10
INPUT
BTUH
Furnace
Width
Cleanable
Filter
Disposable
Filter
50,000
17-1/2
14 x 20
(2) 10 x 20
75,000
17-1/2
14 x 20
(2) 14 x 20
75,000
21
16 x 20
(2) 16 x 20
100,000
21
16 x 20
(2) 16 x 20
100,000
24-1/2
20 x 20
(2) 20 x 20
125,000
24-1/2
20 x 20
(2) 20 x 20
Upflow
An appropriately sized permanent cleanable or
disposable filter shall be used. The filter should be
installed in a side return filter rack or, if bottom return
is to be used, in a suitable filter box under the
furnace. Filters must be located external to the
furnace casing (See Figure 8).
FIGURE 8 – UPFLOW FILTERS
Horizontal
An appropriately sized permanent cleanable or
disposable filter shall be used. The filter should be
installed behind a return grille or other location with
easy access for filter change. Locating the filter in a
crawl space, attic or other inaccessible location will
result in filters not being changed as frequently as
recommended.
GAS PIPING
Use only the type of gas for which the fur-
nace is equipped. Using the wrong gas
could create a hazard, resulting in damage,
personal injury or death.
Before installing gas piping, check with local code
authorities for requirements concerning gas piping.
In the absence of local codes, follow the recommen-
dations contained in NATIONAL FUEL GAS CODE
ANSI Z223.1 for gas piping materials, pipe sizing,
and the requirements for installation. In Canada,
refer to the latest edition of the CAN/CGA-B149
Installation Code and local codes for specifics. It is
recommended that a gas cock shutoff valve be
installed in the gas supply line outside the casing,
where it is readily accessible, as close to the furnace
as is practicable, as shown in Figure 9 and 10.
An 1/8 in. NPT (plugged) pressure tap for test gauge
connection must be installed in the gas supply line
immediately upstream from the furnace, if local
authorities do not allow use of the pressure tap in
the gas valve for this purpose.
Install a dirt leg at the bottom of any vertical riser or
drop, as close to the furnace as possible, to collect
moisture and foreign material. Install a ground joint
union just ahead of the gas control valve. A typical
downflow arrangement is shown in Figure 9. A
typical upflow arrangement is shown in Figure 10.
When making the connection at the gas control
valve, use a wrench on the inlet side of the valve to
prevent any possible twisting of the valve body,
which could cause damage and leaks. When making
up pipe joints, use pipe thread compound which is
resistant to natural and LP (propane) gases.
