Special vacuum drying
This vacuum drying method is selected when there is a suspicion that there may be moisture in
! When moisture was discovered during the refrigerant pipe flushing operation
! When there is a risk of condensation forming inside the pipes during periods of heavy rainfall
! When there is a risk of condensation forming inside the pipes if this refrigerant pipe works
! When there is a risk that rainwater may have entered the pipes during installation
The special vacuum drying method is the same as the standard method except that nitrogen is
introduced into the pipes to break the vacuum on one or more occasions during the course of
1. Vacuum drying (1st time): 2 hours
2. Vacuum breaking (1st time): Use nitrogen to raise pressure to +0.05MPa.
3. Vacuum drying (2nd time): Operate the vacuum pump for at least 1 hour.
4. Carry out maintained vacuum test: 1 hour
5. Additional charge of refrigerant
6. Open stop valve to the full
∗ The gas used for the vacuum breaking operation must be nitrogen.
takes long time
(Since the nitrogen gas used to break the vacuum is dry nitrogen this process serves only to
enhance the overall drying effect of the vacuum drying operation itself.
However, since the effectiveness of this process is severely impaired by a high moisture
level inside the pipes, the utmost care is required during installation to see that water does
not enter or form inside the refrigerant pipes.)
(Observations: Degree of vacuum has reached -755 mmHg. If the degree of vacuum has not
reached -755 mmHg after 2 hours or more then repeat the operations at 2 (vacuum
breaking) and 3 (vacuum drying) above.)
(The use of oxygen brings a serious risk of explosions)
[Special vacuum drying time chart]
Time required: approx. 4 hours.