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Si39-406 Installation
General Information 39
Special vacuum drying
This vacuum drying method is selected when there is a suspicion that there may be moisture in the
pipes.
For example:
„
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 due to a long term of 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 the
operation.
[Operational steps]
1. Vacuum drying (1st time): 2 hours
2. Vacuum breaking (1st time): Use nitrogen to raise pressure to +7.25psi (+0.05MPa).
(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.)
3. Vacuum drying (2nd time): Operate the vacuum pump for at least 1 hour.
(Observations: Degree of vacuum has reached –14.61psi (5 mmHg). If the degree of vacuum
has not reached –14.61psi (5 mmHg) after 2 hours or more then repeat the operations at 2
(vacuum breaking) and 3 (vacuum drying) above.)
4. Carry out maintained vacuum test: 1 hour
5. Additional charge of refrigerant
6. Open stop valve to the full