Install Manual

Page 22

mrcool.com

Unit Installation

Conventional Line Set Installation

Vacuum Lines

WARNING

• Make sure the outlet of the vacuum 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 and liquid valve. Meanwhile, the gas and liquid valves should be kept closed

to avoid a 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, the

evacuation will fail.

5. The evacuation duration typically depends on the unit capacity: for Model MDUO18024036 time is

generally 30 minutes, for model MDUO18048060 time is generally 45 minutes. Verify that the

pressure gauge on the low pressure side of the manifold valve assembly reads -0.1 Mp (-30 in Hg). If it

does not, there is leak somewhere. Close the switch fully and stop the vacuum pump.

6. Wait for 10 minutes 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 0.005 Mp (0.15 in Hg).

7. Open the liquid valve slightly, and allow some refrigerant to be released into 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-sized units, there are maintenance ports for the 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 on the following page.

For installation with a No-Vac

Quick Connect

Line Set, refer to the next section starting on page 24