Rapid 4044, Installation, Operation & Service Manual

Page: 87 / 162

SECTION 19: E
LECTRICAL
79 of 154
19.7 Interlocks
19.7.1 Carbon Dioxide Interlocks
All air handlers that recirc u late air from the heated
space req u ire either a control to limit the temperat u re
rise in proportion to the amo u nt of o u tdoor air or the
u se of a room carbon dioxide sensor. The carbon
dioxide sensor is field pro v ided and set to maintain a
CO2 concentration belo w 5,000 ppm.
19.7.2 Carbon Monoxide Interlocks
Carbon Monoxide Detector is a ship loose sensor
that monitors the CO le
v els in the space. It can either
so u nd an alarm and/ or force the air handler into
100% o u tside air if its threshold set point is
exceeded.
19. 8 Control Options
19. 8 .1 Mild Weather Outside Air Stat
This option is designed to t u rn the b u rner off w hen
the incoming o u tside air is at or abo v e the
temperat u re setpoint. The blo w er is allo w ed to r u n for
contin u ed v entilation. The mild w eather o u tside air
stat is located in the control enclos u re. It has an
adj u stable setting bet w een -20° F (-29° C) and
100° F (38° C).
19. 8 .2 Low Temperature Limit with Override Timer
This option is designed to t u rn the u nit off w hen air is
discharged belo w the temperat u re setpoint for a
period in excess of timer setpoint. The lo w
temperat u re limit s w itch is located in the air handler’s
control enclos u re. The lo w temperat u re limit s w itch
has an adj u stable setting bet w een -20° F (-29° C)
and 100° F (38° C). The timer by-passes the lo w
temperat u re limit s w itch for the first 5 min u tes to allo w
the b u rner to establish a flame w hen the air handler
is t u rned on. If the air handler’s discharge
temperat u re falls to the predetermined lo w
temperat u re limit setpoint, after the 5 min u te
establishing period, the air handler’s blo w er w ill be
t u rned off. To reset the lo w temperat u re limit s w itch,
set the fan s w itch to off and then on again. The air
handler w ill ret u rn to the normal seq u ence of
operations.
19. 8 .3 MUA / Exhaust Failsafe Interlock
This option incorporates the lo w temperat u re limit
w ith o v erride timer and an exha u st fan airflo w s w itch
monitor. The exha u st fan airflo w s w itch is field
pro v ided and field w ired as per the option sheet
s u pplied w ith the u nit. When the air handler is t u rned
on there is a 5 min u te establishing period for the lo w
temperat u re limit s w itch and the exha u st fan
interlock. If the air handler’s discharge temperat u re
falls to the predetermined lo w temperat u re limit
setpoint, after the 5 min u te establishing period, the
air handler fan w ill be t u rned off. If there is a fail u re of
the exha u st fan to acti v ate the field s u pplied airflo w
s w itch, after the 5 min u te establishing period, the air
handler fan w ill be t u rned off. To reset the
MUA/exha u st failsafe interlock, set the fan s w itch to
off and then on again. The air handler w ill ret u rn to
the normal seq u ence of operations.
19. 8 .4 Motorized Inlet Damper
The motorized inlet damper co v ers the o u tside air
inlet of the air handler. When the air handler blo w er is
t u rned on, the damper motor is energized and opens
the damper. The damper motor has an a u xiliary
s w itch that pre v ents the blo w er from starting u ntil that
damper has opened s u fficiently to allo w the req u ired
air v ol u me to pass thro u gh the air handler.
19. 8 .5 Motorized Dischar g e Damper
The motorized discharge damper is mo u nted in the
d u ct do w nstream from the discharge opening of the
air handler. When the air handler fan is t u rned on the
damper motor is energized and opens the damper.
The damper motor has an a
u xiliary s w itch that
pre v ents the blo w er from starting u ntil that damper
has opened s u fficiently to allo w the req u ired air
v ol u me to pass thro u gh the air handler.
19. 8 .6 Control Enclosure Heater
The control enclos u re heater is an electric heater that
keeps the temperat u re in the control enclos u re w ithin
the range for the control components. This option is
intended for extremely cold climates, b
u t
recommended for installations belo w 15° F (-9° C).
The air handler controls are rated to perform at
temperat
u res as lo w as -30° F (-34° C). In
en v ironments w here the air handler may be exposed
to lo w er temperat u res, a control enclos u re heater
may be req u ired.
19. 8 .7 Auxiliary Relay
An a u xiliary relay may be added to an air handler for
either an interlock or a c u stomer defined p u rpose.
Refer to the option sheet s u pplied w ith the air handler
to indicate w hether the relay is w ired for an intended
p u rpose or left u n w ired for a f u t u re interface. Each
relay w ill be do u ble pole do u ble thro w (DPDT) type.
Maxim u m s w itching capacity on the normally open
contact is 8A, and for the booth light relay, 15A.
19. 8 . 8 Smoke Detector
A smoke detector interlock allo w s for the air handler
to operate (either off or on) based on signal inp u t
from the fire alarm.