Sterling RT - Manual (Page 20)

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MAINTENANCE
Open all disconnect switches
and secure in that position before servicing unit.
Failure to do so may result in personal injury or
death from electrical shock.
Gas tightness of the safety shut-
off valves must be checked on at least an annual
basis.
To check gas tightness of the safety shut-off valves,
turn off the manual valve upstream of the appliance
combination control. Remove the 1/8 inch pipe plug on
the inlet side of the combination control and connect a
manometer to that tapping. Turn the manual valve on
to apply pressure to the combination control. Note the
pressure reading on the manometer, then turn the valve
off. A loss of pressure indicates a leak. If a leak is detected,
use a soap solution to check all threaded connections. If
no leak is found, combination control is faulty and must
be replaced before putting appliance back in service.
Rooftop duct furnaces have been developed for outdoor
installation. Should maintenance be required, perform the
following inspection and service routine: Inspect area
near the unit to be sure that there is no combustible
material located within minimum clearance requirements
(refer to Figures 1, 2 and 6). Service panels provide easy
access to the burner controls. To remove the service
door, refer to “Access Panel Removal” section (at the
beginning of this manual).
The pilot burner can be serviced by removing the pilot
plate from the main burner assembly.
To remove the main bur ner drawer assembly for
servicing the burners, proceed as follows:
1. Shut off the main gas valve and electrical power to
the gas duct furnace.
2. To slide out the burner drawer, the following two
procedures (a or b) may be chosen depending on
the complexity of the unit's controls:
a.) Disconnect the pilot burner gas tube. Break the
union between the automatic gas valve and
the burner manifold. Also break the union on
the discharge air end of the furnace (inside the
unit). Loosen the union located directly outside
of the furnace's bottom panel (refer to fi gure 9b).
Swing down this end of the piping to clear the
bottom of the burner drawer. The control and
piping assembly may be tied out of the way of
the pull-out drawer.
b.) Disconnect all wiring to the unit's controls.
Break the union located in the discharge end
of the furnace; loosen the external union, and
swing piping clear of the bottom of the drawer
(same procedure as a).
3. Remove the locking screws holding the burner
drawer in position.
4. Slide the drawer out of the furnace.
5. Bur ners can be removed from the drawer by
raising the front of the bur ner and pushing it
against the hold-in spring until the front of the
burner comes out of the slot.
6. To clean or replace the main burners, slide out the
pullout drawer, and compress the spring by moving
the burner toward the manifold. Slide the opposite
end of the burner downward from the locating slot
while retaining spring is still compressed. Pull the
burners upward and out.
7. Remove any dirt, dust or other foreign matter from
the burners using a wire brush and/or compressed
air. Ensure that all parts are unobstructed. Inspect
and clean pilot burner if necessary.
8. Reassemble the gas duct furnace by replacing all
parts in order.
9. Complete the appropriate unit start-up procedure
as given in the “Start-Up” section of this manual.
10. Check the burner adjustment. See the “Primary Air
Shutter Adjustment” section of this manual.
11. Check all gas control valves and pipe connections
for leaks.
Under no circumstances should
combustible material be located within the
clearances specified in Figure 6. Failure to
provide proper clearance could result in
personal injury or equipment damage from fi re.
12. Check the operation of the automatic gas valve by
lowering the setting of the thermostat, stopping the
operation of the gas duct furnace. The gas valve
should close tightly, completely extinguishing the
fl ame on the main burners.
13. Check the operation of all safety devices.
14. Inspect and ser vice the blower section of the
system.
The outdoor unit should be thoroughly checked before
the start of the heating season. Check the air through-
put as an added precaution to stay within the specifi ed
temperature limits.
If the unit is used with cooling equipment, periodic
maintenance should be scheduled throughout the year.