Page 21 mrcool.com
Unit Installation
Conventional Line Set Installation
Vacuum Lines
WARNING
•Make sure the outlet of the vaccuum pump is away from any potential source of fire and is
well-ventilated.
•Before vacuum pumping, make sure the unit cut-off valves are closed.
•When vacuum pumping, both the liquid pipe and the gas pipe must be pumped.
1. Remove the caps on the liquid valve, gas valve and also the service port.
2. Connect the hose at the low pressure and high pressure sides of the manifold valve assembly to the
service port of the unit’s gas valve and liquid valve. Meanwhile, the gas and liquid valves should be kept
closed to avoid refrigerant leak.
3. Connect the hose used for evacuation to the vacuum pump.
4. Open the switch on the lower pressure side of the manifold valve assembly and start the vacuum pump.
The switch at the high pressure side of the manifold valve assembly should be kept closed. If not, evacuation
will fail.
5. The evacuation duration typically depends on unit capacity. (Model MDUO18048 - 30 minutes
/MDUO18060 - 45 minutes) Verify that the pressure gauge on the low pressure side of the manifold valve
assembly reads -0.1Mp (-75cmHg). If it does not, there is a leak somewhere. Close the switch fully and stop
the vacuum pump.
6. Wait for 10 min to see if the system pressure remains unchanged. During this time, the reading of the
pressure gauge at the low pressure side should not be larger than 0.005Mp (0.38cmHg).
7. Open the liquid valve slightly, and let some refrigerant go to the connection pipe to balance the pressure
inside and outside of the connection pipe, so that air will not come into the connection pipe when removing
the hose. Note that the gas and liquid valve can be opened fully only after the manifold valve assembly is
removed.
8. Return the caps to the liquid valve, gas valve and service port.
9. For large-size units, there are maintenance ports for liquid valve and gas valve. During evacuation, you
may connect the two hoses of the branch valve assembly to the maintenance ports to speed up the
evacuation.
Refer to Fig. 2.20
For installation with a No-Vac® Quick Connect® Line Set, refer to the next section starting on page 23
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