York YCAS Installation Operation & Maintenance Download

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YORK INTERNATIONAL

FORM 201.19-NM6 (804)

1.10 EMS/BAS

CONTROLS

The microprocessor system can accept remote signals
to Start/Stop the chiller, adjust maximum allowable run-
ning current for each compressor, and adjust the chilled
liquid leaving temperature setpoint. These func tions can
easily be controlled by connecting user sup plied “dry”
contacts to terminals in the control panel.

Remote Start/Stop

Remote Start/Stop can be accomplished using a time
clock, manual contact or other “dry” contact in series
with the fl ow switch which is connected to Terminals
13 and 14 in the logic section of the control pan el. The
contact must be closed to allow the chiller to run. Any
time this contact opens, the chill er will shut down and
the NO RUN PERM message will be dis played. The
lo ca tion of the fl ow switch connection is shown in Sec-
tion 1.12.

Nev er bypass a fl ow switch. This will
cause dam age to the chiller and void
any war ran ties.

Wir ing from remote “dry” contacts
(for stop/start and re set func tions)
should not ex ceed 25 ft. (8 m) and
should be run in ground ed con duit
that does not car ry any wiring other
than con trol wiring or shielded cable.
If an in duc tive device (re lay, contactor)
is sup ply ing these con tacts, the coil of
the de vice must be sup pressed with a
sup pres sor YORK Part Number 031-
00808-000 across the in duc tive coil.

Remote Current Reset

The maximum allowable running current for each com-
pres sor can be adjusted remotely to a lower value using
repeated timed closure of “dry” contacts connected to
Terminals 13 and 16 located in the logic section of the
control panel (See Section 1.12). The duration of the
contact clo sure will determine the amount of adjustment.
Gen er al ly, this input is used for purposes of demand limit
and operates as follows:

Closing the input contact for a defi ned period of time
allows reset of the % Cur rent Limit down ward. Con tact

closure of 1 - 11 seconds will allow % Current Lim it ing
to be ad just ed down ward from 105% by a max i mum
of 75%, i.e. to a minimum value of 30% FLA. EMS
Cur rent Lim it ing op er ates independently of the High
Av er age Cur rent Unload (See Sec tion 8.2). The micro
will always look at the two Cur rent Limit Set points and
choose the lower as the con trol ling val ue, when ev er
Remote Cur rent Lim it ing is uti lized. Con tact clo sures
of less than 1 sec ond will be ignored. A closure of 11
sec onds is the max i mum al low able clo sure and pro vides
a Current Limit re duc tion of 75%. The re mote reset cur-
rent can be cal cu lat ed as follows:

REMOTE
RESET

105% FLA

{(Contact Closed Time -1sec) x (75% FLA)}

CURRENT

10 sec

For example, after a 4 second pulse, the offset would
equal:

Remote Reset Curr = 105% FLA - {(4sec - 1 sec) X (75%FLA)}

10 sec

= 105% - 225%FLA sec

10 sec

= 82.5% FLA

To maintain a given offset, the contact clo sure signal
must be repeated (refreshed) every 30 seconds - 30
minutes. The refresh is not accerted sooner than 30
seconds from the end of the last PWM signal, but must
be refreshed before 30 minutes has elapsed. After 30
min utes, if no refresh is pro vid ed, the setpoint will
change back to its original val ue.

After an offset signal, the new Re mote
Current Limit may be viewed on the
EMS Current Lim it ing Dis play under
the Mo tor Current Key (see Sec tion
3.5). How ev er, if this dis play is being
viewed when the re set pulse oc curs, the
setpoint will not change on the dis play.
To view the new off set, fi rst press any
other dis play key on the key pad and
then press the Motor Current Key.

Remote EMS Reset will not operate
when a Re mote Control Center Op-
tion Kit is con nect ed to the mi cro.
The Re mote Con trol Center will al ways
de ter mine the setpoint.

Micro Panel Contents