246801-CTG-C-0407
6Unitary Products Group
APPLYING FILTER PRESSURE DROP TO
DETERMINE SYSTEM AIRFLOW
To determine the approximate airflow of the unit with a filter in
place, follow the steps below:
1. Select the filter type.
2. Select the number of return air openings or calculate the
return opening size in square inches to determine the
proper filter pressure drop.
3. Determine the External System Static Pressure (ESP)
without the filter.
4. Select a filter pressure drop from the table based upon
the number of return air openings or return air opening
size and add to the ESP from Step 3 to determine the
total system static.
5. If total system static matches an ESP value in the airflow
table (i.e. 0.20, 0.60, etc,) the system airflow corre-
sponds to the intersection of the ESP column and Model/
Blower Speed row.
6. If the total system static falls between ESP values in the
table (i.e. 0.58, 0.75, etc.), the static pressure may be
rounded to the nearest value in the table determining the
airflow using Step 5 or calculate the airflow by using the
following example.
Example: For an 80,000 BTUH (23.4 kW) furnace operating
on HI COOL TAP B and ADJUST TAP A, it is found that total
system static is 0.68” w.c. (170 Pa).
To determine the system airflow, complete the following
steps:
Airflow @ 0.60”: 1400 CFM (39.6 m3/min)
Subtract the total system static from 0.60” w.c. (150 Pa) and
divide this by 0.1” w.c. (25 Pa).
0.68 (170 Pa) - 0.60 (150 (Pa) = 0.08 (20 Pa)
0.08 (20 Pa) / 0.1 (25 Pa) = 0.8
Multiply this by 2% to obtain the percentage reduction in air-
flow.
0.8 x 0.02 = 0.016
Multiply percentage reduction in airflow by the airflow in the
table to obtain the airflow reduction.
0.016 x 1400 (39.6 m3/min) = 22 (0.6 m3/min)
Subtract airflow reduction value from airflow in the table to
obtain actual airflow @ 0.68” w.c. (170 Pa) ESP.
1400 (39.6 m3/min) - 22 (0.6 m3/min) = 1378 (39.0 m3/min).
ACCESSORIES
PROPANE (LP) CONVERSION KIT -
1NP0347 - All Models
These accessory conversion kits may be used to convert nat-
ural gas units for propane (LP) operation. Conversions must
be made by qualified distributor or dealer personnel.
COMBUSTIBLE FLOOR BASE -
1CB0314 - for 14-1/2” cabinet models
1CB0317 - for 17-1/2” cabinet models
1CB0321 - for 21” cabinet models
HIGH ALTITUDE PRESSURE SWITCHES -
For installation where the altitude is less than 8,000 feet it is
not required that the pressure switch be changed. For alti-
tudes above 8,000 feet see kits below. Conversion must be
made by qualified distributor or dealer personnel.
1PS0313 - 057, 080, 100 MBH
1PS0314 - 120 MBH
ROOM THERMOSTATS - A wide selection of compatible
thermosets are available to provide optimum performance
and features for any installation.
1H/1C, manual change-over electronic non-programmable
thermostat.
1H/1C, auto/manual changeover, electronic programmable,
deluxe 7-day, thermostat.
1H/1C, auto/manual changeover, electronic programmable.
* For the most current accessory information, refer to the
price book or consult factory.
