S
ERIES
2000 I
NSTALLATION
, O
PERATION
AND
S
ERVICE
M
ANUAL
48
16.7 Interlocks
16.7.1 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.
16.7.2 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.
16.
8
Control Options
16.
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).
16.
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.
16.
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.
16.
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.
16.
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.
16.
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.
16.
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.
16.
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.
