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Unit Type Description
Analog Electronic VariTrane units use an
electronically-controlled air damper for
primary air modulation. The unit types
available are single-duct units (VCCF ,
VCWF , VCEF), series fan-powered units
(VSCF , VSWF , VSEF), parallel fan-
powered units, (VPCF , VPWF , VPEF) and
low-height fan-powered units (LSCF ,
LSWF , LSEF , LPCF , LPWF , LPEF).
Single-Duct Units
The basic unit consists of an air damper
mounted in a sheet metal casing, which
is used to control the volume of air
introduced to the occupied zone. The
unit is designed to modulate either
cooling or heating air. The basic cooling-
only unit can be equipped with reheat
coils located at the discharge of the unit.
Standard choices include an electric coil
with up to three stages of heat or a hot-
water coil.
Figure 1 – Typical Single-Duct Units
VCCF
VCWF
VCEF
VAV-SVX03A-EN
Unit
Information
Fan-Powered Units
VariTrane fan-powered units can be
either parallel or series, with or without
re-heat. See Figure 2.
Note: Low-Height is similar to the series
and parallel fan-powered units. All
series and parallel references from this
point on will also include Low-Height
unless noted.
The fan on a series unit runs continu-
ously whenever the main air-handler
unit is in operation. There are various
options for starting the fan. The fan can
be started three ways: 1) remotely,
2) by a duct-pressure switch, or 3) by a
combination of both. The particular fan
control method will vary from unit to
unit, depending upon job needs.
Typically, the re-heat is off while the air
damper modulates primary air and
responds to zone temperature. If zone
temperature decreases to the point
where a decrease in primary air will not
maintain the desired temperature, the
re-heat will be activated to increase the
temperature of the discharge air.
On a parallel unit, the VariTrane air
damper delivers primary cooling air to
the unit outlet. When the space
temperature decreases beyond air
damper control, the fan is turned on as
the first stage of heat. The fan delivers
Table 1 – Maximum Fan Motor Amperage (FLA)
Fan
Size
Series/Parallel 01
Series/Parallel 02
Series/Parallel 03
Series/Parallel 04
Series/Parallel 05
Series/Parallel 06
Series/Parallel 07
Low Height 08
Low Height 09
Low Height 10
plenum air from above the occupied
space to the unit outlet, which is mixed
with primary air and delivered to the
occupied space.
Note: Either the fan, the air damper or
both can deliver airflow into the
occupied space. In order to prevent
primary airflow from exiting through
the fan when the fan is not running on a
parallel unit, a back-draft damper is
provided. When the fan is not running,
the efficiency of this system is the
same as a standard single duct VAV
unit.
Typically, the control systems applied
to parallel units cause the air damper
to close to zero or a minimum flow
before the fan is activated. After the
fan is activated, the heat will be
activated upon further reduction in
zone temperature. Therefore, little
primary air is mixed with the
heated air.
Fan-powered units are available with
rectangular discharge connection only.
Either straight flange or slip and drive
is available with electric heat. The
electric heater is mounted on the
discharge of the unit. Hot water coils
are connected to the plenum inlet on
parallel units, and to the discharge of
series units.
HP
115
277
VAC
VAC
VAC
1/8
1.6
0.7
1/8
1.6
0.7
1/3
5.4
1.8
1/3
5.4
1.8
1/2
7 .6
2.6
1/2
—
3.8
1
—
4.7
1/8
4.7
1.76
2 x 1/8
2 x 2.1
2 x 0.79
2 x 0.62
2 x 1/8
2 x 4.7
2 x 1.76
2 x 1.52
347
208
VAC
0.7
—
0.7
—
1.5
—
1.5
—
2.1
—
3.8
6.3
3.6
6.9
1.52
—
—
—
5
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