Hvac CVH8, Руководство по обслуживанию

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CVH8, HVH8, TVH8, VA9, HVA9, TVA9: APPLICATION GUIDELINE & SERVICE MANUAL
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
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High Pressure Switch Protection
The outdoor unit is equipped with high pressure switch. If the control
senses the opening of a high pressure switch (open 600+/-5 psig, close
470+/-10 psig @77°F), it will respond as follows:
1. Display the appropriate fault code (see Fig. 31 ).
2. After a 6 minute delay, if there is a call for cooling or heating and
HPS is reset, the PEV opens for 150 seconds to equalize system
pressures. Compressor and fan will then ramp to the next lower
stage of operation until demand is satisfied. Staging down and
resetting to the highest stage will end after 2 hours of accumulated
operation without further HPS trips.
3. A system malfunction will occur after repeated HPS faults and the
stage has reached the lowest level. This could take five consecutive
HPS trips if the first occurred in stage 5 demand, or 1 HPS trip if in
stage 1 demand.
4. In the event of a high-pressure switch trip or high-pressure lockout,
check the refrigerant charge, outdoor fan operation, and outdoor
coil (in cooling) for airflow restrictions, or indoor airflow in
heating.
Low Pressure Protection
The outdoor unit is equipped with suction pressure transducer. If suction
pressure drops below 15 psi at any time, or below 33 psi for 5 minutes,
the compressor and fan will stop running and an error code will be
displayed on user interface.
1. If there is still a demand for unit operation after the 15 minute delay
and pressure has increased to >43psi (cooling) and >35psi (heating)
, system will resume operation.
2. If there are three (3) consecutive trips because of suction pressure
dropping below 15 psi, the low pressure switch will lock out
operation for 4 hours. Trip counter will be reset after 15 minutes of
successful operation.
3. When a change in demanded stage occurs, suction pressure is
checked at each stage in between current and demanded stage. This
is to prevent ramping of compressor speed too quickly and creating
a low pressure situation. As long as suction pressure is >=45psi,
the compressor is able to ramp to next stage. If suction pressure is
lower than required, additional wait time at current stage will occur.
4. In the event of a low-pressure trip or low-pressure lockout, check
the refrigerant charge and indoor airflow (cooling) and outdoor fan
operation and outdoor coil in heating.
Suction Pressure Transducer (SPT)
If accuracy of the transducer is questioned, the technician can check it
while it is attached to the AOC board. Connect a gage manifold to the
suction valve gage port fitting.
At the AOC board, with the wire harness receptacle exposing a portion
of the three pins on the AOC board, a DC voltmeter can read the DC
voltage between ground and supply (input) terminal. Ensure that the
input voltage is 5 VDC. Next, read the DC voltage across the ground
and output terminal. Record the output voltage.
The suction pressure that the pressure transducer is reading can be
calculated by taking the output voltage and subtracting 0.5 from it then
taking that difference and multiplying it by 50. Pressure (psig) = 50.0 x
(DCV out - 0.5). For example, if the measured voltage is 3.0 VDC:
50 X (3.0 - 0.5) = 50 X 2.5 = 125 psig. See Fig. 28 .
A12035
Fig. 28 – Suction Pressure Transducer (SPT)
Output Function Graph
Temperature Thermistors
Thermistors are electronic devices which sense temperature. As the
temperature increases, the resistance decreases. 10Kohm thermistors are
used to sense outdoor air temperature (OAT), coil temperature (OCT)
and the suction line temperature (OST) located between the reversing
valve and the accumulator. A 50Kohm thermistor is used to sense
discharge temperature (ODT).
Refer to Table 9 and Figs. 29 and 30.
A91431
Fig. 29 – 10K Thermistor Resistance Vs Temperature
Table 9 – 10K/50K Resistance Values vs Temperature
10Kohm °C (°F)
TEMPERATURE RESISTANCE (ohms)
25.0 (77.0) 10.0 + / - 2.3%
0.0 (32.0) 32.6 + / - 3.2%
-28.0 (-18.4) 85.5 + / - 3.4%
50Kohm
125.0 (257.0) 1.7 + / - 1.6%
75.0 (167.0) 7.40 + / - 2.0%
25.0 (77.0) 50.0 + / - 2.3%