York YS Service Manual download pdf (Page 19)

The control centre includes unique safety logic to

protect the unit from damaging malfunctions.

Comprehensive information can be displayed in the

event of a unit shutdown including day, time, and reason

for shutdown. Reasons include high condenser

pressure, low oil pressure at compressor, clogged oil

filter, low oil level in oil separator, high oil temperature,

high oil pressure, high compressor discharge

temperature, low evaporator pressure, motor controller

fault, and sensor malfunction.

Background messages are displayed while the unit is

running to inform of any controlling conditions such as:

current limit in effect, low pressure limit in effect, high

pressure limit in effect, leaving chilled water

temperature control, and non-critical sensor error.

System cycling messages are displayed in regard to

day, time, cause of cycling shutdown, and auto start

indication. These include low water temperature,

evaporator/condenser water flow interruption, internal

time clock, and anti-recycle.

Digital programming of operating setpoints from the

keypad include leaving chilled water temperature,

current limiting, pulldown demand limiting, daily

start/stop scheduling of chiller, pumps and tower, and

separate holiday schedule.

Individual LED indicators highlight slide valve loading/

unloading/auto control, program mode, and display

hold.

Manual operation of slide valve loading and unloading is

provided through separate buttons in the service section

of the keypad.

All operating and setpoint information can be

transmitted to a remote printer through the RS-232 port

in the control centre to obtain data logs. This can be

accomplished at any time by pressing the "Print" button

on the control centre keypad, or automatically at

predetermined intervals by programming the panel.

The remote printer will also record time and cause of any

safety or cycling shutdown and a history of the last four

shutdowns.

The control centre is compatible with remote Building

Automation Systems (BAS) and Energy Management

Systems (EMS). The remote control functions available

as standard include start and stop, leaving chilled water

temperature reset and current limit reset through PWM

signal, and "ready to start", "safety" and "cycling"

shutdown status contacts. Further remote control

features are available via an optional York ISN

translator.

2.15 Options and Accessories

Motor Starter

The solid state starter is a reduced voltage starter that

controls and maintains a constant current flow to the

motor during start-up. It is compact and mounted on the

unit adjacent to the motor terminals. Power and control

wiring is factory supplied. The starter enclosure is IP33

rated with a hinged access door with lock and key.

Standard features include: digital readout at the control

centre of 3-phase voltage and current; high and low line

voltage protection; 115 V control transformer; three-leg

sensing overloads; phase rotation and single-phase

failure protection; and momentary power interruption

protection. An integral door interlocked and

pad-lockable fused disconnect switch is also available.

BAS/EMS Remote Control Interface

A communication interface permitting complete

exchange of unit data with any BAS/EMS is available via

an optional ISN translator. The ISN translator also

allows a BAS/EMS to issue commands to the unit to

control its operation. ISN translators are available in two

models for controlling up to four, or up to eight units.

Remote Reset Controls

Optional PCB to allow reset of leaving chilled water

temperature and percent motor current limit by a BAS/

EMS using 4-20 mA, 0-10 Vdc, or discrete stepped

signals rather than the standard pulse width modulated

(PWM) signal requirement.

Factory Insulation of Evaporator

Factory-applied 19 mm thick anti-sweat insulation

(flexible, closed-cell plastic type) is attached with

vapour-proof cement to the evaporator shell, flow

chamber, evaporator tube sheets, suction connection,

and (as necessary) to the auxiliary tubing. This

insulation will normally prevent sweating in

environments with relative humidity up to 75% and dry

bulb temperatures ranging from 10°Cto32°C. 38 mm

thick insulation is also available for environments with

relative humidity up to 90% and dry bulb temperatures

ranging from 10°Cto32°C. Insulation of water boxes

and nozzles is not included.

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York YS Service Manual Page 19

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