Reznor MAPS II Unit Installation Manual - Manual (Page 49)

Form I-MAPS II, P/N 206131 (Rev 13), Page 49
Combustion Air
Proving Switch
The combustion air proving switch is a pressure switch that monitors air pres-
sure to ensure that proper combustion airflow is available. The switch on a
Size 100 furnace is designed to close when a negative pressure is sensed in
the venter housing. The switch on Sizes 150-700 senses the differential pres-
sure between the negative pressure in the venter housing and the pressure
in the cabinet. For location of the combustion air proving switch, see FIGURE
20, page 33, Item 17.
Vent Extension Field
Kit
The gas-fired heat section vents combustion gas horizontally. A field-installed
vent extension kit ( P/N 221120) provides for attaching a vertical vent pipe that
will allow the vent terminal to extend above the unit. For information, contact
your distributor or see Form CP-MAPS-Vnt Ext on www.RezSpec.com.
Sensing Type Size
Startup
(Cold)
Equilibrium
(Hot)
Setpoint ON
Setpoint
OFF
Label
Color
Switch
P/N
Single Negative
Pressure
100 1.2±.2" w.c. 0.65±.1" w.c. 0.68±.1" w.c. 0.5" w.c. Orange 196388
Differential
Pressure
150 1.4±.2" w.c. 0.6±.1" w.c. 0.68±.1" w.c. 0.5" w.c. Orange 196388
200 1.4±.2" w.c. 0.6±.1" w.c. 0.73±.1" w.c. 0.5" w.c. White 196362
250 1.5±.2" w.c. 0.7±.1" w.c. 0.73±.1" w.c. 0.55" w.c. White 196362
300 1.5±.2" w.c. 0.7±.1" w.c. 0.73±.1" w.c. 0.55" w.c. White 196362
350 3.5±.2" w.c. 1.8±.2" w.c. 0.83±.1" w.c. 0.65"w.c. Yellow 197028
400 3.3±.2" w.c. 2.0±.2" w.c. 0.83±.1" w.c. 0.65"w.c. Yellow 197028
450 2.7±.2" w.c. 1.8±.2" w.c. 0.83±.1" w.c. 0.65"w.c. Yellow 197028
500 2.8±.2" w.c. 1.8±.2" w.c. 0.83±.1" w.c. 0.65"w.c. Yellow 197028
550 3.0±.2" w.c. 2.1±.2" w.c. 0.83±.1" w.c. 0.65"w.c. Yellow 197028
600 3.0±.2" w.c. 2.1±.2" w.c. 0.83±.1" w.c. 0.65"w.c. Yellow 197028
650 3.0±.2" w.c. 1.9±.2" w.c. 0.83±.1" w.c. 0.65"w.c. Yellow 197028
700 3.0±.2" w.c. 2.0±.2" w.c. 0.83±.1" w.c. 0.65"w.c. Yellow 197028
On startup when the furnace is cold, the sensing pressure is at the most nega-
tive level, and as the furnace and the flue system warmup, the sensing pressure
becomes less negative. After the system has reached equilibrium (approxi-
mately 20 minutes), the sensing pressure levels off. If a restriction causes the
sensing pressure to become less than the switch setpoint, the pressure switch
will function to shut off the burner. The burner will remain off until the system
has cooled and/or the flue system resistance is reduced. The table below gives
approximate water column negative pressure readings and switch setpoints for
sea level operating conditions.
DANGER: Safe
operation requires
proper venting
flow. Never bypass
the combustion air
proving switch or
attempt to operate
the unit without
the venter running
and proper flow in
the vent system.
Hazardous condi-
tion could result.
See Hazard Levels,
page 2.
9.3.5 High
Temperature Limit
Control
All furnaces are equipped with a temperature activated auto reset limit control.
The control is factory set and is non-adjustable. If the setpoint is reached,
the limit control will interrupt the electric supply to the gas valves. This safety
device provides protection in the case of a lack of airflow due to dirty filters or
a restriction at the inlet or outlet.
The limit control switch is mounted on the side of the heat exchanger with
a capillary sensor that extends across the discharge opening. The switch is
accessible in the blower compartment.
CAUTION: The auto reset limit control will continue to shut down
the heater until the cause is corrected. Never bypass the limit
control; hazardous conditions could result. See Hazard Intensity
Levels, page 2.