Carrier 58MVP User Manual download pdf (Page 5)

When items 1-5 have been completed, the following will occur:

1. The control center goes through a brief self test. This self test

takes approximately 2 sec to complete. After door switch is

closed, red (microprocessor) LED briefly comes on. Then

green LED comes on for 1 sec, followed by 1 sec where both

green and yellow LEDs are on. During this time, the micro-

processor is checking itself.

2. Inducer motor operates for 20 sec at low speed, operates 20

sec at high speed, then turns off.

3. Hot surface ignitor is energized for 15 sec, then de-energized.

4. Main blower motor operates for 20 sec at low speed, operates

for 20 sec at high speed, then turns off.

5. After component operation test is completed, 1 or more fault

codes (11, 22, 41, or 42) will flash. See service label on back

of main furnace door or Fig. 1 for explanation of fault codes.

NOTE: To repeat component test, turn setup switch SW-6 to OFF

and then back to ON.

After component test, perform the following:

1. Release blower panel access door switch and turn setup switch

SW-6 to OFF position.

2. If applicable, replace blower access panel and check LED

status by removing plug in blower access panel.

3. Reinstall main furnace door if all LEDs are off, indicating

furnace is ready to operate when a signal from thermostat is

received.

Step 9—Bypass Humidifier Mode

When setup switch SW-3 BPH is in ON position, RPM calculated

for low heat is multiplied by 1.15 for all furnace model sizes. This

compensates for increased return-air temperature caused by by-

passed air supply.

Step 10—Dehumidification Mode

A dehumidification input is provided via a 1/4-in. male quick-

connect terminal labeled DEHUM, located next to the transformer

secondary connections. The DEHUM input acts differently de-

pending on which style of variable speed furnace control you have.

The older style variable speed furnace control (shown in Fig. 1)

DOES NOT have a DE connection while the newer style variable

speed furnace control (shown in Fig. 1) has a DE connection. The

newer style variable speed furnace control is expected to be

available by mid 1998. Both of these variable speed furnace

controls function the same except the DEHUM logic is reversed.

This logic reversal has come about from historical use of a

standard humidistat to do dehumidification since the contacts open

on high humidity, thus removing the 24-v signal to initiate

dehumidification.

On the older style variable speed furnace controls, a field supplied

relay is required between the thermidistat or humidistat control and

furnace. The relay coil is connected between DHUM output on the

thermidistat control and C

OM terminal on the furnace control or the

humidistat output and C

OM terminal on the furnace control. Its

normally closed contact is connected between R and DEHUM

terminals on the furnace control. (See Fig. 1 and Fig. 2). When a

dehumidify demand exists, relay is de-energized, and normally

closed contacts supply 24-v to the furnace DEHUM terminal. As

a result, the furnace control reduces the blower airflow by 15

percent to 340 CFM per ton during continuous fan or cooling

operation.

On newer style variable speed furnace controls, a field supplied

relay IS NOT required. The DEHUM output on the thermidistat

control or the humidistat output is connected directly to the

DEHUM terminal on the furnace control. In addition, the DE

jumper located next to the DEHUM terminal must be removed to

enable the DEHUM input. (See Fig. 1 and Fig. 3). When a

dehumidify demand exists, the furnace control reduces the blower

airflow by 21 percent to 315 CFM per ton during continuous fan

or cooling operation.

This blower speed reduction compensates for high humidity

conditions during cooling operation on all furnace model sizes.

Reference Thermidistat™ Control Installation, Start-up, and Op-

erating Instructions for further details.

Step 11—Zone Mode

When setup switch SW-5 MZ is in ON position, blower motor

control is the same as above except with the following exceptions:

1. While blower is operating in either low heat or continuous fan,

the coast down calibration is performed once a minute to

update blower RPM for zone damper position changes during

a given cycle.

NOTE: Boards with date codes of 9506 or later will not perform

a coast down calibration if blower pulse width to blower motor is

greater than 60 percent. This prevents nuisance faults from

occurring when a high continuous fan CFM has been selected.

2. While blower is operating in either high heat or cooling,

blower pulse width to blower motor is frozen when blower

RPM is within 10 percent of calculated blower RPM for 5 sec.

Fig.2—Without DE Connection

A98294

24 VAC HOT

DEHUMIDIFY

24 VAC COMM

DHUM

DEHUM

Com

THERMIDISTAT

VARIABLE-SPEED

CONDENSING

FURNACE

Fig. 3—With DE Connection

A98295

24 VAC HOT

DEHUMIDIFY

24 VAC COMM

Com

DHUM

DEHUM

DE

NOTE 1

THERMIDISTAT

VARIABLE-SPEED

CONDENSING

FURNACE

NOTE 1 - Remove DE Connection

To Enable DEHUM Input

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Carrier 58MVP User Manual Page 5

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