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292278-UIM-A-0108

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.

Select the number of return air openings or calculate the return
opening size in square inches to determine the proper filter pres-
sure 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 a ESP value in the airflow table (i.e.
0.20 w.c. (50 Pa), 0.60 w.c. (150 Pa), etc,) the system airflow cor-
responds 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 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 120,000 BTUH (38.06 kW) furnace with 2 return open-
ings 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 follow-
ing steps:

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

Airflow @ 0.50”: 2285 CFM (64.70 m

3

/min)

Airflow @ 0.60”: 2175 CFM (61.59 m

3

/min)

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

2175 - 2285 = -110 CFM (3.11 m

3

/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 (-110) = -88

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

2285 - 88 = 2197

TABLE 17: 

Filter Performance - Pressure Drop Inches W.C. and (kPa)

Airflow Range

Minimum 

Opening Size

Filter Type

Disposable

Washable Fiber

Pleated

CFM

m

3

/min

 in

2

   

cm

2

In W.C.

kPA

In W.C.

kPA

In W.C.

kPA

0 - 750

0 - 21.4

230

1484

0.01

0.00249

0.01

0.00249

0.15

0.03736

751 - 1000

21.25 - 28.32

330

2129

0.05

0.01245

0.05

0.01245

0.20

0.04982

1001 - 1250

28.33 - 35.40

330

2129

0.10

0.02491

0.10

0.02491

0.20

0.04982

1251 - 1500

35.41 - 42.48

330

2129

0.10

0.02491

0.10

0.02491

0.25

0.06227

1501 - 1750

42.49 - 49.55

380

2452

0.15

0.03736

0.14

0.03487

0.30

0.07473

1751 - 2000

49.56 - 56.63

380

2542

0.19

0.04733

0.18

0.04484

0.30

0.07473

2001 & Above

56.64 - Above

463

2987

0.19

0.04733

0.18

0.04484

0.30

0.07473

TABLE 18: 

Field Installed Accessories - Non-Electrical

MODEL NO.

DESCRIPTION

USED WITH

1NP0680

PROPANE (LP) CONVERSION KIT WITH GAS VALVE

ALL MODELS

1SF0101

EXTERNAL SIDE FILTER RACK

ALL MODELS

1CT0302

CONCENTRIC INTAKE/VENT 2”

60, 80, 100 INPUT MBH

1CT0303

CONCENTRIC INTAKE/VENT 3”

100, 120 MBH

1HT0901

SIDEWALL VENT TERMINATION KIT 3”

ALL MODELS

1HT0902

SIDEWALL VENT TERMINATION KIT 2”

ALL MODELS

1BR0317

EXTERNAL BOTTOM FILTER RACK

17-1/2” CABINETS

1BR0321

21” CABINETS

1BR0324

24-1/2” CABINETS

1NK0301

CONDENSATE NEUTRALIZER KIT

ALL MODELS

1SF0101

SIDE RETURN FILTER KIT 1” FILTER

ALL MODELS

1SR0200

SIDE RETURN FILTER KIT 1-4” FILTER

ALL MODELS

1BR0117

BOTTOM RETURN FILTER KIT 1” FILTER

17-1/2” CABINETS

1BR0217

BOTTOM RETURN FILTER KIT 1-4” FILTER

17-1/2” CABINETS

1BR0121

BOTTOM RETURN FILTER KIT 1” FILTER

21” CABINETS

1BR0221

BOTTOM RETURN FILTER KIT 1-4” FILTER

21” CABINETS

1BR0124

BOTTOM RETURN FILTER KIT 1” FILTER

24-1/2” CABINETS

1BR0224

BOTTOM RETURN FILTER KIT 1-4” FILTER

24-1/2” CABINETS

Summary of Contents for FC9C UP Series

Page 1: ...l codes LIST OF SECTIONS FURNACE DESCRIPTION 1 SAFETY 1 DUCTWORK 4 FILTERS 6 GAS PIPING 7 ELECTRICAL POWER 8 COMBUSTION AIR AND VENT SYSTEM 14 CONDENSATE PIPING 20 SAFETY CONTROLS 21 START UP AND ADJU...

Page 2: ...as listed under Clearances to Combustibles in Table 1 Provide clearances for servicing ensuring that service access is allowed for both the burners and blower These models ARE NOT CSA listed or appro...

Page 3: ...e floor and the furnace must be located or protected to avoid physical damage by vehicles The furnace area must not be used as a broom closet or for any other storage purposes as a fire hazard may be...

Page 4: ...OTE When attaching duct flange do not shoot the screw down into the casing Use the formed flange intended for duct flange attachment The duct system is a very important part of the installation If the...

Page 5: ...ndi cate the presence of leaks in the heat exchanger This access cover shall be attached in such a manner as to prevent leaks TABLE 2 Minimum Duct Sizing For Proper Airflow Input Airflow Return1 Recta...

Page 6: ...r this require the use of high velocity fil ters 2 Air flows above 1800 CFM require either return from two sides or one side plus bottom SIDE RETURN FILTER INSTALLATION Locate and mark the side return...

Page 7: ...l At elevations above 4 000 feet the furnace will automatically reduce it s input rate if necessary to maintain good combustion If the natural gas being supplied has also been derated by the gas suppl...

Page 8: ...o Furnace Diag nostics section of the User s Information Maintenance Ser vice Manual provided with this furnace LOW VOLTAGE CONTROL WIRING CONNECTIONS Install the field supplied thermostat by followin...

Page 9: ...age Compressor Y2 Second Stage Compressor C 24 Volt Common R 24 Volt Hot Y1 Single Stage Compressor VARIABLE SPEED MODULATING FURNACE CONTROL G Fan VARIABLE SPEED MODULATING FURNACE Y Y2 Second or Ful...

Page 10: ...Move HUMIDISTAT jumper to YES if humidistat is to be used FL9C FC9C PC9 ID MODELS External Humidistat Optional Open on Humidity Rise 24VAC Humidifier Optional External Humidistat Optional Open on Hum...

Page 11: ...n HM Humidistat Step 1 of Thermostat User Configuration Menu must be set to MLTISTG E W1 First Stage Heat 24VAC Humidifer Optional C 24 Volt Common R 24 Volt Hot Y1 Single Stage Compressor VARIABLE SP...

Page 12: ...l C 24 Volt Common R 24 Volt Hot Y1 Single Stage Compressor VARIABLE SPEED MODULATING FURNACE CONTROL G Fan VARIABLE SPEED MODULATING FURNACE Y Y2 Second or Full Stage Compressor HUM Dehumidification...

Page 13: ...09137 18395 031 01996 340512 031 09178 1 FL9C FC9C PC9 ID MODELS YZE OD MODELS YZH H 5 H 8 C 24 Volt Common R 24 Volt Hot Y1 First Stage Compressor O Reversing Valve Energized in Cool L Malfunction L...

Page 14: ...for a particular model then the vent can have 65 equivalent feet of pipe AND the combustion air intake can have another 65 equivalent feet of pipe 3 Three vent terminal elbows two for the vent and on...

Page 15: ...ystems from the furnace to the out side termination B Ventilated combustion air systems from the furnace to the attic or crawl space termination 6 Disassemble the combustion air and vent piping apply...

Page 16: ...ns 9 inches 23 cm for models 50 000 BTUH 15 kW 12 inches 30 cm for models 50 000 BTUH 15 kW C Clearance to permanently closed window 12 inches 30 cm 12 inches 30 cm D Vertical clearance to ventilated...

Page 17: ...ombustion air systems must be installed so the vent and the combustion air pipes terminate in the same atmospheric zone Refer to Figures 14 or 15 VENTING MULTIPLE UNITS Multiple units can be installed...

Page 18: ...ical vent Care should be taken to locate side vented systems where trees or shrubs will not block or restrict supply air from entering the terminal Also the terminal assembly should be located as far...

Page 19: ...ENTILATED ATTIC TOP ABOVE INSULATION OPTIONAL INLET a OUTLET AIR a VENTILATED CRAWL SPACE GAS WATER HEATER VENTILATED ATTIC TOP ABOVE INSULATION GAS VENT GABLE VENT SOFFIT VENT GAS WATER HEATER INLET...

Page 20: ...bustion Air The ventilated attic space or a crawl space from which the combustion air is taken must comply with the requirements specified in AIR SOURCE FROM OUTDOORS in this instruction or in Section...

Page 21: ...s sensor monitors combus tion airflow through furnace and piping systems If any of the conditions listed above are detected by the pressure sensor the control board will prevent a hazardous condition...

Page 22: ...ing any pressure testing of that system at test pres sures in excess of 1 2 PSI 3 45 kPa The furnace must be isolated from the gas supply piping system by closing the equipment shutoff valve during an...

Page 23: ...3600 then divided by the time it took to measure 0 10 m3 of gas from the gas meter For Propane LP Gas multiply the Heat content of the gas MJ m3 or Default 93 15 times 0 10 m3 of gas measured at the...

Page 24: ...nt screws on main gas valve 2 Turn gas and electrical supplies on and follow the operating instructions to place the unit back in operation 3 Adjust manifold pressure by adjusting gas valve regulator...

Page 25: ...s fan operation can be adjusted as desired This is done my moving the RECIRC jumper on the control board to give the desired airflow The jumper has three positions The A position delivers maximum air...

Page 26: ...rate 6 The firing rate is automatically adjusted to meet demand increas ing gradually to maximum 100 firing rate if the thermostat is not satisfied within a defined time 7 When the thermostat R and W...

Page 27: ...five minutes indi cating that the blower motor or blower wheel has failed Twelve Red Flashes ID plug is not present or not connected properly check for loose plug or loose wires in plug Steady On Red...

Page 28: ...730 530 22 4 16 1 20 7 15 0 C C 630 530 590 500 17 8 15 0 16 7 14 2 D C 80 000 100 000 INPUT 4 Ton 100 000 INPUT 5 Ton 80 000 100 000 INPUT 4 Ton 100 000 INPUT 5 Ton JUMPER SETTINGS CFM CFM m min m mi...

Page 29: ...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 110 88 Subtract airflow reduction value to airflow 0 50 w c 125...

Page 30: ...A 292278 UIM A 0108 Copyright by Unitary Products Group 2008 All rights reserved Supersedes 172078 YIM C 0606 Unitary 5005 Norman Product York OK Group Drive 73069 SECTION XII WIRING DIAGRAM FIGURE 26...

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