38
All wiring t hat terminates at a unit- mounted terminal
must be selected from wiring material s under the NEC
Table 310.15(B)(16), 75 C (or higher) column only. Check
specifications for external disconnect lug sizes to
determine if 60 C wiring materials may be used between
branch circuit origin and the disconnect switch.
There are four different situations that an installer can
encount er with these units. Three are for new unit
installations (base unit has not been connected to a power
supply), unit without factory disconnect switch, unit with
factory disconnect switch, and unit with factory HACR
breake r. The fourth situation is for an existing unit that is
already connected to a power supply and the heaters are
being retrofitted. For each situation, there is usually one
of the fol lowing conditions: (1) without singl e point box,
with single point box
Each situation is discussed below.
New Unit Installation Without Factory Disconnect or
HACR
Unit power supply wires from the ext ernal
(field- supplied) disconnect switch are c onnected to the
base unit’s power connection terminal lugs. Refer to unit
wiring label to identify these terminal s (these may be lugs
on cont actors or at power terminal block). The heater
power wires are also connected at these terminals.
Installation WITH Single Point Box
Remove knockouts for appropriate size conduit from unit
block- off pa nel and single point box. Install conduit (rigid
or electrometallic tubing) through conduit drip boot as
shown (See Fig. 45).
Drip boot will accept conduit sizes 3/4 - in. to 1 - 1/2
inches. The drip boot eliminates the need for watertight
conduit fittings at the single point box.
Unit power supply wires from the external
(field- supplied) disconnect switch are connected to power
lugs on field connection device provided in Single Point
Box. This device may be a terminal block or fuse block
FU2’s line side terminals. The heater power wires are
connected to the load side terminals on the same device.
Existing Unit
An existing unit will usually have been installed following
values marked on the base unit’s informative data plate
for wire sizing, branc h circuit over- current protection and
disconnect switch rating. When electric heaters are added
to air conditioning (cooling) units, these values may be
changed. When electric heaters are added to heat pump
units, one or more of these values will be changed.
Check the installed unit’s field power wires for conductor
size, and determine c onductor rated ampacity per NEC
Table 310.15(B)(16). Compare thi s value to the MIN CKT
AMPS value on the unit infoplate for base unit plus
electric heaters (plus power exhaust if connected). If the
MIN CKT AMPS value is greater than the rated ampacity
of the power supply wires, t he unit power supply
conductors must be replaced.
NOTE: Supply wiring must comply with NEC (National
Electrical Code) and all local requirements.
Check the installed unit’s branch circuit over- current
protection device (fuse or HACR breaker) for rating in
amps. Compare this val ue t o the FUSE OR HACR
BREAKER value on t he unit infoplate for base unit plus
electric heaters (plus power exhaust if connected). If the
FUSE OR HACR BREAKER value is greater than the
rated ampacity of the installed device, the unit branch
circuit over- current protection device must be replaced.
Check the installed unit’s disconnect switch for rating in
amps. Compare this value to MINIMUM UNIT
DISCONNECT value on the unit infoplate for base unit
plus electric heaters (plus power exhaust if connected). If
the MINIMUM UNIT DISCONNECT value is greater
than the rated ampacity of the installed disconnect switch,
the unit disconnect switch must be replaced.
To complete the unit power wiring at the Single Point Box
or base unit t erminals, follow the appropriate directions
under ”New Unit” discussions above.
Complete Unit Inst allation
1. Mark the appropriate block on the unit nameplate for
the accessory heater kW installed. Note the required
MIN CKT AMPS value for this unit- heater
combination. Ensure the field power conductors are
sized to handle this ampacity.
2. Locate heater covers. For all heaters. The heater
cover is the plate removed from heater mounting
bracket.
3. Place adhesive- backed wiring label on flanged side
of heater cover.
4. Fasten heater cover to heater module with 2 screws
provided with heater. Fla nges of cover must face out.
(See Fig 50).
5. Close singl e point box cover and secure with one
screw.
6. Replace control box cover, using remainder of scre ws
saved from Step 4 of Installing Single Point Box
section.
7. Run conduit through (rigid or EMT) the c onduit drip
boot in the rain shield bracket to the single point box.
Provide an appropriate fitting to connect the conduit
to the single point box wall and ground appropriately.
Drip boot eliminates the need for watertight conduit
fittings at the single point box.
8. Run wire through conduit connecting outside power
to the designated terminals at the top of the single
point box. Ground appropriately.
9. Replace indoor and outdoor panels with screws saved
from Step 2 of Disconnect Field Supply section and
Step 3 of Install Single Point Box sec tion. Place
adhesive- backed Max. Air/Max. Static label on
external panel covering heaters (See Fig. 37 and 38).
10. If all other work on the unit is done, reapply unit
power per lock - out/tag- out procedures.
40QQ
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