Pr
o
-
C
Series
10
Optional Stop/Jog Economizer And Wheel
Frost Protection (SMX70 Controller)
The stop/jog economizer option is used during moderate
outdoor air temperatures to stop the recovery wheel. The jog
function is included to allow the wheel to rotate periodically
to self-clean.
When the outdoor temperature is between 55°F (the
cooling coil supply air temperature) and 75°F (the space
return air temperature) the wheel will raise the outdoor air
temperature which will add slightly to the space sensible load.
At the same time, if the outdoor humidity level is higher than
the space humidity level, the recovery wheel will dehumidify
the fresh air slightly reducing the space latent load. If the
local climate is such that these intermediate temperature days
occur mostly at moderate humidity conditions, the stop/jog
economizer can eliminate the heating of the outdoor air and
provide some free cooling to the space.
The stop/jog economizer consists of a temperature
sensor and a circuit board with dip switch selection of
temperature and stop/jog times. When the outdoor
temperature is in the range between the two setpoints, the
timer relay operates the wheel for approximately 30 seconds
in every 30 minutes.
The SMX70 board also has the ability to put the wheel
in stop/jog mode when the outdoor air temperature drops
below a preset value. This is a lower cost option than the
electric preheat. It also has the disadvantage in supplying
untreated outdoor air into the ventilation system whenever
the stop/jog activates.
Optional Rotation Detector Sensor
The SMX70 stop/jog economizer board can be supplied
with a motion detector to monitor the rotation of the energy
recovery wheel. The sensor is a hall effect device that senses
the passage of a small magnet on the perimeter of the ro-
tor. When the sensor fails to register any wheel rotation - it
requires a signal every 20 seconds or 10 minutes depending
on the mode of operation - it energizes the alarm terminal
(24 VAC, .3 amp max) of the SMX70 board. This can be
used to operate a relay (to be supplied by others) for remote
indication of the alarm. The sensor will not create a false
alarm when the SMX70 controller is in stop/jog mode.
The alarm resets itself once the wheel begins to turn
or the system is shut off and restarted.
Please note that the triac output for the alarm signal
requires a load, such as a contactor coil, to operate. This
output may not register on a digital multimeter without the
load, or may cause a lamp with no limiting resistor to light
dimly.
Thermostat Frost Protection
A lower cost solution to frost protection is to use a thermostat
to turn the entire ventilation unit off during periods when
the air is below the calculated frosting temperature. This
should only be used in non-critical ventilation applications
as no outdoor air will be supplied when the unit is switched
off by the thermostat.
Figure 9. SMX70 controller as installed on the electric
panel.
Figure 10. SMX70 Controller settings.
1 2 3 4 5 6 7 8
UP
DOWN
FROST SETPOINTS (DEG.F)
DDDDDDDD DISABLED
UDDDDDDD -14
DUDDDDDD -13
UUDDDDDD -12
DDUDDDDD -11
UDUDDDDD -10
DUUDDDDD - 9
UUUDDDDD - 8
DDDUDDDD - 7
STOP/JOG TEMPERATURE SETPOINTS (DEG. F)
OFF/ON TIME*
ON TIME
OFF TIME
(SECONDS) (MINUTES)
5 DDDD DDDD 0.1 (TEST)
10 UDDD UDDD 10
15 DUDD DUDD 20
20 UUDD UUDD 30
25 DDUD DDUD 40
30 UDUD UDUD 50
35 DUUD DUUD 60
40 UUUD UUUD 70
45 DDDU DDDU 80
50 UDDU UDDU 90
55 DUDU DUDU 100
60 UUDU UUDU 110
65 DDUU DDUU 120
70 UDUU UDUU 130
75 DUUU DUUU 140
80 UUUU UUUU 150
*ON TIME IS SWITCH POSITION 1,2,3,4
*OFF TIME IS SWITCH POSITION 5,6,7,8
DDDDDDDD 40
UDDDDDDD 41
DUDDDDDD 42
UUDDDDDD 43
DDUDDDDD 44
UDUDDDDD 45
DUUDDDDD 46
UUUDDDDD 47
DDDUDDDD 48
UDDUDDDD 49
DUDUDDDD 50
UUDUDDDD 51
DDUUDDDD 52
UDUUDDDD 53
DUUUDDDD 54
UUUUDDDD 55
DDDDUDDD 56
UDDDUDDD 57
DUDDUDDD 58
UUDDUDDD 59
DDUDUDDD 60
UDUDUDDD 61
DUUDUDDD 62
UUUDUDDD 63
DDDUUDDD 64
UDDUUDDD 65
DUDUUDDD 66
UUDUUDDD 67
DDUUUDDD 68
UDUUUDDD 69
DUUUUDDD 70
UUUUUDDD 71
DDDDDUDD 72
UDDDDUDD 73
DUDDDUDD 74
UUDDDUDD 75
DDUDDUDD 76
UDUDDUDD 77
DUUDDUDD 78
UUUDDUDD 79
DDDUDUDD 80
UDDUDDDD - 6
DUDUDDDD - 5
UUDUDDDD - 4
DDUUDDDD - 3
UDUUDDDD - 2
DUUUDDDD - 1
UUUUDDDD 0
DDDDUDDD 1
UDDDUDDD 2
DUDDUDDD 3
UUDDUDDD 4
DDUDUDDD 5
UDUDUDDD 6
DUUDUDDD 7
UUUDUDDD 8
DDDUUDDD 9
UDDUUDDD 10
SMX70 CONTROLLER
TIME
LO
W
HIGH
FROST
LOW
HIGH
Wheel Only Frost Protection
Typically Disabled
Upper Stop/Jog Economizer
Setpoint (Typically 75°F)
Lower Stop/Jog Economizer
Setpoint (Typically 55°F)
Stop/Jog Times
(Typically 30s on,
30 minutes off.)
