Wiring Connections; Outdoor Unit; Indoor Unit - Lennox MHA Series Installation Instructions Manual

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3. Evacuate the system to a reading of 5000 Microns (5
Torr).
4. Break the vacuum by allowing nitrogen into the port
connections (liquid and gas line pipes) until a positive
pressure is achieved.
5. Evacuate the system to a minimum reading of 500
Microns (0.5 Torr).
6. For a moisture­free system, ensure the vacuum is
held without movement for a minimum of 4 hours.
7. If vacuum fails to hold, carry out steps 2 through 6
until vacuum holds.

Wiring Connections

In the U.S.A., wiring must conform with current local
codes and the current National Electric Code (NEC).
In Canada, wiring must conform with current local codes
and the current Canadian Electrical Code (CEC).
WARNING
Electric Shock Hazard. Can cause injury or death. Unit
must be rounded in accordance with national and local
codes.
Line voltage is present at all components when unit is
not in operation. Disconnect all remote electric power
supplies before opening access panel. Unit may have
multiple power sources.
CAUTION
All terminal connections must be made as illustrated
in the following diagrams. Improperly connected wiring
could damage unit or cause communication errors
between indoor and outdoor units.

Outdoor Unit

Refer to unit nameplate for minimum circuit ampacity
and maximum over­current protection size.
Make all electrical power wiring connections at the
outdoor unit.
115VAC Outdoor Unit
Terminal Block
1
2
3
L
Y/G
From Power
Suppl y
Outdoor Unit
115VAC Indoor Unit
Terminal Block
N
1
Y/G

Indoor Unit

Figure 34. Single Zone Wiring
Be sure to reattach all electrical box covers after con­
nections are complete.
Indoor Unit
Indoor unit is powered by the outdoor unit.
Communication, power and ground wiring ­ Use one
stranded 3­conductor with ground wire.
See "Table 9. Single Zone Installation Wiring Require­
ments" on page 15 for wiring requirements.
NOTE: When installing a condensate pump the line voltage
will have to be broken by using the condensate
wiring or through the use of an external relay or
contactor.
All illustrations listed are typical wiring diagrams. Refer
to the wiring diagram on the unit for actual wiring.
Figure 33. Indoor Unit Terminal Block
208/230V Outdoor Unit
Y/G
1
3
Y/G
14
IMPORTANT
Terminal block
The wiring diagram is located
on the inside of the indoor unit's
terminal block cover.
Terminal Block
2
3
L1
L2
Y/G
From Power
Suppl y
Outdoor Unit
Terminal Block
Cover
Screw
Cable Clam p
208/230V Indoor Unit
Terminal Block
Y/G
*
1
3
*
18 and 24K
unit has
five terminal
sets.
Indoor Unit

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