6, Chimney Venting; 7, Barometric Damper Control; 8, Fan And Limit Control - Nordyne O4MD Installation, Operation And Maintenance Manual

The Model CAS-2B-90E Furnace Boot manufactured by
Field Controls, Inc. may be used with the furnace to
obtain combustion air directly from outdoors. Use of this
device does not alter the need for ventilation air;
however, it does provide a good direct source of
combustion air and is connected directly to the oil burner.
6. CHIMNEY VENTING
The flue pipe should be as short as possible with
horizontal pipes sloping upward toward the chimney at a
rate of one-quarter inch to the foot. The flue pipe should
not be smaller in cross sectional area than the flue collar
on the furnace. The flue pipe should connect to the
chimney such that the flue pipe extends into, and
terminates flush with the inside surface of the chimney
liner. Seal the joint between the pipe and the lining. The
chimney outlet should be at least two feet above the
highest point of a peaked roof. All unused chimney
openings should be closed. Chimneys must conform to
local, provincial or state codes, or in the absence of local
regulations, to the requirements of the National Building
Code.
NOTE: THE FURNACE IS APPROVED FOR USE WITH
L-VENT.
IAcAuTION I
THE FURNACE MUST BE CONNECTED TO A FLUE
HAVING SUFFICIENT DRAFT AT ALL TIMES TO
ENSURE SAFE AND PROPER OPERATION OF THE
APPLIANCE.
The flue pipe must not pass through any floor or ceiling,
but may pass through a wall where suitable fire protection
provisions have been installed. Refer to the latest edition
of NFPA 31 for regulations governing the installation of oil
burning equipment. In Canada, refer to the latest edition
of CAN/CSA B-139 for rules governing the installation of
oil burning equipment.
7. BAROMETRIC DAMPER CONTROL
This device is used in conjunction with conventional
chimney venting. This control (or draft regulator)
automatically maintains a constant negative pressure in
the furnace to obtain maximum efficiency. It ensures that
proper pressures are not exceeded. If the chimney does
not develop sufficient draft, the draft control cannot
function properly. The draft regulator, must be installed
within the same room or enclosure as the furnace, and
should not interfere with the combustion air supply to the
burner. The control should normally be located a
minimum of 3 pipe diameters from the furnace breeching
and installed in accordance to the instructions supplied
with the regulator. The flue outlet pressure (measured
between the furnace and draft regulator) should be set to
- 0.02 in. w.c.
8. FAN AND LIMIT CONTROL
The L4064W fan / limit control is a thermally activated
control. There are two active components to the control.
The "fan on" function is actuated by a heater wrapped
bimetallic lever. The internal heater coil is activated
whenever the oil burner is operating, resulting in the start
up of the blower motor within 30 seconds of the ignition
cycle. This is a non-adjustable setting. The second
component is a helical bi-metal sensing element
enclosed in a metal guard. This controls the "fan off"
function and high limit cut off function. This control
provides a delay between the burner ignition and blower
start-up to eliminate excessive flow of cold air when the
blower activates. Blower shutdown is also delayed to
remove any residual heat from the heat exchanger and
improve the annual efficiency of the furnace. "Fan off"
settings of 90 ° F to 100° F (32 ° C to 37°C) will usually be
satisfactory. In a normal cycle, the "fan on" adjustment
has little if any effect on the L4064W model control. If the
blower starts for brief periods after a burner cycle, the
condition can usually be eliminated by increasing the
differential between the "fan on" and "fan off" settings.
If after 1 minute, the blower has not come on, inspection
and / or repair of the fan / limit control wiring, or
replacement of the fan / limit control may be necessary.
The limit switch performs a safety function and breaks
power to the oil burner primary control, which shuts off
the burner if the furnace over-heats. The limit control is
thermally operated and automatically resets. The limit
control is factory installed, pre-set and is not adjustable.
Limit setting for O4MD-091A-12-F: 250°F. Limit Setting
for O4MD-140A-16-F: 220°F.
I' cAUTION I
FAN/LIMIT CONTROL LOCATION IS CRITICAL IN
THE O4MD-091A-12-F HORIZONTAL POSITIONS.
TO OPERATE EFFECTIVELY AS A HIGH LIMIT
CONTROL, THE CONTROL MUST BE INSTALLED
IN THE UPPER POSITION. See Figure 6, page 16.
The limit control and fan control are incorporated in the
same housing and are operated by the same thermal
element. Ensure, prior to installation, that the fan / limit
probe is not in contact with the heat exchanger.
The O4MD-091A-12-F Series furnace is equipped with a
160°F auxiliary limit control located in the blower
compartment.
The O4MD-140A-16-F Series furnace is equipped with
two auxiliary limit controls that are both automatic reset
types. One is a 200°F disc limit located behind the
junction box cover. The other is a 130°F. disc limit
located on the blower fan housing.
7 153B0801