York YS Service Manual download pdf (Page 34)

4.21.4 Multi Unit Sequence Connections

(MUS - TB2: Terminals 1 & 9)

For multiple unit installation applications, Multi Unit

Sequence connections are available to start and stop

each unit. The maintained closure of remote contacts

will permit the unit to operate in all operating modes with

the "COMPRESSOR" switch in the "RUN" position.

Conversely, an opening of the contacts will inhibit the

unit from operating.

4.21.5 Manual Reset Overload

(EMS MRO - TB5, terminals 1 & 53)

Connect these contacts to the manual reset overloads

and/or safety devices in the electro mechanical starter.

An opening of the contacts causes the system to

shutdown.

To restart the chiller, reset the external device in the

starter and the unit will automatically restart.

4.21.6 Auxiliary Safety Shutdown

(ASSI - TB5, terminals 1 & 31)

Momentary or maintained closure of a normally open

switch or relay contacts will cause the unit to shutdown.

The unit will not restart until the contacts open and a

manual reset and restart of the unit is carried out.

4.21.7 Remote Leaving Chilled Water Temperature

Setpoint Reset (RLCWTSP - TB2: terminals.1 & 19)

The locally programmed leaving chilled water

temperature setpoint can be reset bya1to11second

timed closure of remote contacts connected to these

terminals. The signal will only be accepted when the

control centre is in the "REMOTE" operating mode.

An accepted signal will adjust the leaving chilled water

temperature up to 11°C upwards from the locally

programmed value. Unit capacity will be adjusted to

achieve the new setting of leaving chilled water

temperature, providing the compressor motor current is

below the current limit setpoint.

A one-second pulse corresponds to no offset and

therefore no adjustment of the preprogrammed leaving

chilled liquid temperature setpoint. An eleven second

pulse corresponds to the locally preprogrammed

maximum allowable offset (5.5'C or 11.1'C) above the

leaving chilled water temperature setpoint. The amount

of offset varies linearly with pulse-width.

An EMS / BAS interface card option is available to allow

remote reset of the leaving water temperature setpoint

using a 4 to 20 mAdc. current signal, a 0 to 1O Vdc

signal, or a single contact closure.

4.21.8 Remote Current Limit Setpoint

(RCSP - TB2: Terminals 1 & 20)

The motor current limit setpoint can be adjusted

remotely bya1to11second timed closure of remote

contacts connected to these terminals. The input signal

will only be accepted when the control centre is in the

"REMOTE" operating mode. An accepted signal will set

the motor current between 100% and 40% of full load

amps. Unit capacity control will remain from the leaving

chilled water temperature, providing the current limit

setpoint is satisfied. If the compressor motor current

exceeds the current limit setpoint, it will override the

temperature control system to reduce unit capacity.

A one-second pulse corresponds to 100% full load

amperes and an eleven-second pulse corresponds to

40% of full load amperes. The current limit setpoint

varies linearly from 100% to 40% as the pulse-width

changes from 1 to 11 seconds.

An EMS / BAS interface card option is available to allow

remote adjustment of the Current Limit setpoint using a

4 to 20 mAdc. current signal, a 0 to 1O Vdc signal, or a

single contact closure.

4.22 Status Connections

Wiring to the status volt free contacts requires a supply

provided by the customer. Particular care must be taken

deriving the supplies for the volt free terminals with

regard to a common point of isolation. These circuits

when used must be fed via the common point of isolation

so that the voltage is removed when the common point

of isolation to the unit is opened.

In accordance with EN 60204 it is

recommended that the customer wiring to

these terminals uses orange wires. This

will ensure that circuits not switched off by

the unit supply disconnecting device are

distinguished by colour so that they can

easily be identified as live even when the

unit disconnecting device is off.

Unless otherwise stated the volt-free contacts

are rated at 5 amps resistive at 250 Vac and

30 Vdc, 2 amp inductive (0.4 pf) at 250 Vac

and 30 Vdc. All inductive devices (relays)

switched by the volt-free contacts must have

their coil suppressed using standard R/C

suppressors.

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