035-20646-001 Rev. A (1004)
Unitary Products Group
29
APPLYING FILTER PRESSURE DROP TO
DETERMINE SYSTEM AIRFLOW
To determine the approximate airflow of the unit with a filter in place, fol-
low the steps below:
1.
Select the filter type.
2.
Determine the External System Static Pressure (ESP) without the
filter.
3.
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.
4.
If total system static matches a ESP value in the airflow table (i.e.
0.20, 0.60, etc,) the system airflow corresponds to the intersection
of the ESP column and Model/Blower Speed row.
5.
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 a 130,000 Btuh furnace operating on high speed blower,
it is found that total system static is 0.58" w.c. To determine the system
airflow, complete the following steps:
1.
Obtain the airflow values at 0.50" & 0.60" ESP.
Airflow @ 0.50": 2125 CFM
Airflow @ 0.60": 2035 CFM
2.
Subtract the airflow @ 0.50" from the airflow @ 0.60" to obtain air-
flow difference.
2035 - 2125 = -90 CFM
3.
Subtract the total system static from 0.50" and divide this differ-
ence by the difference in ESP values in the table, 0.60" - 0.50", to
obtain a percentage.
(0.58 - 0.50) / (0.60 - 0.50) = 0.8
4.
Multiply percentage by airflow difference to obtain airflow reduc-
tion.
(0.8) x (-90) = -72
5.
Subtract airflow reduction value to airflow @ 0.50" to obtain actual
airflow @ 0.58" ESP.
2125 - 72 = 2053
FIELD INSTALLED ACCESSORIES - NON-ELECTRICAL
MODEL NO.
DESCRIPTION
USED WITH
1NP0347
PROPANE (LP) CONVERSION KIT
ALL MODELS
1CT0302
CONCENTRIC INTAKE/VENT 2”
60, 80, 100 INPUT MBH
1CT0303
CONCENTRIC INTAKE/VENT 3”
120 INPUT MBH
1PS0901
HIGH ALTITUDE PRESSURE SWITCH KIT
(Does Not Include Orifices)
FOR APPLICATION INFORMA-
TION SEE FORM 035-14447-000
1PS0902
1PS0903
1NK0301
CONDENSATE NEUTRALIZER KIT
ALL MODELS
1TK0917
1TK0921
1TK0924
TRANSITION KITS FOR COIL MOUNTING
17 1/2” CABINETS
21” CABINETS
24 1/2” CABINETS
