Si30-408
VRV in General
Cases for Examination
119
1.17 Faulty Heating.
Applicable
Models
VRV in general
Condition
During heating operation with the ceiling mounted built-in type indoor units, cold air was blasted
sometimes causing draft. High-pressure had reached the target value and was stabilized, the
discharge air temperature of indoor unit was approx. 40°C, and same condition was not
reproduced during inspection of the unit.
Cause
Drop of temperature in discharge air due to indoor unit's capacity control. (Temperature set by
the remote controller was as low as 22°C.)
In order to prevent hunting of indoor temperature due to ON/OFF switching of thermostat, VRV
uses an electronic expansion valve mounted to the indoor unit to control the flow rate (capacity
control) of refrigerant. In heating operation, if the temperature of suction air of indoor unit closes
to the temperature set by the remote controller, capacity (flow rate of refrigerant) is adjusted by
closing the opening degree of the electronic expansion valve. Therefore, if the temperature of
liquid pipe of indoor unit drops and subcooling degree increases, the temperature of blow-out air
drops simultaneously.
Measure
Explain that it results under the normal control.
Point of
Diagnosis
1. Check whether the condensation temperature (high-pressure) has reached the value around
the target value of 1.7MPa during the heating operation.
2. Check whether the capacity of indoor unit is not being controlled (the difference between the
temperature of suction air and set value).