The head pressure control consists of a solid-state circuit on
a printed circuit board in an aluminum extrusion (to be fas-
tened to a panel of the unit) and a sensor assembly (to be
mounted to a return bend on the unit outdoor coil). A wire
from the sensor is connected to the circuit board control box
with wirenuts.
The head pressure control is available in two 1-hp models;
one is rated at 208/230 v; the other at 460 v.
BEFORE INSTALLING
Inspect the contents of this accessory package before install-
ing. File a claim with the shipper if contents are damaged or
parts are missing.
Parts necessary for mounting control and sensor are in-
cluded in the package. If sensor assembly is damaged, it can
be replaced separately.
The head pressure control maintains the proper head pres-
sure at any outdoor ambient temperature down to −20 F on
the 542J150,180; 551A/581A155,180; and 559F/579F180,216
units with 3 condenser fans. No field adjustments or calibra-
tions are required.
INSTALLATION
I. INSTALL WIND BAFFLES
Wind baffles must be field fabricated for all units to ensure
proper cooling cycle operation at low outdoor-ambient tem-
peratures. See Fig. 2 for baffle details. Use 20-gage galva-
nized sheet metal or similar corrosion-resistant materials for
the baffles.
CAUTION:
Use extreme care when drilling screw
holes and screwing in fasteners near outdoor coil to avoid
damage to tubing.
Use field-supplied screws to attach baffles to the unit. Screws
should be
1
⁄
4
-in. diameter or larger. Drill required screw holes
for mounting baffles.
II. MOUNT CONTROL
1. Turn off power to unit.
2. Open control box. Using a voltage meter, check that no
power is present at unit terminal block.
3. Remove panel next to control box. Locate space for head
pressure controller above electric heat fusing box (if so
equipped) near outdoor fan and compressor wiring har-
ness. Remove template from back of these instructions
and tape to panel. Drill pilot holes as indicated.
4. Fasten control assembly to unit with four no. 10 sheet
metal screws provided. To ensure electrical ground to
chassis, insert a star lockwasher (provided) under the
head of each screw.
NOTE: When properly positioned (wall mounted vertically
with leads protruding from bottom of extrusion), control is
weathertight.
III. MOUNT SENSOR ASSEMBLY
1. Remove outdoor air section access panel on control box
side of unit and corner post on hairpin end of outdoor
coil.
2. Route sensor wire through partition wall into outdoor
section.
3. Mount sensor on an outdoor coil hairpin bend as shown
in Fig. 3 or 4.
4. Secure sensor on coil hairpin bend with the 2 factory-
supplied no. 4-40 screws, plate washers, and 4-40 nuts.
5. Coil up unused sensor wire and secure it near sensor
or next to controller.
6. Protect sensor wire from physical damage or wind move-
ment as necessary.
Fig.2—WindBaffleDetail
Fig. 3 — Sensor Location on Condenser Coil, 542J, 551A,
and 581A Units
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