If, during the inspection of your furnace, you find any of the following conditions:
•Excessive amounts of dust and lint on components.
•Damaged or deteriorated components or surfaces.
•Leaks or blockage in the vent pipe passages.
•Water on any surface inside or outside of the furnace.
Do not operate the furnace, call a certified dealer / servicing contractor to check and / or clean your furnace, or for more information if you have questions about the operation of your furnace.
If all components appear to be in good operating condition, replace the front panels. Turn ON the gas and electrical power supplies to the fur- nace, and set thermostat to the desired temperature.
Air Filters
Dirty filters greatly restrict the flow of air and may cause damage to the moving parts of the furnace. If the filters become clogged the heat exchangers and blower motor could overheat resulting in a potentially dangerous situation.
The filters should be checked every 3 months. On new construction, check the filters every week for the first four weeks and every three weeks after that, especially if the indoor fan is running continuously. When replacing the filter(s) you must use filters that are the same size as those recommended in Table 1. Use the following procedure to determine the filter size. Never operate your furnace without a suitable air filter.
1.Measure the furnace width. Use the following measurements to determine the cabinet size.
•A
•A 21” wide cabinet is a “C” cabinet.
•A
2.Locate the cabinet size on Table 1, then determine whether you have a bottom, side or top return using the following method.
a.If the return air filters are on the left or right side of the fur- nace it is a side return. Refer to Figure 11.
b.If the air filter is on the bottom of the furnace then you have a bottom return. Refer to Figure 12 or for horizontal applica- tions refer to Figure 9.
c.If the air filters are on the bottom and the side of the furnace then you have a bottom and side return. You must replace both air filters. Brackets with the number two (2) before the fil- ter size requires 2 filters. Refer to Figures 11 & 12.
d.If the air filters are on both sides of the furnace then you have a (2) sided return. You must replace both air filters.
e.If the air filters are in the return air plenum, above the furnace then you have a top return (Downflow Furnace). Refer to Fig- ure 10.
3.After you determine the cabinet size and what return configuration you have, look up the recommended filter size from Table 1. You must replace the air filters with the same size as recommended.
Removing Filters
Externally Mounted Air Filters
The air filter is in a rack that is attached to the casing of the furnace or placed in the return air duct. Figures 9, 10, 11 & 12 indicate possible external air filter box locations.
AIR FILTER RACK
ACCESS DOOR
FILTER
RACK
FURNACE | AIR FLOW |
|
18”
MIN
FIGURE 9: External Air Filter Rack - Horizontal Left Position
AIR FLOW | FILTER RACK |
|
(factory supplied with some furnaces) | ||
| RACK AND FILTERS SECURED | |
| INSIDE BLOWER SECTION | |
| FOR SHIPMENT |
|
| CASING SIZE DIMENSION FH | |
| ||
| 11” | |
| ||
| NOTE: FILTER ACCESS THROUGH | BRANCH |
| DUCTWORK MUST BE PROVIDED | |
| DUCTS | |
| FOR REMOVAL AND CLEANING | |
|
| |
| FILTERS |
|
DUCTWORK | FILTER |
|
RACK |
| |
|
| |
| FH |
|
CROSS SECTION
FIGURE 10: Downflow Filter
AIR FILTER |
| AIR FILTER | |
| RACK | ||
RACK |
| ||
| ACCESS | ||
ACCESS |
| ||
| DOOR | ||
DOOR | FURNACE | ||
| |||
DUCT |
| DUCT | |
|
| ||
AIR FLOW |
| AIR FLOW | |
|
| ||
LEFT SIDE |
| RIGHT SIDE | |
FILTER RACK |
| FILTER RACK |
FIGURE 11: External Air Filter Rack - Left & Right Side Position
| FURNACE |
|
|
| AIR FILTER RACK |
BOTTOM FILTER RACK | ACCESS DOOR | |
AIR FLOW | DUCT |
|
|
| |
FIGURE 12: External Air Filter Rack - Bottom Position
Unitary Products Group | 5 |
