Carrier ZONE-MIZER 50ME - Manual (Page 41)

ZONE CONTROL BOARD
SOME
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Night setback
Night setback control can be added to a 48MA/50ME unit
using field-supplied components. There are 3 sets of fer-
minals on fhe accessory section as shown in Zone Control
Board. Terminal sets are: cooling lockout (CL), night
setback (NS) and “Short To Close Dampers.” Red jurhpers
are factory wired across CL and NS; “Short To Close
Dampers” are bare. If the circuit between CL terminals is
broken, 115-v power to the compressor control circuit
liquid line solenoids and economizer thermostat (if used) is
shut off. If the circuit between NS terminals is broken, 115-v
power to the zone control transformers is shut off. By
replacing both jumpers with appropriate switches and
connecting
proper switch across “Short To Close
Dampers,” NS control is attained. The 3 most common
methods of Night Setback are described below.
For details of actual Night Setback wiring connections,
refer to 48MÀ/50ME wiring booklets.
Method no. 1 — heating night setback cooling
locked out, and continuous indoor fan operation —
This NS system requires a 7-day timer, a night setback relay
and a thermostat (heating type) 24-v service. In this system,
when timer reaches the “Night” position, CL opens,
dampers close and NS opens. The fan continues to operate.
As the temperature falls, the NS thermostat located in
the average temperature space energizes the NS relay
which in turn energizes the zone control transformers.
The individual zones fhen heat until the NS thermostat is
satisfied. The dampers remain closed and cooling is still
locked out. If a day/nighf switch is used, the NS thermostat
is overridden and heating is controlled by the normal
thermostats.
Method no. 2 — heating night setback, cooling locked
out and cycling indoor fans — This system requires a
remote control panel, a 7-day timer, a night setback
relay and a thermostat (cooling type). This system requires
a master unit relay (MUR) and a master cooling relay (MCR)
(24-v wiring). Install the timer and the NS relay in proximity
to the remote control panel. This places all wiring inside the
building in one area.
In this system, the MUR is energized by the NS controls.
This opens a set of normally closed contacts and shuts
down the unit, including indoor fans. The outdoor air
dampers are also closed by the MUR. Cooling lockout is
attained by energizing the MCR. Energizing these 2 relays
turns the unit off and the NS system seems to work in
reverse.
A cooling thermostat is used on heating NS. When tem­
perature rises, the thermostat, in series with the night
switch, energizes the NS relay. Its contacts close and, in
series with the time clock contacts, energize the MUR.
As the space temperature lowers to the NS setting, the NS
thermostat de-energizes the NS relay which de-energizes
the MUR, turning on the unit. The day/night switch over­
rides the NS clock and heating occurs because the NS relay
is Ì le-energized. The factory jumpers remain across CL and
NS terminals. The dampers close when the indoor fans
start. To keep them closed, short across the W-R terminals
on the remote control panel or the “Short To Close
Dampers” terminals during the NS period.
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