Lennox MCFA Service Manual page 87

Length
Max. length for all rooms (m)
Max. length for one IU (m)
Max. height difference between IU and
OU (m)
Max. height difference between IUs (m)
18.2.1. Additional Refrigerant Charge
Additional Refrigerant
Charge
18.2.2. Gas Leak Check with Soap Water:
Apply soap water or a liquid neutral detergent on the
connections with a soft brush to check for leakage in the pipe
connecting points. If bubbles emerge, the pipes are leaking.
18.2.3. Air and Moisture
Air and moisture in the refrigerant system cause the following
problems:
• Increases in system pressure
• Increases in operating current
• Decreases in cooling and heating efficiency
• Blocks in capillary tubing caused by moisture in the
refrigerant circuit freezing
• Corrosion of parts in the refrigerant system caused
by water
The indoor units and the pipes between indoor and outdoor
units must be tested for leakages and evacuated to remove
gas and moisture from the system.
18.2.4. Air Purging using a Vacuum Pump
• Completely tighten the flare nuts on the indoor and
outdoor units. Confirm that both the2-way and 3-way
valves are set to the closed position.
• Connect the charge hose with the push pin of the
Handle Lo to the 3-way valve gas service port.
• Connect the charge hose of the Handle Hi to the
vacuum pump.
• Fully open the Handle Lo of the manifold valve.
• Turn on the vacuum pump to begin evacuation.
• Conduct a 30-minute evacuation. Check whether
the compound meter indicates - 0.1Mpa(14.5Psi).
If the meter does not indicate -0.1Mpa (14.5Psi)
Table 17. Line Set Length - Meters (Feet)
1 Drive 2
40 (131)
25 (82)
15 (49.2)
10 (33)
Table 18. Additional Charge - Grams (Ounces)
Pre-charge pipe length -
Meters (feet)
Grams
Ounces
1 Drive 3
60 (197)
30 (98)
15 (49.2)
10 (33)
1 Drive 2 1 Drive 3
1.5 (49.2) 22.5 (73.8)
15 x (length for all 15 x (length for all
rooms - 15) rooms - 22.5)
0.161 x (length for 0.161 x (length for
all rooms 49.2) all rooms 73.8)
after 30 minutes has elapsed, continue evacuation
for 20 more minutes. If the pressure does not reach
- 0.1Mpa (14.5Psi) after 50 minutes has elapsed,
check if there are any leaks.
• Fully close the Handle Lo valve of the manifold valve
and turn off the vacuum pump. After 5 minutes,
confirm that the gauge needle is not moving.
• Turn the flare nut on the 3-way valve 45°
counterclockwise for 6-7 seconds. Once gas begins
to come out, tighten the flare nut. Make sure the
pressure display on the pressure indicator is higher
than atmospheric pressure. Then remove the charge
hose from the 3-way valve.
• Fully open the 2-way and 3-way valves and securely
tighten the cap on the 3-way valve.
18.2.5. Adding Refrigerant if Pipe Length
Exceeds Charge Less Pipe Length
Connect the charge hose to the charging cylinder and open
the 2-way and 3-way valves. With the charge hose you
disconnected from the vacuum pump, connect it to the valve
at the bottom of the cylinder.
If the refrigerant is R410A, place the cylinder bottom-up to
ensure liquid charging is possible.
• Purge the air from the charge hose.
• Open the valve at the bottom of the cylinder and
press the check valve on the charge set (be careful
of the liquid refrigerant).
• Place the charging cylinder onto the electronic scale
and record the weight.
• Turn on the air conditioner in cooling mode.
• Open the valves (Low side) on the charge set.
Charge the system with liquid refrigerant.
87
1 Drive 4 1 Drive 5
80 (262) 80 (262)
35 (115) 35 (115)
15 (49.2) 15 (49.2)
10 (33) 10 (33)
1 Drive 4 1 Drive 5
30 (98.4)
15 x (length for all 15 x (length for all
rooms - 30) rooms - 37.5)
0.161 x (length for 0.161 x (length for
all rooms xx.x) all rooms xx.x)