START-UP
Use the following information and Start-Up Checklist on
page CL-1 to check out unit PRIOR to start-up.
Unit Preparation — Check that unit has been installed
in accordance with these installation instructions and appli-
cable codes.
Compressor Mounting — Loosen the compressor hold-
down bolts until sidewise movement of the washer under
each holddown bolt head can be obtained. Do not loosen
completely as bolts are self-locking and will maintain
adjustment.
Service Valves — Ensure that the suction and dis-
charge service valves are open. Damage to the compressor
could result if they are left closed.
Internal Wiring — Check all electrical connections in
unit control boxes; tighten as required.
Refrigerant Service Ports — Each refrigerant sys-
tem has one suction port located in the top of the compressor
motor casing. All units also have one service port on the liq-
uid line valve and one on the compressor discharge valve.
Be sure that caps on the ports are tight.
Minimum Outdoor Air Temperature — The mini-
mum outdoor air temperature is −20 F ambient for heating
duty.
Power Exhaust — The optional non-modulating power
exhaust is a two-stage design where the operation of the
exhaust fans is linked to economizer position. When the
supply fan is running and the economizer is 25% open, the
base module closes contacts, activating 2 exhaust fans. When
the economizer position reaches 75% open, the base module
activates the other 2 exhaust fans. The fans will turn off when
the economizer closes below the same points. The econo-
mizer position set points that trigger the exhaust fans
can be modified, but only through use of the Service Tool,
ComfortWorks™, or Building Supervisor software. If single-
stage operation is desired, adjust the economizer set points
to identical values at the desired point to activate all exhaust
fans.
The optional modulating power exhaust is controlled by a
modular electronic sequencer system. This system consists
of a model R353 signal input module and 4 model S353 stag-
ing modules. The signal input module receivesa0to10vdc
signal from the building pressure transducer, which is mounted
adjacent to the supply static transducer behind the filter
access panel. The modules are mounted just below the unit
control board. The left module is the R353, and the 4 mod-
ules on the right are S353 modules for stages 1 through 4.
On the unit wiring label, the R353 is designated PEC, and
the S353 modules are designated PES1 through PES4.
The building pressure transducer range is − 0.5 to
+ 0.5 in. wg. It is powered bya0to10vdcsignal.A factory-
installed hose at the ‘‘Lo’’ connection leads to atmosphere,
and a field-supplied hose must be connected to the ‘‘Hi’’con-
nection and led into the building to a point where building
pressure is to be controlled. There is a plug button in the
bulkhead just above the transducers, for use in leading the
hoses into the building via the return air ductwork.
NOTE: With ‘‘Lo’’ connection to atmosphere and ‘‘Hi’’
connection to building, the unit will attempt to maintain a
positive building pressure. To maintain a negative build-
ing pressure, connect ‘‘Lo’’ to building and ‘‘Hi’’ to the
atmosphere.
There are 3 adjustments at the R353 module, all of which
have been factory set. In the center of the circuit board is a
set of 4 pins with a jumper, labeled J2. This determines the
mode of operation. The bottom 2 pins must be jumpered for
direct operation. Direct operation means that the staging mod-
ules are activated in sequence as the input signal increases.
At the upper right corner of the board is a set of 5 pins and
jumper, which determines the time constant for the control.
The time constant is the delay in response built into the con-
trols. The jumper should be on the middle or bottom 2 pins,
for the maximum time constant. The delay can be decreased,
if desired, by moving the jumper progressively upward,
always jumpering adjacent pins.
At the lower left corner of the board below the terminal
strip is a resistor marked R27. This must be removed in or-
der to obtain the 0 to 10 vdc signal output. There will not be
a resistor on a factory-supplied module, but a resistor may
be present on a replacement module and must be removed.
The R353 module has a terminal block with 7 connec-
tions available for wiring. The 2 right-hand terminals are for
the 24 vac and common connections. The next 2 terminals
are for the 0 to 10 vdc signal. Consult the wiring label for
wire identification if replacing the module. The 3 left-hand
terminals are not used for this application.
The S353 module has an LED (light-emitting diode), a set
of 4 jumper pins, and 2 potentiometers. The LED will light
whenever the module is activated, providing a visual indi-
cation of the number of exhaust fans running. The jumper
pins are arranged in a square format. Two jumpers are used
to determine the mode of operation (direct or reverse). The
2 jumpers must be arranged horizontally for direct action
(factory set).
At the top of the module are 2 potentiometers. The left
potentiometer adjusts the offset. The right potentiometer
adjusts differential. The potentiometers are factory set for a
nominal 0 in. wg building pressure.
The offset set point is defined as the point at which a mod-
ule turns off a fan, and is measured in terms of percent of the
input signal. For control purposes, 0 offset is at an arbitrary
‘‘floor’’ which is established at 10% of the input signal, or
1 vdc. In this example, the first stage will turn off at 30%
(3 vdc), and the offset potentiometer will be set at 20%. The
second stage will turn off at 50% signal (5 vdc), and the off-
set potentiometer will be set at 40%. The fourth stage is at
the maximum 75% offset, which equates to 85% signal or
8.5 vdc. The offset potentiometer is calibrated in 10%
increments.
Table 7 relates building pressure to signal level.
Table 7 — Potentiometer Signal Levels
BUILDING PRESSURE
(in. wg)
SIGNAL LEVEL
(vdc)
−0.50 2
−0.25 4
0.00 6
0.25 8
0.50 10
If the building pressure is controlled at 0 in. wg, offset of
the first stage should be set at 50%, which equates to 60%
of the input signal, or 6 vdc. The other stages can then be set
as desired between 50% and 75%.
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