Coleman LC8T, FC8T Filter Performance, Applying Filter Pressure Drop to Determine System Airflow

036-21603-002 Rev. A (1004)

FILTER PERFORMANCE

The airflow capacity data published in the “Blower Perfor- mance” table listed above represents blower performance WITHOUT filters. To determine the approximate blower per- formance of the system, apply the filter drop value for the fil- ter being used or select an appropriate value from the “Filter Performance” table shown below.

FILTER PERFORMANCE - PRESSURE DROP INCHES W.C.

NOTE: The filter pressure drop values in the “Filter Perfor- mance” table shown below are typical values for the type of filter listed and should only be used as a guideline. Actual pressure drop ratings for each filter type vary between filter manufacturer.

Airflow	Minimum Opening Size				Filter Type
			Disposable		WASHABLE FIBER*		Pleated
Range
	1 Opening	2 Openings	1 Opening	2 Openings	1 Opening	2 Openings	1 Opening	2 Openings
CFM	In³	In³	inwc	inwc	inwc	inwc	inwc	inwc
0 - 750	230		0.01		0.01		0.15
751 - 1000	330		0.05		0.05		0.2
1001 - 1250	330		0.1		0.1		0.2
1251 - 1500	330		0.1		0.1		0.25
1501 - 1750	380	658	0.15	0.09	0.14	0.08	0.3	0.17
1751 - 2000	380	658	0.19	0.11	0.18	0.1	0.3	0.17
2001 & Above	463	658	0.19	0.11	0.18	0.1	0.3	0.17

* Washable fiber are the type supplied with furnace (if supplied).

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 num- ber 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 a ESP value in the airflow table (i.e. 0.20 w.c. (50 Pa), 0.60 w.c. (150 Pa), etc,) the system air- flow corresponds 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 w.c. (144 Pa), 0.75 w.c. (187 Pa), etc.), the static pres- sure may be rounded to the nearest value in the table determin- ing the airflow using Step 5 or calculate the airflow by using the following example.

Example: For a 130,000 BTUH (38.06 kW) furnace with 2 return openings and 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:

Obtain the airflow values at 0.50 w.c. (125 Pa) & 0.60 w.c. (150 Pa) ESP.

Airflow @ 0.50”: 2125 CFM (60.17 m3/min)

Airflow @ 0.60”: 2035 CFM (57.62 m3/min)

Subtract the airflow @ 0.50 w.c. (125 Pa) from the airflow @ 0.60 w.c. (150 Pa) to obtain airflow difference.

2035 - 2125 = -90 CFM (2.55 m3/min)

Subtract the total system static from 0.50 w.c. (125 Pa) and divide this difference by the difference in ESP values in the table, 0.60 w.c. (150 Pa) - 0.50 w.c. (125 Pa), to obtain a percentage.

(0.58 - 0.50) / (0.60 - 0.50) = 0.8

Multiply percentage by airflow difference to obtain airflow reduction. (0.8) X (-90) = -72

Subtract airflow reduction value to airflow @ 0.50 w.c. (125 Pa) to obtain actual airflow @ 0.58 inwc (144 Pa) ESP.

2125 - 72 = 2053

UNIT CLEARANCES TO COMBUSTIBLES (ALL DIMENSIONS IN INCHES)

(ALL SURFACES IDENTIFIED WITH THE UNIT IN AN UPFLOW CONFIGURATION)

APPLICATION	TOP	FRONT	REAR	LEFT SIDE	RIGHT SIDE	FLUE	FLOOR/	CLOSET	ALCOVE	ATTIC	LINE
	In.	In.	In.	In. (cm)	In. (cm)	In. (cm)	BOTTOM				CONTACT
UPFLOW	1	6	0	0	31	6	COMBUSTIBLE	YES	YES	YES	NO
UPFLOW B-VENT	1	3	0	0	0	1	COMBUSTIBLE	YES	YES	YES	NO
HORIZONTAL	32	6	0	1	0	6	COMBUSTIBLE	NO	YES	YES	YES3
HORIZONTAL B-VENT	0	3	0	1	0	1	COMBUSTIBLE	NO	YES	YES	YES3

114-1/2” cabinet models only. All other units “0” clearance.

214-1/2” cabinet left airflow applications only. All other units and right hand airflow applications “0” clearance.

3Line contact only permitted between lines formed by the intersection of the rear panel and side panel (top in horizontal position) of the furnace jacket and building joists, studs or framing.

6 Unitary Products Group