30
OMM 1008-1
Field Wiring Diagram Notes
1.
Compressor terminal boxes are factory-mounted and wired. All line-side wiring must be in accordance with the NEC and be
made with copper wire and copper lugs only. Power wiring between the terminal box and compressor terminals is factory
installed.
2.
Minimum wire size for 115 VAC is 12 ga. for a maximum length of 50 feet. If greater than 50 feet refer to McQuay for
recommended wire size minimum. Wire size for 24 VAC is 18 ga. All wiring to be installed as NEC Class 1 wiring system.
All 24 VAC wiring must be run in separate conduit from 115 VAC wiring. Wiring must be wired in accordance with NEC
and connection to be made with copper wire and copper lugs only.
3.
Voltage unbalance not to exceed 2% with a resultant current unbalance of 6 to 10 times the voltage unbalance per NEMA MG-
1, 1998 Standard. Supply voltage must be +/- 10% of compressor nameplate voltage.
4.
A customer furnished 24 or 120 vac power for alarm relay coil may be connected between UTB1 terminals 84 power and 81
neutral of the control panel. For normally open contacts wire between 82 & 81. For normally closed wire between 83 & 81.
The alarm is operator programmable. Maximum rating of the alarm relay coil is 25VA.
5.
Remote on/off control of unit can be accomplished by installing a set of dry contacts between terminals 70 and 54.
6.
If field supplied pressure differential switches are used, they must be installed across the vessel and not the pump. They must
be suitable for 24 vac and low current application.
7.
Customer supplied 115 VAC 20 amp power for optional evaporator and condenser water pump control power and tower fans
is supplied to unit control terminals (UTB1) 85 power / 86 neutral, PE equipment ground.
8.
Optional customer supplied 115 VAC, 25-VA maximum coil rated, chilled water pump relay (ep1 & 2) may be wired as
shown. This option will cycle the chilled water pump in response to chiller demand.
9.
The condenser water pump must cycle with the unit. A customer supplied 115 VAC 25 VA maximum coil rated, condenser
water pump relay (CP1 & 2) is to be wired as shown. Units with free-cooling must have condenser water above 60°F before
starting.
10.
Optional customer supplied 115 VAC 25 VA maximum coil rated cooling tower fan relays (C1 - C2 standard, C3-C4 optional)
may be wired as shown. This option will cycle the cooling tower fans in order to maintain unit head pressure.
11.
Auxiliary 24 VAC rated contacts in both the chilled water and condenser water pump starters must be wired as shown.
12.
4-20mA external signal for chilled water reset are wired to terminals 71 and 51 on the unit controller; load limit is wired to
terminals 71 and 58 on the unit controller.
13.
Optional Control Inputs. The following 4-20 ma optional inputs are connected as shown:
•
Demand Limit; Terminals 58 and 71 common
•
Chilled Water Reset; Terminals 51 and 71 common
•
Evaporator Water Flow; Terminals 59 and 71 common
•
Condenser Water Flow; Terminals 60 and 71 common
14.
Optional Control Power Source. 115 volt control power can be supplied from a separate circuit and fused at 20 amps inductive
load. Connection is to terminals 85 and 86 common.
15.
4-20 mA external signal for chilled water reset are wired to terminals 71 and 51 on the unit controller; load limit is wired to
terminals 71 and 58 on the unit controller.
Operator Interface Touch Screen
Navigation
The home-view screen shown on page 32 is usually left on (there is a screen-saver built in that is reactivated
by touching the screen anywhere). This VIEW screen contains the STOP and AUTO buttons used to start and
stop the unit when in Local control. Other groups of screens can be accessed from the Home screen by
pressing one of three buttons on the bottom of the screen: HISTORY, VIEW, SET.
•
HISTORY will go to the last history screens viewed and can toggle between the two history screens.
•
Trend History
•
Alarm History
•
VIEW will go to the home View screen. Pressing again will go to the detail View screen used to look in
detail at settings and the operation of the chiller. Pressing VIEW from any other screen will return to the
last displayed View screen. A new button called MENU will appear when in the View mode. See page
35 for details.
•
SET will go to the last Set screen used.
