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Start-up, Unit controls and safety devices, Mût do not jumper low temperar – Carrier 50HQ User Manual

Page 6: Giycoi

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2. Splice yellow and black power leads from eontrol

box to yellow and red motor leads. (Yellow-to-
yellow and black-to-red.)

CONNECT CONTROL POWER WIRING (24-v)
— Power leads are brought thru 1/2-in. hole pro­

vided in unit, Fig. 1 and 2. Extend leads to control

wiring terminal board located on top of control box,

Fig. 7. Connect leads to terminal board as shown

in Fig. 6.

Use Carrier-specified room thermostat and sub­

base for proper unit operation. Be sure that field-

installed jumper wire is connected between subbase
terminals W and Y. Set thermostat heat anticipator

at 1.0 amp for 1-phase units and 0.50 amp for
3-phase units.

FAN SPEED

SELECTOR BLOCK

(MOLEX PLUG)

COMPRESSOR

Fig. 7 — Typical Component Arrangement

(50HQ014-042 Shown)

1-PHASE

CONN. TO

DISCON NECT-
PER NEC

GROUND

LEAD

—^YEL —

—^BLK —

,__.GROUND

—TSlLUG

3-PHASE
CONN. TO

DISCONNECT-

PER NEC

—^YEL —

-TU

yel

_iT^YEL

50HQ.VQ

HEAT PUMP

CONTROL BOX

GROUND

LEAD

GROUND

œilug

50HQ.VQ

HEAT PUMP

CONTROL BOX

I-PHASE

Fig. 6 — Line Power Connections

START-UP

Water Flow and Temperature Data

1. Consider design water flow rates for efficient

operation. See Table 4 for permissible water flow
range.

2. Ensure that water temperature entering unit is

between 60 F minimum and 90 F maximum. If
water temperature below 60 F must be used,
insulate supply line and install a secondary drain
pan under the unit to remove condensate from
heat exchanger and internal plumbing.

CAUTION:

Water

temperature

outside

specified

temperature

rartge

may

cause

damage to

mût Do not jumper low temperar

ture switch in order to use ethytene

giycoi.

3. Ensure that supply water is clean and air is

purged from system. Air in supply water causes
scaling in heat exchanger. Foreign material in

water and/or excessive velocity of water can
cause damage to tubing.

To Start Unit

— Ensure that air filter is in place on

unit filter flanges provided. Do not operate unit

without filter in place. Adjust the thermostat as
follows;

1. Set selector switch at OFF.

2. Turn on main disconnect switch to unit.

3. Set fan switch as desired (ON or AUTO.).

4. Set thermostat dial at desired temperature.

5. Set selector switch at HEAT or COOL.

Check system refrigerant charge. See Service,

Refrigerant Charging on page 7.

Unit

Single-Phase

Compressors

Equipped

With a Compressor Start Thermistor (PTC De­
vice)

— When supply voltage is within limits indi­

cated on nameplate and compressor will not start,
check the thermistor with an ohmmeter.

If the PTC is good, and the compressor does not

start, disconnect the PTC from the starting circuit

and give unit a temporary capacitanee boost. Refer

to Carrier Standard Service Techniques Manual,

Chapter 2, for details on capacitance boost pro­

cedure. If unit does not start with capacitance boost,
compressor may be defective. If unit does start,
check starting capability with PTC assistance. If
questionable, remove PTC, add start capacitor and

start relay per start kit installation instructions.

WARNING: Capadtance boost or iastallatioa
of start capacitor and start relay should be per­
formed by trained personnel. Improper pro-

cedure could cause personal injurj' or equipment

damage.

Unit Controls and Safety Devices

HIGH-PRESSURE

RELIEF

VALVE

(except

50HQ,VQ0I4) is located in compressor. Relief valve
opens at a pressure differential of approximately

550 psi between suction (low side) and discharge

(high side) to allow pressure equalization.

CURRENT AND TEMPERATURE SENSITIVE
OVERLOAD (linebreak) — Internal on all com­

pressors except on 50HQ,VQ014 which has external

shell mounted overload. Overload resets auto­
matically when internal compressor motor tempera­
ture drops to a safe level (overloads may require up

to 45 minutes to reset). When an internal overload is

suspected of being open, eheck by using an ohm-

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