Reznor EEDU Unit Installation Manual - Manual (Page 21)

Form I-EEDU, P/N 150492 R6, Page 21
8.1 Combustion Air
Proving Switch
8.0 Controls
Pressure
Switch
Table
The combustion air proving switch is a pressure sensitive switch that monitors air pres-
sure to ensure that proper combustion airflow is available. The switch is a single pole
- normally open - device which closes when a decreasing pressure is sensed in the
outlet duct of the flue gas collection box.
On startup when the heater is cold, the sensing pressure is at the most negative level,
and as the heater and flue system warm up, the sensing pressure becomes less nega-
tive. After the system has reached equilibrium (about 20 minutes), the sensing pres-
sure levels off.
If a restriction or excessive flue length or turns cause the sensing pressure to become
less than the switch setpoint, the pressure switch will function to shut off the main burn-
ers. The main burners will remain off until the system has cooled and/or the flue system
resistance is reduced. The Table lists the approximate water column negative pressure
readings and switch setpoints for sea level operating conditions.
DANGER
Safe operation of this unit requires proper venting flow. NEVER bypass combustion air proving
switch or attempt to operate the unit without the venter running and the proper flow in the vent
system. Hazardous conditions could result. See Hazard Levels, page 2.
Start-Up Cold
-1.0" w.c.
Equilibrium
-0.60" w.c.
Set Point "Off"
-0.48" w.c.
Set Point "On"
-0.65" w.c.
Access
to limit
switch
from
"outside"
the
furnace
8.2 Limit Switch
View
of limit
switch
from
"inside"
the furnace
FIGURE 19 -
Access to the
limit switch
depends on the
installation.
A non-adjustable high limit switch mounted at the outlet air side of the heat exchanger
acts to shut off the gas supply in the event of air handler motor failure, lack of correct
airflow (See Paragraph 6.3), or restriction due to filters and/or duct design. See FIG-
URE 19 for mounting and service.
Depending on accessibility, the limit switch may be serviced from either the outside of
the unit or from the inside through the access panel in the discharge duct. When units
are installed side by side, the service access panel must be in either the top or bottom
of the ductwork for limit switch service. (See Paragraphs 3.2.3 and 6.3.4.)
8.3 Fan Control
(Optional, Field
Installed)
FIGURE 20A - Installation
of Optional Fan Control Kit,
Option CQ1 (P/N 57960)
Option CQ1 Fan Control, P/N 147611,
Honeywell Model L4064A1347
Inspection
Panel
Field-supplied electric conduit for line voltage
wiring to the field-supplied blower.
Airflow
Direction
Fan Control Option CQ1
is rated for maximum
motor size of 3/4HP,
1Ph @ 115 or 230 VAC.
Larger motors or 3Ph
require use of a contactor
or starter.
Recommended dial setting
for most conditions is
130°F ON and 100°F OFF.
WARNING
If you turn off the power
supply, turn off the gas.
See Hazard Levels, page
2.
NOTE: Required with makeup air gas control options; see Paragraphs 8.4.3 and 8.4.4.
1. Fan control provides the following: a) Delay of fan operation preventing circulation
of cold air, and b) Fan operation as long as the unit is hot.
2. The fan control provides additional safety by keeping the fan in operation in the
event that the gas valve fails to close when the thermostat is satisfied.