Continuous Blower Mode; Heat Pump Mode; Component Test - Carrier 58MXA Installation, Start-Up, And Operating Instructions Manual

The cooling operation described in item 2 above also applies
to operation with a Tl"_ermidistat The exceptions are listed
below:
a. When the R to G-and-Y1 circuit is closed and there is a
demand fbr dehumidification, the furnace blower motor
BLWM will continue running at low-cool speed (same
speed as FAN).
b. When the R to G-and Y/Y2 circuit is closed and there is a
demand for dehumidification, the furnace blower motor
BLWM will drop the blower speed flora COOL to HEAT
fbr a maximum of i0 minutes before reverting back to
(OOL speed. If there is still a demand h_r dehumidification
after 20 minutes, the furnace control CPI_ will drop tl-_e
blower speed back to HEAT speed. This alternating 10-
minute cycle will continue as tong as there is a call for
cooling.
c. When the "call for cooling" is satisfied while there is a
demand for dehumidification, the cooling blower-off delay
is decreased fi'om 90 seconds to 5 seconds,
CONTIN/OUS BLOWER MODE
When the R to G circuit is closed by the thermostat, the blower
motor BLWM will operate on continuous-blower speed (can
be adjusted to FAN, HEAT, or COOL speed) at the tl",ermo-
star. Factory- default is FAN" speed. Tem_inal EAC-1 is
energized as long as the blower motor BLWM is energized
During a call fbr heat, the blower BLWM will stop during
igniter warn>up (17 seconds), ignition (7 seconds), and
blower-ON delay (66 or 45 seconds for 040 through 120 sizes
or fbr 140 size), allowing the fiu'nace heat exchangers to heat
up more quickly, then restarts at the end of the blower-ON
delay period at HEAT speed.
In heating, the filmace control CPU will hold the blower
motor BLWM at HEAT speed during the selected blower-OFF
delay period before reverting to continuous-blower speed.
When the thermostat "calls h_r tow-cooling", the blower motor
BLWM will switch to operate at tow-cool speed (same speed
as FAN) When the them_ostat is satisfied, the blower motor
BLWM will operate an additional 90 seconds on lmv-coot
speed (same speed as FAN) befbre reve*ting back to
continuous-blower speed
When the thermostat "calls for high-cooling", the blowe*
motor BLWM will operate at COOL speed. When the the*-
mostat is satisfied, the blower motor BLWM will operate an
additional 90 seconds on (OOL speed before reverting back
to continuous-blower speed
When the R to G circuit is opened, the blower motor BLWM
will continue operating for an additional 5 seconds, if'no other
fhnction requires blower motor BLWM operation
Continuous Blower Speed Selection from Thermostat -To
select different continuous-blower speeds from the room
thermostat, momentarily trim off the FAN' switch or push-
button on the room thermostat for 1-3 seconds are*" the blower
motor BLWM is operating. The fhmace control CPU will shift
the continuous=blower speed fi'om the fi_ctoW setting of FAN
to HEAT speed. Momentarily turning off the FAN" switch
again at the thermostat will shik the continuous-blower speed
fi'om HEAT to COOL. Repeating the procedure will shift the
continuous-blower speed fi'om COOL back to FAN" speed.
The selection can be changed as many times as desired and is
stored in the memoD" to be automatically used following a
power inten'uption.
41
HEAT PUMP MODE
(See Fig. 52, 53, 54, and 55 %r them_ostat connections)
When installed with a heat pump, the furnace control auto-
matically changes the blower timing sequence to avoid long
blower ofttimes during demand defrost cycles When the R to
W-and-Y 1 or R to W-and-Y l-and-G circuits are energized the
fhmace control (PU will switch to or mrn on the blower
motor BLWM at HEAT speed, and begin a heating cycle The
blower motor BLWM wilt remain on until the end of the
prepurge period, then shut off for 24 seconds _hen come back
on at HEAT speed When tl_e W input signal disappears, the
fimaace control begins a normal inducer post-purge period and
the blower remains rmming at HEAT speed fPr the selected
blower-OFF delay period then switches to low-cool speed
(same speed as FAN) If the R to W-and-Yl-and-G signals
disappear at tl-_e same time, the blower motor BLWM will
remain on fbr the selected blower-OFF delay period. If the R
to W-and-Y1 signals disappear, leaving the G signal, the
blower motor BLWM will remain on for the selected blower-
OFF delay period then switch to continuous-blower speed.
When the R to W-and-Y/Y2, R to W-and-Y Y2-and-G, R to
W-and-Yl-and-YY2, or R to W-and-Yl-and-YiY2-and-G
circuits are energized the hm_ace control (PU will switch to
or mm on the blower motor BLWM at HEAT speed, and
begin a heating cycle The blower motor BLWM will remain
on until the end of the prepurge period, then shut off for 24
seconds then come back on at HEAT speed. When the W input
signal disappears, the fi/mace contIol begins a normal inducer
post-purge period and the blower switches to COOL speed
after a 3-second delay. If the R to W-and-YiY2-and-G or R to
W-and-Yl-and-YY2-and-G signals disappear at the same
time, the blower motor BLWM will remain on fbr the selected
blower-OFF delay period. If the R to W-and-YY2 or R to
W-and-Yl-and-Y Y2 signals disappear, leaving the G signal,
the blower motor BLWM will remain on for the selected
blower-OFF delay period then switch to continuous-blower
speed.
COMPONENT TEST
NOTE: The furnace contlol component test allows all compo-
nents to run fbr a short time; except the gas valve and humidifier
terminal HUM are not energized fbr safety reasons. The EA(-I
terminal is energized when the blower is energized. This fkature
helps diagnose a system problem in case of a component fitilure.
The component test feature will not operate if any thermostat
signal is present ant the control and not until all time delays are
completed.
To Begin Component Self=Test:
ELECTRICAL SHOCK HAZARD
Failure to fbllow this warning could result in electrical shock,
personal i_.imy,
or death.
Blower access panel door switch opens l15-v power to
control. No component operation can occur. Caution must be
taken when manually closing this switch fPr service purposes.
1. Remove blower access door.
2. Disconnect the thermostat R lead f?om furnace control.
3. Manually close blower door switch.
4. For approximately 2 sec, short (lumper) the Cox_-24v tem_inal
on contlol to the TEST/TWIN 3/16-inch quick-connect termi-
nal on control until the LED goes oftl Remover jumper from
terminals. (See Fig. 3!.)