Lennox ZHA036 Installation Instructions Manual Download Page 17

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Page 17

507111-02 2/2015

C - Refrigerant Charge and Check

WARNING-Do not exceed nameplate charge under
any condition.

This unit is factory charged and should require no further
adjustment. If the system requires additional refrigerant,

reclaim the charge,

evacuate the system,

and

add

required nameplate charge.

NOTE - System charging is not recommended below
60

F (15

C). In temperatures below 60

F (15

C),

the

charge

must

be weighed into the system.

If weighing facilities are not available, or to check the
charge, use the following procedure:

IMPORTANT - Charge unit in standard cooling mode
high stage only.

1- Make sure outdoor coil is clean. Attach gauge

manifolds and operate unit at full CFM in cooling mode
with economizer disabled until system stabilizes
(approximately five minutes). Make sure all outdoor air
dampers are closed.

2- Compare the normal operating pressures (see tables

4 - 9) to the pressures obtained from the gauges.
Check unit components if there are significant
differences.

3- Measure the outdoor ambient temperature and the

suction pressure. Refer to the appropriate circuit
charging curve to determine a target liquid
temperature.

Note - Pressures are listed for sea level applications.

4- Use the same thermometer to accurately measure the

liquid temperature (in the outdoor section).

If measured liquid temperature is higher than

the target liquid temperature, add refrigerant to
the system.

If measured liquid temperature is lower than

the target liquid temperature, recover some
refrigerant from the system.

5- Add or remove charge in increments. Allow the

system to stabilize each time refrigerant is added or
removed.

6- Continue the process until measured liquid

temperature agrees with the target liquid
temperature. Do not go below the target liquid
temperature when adjusting charge. Note that
suction pressure can change as charge is adjusted.

7- Example ZHA036: At 95°F outdoor ambient and a

measured suction pressure of 130psig, the target
liquid temperature is 105.5°F. For a measured liquid
temperature of 106°F, add charge in increments until
measured liquid temperature agrees with the target
liquid temperature.

D - Compressor Controls

See unit wiring diagram to determine which controls are
used in each unit. Optional controls are identified on
wiring diagrams by arrows at junction points.

1- Defrost Switch (S6)

Defrost switch closes to initiate defrost when liquid
line temperature falls to 42



F (5.6



C). Defrost switch

opens when liquid line temperature reaches 70



(21



C) to terminate defrost. If the liquid line

temperature does not rise above 70



F (21



C), the

CMC1 will terminate defrost after 14 minutes. The
defrost switch is located on the liquid line between the
outdoor expansion valve and the distributor

2- Defrost Control (CMC1)

Defrost is liquid line temperature initiated and
operates for 14 minutes unless terminated by liquid
line temperature.

When the liquid line temperature drops below 42°F
(5.6



C), the defrost switch closes and signals the

defrost control

that a defrost cycle is needed. If

the defrost switch is still closed after 90 minutes
(default), a defrost cycle begins and operates for
up to 14 minutes. The defrost switch can terminate
the defrost cycle before the 14 minutes elapses if
liquid line temperature reaches 70



F (21



Electric heat is energized during defrost to maintain
discharge air temperature.

TABLE 4

ZHA036 NORMAL OPERATING PRESSURES

Outdoor Coil Entering Air Temperature



105



115

