9
ALWAYS the nominal capacity of the outdoor
unit. In some cases the nominal system
capacity is not the same as the nominal capacity
of the indoor coil.
Selecting the AC Cooling Airflow
A/C cooling is referred to in the User’s manual of
the IQ Drive Programmable thermostat.
Selecting the Heating Airflow
Furnace temperature rise depends on airflows
rate. To select the air flow, enter the program-
ming screen on the IQ thermostat. Select the
furnace input rate and then select the desired
temperature rise (see Table 1).
NOTE:
To set too high temperature rise of the
furnace may result in air limit operation.
VENTING AND COMBUSTION AIR
REQUIREMENTS
These condensing furnaces may be installed
with outdoor combustion air piped directly to the
furnace, or without such special piping. Codes
refer to the former as "direct vent" or "two pipe"
installation. Installation with air taken from
around the furnace is sometimes referred to as
"one pipe" installation - i.e. only the vent (ex-
haust) pipe is provided.
Provisions must be made for adequate supply of
air for combustion and ventilation. For United
States installations, the adequacy of air provi-
sions can be determined by consulting the cur-
rent version of the National Fuel Gas Code (ANSI
Z223.1/NPFA-54). For Canadian installations,
requirements are specified in the National Stan-
dard of Canada (CAN/CGA B149.1 & .2). Consult
local codes for special requirements.
An important consideration in selecting one or
two pipe installation is the quality of the combus-
tion air. Indoor air is sometimes contaminated
with various household chemicals which can
cause severe corrosion in the furnace combus-
tion system.
NOTE:
If the furnace is operated without ad-
equate air for combustion and ventilation, it may
not perform properly. Furnace components
may be strained by high temperature and could
fail prematurely.
!
WARNING:
Furnace installation using methods
other than those described in the fol-
lowing sections must comply with the
National Fuel Gas Code and all appli-
cable local codes to provide sufficient
combustion air for the furnace.
Combustion Air Quality
The recommended source of combustion air is
to use the outdoor air supply. However, the use
of indoor air in most applications is acceptable
except as follows:
1.
If the furnace is installed in a confined space
it is recommended that the necessary com-
bustion air come from the outdoors by way
of attic, crawl space, air duct, or direct
opening.
2.
If outdoor combustion air is used, there
must be no exposure to the installations or
substances listed in Item 3 below.
3.
The following types of installation may re-
quire
Outdoor Air
for combustion, due to
chemical exposures:
• Commercial buildings
• Buildings with indoor pools
• Furnaces installed in laundry rooms
• Furnaces installed in hobby or craft rooms
• Furnaces installed near chemical stor-
age areas
Exposure to the following substances in the
combustion air supply may also require
Outdoor Air
for combustion:
• Permanent wave solutions
• Chlorinated waxes and cleaners
• Chlorine based swimming pool chemi-
cals
• Water softening chemicals
• De-icing salts or chemicals
• Carbon tetrachloride
• Halogen type refrigerants
• Cleaning solvents (such as perchloroet-
hylene)
• Printing inks, paint removers, varnishes,
etc.
• Hydrochloric acid
