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AIRFLOW ADJUSTMENT
Each 37HS volume controller is equipped with a maxi-
mum cfm lever for setting the required unit airflow in the
field. The lever is located at the bottom of the controller. See
Fig. 32. The controller has a star wheel located at the top of
the controller for setting the minimum airflow. The star wheel
is also shown in Fig. 32.
Maximum Airflow (Cfm) Adjustment —
maximum airflow adjustment lever is common to all sizes
and is divided into levels of percent cfm. Table 2 shows the
approximate unit airflow that will be obtained by each lever
setting for each unit size.
Table 2 — Maximum Airflow Settings
LEVER SETTING
(% CFM)
37HS1
120
120
100
100
80
40
The maximum cfm is the unit airflow obtained when the
thermostat is calling for full cooling in a VAV system; it is
the design cfm for the space conditioned by the unit or units
regulated by one controller.
The variation in maximum airflow for a given setting of
the lever is a function of the unit plenum size, the model and
the number of units in an air series on one controller. See
Tables 3 and 4.
Table 3 — Maximum Cfm Through the Inlet Collar
of a Single Unit or of Units in Air Series
PLENUM
MODEL
SIZE
(in.)
5 x 7
7 x 7
37HS1
9 x 9
11 x 11
7 x 7
37HS2
9 x 9
11 x 11
9 x 9
37HS4
11 x 11
13 x 13
The 37HS
UNIT AIRFLOW (CFM)
37HS2
37HS4
240
480
200
400
80
160
320
40
80
160
INLET
MAXIMUM TOTAL
COLLAR
AIRFLOW
DIAM
(Cfm)
(in.)
4
110
6
400
8
800
10
1100
6
400
8
800
10
1100
8
800
10
1100
12
1600
Table 4 — Maximum Number of Units in an
Air Series on One Control
PLENUM
NUMBER OF UNITS ON ONE CONTROLLER
SIZE (in.)
MODEL
FIRST UNIT
IN AIR
SERIES
5 x 7*
7 x 7
37HS1
9 x 9
11 x 11
7 x 7
37HS2
9 x 9
11 x 11
9 x 9
37HS4
11 x 11
13 x 13
*The 37HS1 unit with a 5 x 7 size plenum is available with blank end only;
multiple units of this size would not be used on one control.
NOTE: The conditions stated in Table 3 must be included in evaluations for
selecting the number of units in an air series.
To set maximum cfm with zero minimum cfm:
1. Set diffuser or wall thermostat for maximum cooling.
2. Turn the minimum cfm star wheel counterclockwise un-
til the internal stop is reached. Do not attempt to override
stop. (Minimum cfm has been set at zero, and the unit
will turn off when required.)
3. Adjust maximum cfm lever to desired percent cfm.
Minimum Airflow (Cfm) Adjustment —
plications require both a design maximum cfm and a mini-
mum cfm. The 37HS controller can be set to provide both
airflow requirements.
To set maximum and minimum cfm:
1. Set diffuser or wall thermostat for maximum cooling.
2. Turn the minimum cfm star wheel counterclockwise un-
til the internal stop is reached. Do not attempt to override
stop.
3. Shut off unit by adjusting thermostat to zero cooling, or
disconnect tube from volume controller to thermostat.
4. Place a standard airflow hood against the outlet of the
master unit and slowly turn the minimum cfm star wheel
on the controller clockwise until the desired minimum cfm
is reached.
5. Return the thermostat to the desired setting and/or recon-
nect tube between volume controller and thermostat.
6. Adjust maximum cfm lever to desired percent cfm.
9
Units in Air Series
Single
Unit
2
3
4
X
—
—
—
X
X
X
X
X
X
X
X
X
X
X
X
X
—
—
—
X
X
X
X
X
X
X
X
X
—
—
—
X
X
X
X
X
X
X
X
5
—
—
X
X
—
—
—
—
—
—
Some ap-
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