schedule after the holiday passes.
If an error is made while programming, press CANCEL.
This will clear all programmed (*) holiday days. The
schedule can then be reprogrammed.
The 0 key will not cancel out a * and cannot be used
for correcting a programming error.
Manual Override
When the MANUAL OVERRIDE key is pressed, the
Daily Schedule programmed into the chiller will be ig-
Содержание YCAJ44HE8
Страница 16: ...16 YORK INTERNATIONAL WIRING DIAGRAMS LD02165 FIG 5 ELEMENTARY DIAGRAM...
Страница 17: ...FORM 150 60 NM3 17 YORK INTERNATIONAL FIG 5 ELEMENTARY DIAGRAM Cont d LD02166...
Страница 20: ...20 YORK INTERNATIONAL CONNECTION DIAGRAM ELECTRICAL BOX FIG 7 CONNECTION DIAGRAM LD02171...
Страница 21: ...FORM 150 60 NM3 21 YORK INTERNATIONAL FIG 7 CONNECTION DIAGRAM Cont d LD02172...