Carrier 50MQ User Manual

Number One
Air Conditioning
Maker

e

Division ot Carrier Corporatio
Syracuse New York

Single-Package Heat Pump Units

The 50MQ units are completely self-contained
cooling and heating systems with provision for
addition of accessory electric heaters. They are
air-to-air heat pumps designed for outdoor installa
tion. They may be connected into existing duct
systems which are properly sized and designed to
handle an air quantity of 400 to 500 cfm per ton

of cooling. Required connections include air ducts,

condensate drain, line and control power wiring.

Field-supplied filter must be installed in return air
duct. (See Table 1 for filter size.)

INSTALLER'S PRELIMINARY SURVEY

Step 1 — Inspect Equipment — File claim with

shipping company if shipment is damaged or
incomplete.

Step 2 — Complete or Consider the Following

before installing the 50MQ unit;

a. Consult local building codes for special installa

tion requirements.

b. Provide sufficient space for coil air flow clear

ance, wiring, and servicing unit. (See Fig. 1.)

Table 1 — Installation Data (See Fig. 1.)

UNIT
OPER WT (lb)
DIMENSIONS

{ft-in») A

DUCT CONN.

(ft-in.)

Supply j

Return

FILTER SIZEt (in.)

Disposable

Permanent

‘Dimension "C"
t Recommended

50MQ022 50MQ027 50MQ032

315

B 3-

c*

2- 3Ys

D

1-1OY4

E

0- 6^6

F

0-10“/,6

G

1 -- 1 6

, , H

K

20 X 25

15 X 20

includes 1 1/4-in built-in base support channels (2)

field-supplied filters are 1-in. thick

330 340

2- 3%

1-1OV4

0-

0-10“/,6

1 — 1 6 1 — 1 ^/] 6

Sid e'b y- Si (d€ Rect an gu or

20 X 25 15 X 20(2)

20 X 20 20 X 20

6‘/4

3-

2

2- 3% 2- 7%

1-10^4

0- óV.e
0-10“/Ì6

1- 9%
0-

\QX

1 -

9%

1-

7%

, ,,T

4-0 OVERHEAD AIR
SPACE REQUIRED

50MQ037

353

1-1OY4

0- 6V,6
0-10“,(e

1-

1 5 X 20

20 X 20

20 X 25

c. Locate unit where supply and return air ducts

can be conveniently brought out to unit duct
connections.

d. Unit may be placed with duct side as close to

building as condensate drain, top removal, duct

connections and power connections will permit

Position unit so water or ice from roof will not

drop directly on top of unit or in front of coil

e. Make provisions for condensate drainage and

defrost water disposal. See Mounting Pad and

Cooling Cycle Condensate Disposal.

f. Roof installation method for 50MQ will depend

on building construction and special require
ments of local building codes. Ensure roof will
support unit weight. See Mounting Pad for
details.

a OIAM HOLE-

CONTROL
WIRING CONN

l| DIAM HOLE-UNIT

LINE WIRING CONN „

O SUPPLY AIR

^ RETURN AIR

Certified dimension drawings available on request

REAR VIEW

SPACE REQUIRED FOR SERVICE ON
REAR OF UNIT IS I'-O"

Fig. 1 — Dimensions and Connections

CHANNELS-2)

■g ID SIDE CONDENSATE

DRAIN FITTING

© Carrier Corporation 1974

Form No 50MQ-1SI

MOUNTING PAD

Step 3 — On the Ground: Mount Unit on a Solid,

Level Concrete Pad. See Fig. 2 for pad dimensions.

Ensure pad does not obstruct coil slots in unit base
pan. (Slots drain water during heating cycle).
Construct pad a minimum of 6 in. thick to provide

clearance under base pan coil slots for drainage and

ice buildup. In areas where prolonged subfreezing

temperatures, drifting or heavy snows occur, in
crease clearance to 12 to 18 inches. If climatic
conditions dictate, construct an angle iron frame to
support unit 12 to 18 in. off concrete base. Cross
angle of frame must not obstruct base pan coil
slots. Extend a 24-in. gravel apron around pad for
condensate and defrost water drainage field.

Step 4 — On the Roof: Mount Unit on a Level
Platform or Frame. Unit must be elevated for

proper clearance as described under ground in
stallation above. Roof design and water drainage
must be planned to prevent unit and its duct
flashing from sitting in water.

for system air duct design. When designing and
installing ductwork, consider the following.

a. When connecting ductwork to unit, do not drill

holes in area shown below. Coil may be
damaged.

b. All units should have field-supplied filters in

stalled in return air ductwork. Recommended

sizes for filters are shown in Table 1.
c Avoid abrupt duct size increases and reductions.
d. Use flexible connectors between ductwork and

unit to prevent transmission of vibration. When

electric heater is installed, use fireproof asbes-

• tos (or similar heat resistant material) con
nector between ductwork and unit discharge
connection. Heat resistant duct connector must
extend 24 in. from electric heater element.

e. Size ductwork for cooling air quantity (cfm).

The minimum air quantity for safe electric
heater operation is;

m

Fig. 2 — Concrete Pad Dimensions

DUCTWORK

Step 5 — Connect Supply and Return Air Ductwork

to unit supply and return air duct connections. Refer
to Fig. 1 and Table 1 for unit supply and return air
connection sizes and locations.

Flanges are provided on unit for rectangular
duct connections. Fig. 3 shows a typical duct
system with 50MQ installed. Do not operate unit
longer than 5 minutes without ductwork. If neces
sary, refer to Carrier System Design Manual, Part 2,

INDOOR

UNIT FAN 5.0

SPEED

50MQ022
50MQ027 Med = H i 900
50MQ032
50MQ037

Med-Lo

Med-Lo
Med-Lo

ELECTRIC HEATER KW

7.5 1 10.0 j 15.0

Cfm

733 733 1

900 I 900

]068 1068 1
1230

1068 Í 1068

1230 ' 1230 j1230

20.0

733 j

-

-

1230

Heater limit switches may trip at air quantities
below those recommended.

f. All external ductwork must be insulated and

weatherproofed. Ducts passing thm uncondi

tioned space must be insulated and covered
with vapor barrier in accordance with the latest
issue of SMACNA’s (Sheet Metal and Air
Conditioning Contractors National Association)

and NESCA’s (National Environmental Systems
Contractors Association) minimum installation

standards for residential heating and air condi

tioning systems.

g. Secure all ducts to building structure. Weather

proof duct openings in wall or roof according

to good construction practices.

— POWER WIRING

-------

CONTROL WIRING

OUTDOOR air flow

INDOOR AIR FLOW pUMP

«Separate fused disconnect required for electric heater.

Fig. 3 — Typical Installation

COOLING CYCLE CONDENSATE DISPOSAL

Condensate may be drained directly onto gravel
apron or connected by drain line(s) to a dry well
Condensate disposal methods must comply with

local codes and practices.

Step 6 - Connect a Drain Line to rubber conden

sate drain fitting on side of unit (see Fig. 1). Use

clamp provided. Install factory-supplied conden
sate trap (taped to indoor fan housing for ship
ment) at end of drain line. If a drain line is not

used, connect condensate trap to unit drain fitting

as shown in Fig 4.

ELECTRIC HEATER INSTALLATION

For complete heater installation data, including

accessory outdoor thermostat and emergency heat
switch, refer to accessory electric heater Installa
tion, Start-Up and Service booklet. Complete

control wiring connections are shown in this
booklet.

CONDENSATE DRAIN FITTING

WITFI CLAMP

Fig. 4 - Condensate Drain Connection

CONDENSATE
DRAIN TRAP

ELECTRICAL DATA AND WIRING

Field wiring must comply with local and
national fire, safety and electrical codes. Voltage to
unit must be within ±10% of voltage indicated on
nameplate. On 3-phase units, phases must be
balanced within 2%.

Operation of unit on improper line voltage or ; with e.xcessive phase unbalance constitutes abuse and is not covered by Carrier Warranty.

See Table 2 for recommended wire and fuse sizes

Step 7 — Install a Branch Circuit Fused Disconnect

of adequate size to handle unit starting current.
Locate disconnect within sight of and readily
accessible from the unit. (Use a separate fused
disconnect(s) for each electric circuit as required.)

Step 8 — Bring Line Power Leads Into Unit.

Extend leads from fused disconnect thru hole pro

vided (Fig. 1) into line wiring splice box (Fig, 5).

Step 9 — Connect Ground Lead to Ground Lug in
Splice Box before connecting power wiring. See Fig.

6. Connect line power leads to yellow and black
pigtails on single-phase units or yellow, blue and

black pigtails on 3-phase units. Use wire nuts

'provided. Tape each connection. Wire nuts are

suitable for copper or aluminum wire since they
contain joint compound.

Step 10 — Set Indoor Fan Motor Speed — (Refer

to page 2 for minimum allowable air quantity for

safe electric heater operation). Four-speed indoor

fan motor is factory wired for high speed opera
tion. Fan motor is equipped with spade-type speed
selector terminals marked 1, 2, 3 and 4. For lower
fan speed, remove black unit lead from motor
spade terminal 1 and connect to spade terminal 2,
3 or 4. On alternate fan motors remove black

motor lead from unit connection and replace with

blue, orange or red motor lead.

MOTOR LEAD
MOTOR TERMINAL

FAN SPEED

Black

Hig h

B lue

2

Medium

Hig h

Orange Red

3

Med ium

Low

4

Low

Step 11 — Control Power Wiring (24 v) is brought

through 7/8-in. hole provided in unit. Fig. 1.
Extend leads to unit control wiring terminal board.
Fig. 5. Connect leads to terminal board as directed
in Fig. 7.

HEATER INSTALLATION
AREA

INDOOR FAN MOTOR

CONTROL WIRING
TERMINAL BOARD

WIRING KNOCKOUTS

■AND HOLES
(HIDDEN) SEE FIG t

LINE WIRING
SPLICE BOX

LINE VOLTAGE PIGTAILS

Fig. 5 — Unit Wiring Terminal Location

Table 2 — Unit Electrical Data

OPER

MODEL V/PH

50MQÒ22
50MQ027
S0MQ032
50MQ037

50MQ022
50MQ027
50MQ032
50MQ037

50MQ032
50MQ037

FLA — Full Load Amps
LRA — Locked Rotor Amps
IFM — Indoor Fan Motor
OFM — Outdoor Fan Motor

"Permissible limits of the voltage range at which the units will

operate satisfactorily.

tRequIred when using nonmetallic conduit.

■ —

200/1

230/1 254

200/230/3
200/230/3

VOLTAGE*
Max

220

254 180
254 180

Min

180

207

COMPRESSOR

LRA FLA FLA

75 14.1 2 2
80 16.2 2.2 2.2
99

112

68 12 8
72
88 18 0

100

75 13.0/11.5 3.6/3.1

80

IFM OFM

20.8 3.6 2 2

26.5

14 0

23.0 3.4

15.0/12 8

3.9 2.2 8 35 10

2.0 1 9 12 32

2.0
3 1

3.9/3.4

NO TE S :

1. Fan motors are 200w or 230-v, single-phase.

2. All units equipped with 24-v transformer for external control circuit.

3. Copper wire sizes based on 60 C. Aluminum field wiring may be used
when spiice connected to copper pigtails from unit with factory­supplied wire nuts. Use latest National Electrical Code for aluminum
wire sizing.

BRANCH CIRCUIT

Power Max Gnd Max

FLA

2.2 10 40 10

1.9 10
1 9

1.9 8 45 10

2.2/1.9 10/12 50/42 10/12 35/30

2.2/1.9

Wire Ft

Size

(AWG)

10

10

10/10 45/60 10/10 35/30

W ire

8

35 10
43

47 10
36 10 45

Wire Fuse

Sizet

(AWG)

10 50

12

Amps

35
40

60

30

35

50

The 50MQ unit transformer supplies 24-v
power for complete system including accessory
electric heater up to 10 kw. Electric heaters over

10 kw are equipped with 24-v transformer used to

power heater controls.

HH07AT070 THERMOSTAT
HH93AZ076 SUBBASE

GROUND LUG

(IN SPLICE BOX)

Fig. 6 — Line Power Connections

UNIT CONTROL

WIRING TERMINAL BOARD

HH07AT070 THERMOSTAT

HH93AZ074 SUBBASE

50 MO

UNIT CONTROL

WIRING

TERMINAL BOARD

---------

Field Wiring, min 18 AWG

---------

Factory Supplied Wires

HR — Heater Relay
R — Relay

SEQ — Sequencer

Splice

Fig. 7 — Control Circuit Connections

5

START-UP

The 50MQ units are equipped with a crankcase
heater. It is recommended that heater be energized
a minimum of 24 hours before starting unit. To
energize heater only, turn the thermostat to “Off’
position and close electrical disconnect to 50MQ
unit.

Heat Anticipator Settings for Room Thermostat
(HH07AT070) — Set anticipator settings for room

thermostat according to Table 3. These settings
may be changed slightly to provide a greater degree
of comfort for a particular installation.

Accessory Outdoor Thermostat provides adjustable

outdoor control of accessory electric heater over

10 kw. This thermostat makes contact when a drop

in outdoor temperature occurs. It energizes a

second stage of electric heat when the outdoor
temperature setting is reached, provided the room
thermostat is on the second stage of heating. Refer
to heat load of building for correct outdoor
thermostat setting. The accessory emergency heat
er relay is manually operated to lock out compres
sor and bypass the outdoor thermostat for electric
heater operation during heat pump shutdown. See
88EH electric heater Installation, Start-Up and
Service Instructions for installation of outdoor
thermostat and emergency heater relay.

To Start Unit — (Ensure crankcase heater has been

energized for 24 hours.) Adjust the thermostat as

follows;

1. Set selector switch at “Off.”

2. Set fan switch as desired (“Fan”) (“Auto.”).

3. Turn on main disconnect switch(es) to unit.

4. Set thermostat dial to the desired temperature.

5. Set selector switch at “Heat” or “Cool.” Check
system refrigerant charge. See Refrigerant

Charging.

50MQ Unit Single-Phase Compressors of the split

capacitor (PSC) type require an equalized system
pressure to start. When supply voltage is within
permissible limits and compressor does not start,
give compressor a temporary capacitance boost.
Use an 88-108 microfarad start capacitor with a
bleed resistor wired across the terminals. Connect
wires with insulated probes to each capacitor

terminal. Touch probes to each side of run

capacitor or to compressor motor terminals R and

S. Start compressor; pull probes away after 3

seconds Discharge start capacitor. (Two or more

bumps may be necessary to start compressor.) Run
compressor for 20 to 30 minutes, then shut off and
allow system pressure to equalize. Try restarting
without boost capacitor. If after 2 attempts (with
out boost capacitor) the compressor does not start,
add an accessory start capacitor relay package.

UNIT CONTROLS

High-Pressure Relief Valve (Safety Control) is

located in compressor. Relief valve opens at a

Table 3 — Thermostat Anticipator Settings

FIRST-STAGE

UNIT

50MQ022, 7.5
027,032,
037

ANTICIPATOR

SETTING

.4

ACCESSORY

ELECTRIC

HTR (Kw)

240 V

208 V

5.0 3.75"

5.6

10 0

15.0 1 1.3

20 0

7 5

15.0

SECOND-STAGE

ANTICIPATOR

SETTINGS i

4 *
56 !
56

.4 ;i

.4 1

pressure differential of approximately 600 psi
between suction (low side) and discharge (high
side) to allow pressure equalization. The valve also
permits pressure equalization when high-side —
low-side pressure differential reaches 90 psig at
shutdown. Compressor can then start unloaded. A
hissing sound during pressure equalization indicates
pressures are equalizing and does not indicate bad
valves.

Internal Current and Temperature Sensitive Over

load (Safety Control) resets automatically when

internal compressor motor temperature drops to a
safe level (overloads may require up to 45 minutes
to reset). When an internal overload is suspected of
being open, check by using an ohmmeter or
continuity tester. If necessary, refer to Carrier
Standard Service Techniques Manual, Chapter 2,

for complete instructions.

Defrost Control, consisting of a defrost timer,

defrost thermostat and defrost relay, interrupts
normal system heating operation if enough frost

forms on outdoor coil to impair unit performance.

Defrost control simultaneously stops outdoor fan,

de-energizes reversing valve solenoid to return
system to cooling cycle (outdoor unit as con
denser, indoor unit as evaporator), and activates
accessory electric heater. Unit can defrost every 90

minutes, but will defrost only if required.

For the heat pump to defrost, 2 conditions are

necessary:

1. Defrost timer contacts must be closed.

2. Refrigerant temperature from outdoor unit
must be cold enough to cause defrost ther
mostat contacts to close. Contacts close at 35

(+0, -6) F.

Every 90 minutes of elapsed running time, the

defrost timer contacts close for 10 seconds. If the
defrost thermostat contacts are closed, the unit

defrosts. The defrost timer limits defrosting period
to 10 minutes. Normally the frost is removed and
the defrost thermostat contacts will open to
terminate defrosting before 10 minutes have
elapsed. Defrost thermostat contacts open at 65
(+0, -6) F. When defrosting is terminated, the
outdoor fan motor and reversing valve solenoid are
energized returning unit to heating cycle.

HEAT PUMP CIRCUITS shown in Fig. 8 are
refrigerant flow diagrams for heating and cooling
cycles.

Unit Piping

strainers

Fig. 8 — 50MQ Refrigerant Flow Diagrams

STRAINERS

SERVICE

Table 4 — Service Data

UNIT
R-22 CHG

(Ib-oz)*

Refrig Control

INDOOR FAN

Rpm
Diameter (in.)

Width (in.)

Range Cfm
Motor Hp

OUTDOOR FAN

Cfm
Rpm
Diameter (in.)
Motor Hp

»Factory refrigerant charge.

50MQ022 50MQ027

5.0 ) 5 7 5 7

733-915

1/4

50MQ032

Acc uR a ter ^

Cen tr ifu ga l — Dir ec t D r ive

1050-950-850-800
9
8

9 10

8 8

900-1125 1068-1332

1/4 1/3

Pro pe lle r — Di re ct D r ive

3000
1050

20

1/4

50MQ037

10

8

1230-1540

1/3

REFRIGERANT CHARGING

Unit refrigerant system is factory charged.
When recharging is necessary during heating or
cooling season, weigh in total charge indicated in
Table 4. (Charge must be weighed in during heating
season.) Blow any refrigerant remaining in system
before recharging. Standard 1/4-in. Schrader
Service Connections (Fig. 9) are provided on high

and low sides of refrigerant system for evacuation
and charging.

Dial-a-charge charging cylinder is an accurate
device used to recharge systems by weight. These
cylinders are available at refrigeration supply firms.

A Carrier Chargemaster® charging device

(Carrier Part No. 38GC680004) may be used to
check or adjust refrigerant charge during cooling

season The Chargemaster may also be used as an

alternate method of recharging system.

Chargemaster Operation — Operate unit 10 min

utes before using Chargemaster.

1. Tape Chargemaster feeler bulb to unit suction
line. Insulate bulb. Ensure suction line is clean

for good contact with bulb.

2. Connect refrigerant drum to Chargemaster inlet
port with drum in position for vapor charging.

3. Connect Chargemaster outlet port (loosely) to
unit suction line Schrader valve.

4. Crack valves on refrigerant drum and Charge-

master to purge lines from drum to suction line
Schrader valve. After purging lines, close valve
on Chargemaster only. Tighten Chargemaster®
connection at suction line Schrader valve.

5. Measure outdoor air dry-bulb temperature at
unit.

6. Read evaporator temperature at red needle
position on Chargemaster temperature gage and

suction line temperature at black needle

position

CAUTION: Do not read evaporator tem
perature with Chargemaster valve open.

7. Enter 50MQ Chargemaster Charging Chart,

Table 5, at outdoor air temperature (step 5)

and evaporator temperature (step 6). Find the

suction line temperature required for correct

system charge. If actual suction line tem

perature (step 6) is higher than table value, the

system is undercharged. If suction line tem
perature is lower than table value, the system is
overcharged.

Example- At outdoor air temperature of 85 F

and evaporator temperature of 40 F, the system
will be correctly charged at 48 F (±2 F) suctior
line temperature.

8. Add charge by slowly opening Chargemaster®
valve. If necessary, reduce charge by bleeding at
liquid line Schrader valve. Check outdoor air

and evaporator temperature during procedure.
If they change, refer back to Chargemaster
Charging Chart for new value.

Correct use of Chargemaster ensures an opti

mum refrigerant charge will be in system when
conditions and system components are normal.
However, the Chargemaster does not solve or fix

system abnormalities It indicates correct charge
for condition of system. It will not make correc
tions for dirty filters, slow fans, excessively long or
short suction lines, or other abnormal conditions.
This charging device ensures that a correct relation
ship exists between outdoor temperature, evap
orator temperature, and suction line temperature
on a specific system.

Table 5 — 50MQ Chargemaster® Charging Chart

6. Remove compressor hold-down bolts. Lift com
pressor out.

CAUTION: Aluminum tubing is used in
50MQ unit coils. Do not overiieat or place
excessive strain on tubing or damage may
result.

Table 6 — Compressor Data

MODEL

50MQ022
50MQ027
50MQ032
50MQ037

50MQ022
50MQ027
50MQ032

50MQ037
5ÒMQ032

50MQ037

V/PH

200/1

230/1

200-230/3

PRODUCTION

COMPRESSOR

MB2423CB
MB2723CB
MB3423CB
MB4023CB

M52423CB
MD2723CB
MC3423CB
MC4023CB

MF3423CB ~
MF4023CB

OIL

RECHARGE (oz)

44

OUTDOOR

TEMP

(F)

60
65 40
70
75 37 46
80
85 42 -48
90 44

95 40 45 5 C
100 44
105

‘Saturated temperature which is the equivalent temperature of

pressure taken at the heat pump suction Schrader fitting.

EVAPORATOR TEMPERATURE (F)*

38 2ÏÔ

Te

Ó6

64

55

55

42 44

mperatu

62
54 61
49

42

28

30

32

Suet on Line

50

65
48
36

34

36,

72
56 Ó6

56

46

40

47

46 48 50|

res

60

55

55
50

60
54 59
50

54 58

COMPRESSOR REMOVAL

See Table 6 for compressor information and

Fig 10 for component location.

1. Shut off power to unit. Vent refrigerant to
atmosphere or use refrigerant removal methods
shown in Carrier Standard Service Techniques
Manual, Chapter 1.

2. Remove unit corner access panel. Fig. 1.

3. Remove core from suction and discharge line
Schrader valves.

4. Disconnect compressor wiring at compressor

terminal box. Carefully unsweat suction and
discharge (hot gas) lines at compressor. Do not
stress or move compressor discharge line or it
may break at condenser connection.

CAUTION: Excessive movement of copper
lines at compresksor may cause a break where

lines connect to evaporator or condenser.

5. Remove crankcase heater from compressor
base.

Filter-Drier — Install a filter-drier in compressor

suction line when refrigerant system is opened for
service as described under Compressor Removal.
Fig. 9 shows suggested position of drier. Check
filter-drier pressure drop at drier service port and
unit suction line Schrader fitting. Ensure pressure

drop does not exceed 2 psi.

CONTROL BOX
4-WAY VaL^:

DISCHARGE LINcl
(HIGH SIDE)IS2!r

SCHRADER FITTING

$

FILTER-DRIER
SERVICE

FILTER-DRIER

(FIELD SUPPLIED)

SUCTION LINE

accumulator;

SUCTION LINE
(LOW SIDE)"
SCHRADER FITTING

COMPRESSO!

COMPRESSOR HOLD
DOWN BOLTS (4)

COMPRESSOR ’

TERMINAL BOX

Fig. 9 — Compressor Removal

MAINTENANCE

Lubrication

COMPRESSOR contains factory oil charge. Re
place oil when lost. See Table 6 for oil recharge. If
necessary, refer to Carrier Standard Service Tech
niques Manual, Chapter 1, pg 1-21, for oil re
charging procedure. Use Carrier PP33-1, Texaco
Capella B or Suniso 3G oil.

FAN MOTOR BEARINGS are prelubricated for 3
years heavy duty or 5 years normal duty. When
lubrication is necessary, send motor to authorized
motor repair shop.

Evaporator (Indoor Coil)

OUTDOOR FAN AND MOTOR REMOVAL ­Remove screws holding outdoor coil fan grille in
place. Disconnect fan motor leads from controllers
and capacitor. Lift complete fan, motor and orifice
assembly (Fig. 10) out of unit. After replacing fan
motor assembly, reconnect fan motor leads.

CAUTION: Before performing recommended ;
maintenance, be sure main power switch to unit

is turned off.

COIL ” Lift or remove unit top cover for access to

indoor coil. See Fig. 10. Inspect coil periodically.

Clean as described under Condenser (Outdoor Coil)

below.
Condensate Drain

with bottle brush,

Clean condensate drain trap

then flush condensate pan
beneath evaporator coil with clean water. Ensure
water flows freely thru condensate drain.

INDOOR FAN WHEEL should be centered in fan
housing. To adjust fan, remove fan motor orifice
assembly as described below. Loosen setscrew
holding fan to motor shaft. Adjust fan and
retighten setscrew.

Indoor Fan Removal — See Fig. 10. Disconnect fan
motor wiring. Remove sheet metal screws (6)
holding fan orifice in place. Remove fan motor

bracket mounting screws (3). Slide out complete
fan, motor and orifice assembly.

Cleaning Indoor Fan Wheel — Remove caked-on
dirt from fan wheel and housing with brush;
remove grease with mild solvent. When replacing
blower assembly, ensure fan wheel is centered in
housing.

Condenser (Outdoor Coil)

COIL “ Lift or remove top cover for access to
outdoor coil. See Fig. 10. Inspect coil periodically.
Clean coil with water at the beginning of every
cooling season or more often if required. Use
ordinary garden hose at a pressure high enough to
clean efficiently. For best results, spray coil fins

from inside-to-outside the unit or top to bottom
between rows of tubing. Flush dirt from base pan
by spraying water thru top of unit. Avoid splashing

mud on coil or water on the fan motor.
OUTDOOR FAN POSITION - Required fan posi

tion is shown in Fig. 11. Adjust fan by loosening
setscrews and moving blades up or'down.

UNIT TOP CCVER

OUTDOOR FAN-ORIFICE
FAN MOTOR ASSEMBLY

NDOOR COIL

OUTDOOR COIL

4-WAY VALVE

CONTROL BOX

ACCUMULATOR

LINE WIRING

AIR FLOW

INDOOR FAN­ORIFICE MOTOR

SPLICE BOX

Fig. 10 — Component Location

FANBLAOe

/

TOP OF

SLADE

L

------'------'------------

SETscf?ew

MOTOR

• -JiVMXl '

2,00 iri \

№

Fig. 11 — Outdoor Fan Position

Return Air Filter (Field Supplied) — Replace

throwaway filter twice a year. Clean permanent-

type filter a minimum of twice yearly. Flush
permanent filter with hot water, steam or soak in
mild solution of soap or detergent and water.
Allow filters to dry and replace. Refer to filter
manufacturer’s instructions, as required, for other
types of filters.

TROUBLESHOOTING CHART - COOLING CYCLE

TROUBLESHOOTING CHART - HEATING CYCLE

NO HEATING OR
INSUFFICIENT HEATING

CONTACTOR

OPEN

OPENING IN
POWER CIRCUIT

DEFECTIVE LOW
VOLTAGE
TRANSFORMER

REMOTE CONTROL
CENTER DEFECTIVE

CONTROL RELAY
COIL OR CONTACTS
DEFECTIVE

REVERSING VALVE
RELAY DEFECTIVE

CONTACTOR COIL
OPEN OR SHORTED

KLIXON OR OVER
LOAD DEFECTIVE

COMPRESSOR
WILL NOT RUN

CONTACTOR
CLOSED

COMPRESSOR
POWER SUPPLY
OPEN

LOOSE LEADS
AT COMPRESSOR

FAULTY START

CAPACITOR OR RELAY
SINGLE PHASE ONLY

COMPRESSOR
STUCK

INTERNAL
OVERLOAD

DIRTY FILTERS
OR INDOOR COIL

INDOOR FANS
CYCLING ON
OVERLOAD

DEFECTIVE FAN
MOTOR CAPACITOR

LOOSE LEADS AT
FAN MOTOR

FAN MOTOR
BURNED OUT

DAMAGED
REVERSING VALVE

RESTRICTION IN
DISCHARGE LINE

1

COMPRESSOR RUNS
BUT CYCLES ON

LOW LINE VOLTAGE
OR UNBALANCED
3-PHASE LINE

DEFECTIVE RUN
CAPACITOR
(SINGLE PHASE)

COMPRESSOR
BEARINGS

HIGH LOAD
CONDITION

OVERCHARGE OR
NONCONDENSABLES

REVERSING VALVE
JAMMED IN MID
POSITION

1

1 ■■ "

LOW SUCTION
LOW HEAD

OUTDOOR FAN
STOPPED

LOOSE LEADS AT
OUTDOOR FAN
MOTOR

INTERNAL FAN
MOTOR KLIXON

OPEN

FAN MOTOR
BURNED OUT

DEFROST RELAY
N.C. CONTACTS
OPEN

—1 p

COMPRESSOR RUNS -

INSUFFICIENT HEATING

OUTDOOR fan
RUNNING

RESTRICTED
LIQUID LINE

ACCU RATER '
RESTRICTED OR
ICE CLOGGED

UNDERCHARGED

OUTDOOR COIL

^ DIRTY

OUTDOOR COIL
HEAVILY FROSTED

DEFECTIVE DEFROST
THERMOSTAT

1

STRIP HEATERS
NOT OPERATING

OUTDOOR
THERMOSTAT
DEFECTIVE

ODT SETTING
TOO LOW

CAP TUBE PINCHED
OR BULB NOT
SENSING TRUE ODT

STRIP HEATER RELAY
OR CONTACTOR
DEFECTIVE

OPENING IN POWER
CIRCUIT TO HEATER
ELEMENTS

BLOWN FUSE LINK

BROKEN HEATER
ELEMENT

OVERCHARGE OR
NONCONDENSABLES
IN SYSTEM

DEFROST THERMOSTAT
IN POOR PHYSICAL
CONTACT WITH LINE

DEFECTIVE DEFROST
RELAY OR DEFROST
TIMER

REVERSING VALVE
STUCK

BAD ELECTRICAL CON­NECTiON ANYWHERE IN

DEFROST CIRCUIT

4 INTERNAL PRESSURE

RELIEF OPEN

OPEN (KLIXON)
OVER-TEMPERATURE
THERMOSTAT

DEFECTIVE ROOM
THERMOSTAT
(2ND STAGE)

For replacement items use Carrier Specified Parts.

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.

Tab 12

Form50MQ-1SI New

Printed in U.S.A.

12-74

Codes D and MS Catalog No 535-070