Carrier 50HCQA Installation Manual download pdf (Page 46)

Phase Loss Protection

The phase loss protection option will monitor the three-phase electrical

system to provide phase reversal and phase loss protection.

Phase Reversal Protection

If the control senses an incorrect phase relationship, the relay (K1) will

be de-energized (opening its contact). If the phase relationship is

correct, the relay will be energized. The control has a self-bypass

function after a pre-set time. If the control determines that the three

phases stay in a correct relationship for 10 consecutive minutes, the

relay will stay energized regardless of the phase sequence of three

inputs as long as 24-vac control voltage is applied. This self-bypass

function will be reset if all three phases are restored in a phase loss

event.

Phase Loss Protection

If the reverse rotation board senses any one of the three phase inputs

has no AC voltage, the relay will be de--energized (opening its

contact). This protection is always active as long as 24-vac control

voltage is applied, and is not affected by the self by-pass function of

the phase sequence monitoring function. However, in the event of

phase loss, the relay will be re-energized only if all three phases are

restored and the three phases are in the correct sequence.

A red LED is provided to indicate the function of the board. See

the table below.

LED STATUS FUNCTION

On Continuously Relay contact closed (normal operation).

Blinking

Relay contact open (phase loss or phase

reversal has occurred) — No power will be

supplied to the control system.

Off 24 vac control power not present (off).

Thermistor Troubleshooting

The electronic control uses thermistors to sense temperatures used

to control operation of the unit. Resistances at various temperatures

are listed in Table 17 and 18. Thermistor pin connection points are

shown in the Major System Components section. The general

locations of the thermistors are shown the Major System

Components section.

Air Temperatures

Air temperatures are measured with 10 kilo-ohm thermistors. This

includes supply-air temperature (SAT), outdoor-air temperature

(OAT), space temperature sensors (T55, T56, T58), and return air

temperature (RAT).

The supply air temperature (SAT) and outdoor air temperature

(OAT) thermistors use a snap-mount to attach through the unit

sheet metal panels. The snap-mount tabs must be flattened on the

tip end of the sensor to release for removal from the panel. (See

Fig. 16.) To reinstall, make sure the snap-mount tabs extend out.

Refrigerant Temperatures

Condenser coil temperatures are measured with 5 kilo-ohm

thermistors. These measurements provide an approximate saturated

condensing temperature for each circuit (SCT.A, SCT.B). Fig. 20--21

show the factory locations for the SCT thermistors. Ensure that

thermistors are placed at the correct location and are snapped securely

over the return bend so that contact is made between the thermistor

and the tube.

C07015

Fig. 16 -- SAT and OAT Thermistor Mounting

Thermistor/Temperature Sensor Check

A high quality digital volt-ohmmeter is required to perform this

check.

Connect the digital voltmeter across the appropriate thermistor

terminals at the J8 terminal strip on the Main Base Board (see

Major System Components section).

Using the voltage reading obtained, read the sensor temperature

from Table 17 and 18.

To check thermistor accuracy, measure temperature at

probe location with an accurate thermocouple-type

temperature-measuring instrument. Insulate thermocouple to avoid

ambient temperatures from influencing reading. Temperature

measured by thermocouple and temperature determined from

thermistor voltage reading should be close, within 5F if care was

taken in applying thermocouple and taking readings.

If a more accurate check is required, unit must be shut down and

thermistor removed and checked at a known temperature (freezing

point or boiling point of water) using either voltage drop measured

across thermistor at the J8 terminal, or by determining the

resistance with unit shut down and thermistor disconnected from

J8. Compare the values determined with the value read by the

control in the Temperatures mode using the Scrolling Marquee

display.

Sensor Trim

Corrective offsets can be applied to the space temperature and the

supply air temperature sensor readings. These corrections are set in

the ConfigurationTRIM menu for the display, or in the

MaintenanceTRIM table for CCN. See the Indoor Air Quality

section for available adjustments to IAQ and OAQ sensor readings.

The space temperature may be corrected by entering either a

calibration temperature value in SPT.C, or an offset temperature

value in SPT.T. The supply-air temperature may be corrected by

entering either a calibration temperature value in SAT.C,oran

offset temperature value in SAT.T. If installed, the return air

temperature may be corrected by entering either a calibration

temperature value in RAT.C, or an offset temperature value in

RAT.T. Temperature corrections should only be made if sensor

readings are compared to an accurate reference temperature

measurement device.

ComfortLINK v2.X

1 2 ... 41 42 43 44 45 46 47 48 49 50 51 ... 103 104

Comments to this Manuals

No comments

Carrier 50HCQA Installation Manual Page 46

Comments to this Manuals

Related products and manuals for Heat pumps Carrier 50HCQA