8
Step 4 — Pressure and Vacuum Test Sys-
tem —
Use nitrogen to carry out the system pressure test for
leaks. Gage ports on the service valves for the suction and liq-
uid lines at the outdoor unit should be used for pressure test,
and the service valves should be in closed position. Use of
proper gage is required to record nitrogen pressure. The system
pressure test is done in two steps:
1. Charge system with nitrogen up to 150 psig. Watch the
pressure gage for 4 hours. Drop in pressure indicates leak
in the system. Rectify leak before moving to next step.
2. Remove nitrogen and recharge the system with nitrogen
up to 500 psig. Watch the pressure gage for 6 hours. If
there is no drop in pressure, remove the nitrogen and start
vacuuming the system.
Vacuuming should be performed on both suction and liquid
sides through the gage ports on the service valves at the out-
door unit. The service valves should be in closed position. Vac-
uum the system down and hold the system for 1
1
/
2
hr at or be-
low 500 micron. At this point, the system is ready to be
charged with R-410A refrigerant. See Table 5 for the refriger-
ant amount to be added.
OUTDOOR UNIT
INDOOR UNITS
INDOOR UNIT
T
O
INDOOR
UNIT ELEV
A
TION
DIFFERENTIAL
MAXIMUM PIPING EQUIVALENT LENGTH
MAX. PIPING EQUIV. LENGTH
FROM FIRST LINE BRANCH PIPE
FIRST LINE BRANCH PIPE
L3
L1
L2
L4
L5
L6
A38-7433
INDOOR UNIT
T
O
OUTDOOR UNIT
ELEV
A
T
ION DIFFERENTIAL
A
B
C
D
E
PIPING LENGTH
ALLOWABLE VALUE (ft)
PIPES
TOTAL PIPING LENGTH (ACTUAL)
328
L1 + L2 + L3 + L4 + L5 + L6 + A + B + C + D + E
MAXIMUM PIPING (L)
Actual
148
L1 + L3 + L4 + L5 + L6 + E
Equivalent
164
FIRST TO FARTHEST INDOOR UNIT
66
L3 + L4 + L5 + L6 + E
ELEVATION DIFFERENTIAL
ALLOWABLE VALUE (ft)
INDOOR UNIT TO OUTDOOR UNIT
Outdoor Unit Above
98
Outdoor Unit Below
66
INDOOR UNIT TO INDOOR UNIT
26
Fig. 9 — Allowable Piping Length and Drop Height
