Installation & Maintenance Manual Owner's manual
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AIR DISTRIBUTION
Two basic air control systems are used to deliver
conditioned air to the occupied space: “constant” fan
operation and “intermittent” fan operation.
INTERMITTENT FAN OPERATION
This air control system is available on duct furnaces
when the fan time delay relay is ordered (optional). The
thermostat turns the gas on whenever the temperature
drops below the thermostat setting. The fan time delay
relay allows the unit to fire for a period of 60 seconds
before fan operation. It also allows the fan to operate for
120 seconds after burner shutdown.
LIGHTING
Purge the gas line of air before attempting to light the
pilot in the unit. Wait 5 minutes for unburned gas to
vent. Check for gas leaks.
Never use an open flame to
detect gas leaks. Explosive conditions may
exist which could result in personal injury or
death.
AIR THROUGHPUT
Static Pressure through the duct furnace should not
exceed 2.0 inches (0.50 kPa) water column. The
standard outdoor duct furnaces are operated at a
temperature rise range of 20° to 60F° (17° to 50C°) rise.
The furnaces are also available at a higher temperature
rise range of 30° - 90F° (17° - 50C°).
NOTICE: It is important that the final temperature
leaving the furnace does not exceed 150°F (66°C).
When final air throughput adjustments are being
made, a quick check of the final temperature can
be made by locating a thermometer approximately
6 to 12 inches (152 to 305 mm) downstream from
the air discharge and approximately 3 to 4 inches
(76 to 102 mm) from the bottom of the duct. The
unit should be operated at least 15 to 20 minutes
before temperature readings are made.
A unit should never be allowed to cycle
over a prolonged period on the high limit. The high
limit is not an operating control. It is a safety control
to prevent a fire. If cycling on the high limit is noted,
corrective measures should be taken immediately.
Failure to do so could cause unit damage and
possible fire.
The unit is furnished with an intermittent pilot ignition
system. A lighting instruction plate is permanently
attached to the unit for the pilot system supplied with the
unit. To set the intermittent pilot ignition system
in operation, proceed as follows:
1. Turn on the main manual valve and pilot valve.
AIR FILTERS
It is recommended that air filters be changed or cleaned
at least twice a year. More frequent attention will be
required if the air being handled is unusually dirty. Air
flow reduction, caused by clogging air filters, will
increase the discharge air temperature and may cause
nuisance tripouts.
Filters (by others) should be serviced regularly and
changed or washed when necessary to maintain the
required throughput. In a dusty environment, filters may
clog up in less than one month.
CLOGGED FILTER SWITCH
The clogged filter switch is a field installed option.
When the furnace air filter becomes clogged, the
suction increases on the downstream side of the filter,
causing air to be drawn through a port of the back of
the clogged filter switch. When suction becomes
greater than the set point of the clogged filter switch, it
releases the red flag marked CHANGE FILTER. The
flag shows in clear plastic window on the front of the
case. The contacts make to actuate the light when the
air filter needs cleaning or changing.
For adjustments and checkout, refer to the
Maintenance section of this manual.
CONSTANT FAN OPERATION
Duct Furnaces: This air control system is standard on
duct furnaces without a fan time delay relay. The blower
operates constantly, circulating air through the unit,
through the discharge, continuously into the occupied
zone, and back to the return. The thermostat turns the
gas valve on or off, raising the temperature of the air to
maintain comfort conditions in the occupied area.