ICP F9MVE0401410A, Service And Technical Support Manual

SERVICE AND TECHNICAL SUPPORT MANUAL

Gas Furnace: (F/G)9MVE

Specifications  subject to change without notice.

31

440 04 4800 00

valve GV

−

M, stopping gas flow to the burners, and

de

−

energizing the humidifier terminal HUM. The

inducer motor IDM will remain energized for a

15

−

second post

−

purge period. The blower motor

BLWM and air cleaner terminal EAC

−

1 will remain

energized at low

−

heat airflow or transition to low

−

heat

airflow for 90, 120, 150, or 180 seconds (depending

on selection at blower

−

OFF delay switches). The

furnace control CPU is factory

−

set for a 120

−

second

blower

−

OFF delay.

2.

Two

−

Stage Thermostat and Two

−

Stage Heating

See 

Figure 18

−

Figure 21

 for thermostat connections.

NOTE

:  In this mode the low

−

heat only switch SW1

−

2 must be

ON to select the low

−

heat only operation mode in response to

closing the thermostat R

−

to

−

W1 circuit. Closing the thermostat

R

−

to

−

W1

−

and

−

W2 circuits always causes high

−

heat operation,

regardless of the setting of the low

−

heat only switch.

The wall thermostat “calls for heat”, closing the R

−

to

−

W1 circuit

for low

−

heat or closing the R

−

to

−

W1

−

and

−

W2 circuits for

high

−

heat. The furnace control performs a self

−

check, verifies

the low

−

heat and high

−

heat pressure switch contacts LPS and

HPS are open, and starts the inducer motor IDM in

high

−

speed.

The start up and shut down functions and delays described in

item 1. above apply to the 2

−

stage heating mode as well,

except for switching from low

−

 to high

−

Heat and vice versa.

a.

Switching from Low

−

 to High

−

Heat

−

 If the

thermostat R

−

to

−

W1 circuit is closed and the

R

−

to

−

W2 circuit closes, the furnace control CPU will

switch the inducer motor IDM speed from low to high.

The high

−

heat pressure switch relay HPSR is

de

−

energized to close the NC contact. When

sufficient pressure is available the high

−

heat pressure

switch HPS closes, and the high

−

heat gas valve

solenoid GV

−

HI is energized. The blower motor

BLWM will transition to high

−

heat airflow five seconds

after the R

−

to

−

W2 circuit closes.

b.

Switching from High

−

 to Low

−

Heat

−

If the

thermostat R

−

to

−

 W2 circuit opens, and the R

−

to

−

W1

circuit remains closed, the furnace control CPU will

switch the inducer motor IDM speed from high to low.

The high

−

heat pressure switch relay HPSR is

energized to open the NC contact and de

−

energize

the high

−

heat gas valve solenoid GV

−

HI. When the

inducer motor IDM reduces pressure sufficiently, the

high

−

heat pressure switch HPS will open. The gas

valve solenoid GV

−

M will remain energized as long

as the low

−

heat pressure switch LPS remains closed.

The blower motor BLWM will transition to low

−

heat

airflow five seconds after the R

−

to

−

W2 circuit opens.

3.

Cooling mode

The thermostat “calls for cooling”.
a.

Single

−

Speed Cooling

−

See 

Figure 18

 and 

Figure 20

 for thermostat

connections 

The thermostat closes the R

−

to

−

G

−

and

−

Y circuits.

The R

−

to

−

 Y circuit starts the outdoor unit, and the

R

−

to

−

G

−

and

−

Y/Y2 circuits start the furnace blower

motor BLWM on cooling airflow. Cooling airflow is

based on the A/C selection shown in 

Table 5

. The

electronic air cleaner terminal EAC

−

1 is energized

with 115 vac when the blower motor BLWM is

operating. 

When the thermostat is satisfied, the R

−

to

−

G

−

and

−

Y

circuits are opened. The outdoor unit will stop, and

the furnace blower motor BLWM will continue

operating at cooling airflow for an additional 90

seconds. Jumper Y/Y2 to DHUM to reduce the

cooling off

−

delay to 5 seconds. (See 

Figure 4

)

b.

Two

−

Stage Thermostat and Two

−

Speed Cooling 

See 

Figure 19

 and 

Figure 21

 for thermostat

connections

The thermostat closes the R

−

to

−

G

−

and

−

Y1 circuits for

low

−

cooling or closes the R

−

to

−

G

−

and

−

Y1

−

and

−

Y2 circuits for

high

−

cooling. The R

−

to

−

Y1 circuit starts the outdoor unit on

low

−

cooling speed, and the R

−

to

−

G

−

and

−

Y1 circuit starts the

furnace blower motor BLWM at low

−

cooling airflow which is the

CF (continuous fan) selection as shown in 

Figure 5

. The

R

−

to

−

Y1

−

and

−

Y2 circuits start the outdoor unit on high

−

cooling

speed, and the R

−

to

−

  G

−

and

−

Y/Y2 circuits start the furnace

blower motor BLWM at high

−

cooling airflow. High

−

cooling

airflow is based on the A/C (air conditioning) selection shown in

Figure 5

. 

The electronic air cleaner terminal EAC

−

1 is energized with 115

vac whenever the blower motor BLWM is operating. 

When the thermostat is satisfied, the R

−

to

−

G

−

and

−

Y1 or R

−

to

−

G

−

and

−

Y1

−

and

−

Y2 circuits are opened. The outdoor unit

stops, and the furnace blower BLWM and electronic air cleaner

terminal EAC

−

1 will remain energized for an additional 90

seconds. Jumper Y1 to DHUM to reduce the cooling off

−

delay

to 5 seconds. (See 

Figure 16

)

4.

Dehumidfy Mode

See 

Figure 18

−

Figure 24

 for thermostat connections. 

The H output on the humidify sensing thermostat should

be connected to the furnace control thermostat terminal

DHUM. When there is a dehumidify demand, the DHUM

input is activated, which means 24 vac signal is removed

from the DHUM input terminal. In other words, the DHUM

input logic is reversed. The DHUM input is turned ON

when no dehumidify demand exists.

Activation/Deactivation

Once 24 vac is detected by the furnace control on the

DHUM input, the furnace control operates in dehumidify

mode. If the DHUM input is low for more than 48 hours,

the furnace control reverts back to non

−

dehumidify

mode. 

The cooling operation described in Item 3, Cooling

mode. above also applies to operation with a humidity

sensing thermostat. The exceptions are listed below:
a.

Low Cooling

−

When the R

−

to

−

G

−

and

−

Y1 circuit is

closed and there is a demand for dehumidification,

the low cooling airflow demand is reduced by 10

percent.

b.

High

−

Cooling

−

When the R

−

to

−

G

−

and

−

Y/Y2 circuit is

closed and there is a demand for dehumidification,

the high cooling airflow demand is reduced by 10

percent.

c.

Cooling off

−

delay

−

When the “call for cooling” is

satisfied and there is a demand for dehumidification,

the cooling blower

−

off delay is decreased from 90

seconds to 5 seconds.

5.

Continuous Blower Mode

When the R

−

to

−

G circuit is closed by the thermostat, the

blower motor BLWM will operate at continuous blower

airflow. Continuous blower airflow selection is initially

based on the CF (continuous fan) selection shown in

Figure 5

. Factory default is shown in 

Figure 5

. Terminal

EAC

−

1 is energized as long as the blower motor BLWM

is energized. 

During a call for heat, the furnace control CPU will

transition the blower motor BLWM to continuous blower

airflow, low

−

heat airflow, or the mid

−

range airflow,

whichever is lowest. The blower motor BLWM will remain

ON until the main burners ignite then shut OFF and

remain OFF for the blower

−

ON delay (45 seconds in

low

−

heat, and 25 seconds in high

−

heat), allowing the

furnace heat exchangers to heat up more quickly, then

restarts at the end of the blower

−

ON delay period at