Carrier 50DL - Manual (Page 14)

Fig. 18 — Removing Return Spring
Mechanism
STARTING POSITON
NOTE POSITION
OF RED DOT
CENTERLINE
ADJUST CAMS
OPERATIONAL
Each adjustment mark repre­
sents 10 degrees of motor rota­
tion Use marks and center of
cam roller as adjustment guide Loosen operational cam adjust­
ment screw Rotate both cams
clockwise the number of de­
grees motor must travel before
switch makes Tighten screw
Red dot will be to right of centerline if switch is properly adjusted
Fig. 19 Adjusting Switch Make and
Break Points
CAPACITY CONTROL, HEATING — Stages 1
and 2 of heaters are controlled by heating relays
HRl and HR2, respectively. Using a suitable
ammeter, check heater current draw for heating
assemblies or elements. When checking second-
stage heater operation, be sure heating thermostat
is set high enough to activate second-stage heaters.
Also, check operation of outdoor air thermostats if
additional staging is provided.
Modu-Pac® Variable Volume Units — Units
suitable for use with Modu-Pac variable air volume
systems (i.e. Carrier 37 Series terminal units) are
equipped with electric unloaders on the no. 1 com­
pressor and hot gas bypass on the no. 1 refrigerant
system.
Before starting unit, open compressor service
valves and liquid line shutoff valve. Be sure com­
pressor crankcase heaters are on and crankcase oil
level is half full. See Compressor and Crankcase
Heaters as applicable.
CONTROL SEQUENCE CHECKOUT
1. Turn on unit main power supply. Be sure unit is
ready to operate. Turn off compressor circuit
breakers.
2. Set the control band knob (Fig. 12) on micro­
processor to 8° (50DL044) or 6° (50DL054,064).
3. If unit is not in DAY (OCCUPIED) mode, turn
on unit by overriding time clock with manual
bypass switch on remote box cover.
4. To check for cooling, turn set point knob
(Fig. 14) on microprocessor to 40 F. As cor­
responding stage of cooling come on, the LED’s
should glow. Indicator light, located on remote
box cover, should also be lit.
5. Turn set point knob on microprocessor to 90 F.
The LED’s on microprocessor should go out as
corresponding stages turn off (providing ambient
temperature is below 90 F).
6. To check for heating on units with electric heat,
set morning warmup thermostat (Fig. 12),
located in variable volume box, to its maximum
position. If return air temperature is below the
set point, first stage of heat should come on. The
outdoor dampers should be tightly closed. Light
marked HEATING on the cover of remote box
should come on. NOTE: If unit has been in cool­
ing mode, it will be necessary to shut off unit
power momentarily in order to check out heating
mode; once unit goes into cooling mode, a hold­
ing relay locks out heating mode.
7. The morning warmup thermostat is a 2-stage
device. When first stage is satisfied, control shuts
down electric heat (if used). An adjustable dead­
band of 3F to 10 F exists between first and
second stage. In the deadband zone, indoor air
fan runs but cooling mode will not begin until
return air temperature exceeds adjustable set
point of the second stage. Note that the difference
between heating and cooling set points will
always be 3 F to 10 F.
8. When checkout is complete and unit operation is
satisfactory, turn off bypass switch, position the
set point knob on microprocessor to desired
setting (approximately 55 F) and replace all
unit panels.
ECONOMIZER OPERATION — Refer to Con­
stant Volume Units, Economizer Operation.
7-DAY TIME CLOCK ADJUSTMENT
Setting ON and OFF Times (Fig. 20) — NOTE:
14 trippers (7 sets, one set for each day) are included.
If more than 7 ON-OFF operations per week are
required, additional trippers are needed.
1. To set ON (OCCUPIED) time, slip the ON
tripper over edge of time dial and position at
desired day of the week and time of the day (AM
or PM). (When switch is turned on, normally
open contacts close and normally closed con­
tacts open.)
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